Review Article Fabrication, Characterization, Properties ...downloads.hindawi.com/journals/jnm/2014/471485.pdfReview Article Fabrication, Characterization, Properties, and Applications

Review ArticleFabrication Characterization Properties and Applications ofLow-Dimensional BiFeO3 Nanostructures

Heng Wu Jun Zhou Lizhi Liang Lei Li and Xinhua Zhu

National Laboratory of Solid State Microstructures School of Physics Nanjing University Nanjing 210093 China

Correspondence should be addressed to Xinhua Zhu xhzhu1967aliyuncom

Received 25 April 2014 Revised 25 June 2014 Accepted 25 June 2014 Published 25 August 2014

Academic Editor Seungbum Hong

Copyright copy 2014 Heng Wu et alThis is an open access article distributed under theCreative CommonsAttribution License whichpermits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

Low-dimensional BiFeO3nanostructures (eg nanocrystals nanowires nanotubes and nanoislands) have received considerable

attention due to their novel size-dependent properties and outstanding multiferroic properties at room temperature In recentyears much progress has been made both in fabrications and (microstructural electrical and magnetic) in characterizations ofBiFeO

3low-dimensional nanostructures An overview of the state of art in BiFeO

3low-dimensional nanostructures is presented

First we review the fabrications of high-quality BiFeO3low-dimensional nanostructures via a variety of techniques and then the

structural characterizations and physical properties of the BiFeO3low-dimensional nanostructures are summarizedTheir potential

applications in the next-generation magnetoelectric random access memories and photovoltaic devices are also discussed Finallywe conclude this review by providing our perspectives to the future researches of BiFeO

3low-dimensional nanostructures and

some key problems are also outlined

1 Introduction

Multiferroics are formally defined as materials that exhibitmore than one primary ferroic order parameter simultane-ously [1 2] The coupling of different order parameters suchas magnetoelectric coupling reveals the mutual regulation ofmagnetic and electric field which has potentially enormouscommercial value in the next generation of informationtechnology areas (eg multistate storage) [3ndash7] Among thesingle-phase multiferroics BiFeO

3(BFO) has high Curie

temperature (119879119862= 850

∘C) high Neel temperature (119879119873=

370∘C) and large residual polarization intensity (150120583C

cm2) at room temperature which is widely investigated asmodel system of single-phase multiferroics However as onekind of G-type antiferromagnetic material BFO has spiralspin structure with a periodicity of 62 nm this weak linermagnetoelectirc coupling makes it hard to be used in multi-functional devices [8] Recently it is found that the BFOnanoparticles exhibit relatively strong ferromagnetism astheir sizes are below 62 nm [9] Therefore an enhanced mag-netoelectric coupling can be achieved in the nanosized BFOmaterials which play an important role in microelectronic

devices [10ndash12] Recent advances in science and technology ofsemiconductor integrated circuit have resulted in the featuresizes of microelectronic devices downscaling into nanoscaledimensions At nanoscale the BFO materials display novelphysical properties that are different from their bulk andfilm counterparts Understanding the size effects of the BFOmaterials at nanoscale is of importance for developing thenext generation of revolutionary electronic nanodevices Dueto the size effects being dependent on the structure and finitesize considerable efforts have been made in the controllablesynthesis of low-dimensional BFO nanostructures such asnanowires nanotubes and their arrays Much progress hasalso been achieved in the structure and property character-ization Furthermore BFO nanostructures are also receivedextensive attention in the study of heterostructures [13] anddomain characterizations [14ndash16] This paper provides anoverview of recent advances on the fabrication structuralcharacterization and physical properties of low-dimensionalBFO nanosized materials Their potential applications arealso discussed and some problems that need to be solved infuture researches are also pointed out

Hindawi Publishing CorporationJournal of NanomaterialsVolume 2014 Article ID 471485 14 pageshttpdxdoiorg1011552014471485

2 Journal of Nanomaterials

2 Fabrication of Low-DimensionalBFO Nanostructures

Generally nanostructured materials can be classified intofour classes by their dimensions which are zero-dimensioned(0D) structures such as nanoparticles one-dimensioned(1D) materials such as nanowires nanorods and nanotubestwo-dimensioned (2D) materials such as thin film andnanoislands and three-dimensioned (3D) materials such asnanowirestubes arrays respectively Up to date two differentapproaches have been developed to fabricate nanostructuredBFO one is the bottom-up approach which means synthesiz-ing nanostructures from atoms or molecules by assemblingtiny into large the other one is top-down approach whichmeans dividing etching or carving thin film or bulkmaterialsinto nanostructures as cutting big into small In this sectionwe introduce the most used techniques for fabrication oflow-dimensional BFO nanostructures and discuss their dif-ferences

21 Sol-Gel Process Sol-gel process is a kind of bottom-upapproach which generally involves the use of metal alkoxidesand undergoes hydrolysis and condensation polymerizationreactions to produce gels After annealing the gels transformthe porous gels into a dense target productThemain process-ing factors of sol-gel process are the water ratio in solutionpH value of solution and its temperature To synthesizeBFO nanoparticles by sol-gel process Bi(NO

3)3sdot 5H2O and

Fe(NO3)3sdot 9H2O are normally used as the raw materials

For example Kim et al [17] synthesized the BFO powders(average sizes sim200 nm) by dissolving Bi(NO

3)3sdot 5H2O into

the mixture of 2-methoxyethanol and acetic acid and as thesolution became transparent they dissolved Fe(NO

3)3sdot 9H2O

in it and kept the mixture at room temperature with stirringThen the precursor solution was dried at 80∘C for about12 h to obtain the BFO xerogel powder They grinded thexerogel powders and annealed them at 600∘C in air or N

2

atmosphere to obtain the BFO nanosized powders Gao etal [18] dissolved the Bi(NO

3)3sdot 5H2O and Fe(NO

3)3sdot 9H2O

with stoichiometric proportions into 2-methoxyethanol andadjusted the solution pH value to 4-5 by adding nitricacid subsequently Then citric acid in 1 1 molar ratio withthe metal nitrates and polyethylene glycol as a dispersantwas added into the solution respectively After stirring thesolution at 50∘C for 05 h the solution was kept at 80∘C for4 days to obtain the dried gel After calcination at 500∘C for2 h perovskite-type BFO nanoparticles with average diameterof sim80ndash120 nm were obtained Similarly Park et al [9] alsoemployed the sol-gel process to synthesize single-crystallineBFO nanoparticles and tuned their sizes from less than 15 nmto sim100 nm by changing the annealing temperatures Obvi-ously the sizes of BFO nanoparticle were increased with theannealing temperature However the ideal synthetic pathwayfor the BFO nanoparticles is to obtain the appropriate sizeshape and crystallinity in the absence of the additionalpostannealing steps Therefore modified sol-gel techniquesare developed to synthesize the BFO nanoparticles Amongthem hydrothermal method is one of the examples in whichthere is no necessity for high-temperature calcination

22 Hydrothermal Method Hydrothermal method is alsocalled the autoclave method which involves heating anaqueous suspension of insoluble salts in an autoclave at amoderate temperature and pressure so that the crystallizationof a desired phase will take place The hydrothermal methodis very popular method for synthesizing the perovskitenanoparticles because the synergetic effects from solventtemperature and pressure can offer stable final products andprevent the formation of impurity phases The hydrothermalmethod is used to synthesize the BFO nanoparticles Forexample Chen et al [19] utilized Bi(NO

3)3sdot 5H2O and

Fe(NO3)3sdot 9H2O as raw materials and adjusted the concen-

tration of KOH at the region 1M to 9M to synthesize BFOnanoparticles with different morphologies at 200∘C for 6 hHan et al [20] used Bi(NO

3)3sdot 5H2O Fe(NO

3)3sdot 9H2O and

8M KOH to synthesize pure BFO powders at the temper-atures of 175ndash225∘C and the hold time of 6 h respectivelyWang et al [21] used Bi(NO


3)3sdot 9H2O

as raw materials and synthesized the different morphologiesof BFO nanoparticles by adding KNO

3mineralizer or not

All the above results demonstrate that the concentrationof KOH determines the phase structure of the synthesizedproducts The pure BFO nanoparticles with diameters of100ndash300 nm were synthesized when the concentration ofKOH was 7M and 12M If the concentration of KOH wasbelow the synthesized products were mainly composed ofperovskite-type BFO accompanied with impurity phase oforthorhombic-type Bi

2Fe4O9 In hydrothermal procedure

the growth rate of BiFeO3was decreased by adding the KNO

3

mineralizer and thin plate-like BiFeO3could be obtained as

increasing the reaction timeIn addition the solvothermal method is also a popular

method to synthesize the BFO nanomaterials which is sim-ilar to the hydrothermal method The only difference is thatthe precursor solution for a solvothermal method is usuallyan organic medium such as ethanol or acetone while thatfor a hydrothermal method is usually an aqueous mediumsuch as water Liu et al [22] employed solvothermal methodto synthesize single-crystalline BFO nanowires (45ndash200 nmin diameter several nanometers to several micrometers inlength) in acetone solvent They dissolved Bi(NO

3)3sdot 5H2O

and Fe(NO3)3sdot9H2O in 1 1 molar ratio then added deionized

water and stronger ammonia water to adjust pH value ofthe solution to 10-11 After washing the sediment by distilledwater until it is neutral 5M NaOH was added and keptstirring for 30min Then they heated the solution at 180∘Cfor 72 h hand obtained the single-crystalline BFO nanowires

Moreover the morphology of the final products derivedfrom solvothermal method can be effectively controlledby selecting the types of organics and their amount Forexample Zhang et al [23] synthesized BFO nanoparticlesand nanowires assembled by nanoparticles via changing theamount of the PVP or PEG (polyethylene glycol) polymer

23 Template Method Template method is based on chemi-cal self-organization to synthesize nanostructured materialsby the assistance of template which is porous with nanosizedpores By electrochemical deposition sol-gel or chemicalvapor deposition technology atoms or ions are deposited on

Journal of Nanomaterials 3

Table 1 Summary of various approaches for fabricating the BFO low-dimensional nanostructures

Approaches Advantages Disadvantages StructuresBottom-up

Sol-gel Facile regulation Long reaction time NanoparticleLow reaction temperature

Template Easy process Limited aspect ratio Nanowiretubeuniform size and array

HydrothermalEasy process

Harsh reaction condition Nanoparticlewirehigh crystallinitylow reaction temperature

Top-down

FIB High resolution Surface damage Nanoislandarrayuniform size and array low throughput

the tube walls and form the nanostructure Template methodcan be employed to fabricate one-dimensioned materialswhich have well dispersion and are easy to adjust aspectratio of nanowires tubes and rods by changing the structuralparameters of the used templates Since the nanostruc-tures fabricated by template method have similar structuralproperties (eg sizes shape) to the templates thereforethe pore sizes and their aspect ratios of the templates arecrucial parameters for controlling the dimensions of the finalnanostructures Park et al [24] first reported on the synthesisof BFO nanotubes by using porous anodic alumina (AAO)templates with pore-size of 100 or 200 nm They dissolvedBi(NO


3)3sdot 9H2O with a molar ratio

of 1 1 to ethylene glycol and deposited the sol onto thesurface of the AAO template by using a syringe Finally theyobtained BFO nanotubes with outer diameters in the rangeof 240 to 300 nm (for 200 nm pore-sized template) or 140 to180 nm (for 100 nm pore-sized template) and lengths rangingfrom several microns to as much as 50 120583m However thesynthesized BFOnanotubes are polycrystalline because of therandomnucleation on thewalls of pores Zhang et al [25] alsoemployed the similar method to synthesize BFO nanowiresarray via injecting the sol on the template and annealed itsubsequently Gao et al [26] synthesized polycrystalline BFOnanowires with a diameter of 50 nm and 5 120583m in length bythe similar method

Synthesis of the BFO nanostructures by template methodprovides some advantages such as the structure of the nanoar-ray subject to the structure of the template the channels of thetemplate controlling the dimension of the materials templatepore walls preventing the aggregation of the material and alarge amount of nanowires or nanotubes mass produced

24 Focus Ion Beam (FIB) Milling Method The commontop-down approach to fabricate nanostructured materials isfocused ion beam (FIB) milling method The typical techno-logy is to utilize focused Ga+ ions to bombard the thin filmor bulk material to obtain the designed nanostructures Theadvantages of FIB milling method are controllable morphol-ogy of structure or even patterns facile operation and andso forth However the disadvantages are high cost and the

resolution of FIB ismicron or submicron scale which is largerthan the nanostructure

Recently Morelli et al [27] fabricated BFO nanoislandsby template-assisted FIBmethod based on epitaxial BFO thinfilms grown on SrTiO

3(100) substrates Arrays of 45 nm-

thick aluminium dots were first evaporated on BFO thinfilms through template with aperture diameter of 400 nmA focused ion beam with gallium ions was used to millthe specimen covered by Al dots Chemical etching of theremaining Al was performed in 10 aqueous solution ofpotassium hydroxide (KOH) at room temperature for 90 sArrays of epitaxial BFO nanoislands with diameter sim250 nmwere obtainedThe features of top-down approaches are theirprecisely positioning and controlling the shapes and sizesof the designed BFO nanostructures However their time-consuming and low-throughput characters of these processesare the shortcomings of the top-down approaches

Table 1 summarizes various approaches for fabricating theBFO low-dimensional nanostructures

3 Characterization of BFO Nanostructures

Up to date various approaches including X-ray diffrac-tion (XRD) scanning electron microscopy (SEM) (high-resolution) scanning transmission electron microscopy (HR)STEM as well as X-ray energy dispersive spectrum (EDS)electron energy loss spectra (EELS) and selected area elec-tron diffraction (SAED) have been developed to probe boththe macroscopic and the microscopic details of BFO low-dimensional nanostructures In this section we will brieflysummarize the recent the atomic-scale microstructural fea-tures of BFO low-dimensional nanostructures revealed anumber of techniques

31 BFO NanoparticlesNanoislands Park et al [9] firstreported the synthesis of pure crystalline BFO nanoparticlesby sol-gel method Figure 1 shows the structural character-izations of BFO nanoparticles with the average diameter of95 nm by techniques of TEM SAED EDS and HRTEMZhu et al [28] also reported on the microwave-hydrothermalsynthesis of spherical BFO nanoparticles their TEM and


(a) (b)

Inte

nsity

(au

)

2 4 6 8 10 12 14 16

C

OFe

Fe

Fe

Cu

Cu

CuBI

BI

BI BI

BI

Energy (keV)

(c) (d)

Figure 1 (a) TEM image (b) SAED pattern (c) EDS and (d) HRTEM image of an individual BiFeO3nanoparticle (with a diameter of 95 nm)

synthesized by sol-gel method

HRTEM images are shown in Figure 2 The HRTEM patterndemonstrates the well crystallization of as-prepared BFOnanocrystals

Besides the BFO nanoparticles epitaxial BFO nanois-lands were also synthesized by chemical self-assembledmethod [29] their phase structure and morphology werecharacterized by XRD and atomic force microscopy (AFM)Figure 3 shows the XRD patterns of the BFO nanoislandsannealed at different temperatures there is almost no otherimpurity peaks except the diffraction peaks of single crys-talline SrTiO

3substrate and the (100) crystal orientation

of BFO The AFM images shown in Figure 4 revealedthat with increasing the postannealing temperature from600∘C to 800∘C the morphology of BFO nanoislands inthe (100) growth plane evolved from triangled to squaredand then to plated shapes Fractal ferroelectric domainsand self-bias polarization were also found in a single BFO

nanoisland which were revealed by piezoforce microscopy(PFM) images

Zhou et al [30] also fabricated the BFO nanoring struc-ture by combing sol-gel AAO template-assisted and planarTEM sample preparation methodology Figure 5(a) showsthe STEM image of the nanorings where the atoms withhigh atomic numbers (such as Bi Fe) exhibit bright imagecontrast therefore the BFO nanorings demonstrate highwhite bright contrast Figure 5(b) shows the line scan of theintensity distribution of the STEM image contrast of the BFOnanorings from which the inner diameter of the nanoringwas determined to be about 170 nm and its thickness wasabout 20 nm Therefore the BFO nanorings were formed inthe walls of the AAO template The EDS data reveal that theBFO nanorings are composed of Bi Fe and O elements andthat the chemical composition of the nanorings is close toBiFeO

3


(a) (b)

Figure 2 (a) TEM image of BiFeO3nanocrystals and the inset is selected area electron diffraction pattern (b) HRTEM image of a single

BiFeO3nanocrystal with a diameter of sim12 nm

32 One-Dimensional BFO Nanostructures and Their ArraysZhang et al [25 31] fabricated the BFO nanowire andnanotube arrays by a template synthesis involving the sol-gel technique Figure 6 shows the SEM images of the BFOnanowire and nanotube arrays respectively The TEM imageof a single BFO nanotube is shown in Figure 6(c) thecorresponding SAED pattern and the EDX spectrum areshown as insets

33 Domain Structures of BFO Thin Films Chu et al [32]characterized the ferroelectric polarization direction anddomain structures of BFO films with different thicknesses(120 15 and 2 nm) grown on SrTiO

3(001) (top) and DySrO

3

(110) substrates (bottom) by PFM Due to the competitionbetween the normal strain caused by lattice mismatch andshear strain caused by the rhombohedral symmetry fer-roelectric polarization direction and domain structures arechanged with the decrease of the film thickness as shownin Figure 7 With decreasing the thickness of BFO filmsdeposited on SrTiO

3(001) the domain morphology evolved

from stripe domain structures (Figure 7(a)) to intricatedomain structures with fluctuate mottled contrast (Figures7(b) and 7(c)) However the domain size became largeras decreasing the thickness of BFO films deposited onDySrO

3(110) substrates Such a difference arises from the

normal strain since it cannot be released at such thicknessestherefore BFO films on SrTiO

3have larger elastic strain

energy which leads to smaller domain structures

4 Physical Properties of Low-DimensionalBFO Nanostructures

41 BFO Nanoparticles Park et al [9] synthesized the BFOnanoparticles by sol-gel method and investigated the size-driven magnetism of the BFO nanoparticles as shown in

Figure 8 As the sizes of the BFO nanoparticles were reducedtheirmagnetismwas significantly enhanced Especially whenthe particle size was 14 nm the magnetization was about 3times larger than that of the BFO particle with size of 100 nmThis is important for enhancing the magnetic properties ofthe BFO nanoparticles with antiferromagnetic ground state

Recently it is reported that low-dimensional nanostruc-tured BFO such as nanoparticles and nanowires exhibitgood photocatalytic activities in visible-light region As anovel visible-light-responsive photocatalysts for degradationof organic compounds BFO nanostructures have been widelyinvestigated For example Zhu et al [28] reported themicrowave-hydrothermal synthesis of spherical perovskite-type BFO nanocrystals with diameters of 10ndash50 nm andhexagonal-shaped sillenite-type ones with sizes of 18ndash33 nmat low temperatures They found that the sillenite-typebismuth ferritic nanocrystals exhibit higher photocatalyticability than the perovskite-type ones which was ascribed totheir small mean particle sizes and the unique hexagonal-shape morphology and also the structural characteristicsof sillenite-type compound Gao et al [18] also reportedvisible-light photocatalytic property of BFO nanocrystals Ascompared with the traditional TiO

2-based photocatalysts

which are the only response to UV irradiation due to its largeband gap (32 eV) the BFOnanocrystals exhibit their obviousadvantage making use of the visible-light due to their smallband gaps This is invaluable in increasing the photocatalyticreaction by using the visible sunlight

42 BFONanoislands Up to date much work about the low-dimensional BFO nanostructures is mainly focused on theBFO nanoparticles (0D) and nanofilms (2D) and little workis reported on the BFO nanoislands Geometrically BFOnanoislands are a class of systems that bridge the gap betweenthe BFO nanoparticles and BFO ultrathin films Compared


Inte

nsity

(au

)In

tens

ity (a

u)

Inte

nsity

(au

)In

tens

ity (a

u)

650∘C

700∘C

750∘C

800∘C

10 20 30 40 50 60 70 80

10 20 30 40 50 60 70 80

10 20 30 40 50 60 70 80

2120579 (deg)

2120579 (deg)

2120579 (deg)

10 20 30 40 50 60 70 80

2120579 (deg)

BFO

(100

)

STO

(100

)

BFO

(111

)

BFO

(200

)

BFO

(300

)

STO

(200

)

STO

(300

)

Figure 3 XRD patterns of the epitaxial BiFeO3nanoislands

fabricated on SrTiO3(100) single crystal substrates by chemical

assembled method and postannealed at 650∘C 700∘C 750∘C and800∘C for 1 hour The diffraction peaks labeled by 998771 were from theSrTiO

3(100) single crystal substrates diffracted by the Cu-K120573 line

due to the remaining Cu-K120573 radiation

with BFO thin films they have free-standing sidewalls thattend to suppress the formation of a nonuniform in-planepolarization due to the appearance of depolarizing fieldsimilar to the ferromagnetic particles On the other handrelative to the (confined in all three dimensions) nanoparti-cles the BFO nanoislands have large aspect ratio and likelyto behave similarly to thin films when the polarization isout of plane Therefore it is expected that multiferroic BFOnanoislands should exhibit some kind of a ldquoparticle-to-thin

filmrdquo crossover behavior and related novel effects dependingon the aspect ratio and the type of bulk polarization orderingFurthermore due to the geometrical similarity between themultiferroic BFO nanoislands and microelectronic devicesbased on the multiferroic BFO nanomaterials it is usefulfor simulating working conditions of real microelectronicdevices [33 34]

Recently Hang et al [29] reported the epitaxial growthof multiferroic BFO nanoislands on SrTiO

3(100) and Nb-

doped SrTiO3(100) single crystal substrates by chemical

self-assembled method By this method they synthesizedthe epitaxial multiferroic BFO nanoislands via postannealingprocess in the temperature range of 650ndash800∘C and thelateral sizes of the BFO nanoislands were in the range of 50ndash160 nm and height of 6ndash12 nm With increasing the postan-nealing temperature themorphology of the BFOnanoislandsin the (100) growth plane evolved from triangled to squaredand then to plated shapes Ferroelectric characteristics ofa single epitaxial BFO nanoisland (with lateral size of sim50 nm and height of 12 nm) grown onNb-doped SrTiO

3(100)

single crystal substrate was characterized by PFM imagesThe results demonstrated that fractal ferroelectric domainsexisted in the single BFO nanoisland and self-biased polar-izationwas also observedwithin thismultiferroic nanoislandThis phenomenon can be ascribed to the interfacial stresscaused by the lattice misfit between the BFO nanoisland andthe SrTiO

3single crystal substrate

By using the top-down approach such as FIB millingmethod Morelli et al [27] fabricated the arrays of epitaxialBFO islands with flat top surfaces and lateral sizes downto 250 nm by starting from a continuous BFO thin filmPFM images showed that the as-fabricated BFO nanoislandspreserved ferroelectric properties with switchable polariza-tion and exhibited retention of polarization state at least forseveral days As compared with the parent thin film the BFOnanoislands exhibit a certain degree of imprint behavior asshown in Figure 9 That is due to the existence of the defectsat the interface between the BFO film and SrRuO

3substrate

and on the sidewalls of the islands

43 BFO Nanowires Nanotubes andTheir Arrays In the lastdecade low-dimensional BFO nanostructures have receivedmuch attention because of their superior physical and chem-ical properties Among them BFO nanowires and nanotubesare especially attractive for nanoscience studies and nan-otechnology applications which are ascribed to that the BFOnanowires andor nanotubes are not only used as the buildingblocks of future nanodevices but also offer fundamentalscientific opportunities for investigating the intrinsic sizeeffects of physical properties

Nowadays BFO nanowires nanorods nanotubes andtheir arrays have been fabricated by the template-aidedsynthesis However all the products prepared by this methodexhibit polycrystalline structures due to the heterogeneousnucleation on the pore walls there are very few reports onthe synthesis of single crystalline nanowires through thismethod To better understand the intrinsic size effects ofphysical properties high quality of one-dimensional sin-gle crystalline BFO nanowires is highly required Recently


100

25

00 25 50 75 100

50nm

25nm

00nm

(120583m)

(120583m

)

(a)

650∘C

x 2000 120583mdivz 500 nmdiv

24

68

(120583m)(120583m)

(b)

5002500

500

250

0

100nm

50nm

00nm

(120583m)

(120583m

)

(c)

800∘C

x 1000 120583mdivz 10000 nmdiv

12

34

200

(120583m)

(120583m)

(d)

100

75

50

25

01007550250

100nm

50nm

00nm

(120583m

)

(120583m)

(e)

900∘C

x 2000 120583mdivz 10000 nmdiv

24

68

200

(120583m)

(120583m)

(f)

Figure 4 AFM images of the epitaxial BiFeO3nanoislands postannealed at ((a) (b)) 650∘C ((c) (d)) 800∘C ((e) (f)) 900∘C for 1 h The

left AFM images are two-dimensional ones and the right ones are the corresponding 3-dimensional ones The insets in (a) and (c) are theenlarged AFM images of the local surface areas

Liu et al [22] reported the synthesis of single-crystalline BFOnanowires (45ndash200 nm in diameter) by solvothermal methodand measured their magnetic properties by superconductingquantum interference device (SQUID) at room temperatureand low temperatures as shown in Figure 10 Li et al [35]also synthesized the BFO nanowires by solvothermal method(40ndash200 nm in diameter and several micrometers in length)and characterized a single BFO nanowire by PFM Theresults shows the 119909 and 119911-PFM hysteresis loops which clearlyreveals the ferroelectric property of a single BFO nanowire

The BFO nanowire (with diameter of 20 nm) arrays arealso fabricated by template-assisted sol-gel technique [36]Their ferroelectric and dielectric properties are demonstratedin Figure 11 Figure 11(a) shows the polarization of BFOnanowire arrays as a function of applied electric field about600 kVcm with a frequency (]) = 10 kHz at room tempera-tureThe observed P-E hysteresis loop exhibits well-saturatedrectangular shape due to the presence of less oxygen-relateddefects and phase purity of the nanowires The high valueof saturation polarization was around 54120583Ccm2 observed


(a)

8

7

6

5

4

3

2

times104

0 100 200 300 400 500 600

Scanned distance (nm)In

tens

ity (a

u)

(b)

Figure 5 (a) STEM image of the BiFeO3nanorings (b) line scan of the intensity distribution of the STEM image contrast of the BiFeO

3

nanorings (the scanned line indicated in (a))

(a) (b)

Cu

CuFe

Fe

BIBI

6 8 10 12 14

B

(c)

Figure 6 (a) SEM image of the BiFeO3nanowire array (b) top-view of the nanochannel porous alumina filled with BiFeO

3nanotubes (c)

TEM image of an isolated BiFeO3nanotube the left inset shows the corresponding SAEDpattern and the right inset shows the EDX spectrum

at 535 kVcm applied electric field Figure 11(b) displays therelative dielectric constant (120576) of the BFO nanowire arrays asa function of frequency Amonotonous decrease of dielectricconstant and dielectric loss was observed asMaxwell-Wagnertype interfacial polarization and in increasing the frequencywhich was ascribed to good agreement with Koops phe-nomenological theory The dielectric constant was measuredto be as high as 492 at 1 KHz which was due to space chargepolarization resulting from the inhomogeneous dielectricstructure Recently BFO nanotubes are also being preparedby a template synthesis involving the sol-gel technique[31] Their ferroelectric and piezoelectric properties werecharacterized by PFMmeasurements The piezoresponse 119889

33

hysteresis loop of an individual BFO nanotube was measuredusing the conductive atomic force microscope tip appliedwith a 165 kHz ac electric field plus a swept dc voltage andthe result is shown in Figure 12(a) The decrease in 119889

33at

high electric field as shown in Figure 12(a) is ascribed toa consequence of the field-induced lattice hardening which

is typical for perovskite piezoelectrics The significant piezo-electric characteristics illustrate the ferroelectric behavior ofthe BFO nanotubes The dielectric constant and dielectricloss of the BFO nanotube arrays were also measured at roomtemperature as a function of the frequency in the rangeof 103ndash106Hz as shown in Figure 12(b) Both the dielectricconstant and the dielectric loss show a remarkable decreaseof up to 103Hz and remain fairly constant afterward Thedecrease in the dielectric constant with increasing the fre-quency represents the anomalous dispersion of the dielectricconstant at low and intermediate frequencies which has beenexplained by the phenomenon of dipole relaxation whilethe variation in dielectric loss with frequency represents therelaxation absorption of the dielectrics

5 Applications of BFO Nanostructures

BFO is one of several rare single-phase multiferroic materialsthat are both ferroelectric and weakly ferromagnetic at


2120583m

(a)

1120583m

(b)

03 120583m

(c)

2120583m

(d)

1120583m

(e)

03 120583m

(f)

Figure 7 In-plane PFM images measured on (a) 120 (b) 15 and (c) 2 nm thick BFO samples on SrTiO3and in-plane PFM images measured

on (d) 120 (e) 15 and (f) 2 nm thick BFO samples on DySrO3substrates

2

1

0

minus1

minus2minus40 minus20 0 20 40

2

1

0

0 100 200 300

M(e

mu

g)

M(e

mu

g)

Size (nm)

H (kOe)

14nm41nm51nm75nm

95nm245nmBulk

(a)

M(e

mu

g)

M(e

mu

g)

H (Oe)

14nm41nm51nm75nm

95nm

14nm41nm51nm

75nm95nm

245nmBulk

03

00

minus03

minus2500 0 2500 5000

18

12

06

00

0 2 4 6 8

1d (10minus2 nmminus1)

(b)

Figure 8 (a)Hysteresis loopsmeasured at 300K for BiFeO3nanoparticles with indicated sizes (b) expanded plots ofmagnetization of BiFeO

3

nanoparticles with the return branches of the hysteresis loops omitted for clarity


50

40

30

20

10

0

minus10

minus20


FilmIsland

Piez

ores

pons

e (pm

V)

Applied bias (V)

Figure 9 Local remanent piezoresponse hysteresis plots as resulting from measurements performed on an island (triangles) and on an areaof the parent film (squares)

0018

0016

0014

0012

0010

0008

0006

0004

00020 50 100 150 200 250 300 350 400

M(e

mu

g)

T (K)

ZFC

ZFC

FC

FC

Tf

(a)

M(e

mu

g)

H (Oe)

015

010

005

000

minus005

minus010

minus015

minus6000 minus4000 minus2000 0 2000 4000 6000

300K5K

(b)

Figure 10 (a) Temperature dependence of zero-field-cooled (ZFC) and field-cooled (FC) susceptibility measured in a field of 100 Oe forBiFeO

3nanowires (b)M-H hysteresis loops for BiFeO

3nanowires measured at 5 K and 300K

room temperature Recent studies demonstrate that the BFOnanomaterials have spontaneous polarization enhancementswitchable ferroelectric diode effects photovoltaic effectspiezoelectric and THz radiation properties which havepotential applications in the fields of next-generation lead-free nondestructive memories spin valve devices actuatorsand ultrahigh speed telecommunication devices [37]

BFO nanoparticles also exhibit good photocatalytic activ-ities in visible-light region which can be used as novel visible-light-responsive photocatalysts for degradation of organiccompounds For example Zhu et al [28] synthesized spheri-cal perovskite-type single-crystalline BFO nanoparticles withdiameters of 10ndash50 nm by microwave hydrothermal process

which exhibited efficient photocatalytic activity for the degra-dation of rhodamineB in aqueous solution under visible-lightirradiation Gao et al [18] also synthesized BFO nanoparti-cles which promoted the degradation rate of methyl orangeto a high level under visible-light irradiation In additionYu et al [38] reported that perovskite-structured BiFeO

3

nanoparticles also exhibited excellent gas-sensing propertieswhich were potentially useful for high-quality gas sen-sors

Due to the coupling of ferroelectric and antiferromag-netic vectors reversing the ferroelectric polarization byan extern electric field also rotates the antiferromagneticspins Chu et al [39] presented electric-field control of local


60

40

20

0

minus20

minus40

minus60


Pola

rizat

ion

(120583C

cm2)

Electric field (kVcm)

(a)

600

500

400

300

200

100

0

1000 10000 100000 1000000

12

10

08

06

04

02

00

Die

lect

ric co

nsta

nt (120576

)

Frequency (Hz)

Die

lect

ric lo

ss (t

an 120575)

(b)

Figure 11 (a) Polarization versus applied electric field hysteresis loop (b) relative dielectric constant and dielectric loss versus the frequencytraits of BiFeO

3nanowires

02

01

00

minus01

minus02

minus03

minus40 minus20 0 20 40

Piez

ores

pons

e (au

)

DC bias (V)

(a)

400

350

300

250

200

150

100

501000 10000 100000 1000000

10

05

00

minus05

Die

lect

ric co

nsta

nt

Frequency (Hz)

tan 120575

(b)

Figure 12 (a) Piezoelectric hysteresis loop of a single BiFeO3nanotubemeasured by PFM (b) dielectric constant and dielectric lossmeasured

at room temperature as a function of the frequency

ferromagnetism through the coupling between the multifer-roic BFO and a ferromagnet (CoFe in their work) They grewheterostructures of Au (2 nm)CoFe (25ndash20 nm)BFO (50ndash200 nm)SrRuO

3(25ndash50 nm) on SrTiO

3(001)-oriented sub-

strates When applied an external in-plain electric field theyobserved that the average magnetization direction in CoFethe ferromagnet rotates by 90∘ The average magnetizationdirection changes back to the original state when applyingthe electric field again If one suggests the original state as thebinary signal ldquo0rdquo the rotated state of themagnetization direc-tion is represented the signal ldquo1rdquoTherefore the repeated suchheterostructures can be used as essential building blocks tofabricate magnetoelectric random access memory elements

Due to worldwide energy crisis the investigation ofmaterials for thin film photovoltaic cells is essential to renew-able energy production The large saturation polarization

(sim90 120583Ccm2) in BFO thin film and the band gap of BFO(119864119892sim 267 eV) smaller than many other ferroelectric pero-

vskites make BFO the remarkable candidate for the photo-voltaic cells Yang et al [40] reported photovoltaic devicesbased on BFO thin films and demonstrated the highestefficiency for the ferroelectric-based photovoltaic They grewepitaxial ferroelectric BFO thin film bymetal-organic chemi-cal vapor deposition on (001)-oriented SrTiO

3substrateswith

50 nm epitaxial SrRuO3as bottom electrodes Figure 13(a)

shows a set of polarization-electric field hysteresis loops asa function of the test frequency which reveals a strong diode-like behavior characterized by a large directional leakage atnegative voltages Figure 13(b) shows the I-V curves takenboth in dark and under 285mWcm2 white-light illuminationwhich reveals diode-like behavior and a photovoltaic effectof the heterostructure External quantum efficiency (EQE)


3000

2000

1000

0

minus1000

minus2000


Pola

rizat

ion

(120583C

cm2)

Voltage (V)

1kHz2kHz

10kHz20kHz

(a)

3

2

1

0

minus1

minus2

minus3minus15 minus10 minus05 00 05 10 15

J sc

(mA

cm

2)

Voltage (V)

Dark current+40V 3 msec pulse

minus40V 3 msec pulse

(b)

12

10

8

6

4

2

0

200 300 400 500 600 700

Wavelength (nm)

Exte

rnal

qua

ntum

effici

ency

()

6 5 4 3 2

Photon energy (eV)

(c)

Figure 13 (a) Polarization-electric field hysteresis loops at various frequencies reveal diode-like behavior in one direction (b) light (redand blue) and dark (black curve running through the origin) I-V measurements completed at 285 suns intensity reveal photovoltaic effectsin these device structures There is no observed change in the light I-V response upon application of an electric field and (c) average EQEmeasurements for five different contacts on a single sample reveal efficiencies sim10 under illumination with band gap light

measurement is showed in Figure 13(c) which reveals that themaximum conversion efficiency (sim10) is observed when thephoton energy is larger than the band gap of BFO and drop-off at the shortest wavelength (lt325 nm)

6 Conclusions

This paper reviews the recent research progress of low-dimensional BFOnanostructures including their fabricationproperty structural characterization and applications Pero-vskite-type BFO as one of the few known single-phasemultiferroics that possesses ferroelectricity and antiferro-magnetism at room temperature Its low-dimensional nanos-tructures are much attractive in the applications of multistatestorage magnetoelectric sensor and spintronic devices Asthe feature sizes of the microelectronic enter into nanoscalethere are still some problems that need to be solved in fab-rication characterization and application of BFO low-dimensional nanostructures For instance in BFOnanostruc-

tures there exist quantum size effect (ferroelectric and mag-netoelectric) size effect and surfaceinterface effect all theseeffects must be considered together from experimental andtheoretical researches which are fundamental to develop-ing the new generation of revolutionary electronic nanode-vices Although the BFO has good ferroelectricity its weakferromagnetism is highly required to be enhanced whichcould be achieved in low-dimensional nanostructuresThere-fore deeper understanding of the fundamentals of the BFOlow-dimensional nanostructures with the development ofadvanced technology and exploring the coexistrnce of ferro-electricity and ferromagnetismwith strong coupling betweenthem will be the future direction of BFO nanomaterialsresearches

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper


Acknowledgments

This work was partially supported by National Natural Sci-ence Foundation of China (Grant nos 11174122 and 11134004)National Basic Research Program of China (Grant nos2009CB929503 and 2012CB619400) and the open projectfrom National Laboratory of Solid State MicrostructuresNanjing University

References

[1] H Schmid ldquoMulti-ferroic magnetoelectricsrdquo Ferroelectrics vol162 no 1 pp 317ndash338 1994

[2] B B van Aken J R Rivera H Schmid and M Fiebig ldquoObser-vation of ferrotoroidic domainsrdquo Nature vol 449 no 7163 pp702ndash705 2007

[3] N A Spaldin and M Fiebig ldquoThe renaissance of magnetoelec-tric multiferroicsrdquo Science vol 309 no 5733 pp 391ndash392 2005

[4] C Ederer and N A Spaldin ldquoWeak ferromagnetism and mag-netoelectric coupling in bismuth ferriterdquo Physical Review BCondensed Matter and Materials Physics vol 71 no 6 ArticleID 060401 4 pages 2005

[5] C Ederer and N A Spaldin ldquoInfluence of strain and oxygenvacancies on the magnetoelectric properties of multiferroicbismuth ferriterdquo Physical Review B vol 71 no 22 Article ID224103 9 pages 2005

[6] M Kumar and K L Yadav ldquoStudy of room temperature mag-netoelectric coupling in Ti substituted bismuth ferrite systemrdquoJournal of Applied Physics vol 100 no 7 Article ID 074111 4pages 2006

[7] D H Wang W C Goh M Ning and C K Ong ldquoEffect ofBa doping on magnetic ferroelectric and magnetoelectric pro-perties in mutiferroic BiFeO

3at room temperaturerdquo Applied

Physics Letters vol 88 no 21 Article ID 212907 3 pages 2006[8] T Zhao A Scholl F Zavaliche et al ldquoElectrical control of anti-

ferromagnetic domains in multiferroic BiFeO3films at room

temperaturerdquoNatureMaterials vol 5 no 10 pp 823ndash829 2006[9] T Park G C Papaefthymiou A J Viescas A RMoodenbaugh

and S S Wong ldquoSize-dependent magnetic properties of single-crystalline multiferroic BiFeO

3nanoparticlesrdquo Nano Letters

vol 7 no 3 pp 766ndash772 2007[10] H Zhang and K Kajiyoshi ldquoHydrothermal synthesis and size-

dependent properties of multiferroic bismuth ferrite crystal-litesrdquo Journal of the American Ceramic Society vol 93 no 11pp 3842ndash3849 2010

[11] R R Das D M Kim S H Baek et al ldquoSynthesis and ferro-electric properties of epitaxial BiFeO

3thin films grown by

sputteringrdquo Applied Physics Letters vol 88 no 24 Article ID242904 3 pages 2006

[12] RMazumder P S Devi D Bhattacharya P Choudhury A Senand M Raja ldquoFerromagnetism in nanoscale BiFeO

3rdquo Applied

Physics Letters vol 91 no 6 Article ID 062510 3 pages 2007[13] S M Stratulat X L Lu A Morelli D Hesse W Erfurth and

M Alexe ldquoNucleation-induced self-assembly of multiferroicBiFeO

3- CoFe

2O4nanocompositesrdquo Nano Letters vol 13 no 8

pp 3884ndash3889 2013[14] R Nath S Hong J A Klug et al ldquoEffects of cantilever buck-

ling on vector piezoresponse force microscopy imaging of fer-roelectric domains in BiFeO

3nanostructuresrdquo Applied Physics

Letters vol 96 no 16 Article ID 163101 3 pages 2010

[15] M Park S Hong J A Klug et al ldquoThree-dimensional ferroele-ctric domain imaging of epitaxial BiFeO

3thin films using angle-

resolved piezoresponse force microscopyrdquo Applied Physics Let-ters vol 97 no 11 Article ID 112907 3 pages 2010

[16] R Nath S Hong J A Klug et al ldquoEffects of cantilever buck-ling on vector piezoresponse force microscopy imaging of fer-roelectric domains in BiFeO


Letters vol 96 Article ID 163101 2010[17] J K Kim S S Kim and W J Kim ldquoSol-gel synthesis and

properties of multiferroic BiFeO3rdquoMaterials Letters vol 59 no

29-30 pp 4006ndash4009 2005[18] F Gao X Chen K Yin et al ldquoVisible-light photocatalytic pro-

perties of weak magnetic BiFeO3nanoparticlesrdquo Advanced

Materials vol 19 no 19 pp 2889ndash2892 2007[19] X-Z Chen Z-C Qiu J-P Zhou G Zhu X-B Bian and P

Liu ldquoLarge-scale growth and shape evolution of bismuth ferriteparticles with a hydrothermal methodrdquo Materials Chemistryand Physics vol 126 no 3 pp 560ndash567 2011

[20] S H Han K S Kim H G Kim et al ldquoSynthesis and charac-terization of multiferroic BiFeO

3powders fabricated by hydro-

thermal methodrdquo Ceramics International vol 36 no 4 pp1365ndash1372 2010

[21] Y Wang G Xu Z Ren et al ldquoMineralizer-assisted hydrother-mal synthesis and characterization of BiFeO

3nanoparticlesrdquo

Journal of the American Ceramic Society vol 90 no 8 pp 2615ndash2617 2007

[22] B Liu BHu andZDu ldquoHydrothermal synthesis andmagneticproperties of single-crystalline BiFeO

3nanowiresrdquo Chemical

Communications vol 47 no 28 pp 8166ndash8168 2011[23] L Zhang X Cao Y Ma X Chen and Z Xue ldquoPolymer-

directed synthesis and magnetic property of nanoparticles-assembled BiFeO

3microrodsrdquo Journal of Solid State Chemistry

vol 183 no 8 pp 1761ndash1766 2010[24] T J Park Y Mao and S S Wong ldquoSynthesis and characteriza-

tion of multiferroic BiFeO3nanotubesrdquo Chemical Communica-

tions no 23 pp 2708ndash2709 2004[25] X Y Zhang J Y Dai and C W Lai ldquoSynthesis and characteri-

zation of highly ordered BiFeO3multiferroic nanowire arraysrdquo

Progress in Solid State Chemistry vol 33 no 2ndash4 pp 147ndash1512005

[26] F Gao Y Yuan K F Wang et al ldquoPreparation and photoab-sorption characterization BiFeO

3nanowiresrdquo Applied Physics

Letters vol 89 no 10 Article ID 102506 3 pages 2006[27] A Morelli F Johann N Schammelt D McGrouther and I

Vrejoiu ldquoMask assisted fabrication of nanoislands of BiFeO3by

ion beam millingrdquo Journal of Applied Physics vol 113 no 15Article ID 154101 4 pages 2013

[28] X H Zhu QM Hang Z B Xing et al ldquoMicrowave hydrother-mal synthesis structural characterization and visible-lightphotocatalytic activities of single-crystalline bismuth ferricnanocrystalsrdquo Journal of the American Ceramic Society vol 94no 8 pp 2688ndash2693 2011

[29] Q M Hang X H Zhu Z J Tang Y Song and Z G LiuldquoSelf-assembled perovskite epitaxial multiferroic BiFeO

3nano-

islandsrdquo Advanced Materials Research vol 197-198 pp 1325ndash1331 2011

[30] J Zhou S Liang S Y Li Z D Liu Y Y Zhu and X HZhu ldquoAdvances in low-dimensional BiFeO

3multiferroic nano-

structuresrdquo Journal of Chinese Electron Microscopy Society vol32 no 6 pp 504ndash524 2013


[31] X Y Zhang C W Lai X Zhao D Y Wang and J Y Dai ldquoSyn-thesis and ferroelectric properties of multiferroic BiFeO

3nan-

otube arraysrdquo Applied Physics Letters vol 87 no 14 Article ID143102 3 pages 2005

[32] Y H Chu T Zhao M P Cruz et al ldquoFerroelectric size effectsin multiferroic BiFeO

3thin filmsrdquo Applied Physics Letters vol

90 no 25 Article ID 252906 3 pages 2007[33] I Naumov and A M Bratkovsky ldquoUnusual polarization pat-

terns in flat epitaxial ferroelectric nanoparticlesrdquo PhysicalReview Letters vol 101 no 10 Article ID 107601 4 pages 2008

[34] S K Streiffer and D D Fong ldquoPhase transitions in nanoscaleferroelectric structuresrdquo MRS Bulletin vol 34 no 11 pp 832ndash837 2009

[35] S Li R Nechache C Harnagea L Nikolova and F RoseildquoSingle-crystalline BiFeO

3nanowires and their ferroelectric

behaviorrdquo Applied Physics Letters vol 101 no 19 Article ID192903 3 pages 2012

[36] G S Lotey and N K Verma ldquoMagnetoelectric coupling inmultiferroic BiFeO

3nanowiresrdquo Chemical Physics Letters vol

579 no 30 pp 78ndash84 2013[37] M Bibes and A Barthelemy ldquoMultiferroics towards a magne-

toelectric memoryrdquo Nature Materials vol 7 no 6 pp 425ndash4262008

[38] X L Yu YWang Y M Hu C Cao and H L Chan ldquoGas-sens-ing properties of perovskite BiFeO

3nanoparticlesrdquo Journal of

the American Ceramic Society vol 92 no 12 pp 3105ndash31072009

[39] Y H Chu L W Martin M B Holcomb et al ldquoElectric-fieldcontrol of local ferromagnetism using a magnetoelectric multi-ferroicrdquo Nature Materials vol 7 no 6 pp 478ndash482 2008

[40] S Y Yang L W Martin S J Byrnes et al ldquoPhotovoltaic effectsin BiFeO

3rdquo Applied Physics Letters vol 95 no 6 Article ID

062909 3 pages 2009

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of



CeramicsJournal of


CompositesJournal of

NanoparticlesJournal of



International Journal of

Biomaterials


NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of


The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014


CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research



MetallurgyJournal of


BioMed Research International

MaterialsJournal of


Nano

materials


Journal ofNanomaterials


2 Fabrication of Low-DimensionalBFO Nanostructures

Generally nanostructured materials can be classified intofour classes by their dimensions which are zero-dimensioned(0D) structures such as nanoparticles one-dimensioned(1D) materials such as nanowires nanorods and nanotubestwo-dimensioned (2D) materials such as thin film andnanoislands and three-dimensioned (3D) materials such asnanowirestubes arrays respectively Up to date two differentapproaches have been developed to fabricate nanostructuredBFO one is the bottom-up approach which means synthesiz-ing nanostructures from atoms or molecules by assemblingtiny into large the other one is top-down approach whichmeans dividing etching or carving thin film or bulkmaterialsinto nanostructures as cutting big into small In this sectionwe introduce the most used techniques for fabrication oflow-dimensional BFO nanostructures and discuss their dif-ferences

21 Sol-Gel Process Sol-gel process is a kind of bottom-upapproach which generally involves the use of metal alkoxidesand undergoes hydrolysis and condensation polymerizationreactions to produce gels After annealing the gels transformthe porous gels into a dense target productThemain process-ing factors of sol-gel process are the water ratio in solutionpH value of solution and its temperature To synthesizeBFO nanoparticles by sol-gel process Bi(NO

3)3sdot 5H2O and

Fe(NO3)3sdot 9H2O are normally used as the raw materials

For example Kim et al [17] synthesized the BFO powders(average sizes sim200 nm) by dissolving Bi(NO

3)3sdot 5H2O into

the mixture of 2-methoxyethanol and acetic acid and as thesolution became transparent they dissolved Fe(NO

3)3sdot 9H2O

in it and kept the mixture at room temperature with stirringThen the precursor solution was dried at 80∘C for about12 h to obtain the BFO xerogel powder They grinded thexerogel powders and annealed them at 600∘C in air or N

2

atmosphere to obtain the BFO nanosized powders Gao etal [18] dissolved the Bi(NO


3)3sdot 9H2O

with stoichiometric proportions into 2-methoxyethanol andadjusted the solution pH value to 4-5 by adding nitricacid subsequently Then citric acid in 1 1 molar ratio withthe metal nitrates and polyethylene glycol as a dispersantwas added into the solution respectively After stirring thesolution at 50∘C for 05 h the solution was kept at 80∘C for4 days to obtain the dried gel After calcination at 500∘C for2 h perovskite-type BFO nanoparticles with average diameterof sim80ndash120 nm were obtained Similarly Park et al [9] alsoemployed the sol-gel process to synthesize single-crystallineBFO nanoparticles and tuned their sizes from less than 15 nmto sim100 nm by changing the annealing temperatures Obvi-ously the sizes of BFO nanoparticle were increased with theannealing temperature However the ideal synthetic pathwayfor the BFO nanoparticles is to obtain the appropriate sizeshape and crystallinity in the absence of the additionalpostannealing steps Therefore modified sol-gel techniquesare developed to synthesize the BFO nanoparticles Amongthem hydrothermal method is one of the examples in whichthere is no necessity for high-temperature calcination

22 Hydrothermal Method Hydrothermal method is alsocalled the autoclave method which involves heating anaqueous suspension of insoluble salts in an autoclave at amoderate temperature and pressure so that the crystallizationof a desired phase will take place The hydrothermal methodis very popular method for synthesizing the perovskitenanoparticles because the synergetic effects from solventtemperature and pressure can offer stable final products andprevent the formation of impurity phases The hydrothermalmethod is used to synthesize the BFO nanoparticles Forexample Chen et al [19] utilized Bi(NO

3)3sdot 5H2O and

Fe(NO3)3sdot 9H2O as raw materials and adjusted the concen-

tration of KOH at the region 1M to 9M to synthesize BFOnanoparticles with different morphologies at 200∘C for 6 hHan et al [20] used Bi(NO

3)3sdot 5H2O Fe(NO

3)3sdot 9H2O and

8M KOH to synthesize pure BFO powders at the temper-atures of 175ndash225∘C and the hold time of 6 h respectivelyWang et al [21] used Bi(NO


3)3sdot 9H2O

as raw materials and synthesized the different morphologiesof BFO nanoparticles by adding KNO

3mineralizer or not

All the above results demonstrate that the concentrationof KOH determines the phase structure of the synthesizedproducts The pure BFO nanoparticles with diameters of100ndash300 nm were synthesized when the concentration ofKOH was 7M and 12M If the concentration of KOH wasbelow the synthesized products were mainly composed ofperovskite-type BFO accompanied with impurity phase oforthorhombic-type Bi

2Fe4O9 In hydrothermal procedure

the growth rate of BiFeO3was decreased by adding the KNO

3

mineralizer and thin plate-like BiFeO3could be obtained as

increasing the reaction timeIn addition the solvothermal method is also a popular

method to synthesize the BFO nanomaterials which is sim-ilar to the hydrothermal method The only difference is thatthe precursor solution for a solvothermal method is usuallyan organic medium such as ethanol or acetone while thatfor a hydrothermal method is usually an aqueous mediumsuch as water Liu et al [22] employed solvothermal methodto synthesize single-crystalline BFO nanowires (45ndash200 nmin diameter several nanometers to several micrometers inlength) in acetone solvent They dissolved Bi(NO

3)3sdot 5H2O

and Fe(NO3)3sdot9H2O in 1 1 molar ratio then added deionized

water and stronger ammonia water to adjust pH value ofthe solution to 10-11 After washing the sediment by distilledwater until it is neutral 5M NaOH was added and keptstirring for 30min Then they heated the solution at 180∘Cfor 72 h hand obtained the single-crystalline BFO nanowires

Moreover the morphology of the final products derivedfrom solvothermal method can be effectively controlledby selecting the types of organics and their amount Forexample Zhang et al [23] synthesized BFO nanoparticlesand nanowires assembled by nanoparticles via changing theamount of the PVP or PEG (polyethylene glycol) polymer

23 Template Method Template method is based on chemi-cal self-organization to synthesize nanostructured materialsby the assistance of template which is porous with nanosizedpores By electrochemical deposition sol-gel or chemicalvapor deposition technology atoms or ions are deposited on








Top-down

















(a) (b)

Inte

nsity

(au

)

2 4 6 8 10 12 14 16

C

OFe

Fe

Fe

Cu

Cu

CuBI

BI

BI BI

BI

Energy (keV)

(c) (d)









3


(a) (b)






3
















Inte

nsity

(au

)In

tens

ity (a

u)

Inte

nsity

(au

)In

tens

ity (a

u)

650∘C

700∘C

750∘C

800∘C

10 20 30 40 50 60 70 80

10 20 30 40 50 60 70 80

10 20 30 40 50 60 70 80

2120579 (deg)

2120579 (deg)

2120579 (deg)

10 20 30 40 50 60 70 80

2120579 (deg)

BFO

(100

)

STO

(100

)

BFO

(111

)

BFO

(200

)

BFO

(300

)

STO

(200

)

STO

(300

)









3(100) and Nb-



3(100)




3substrate





100

25

00 25 50 75 100

50nm

25nm

00nm

(120583m)

(120583m

)

(a)

650∘C

x 2000 120583mdivz 500 nmdiv

24

68

(120583m)(120583m)

(b)

5002500

500

250

0

100nm

50nm

00nm

(120583m)

(120583m

)

(c)

800∘C

x 1000 120583mdivz 10000 nmdiv

12

34

200

(120583m)

(120583m)

(d)

100

75

50

25

01007550250

100nm

50nm

00nm

(120583m

)

(120583m)

(e)

900∘C

x 2000 120583mdivz 10000 nmdiv

24

68

200

(120583m)

(120583m)

(f)






(a)

8

7

6

5

4

3

2

times104

0 100 200 300 400 500 600


tens

ity (a

u)

(b)


3


(a) (b)

Cu

CuFe

Fe

BIBI

6 8 10 12 14

B

(c)


3nanotubes (c)



33


33at






2120583m

(a)

1120583m

(b)

03 120583m

(c)

2120583m

(d)

1120583m

(e)

03 120583m

(f)



2

1

0

minus1


2

1

0

0 100 200 300

M(e

mu

g)

M(e

mu

g)

Size (nm)

H (kOe)

14nm41nm51nm75nm

95nm245nmBulk

(a)

M(e

mu

g)

M(e

mu

g)

H (Oe)

14nm41nm51nm75nm

95nm

14nm41nm51nm

75nm95nm

245nmBulk

03

00

minus03

minus2500 0 2500 5000

18

12

06

00

0 2 4 6 8


(b)


3



50

40

30

20

10

0

minus10

minus20


FilmIsland

Piez

ores

pons

e (pm

V)

Applied bias (V)


0018

0016

0014

0012

0010

0008

0006

0004

00020 50 100 150 200 250 300 350 400

M(e

mu

g)

T (K)

ZFC

ZFC

FC

FC

Tf

(a)

M(e

mu

g)

H (Oe)

015

010

005

000

minus005

minus010

minus015


300K5K

(b)







3




60

40

20

0

minus20

minus40

minus60


Pola

rizat

ion

(120583C

cm2)


(a)

600

500

400

300

200

100

0

1000 10000 100000 1000000

12

10

08

06

04

02

00

Die

lect

ric co

nsta

nt (120576

)

Frequency (Hz)

Die

lect

ric lo

ss (t

an 120575)

(b)


3nanowires

02

01

00

minus01

minus02

minus03


Piez

ores

pons

e (au

)

DC bias (V)

(a)

400

350

300

250

200

150

100

501000 10000 100000 1000000

10

05

00

minus05

Die

lect

ric co

nsta

nt

Frequency (Hz)

tan 120575

(b)










3substrateswith




3000

2000

1000

0

minus1000

minus2000


Pola

rizat

ion

(120583C

cm2)

Voltage (V)

1kHz2kHz

10kHz20kHz

(a)

3

2

1

0

minus1

minus2


J sc

(mA

cm

2)

Voltage (V)



(b)

12

10

8

6

4

2

0

200 300 400 500 600 700

Wavelength (nm)

Exte

rnal

qua

ntum

effici

ency

()

6 5 4 3 2

Photon energy (eV)

(c)



6 Conclusions






Acknowledgments


References




















3rdquo Applied



3- CoFe





















3nanoparticlesrdquo



















3nano-



3multiferroic nano-




3nan-




















062909 3 pages 2009








CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials










Top-down

















(a) (b)

Inte

nsity

(au

)

2 4 6 8 10 12 14 16

C

OFe

Fe

Fe

Cu

Cu

CuBI

BI

BI BI

BI

Energy (keV)

(c) (d)









3


(a) (b)






3
















Inte

nsity

(au

)In

tens

ity (a

u)

Inte

nsity

(au

)In

tens

ity (a

u)

650∘C

700∘C

750∘C

800∘C

10 20 30 40 50 60 70 80

10 20 30 40 50 60 70 80

10 20 30 40 50 60 70 80

2120579 (deg)

2120579 (deg)

2120579 (deg)

10 20 30 40 50 60 70 80

2120579 (deg)

BFO

(100

)

STO

(100

)

BFO

(111

)

BFO

(200

)

BFO

(300

)

STO

(200

)

STO

(300

)









3(100) and Nb-



3(100)




3substrate





100

25

00 25 50 75 100

50nm

25nm

00nm

(120583m)

(120583m

)

(a)

650∘C

x 2000 120583mdivz 500 nmdiv

24

68

(120583m)(120583m)

(b)

5002500

500

250

0

100nm

50nm

00nm

(120583m)

(120583m

)

(c)

800∘C

x 1000 120583mdivz 10000 nmdiv

12

34

200

(120583m)

(120583m)

(d)

100

75

50

25

01007550250

100nm

50nm

00nm

(120583m

)

(120583m)

(e)

900∘C

x 2000 120583mdivz 10000 nmdiv

24

68

200

(120583m)

(120583m)

(f)






(a)

8

7

6

5

4

3

2

times104

0 100 200 300 400 500 600


tens

ity (a

u)

(b)


3


(a) (b)

Cu

CuFe

Fe

BIBI

6 8 10 12 14

B

(c)


3nanotubes (c)



33


33at






2120583m

(a)

1120583m

(b)

03 120583m

(c)

2120583m

(d)

1120583m

(e)

03 120583m

(f)



2

1

0

minus1


2

1

0

0 100 200 300

M(e

mu

g)

M(e

mu

g)

Size (nm)

H (kOe)

14nm41nm51nm75nm

95nm245nmBulk

(a)

M(e

mu

g)

M(e

mu

g)

H (Oe)

14nm41nm51nm75nm

95nm

14nm41nm51nm

75nm95nm

245nmBulk

03

00

minus03

minus2500 0 2500 5000

18

12

06

00

0 2 4 6 8


(b)


3



50

40

30

20

10

0

minus10

minus20


FilmIsland

Piez

ores

pons

e (pm

V)

Applied bias (V)


0018

0016

0014

0012

0010

0008

0006

0004

00020 50 100 150 200 250 300 350 400

M(e

mu

g)

T (K)

ZFC

ZFC

FC

FC

Tf

(a)

M(e

mu

g)

H (Oe)

015

010

005

000

minus005

minus010

minus015


300K5K

(b)







3




60

40

20

0

minus20

minus40

minus60


Pola

rizat

ion

(120583C

cm2)


(a)

600

500

400

300

200

100

0

1000 10000 100000 1000000

12

10

08

06

04

02

00

Die

lect

ric co

nsta

nt (120576

)

Frequency (Hz)

Die

lect

ric lo

ss (t

an 120575)

(b)


3nanowires

02

01

00

minus01

minus02

minus03


Piez

ores

pons

e (au

)

DC bias (V)

(a)

400

350

300

250

200

150

100

501000 10000 100000 1000000

10

05

00

minus05

Die

lect

ric co

nsta

nt

Frequency (Hz)

tan 120575

(b)










3substrateswith




3000

2000

1000

0

minus1000

minus2000


Pola

rizat

ion

(120583C

cm2)

Voltage (V)

1kHz2kHz

10kHz20kHz

(a)

3

2

1

0

minus1

minus2


J sc

(mA

cm

2)

Voltage (V)



(b)

12

10

8

6

4

2

0

200 300 400 500 600 700

Wavelength (nm)

Exte

rnal

qua

ntum

effici

ency

()

6 5 4 3 2

Photon energy (eV)

(c)



6 Conclusions






Acknowledgments


References




















3rdquo Applied



3- CoFe





















3nanoparticlesrdquo



















3nano-



3multiferroic nano-




3nan-




















062909 3 pages 2009








CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




(a) (b)

Inte

nsity

(au

)

2 4 6 8 10 12 14 16

C

OFe

Fe

Fe

Cu

Cu

CuBI

BI

BI BI

BI

Energy (keV)

(c) (d)









3


(a) (b)






3
















Inte

nsity

(au

)In

tens

ity (a

u)

Inte

nsity

(au

)In

tens

ity (a

u)

650∘C

700∘C

750∘C

800∘C

10 20 30 40 50 60 70 80

10 20 30 40 50 60 70 80

10 20 30 40 50 60 70 80

2120579 (deg)

2120579 (deg)

2120579 (deg)

10 20 30 40 50 60 70 80

2120579 (deg)

BFO

(100

)

STO

(100

)

BFO

(111

)

BFO

(200

)

BFO

(300

)

STO

(200

)

STO

(300

)









3(100) and Nb-



3(100)




3substrate





100

25

00 25 50 75 100

50nm

25nm

00nm

(120583m)

(120583m

)

(a)

650∘C

x 2000 120583mdivz 500 nmdiv

24

68

(120583m)(120583m)

(b)

5002500

500

250

0

100nm

50nm

00nm

(120583m)

(120583m

)

(c)

800∘C

x 1000 120583mdivz 10000 nmdiv

12

34

200

(120583m)

(120583m)

(d)

100

75

50

25

01007550250

100nm

50nm

00nm

(120583m

)

(120583m)

(e)

900∘C

x 2000 120583mdivz 10000 nmdiv

24

68

200

(120583m)

(120583m)

(f)






(a)

8

7

6

5

4

3

2

times104

0 100 200 300 400 500 600


tens

ity (a

u)

(b)


3


(a) (b)

Cu

CuFe

Fe

BIBI

6 8 10 12 14

B

(c)


3nanotubes (c)



33


33at






2120583m

(a)

1120583m

(b)

03 120583m

(c)

2120583m

(d)

1120583m

(e)

03 120583m

(f)



2

1

0

minus1


2

1

0

0 100 200 300

M(e

mu

g)

M(e

mu

g)

Size (nm)

H (kOe)

14nm41nm51nm75nm

95nm245nmBulk

(a)

M(e

mu

g)

M(e

mu

g)

H (Oe)

14nm41nm51nm75nm

95nm

14nm41nm51nm

75nm95nm

245nmBulk

03

00

minus03

minus2500 0 2500 5000

18

12

06

00

0 2 4 6 8


(b)


3



50

40

30

20

10

0

minus10

minus20


FilmIsland

Piez

ores

pons

e (pm

V)

Applied bias (V)


0018

0016

0014

0012

0010

0008

0006

0004

00020 50 100 150 200 250 300 350 400

M(e

mu

g)

T (K)

ZFC

ZFC

FC

FC

Tf

(a)

M(e

mu

g)

H (Oe)

015

010

005

000

minus005

minus010

minus015


300K5K

(b)







3




60

40

20

0

minus20

minus40

minus60


Pola

rizat

ion

(120583C

cm2)


(a)

600

500

400

300

200

100

0

1000 10000 100000 1000000

12

10

08

06

04

02

00

Die

lect

ric co

nsta

nt (120576

)

Frequency (Hz)

Die

lect

ric lo

ss (t

an 120575)

(b)


3nanowires

02

01

00

minus01

minus02

minus03


Piez

ores

pons

e (au

)

DC bias (V)

(a)

400

350

300

250

200

150

100

501000 10000 100000 1000000

10

05

00

minus05

Die

lect

ric co

nsta

nt

Frequency (Hz)

tan 120575

(b)










3substrateswith




3000

2000

1000

0

minus1000

minus2000


Pola

rizat

ion

(120583C

cm2)

Voltage (V)

1kHz2kHz

10kHz20kHz

(a)

3

2

1

0

minus1

minus2


J sc

(mA

cm

2)

Voltage (V)



(b)

12

10

8

6

4

2

0

200 300 400 500 600 700

Wavelength (nm)

Exte

rnal

qua

ntum

effici

ency

()

6 5 4 3 2

Photon energy (eV)

(c)



6 Conclusions






Acknowledgments


References




















3rdquo Applied



3- CoFe





















3nanoparticlesrdquo



















3nano-



3multiferroic nano-




3nan-




















062909 3 pages 2009








CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




(a) (b)






3
















Inte

nsity

(au

)In

tens

ity (a

u)

Inte

nsity

(au

)In

tens

ity (a

u)

650∘C

700∘C

750∘C

800∘C

10 20 30 40 50 60 70 80

10 20 30 40 50 60 70 80

10 20 30 40 50 60 70 80

2120579 (deg)

2120579 (deg)

2120579 (deg)

10 20 30 40 50 60 70 80

2120579 (deg)

BFO

(100

)

STO

(100

)

BFO

(111

)

BFO

(200

)

BFO

(300

)

STO

(200

)

STO

(300

)









3(100) and Nb-



3(100)




3substrate





100

25

00 25 50 75 100

50nm

25nm

00nm

(120583m)

(120583m

)

(a)

650∘C

x 2000 120583mdivz 500 nmdiv

24

68

(120583m)(120583m)

(b)

5002500

500

250

0

100nm

50nm

00nm

(120583m)

(120583m

)

(c)

800∘C

x 1000 120583mdivz 10000 nmdiv

12

34

200

(120583m)

(120583m)

(d)

100

75

50

25

01007550250

100nm

50nm

00nm

(120583m

)

(120583m)

(e)

900∘C

x 2000 120583mdivz 10000 nmdiv

24

68

200

(120583m)

(120583m)

(f)






(a)

8

7

6

5

4

3

2

times104

0 100 200 300 400 500 600


tens

ity (a

u)

(b)


3


(a) (b)

Cu

CuFe

Fe

BIBI

6 8 10 12 14

B

(c)


3nanotubes (c)



33


33at






2120583m

(a)

1120583m

(b)

03 120583m

(c)

2120583m

(d)

1120583m

(e)

03 120583m

(f)



2

1

0

minus1


2

1

0

0 100 200 300

M(e

mu

g)

M(e

mu

g)

Size (nm)

H (kOe)

14nm41nm51nm75nm

95nm245nmBulk

(a)

M(e

mu

g)

M(e

mu

g)

H (Oe)

14nm41nm51nm75nm

95nm

14nm41nm51nm

75nm95nm

245nmBulk

03

00

minus03

minus2500 0 2500 5000

18

12

06

00

0 2 4 6 8


(b)


3



50

40

30

20

10

0

minus10

minus20


FilmIsland

Piez

ores

pons

e (pm

V)

Applied bias (V)


0018

0016

0014

0012

0010

0008

0006

0004

00020 50 100 150 200 250 300 350 400

M(e

mu

g)

T (K)

ZFC

ZFC

FC

FC

Tf

(a)

M(e

mu

g)

H (Oe)

015

010

005

000

minus005

minus010

minus015


300K5K

(b)







3




60

40

20

0

minus20

minus40

minus60


Pola

rizat

ion

(120583C

cm2)


(a)

600

500

400

300

200

100

0

1000 10000 100000 1000000

12

10

08

06

04

02

00

Die

lect

ric co

nsta

nt (120576

)

Frequency (Hz)

Die

lect

ric lo

ss (t

an 120575)

(b)


3nanowires

02

01

00

minus01

minus02

minus03


Piez

ores

pons

e (au

)

DC bias (V)

(a)

400

350

300

250

200

150

100

501000 10000 100000 1000000

10

05

00

minus05

Die

lect

ric co

nsta

nt

Frequency (Hz)

tan 120575

(b)










3substrateswith




3000

2000

1000

0

minus1000

minus2000


Pola

rizat

ion

(120583C

cm2)

Voltage (V)

1kHz2kHz

10kHz20kHz

(a)

3

2

1

0

minus1

minus2


J sc

(mA

cm

2)

Voltage (V)



(b)

12

10

8

6

4

2

0

200 300 400 500 600 700

Wavelength (nm)

Exte

rnal

qua

ntum

effici

ency

()

6 5 4 3 2

Photon energy (eV)

(c)



6 Conclusions






Acknowledgments


References




















3rdquo Applied



3- CoFe





















3nanoparticlesrdquo



















3nano-



3multiferroic nano-




3nan-




















062909 3 pages 2009








CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




Inte

nsity

(au

)In

tens

ity (a

u)

Inte

nsity

(au

)In

tens

ity (a

u)

650∘C

700∘C

750∘C

800∘C

10 20 30 40 50 60 70 80

10 20 30 40 50 60 70 80

10 20 30 40 50 60 70 80

2120579 (deg)

2120579 (deg)

2120579 (deg)

10 20 30 40 50 60 70 80

2120579 (deg)

BFO

(100

)

STO

(100

)

BFO

(111

)

BFO

(200

)

BFO

(300

)

STO

(200

)

STO

(300

)









3(100) and Nb-



3(100)




3substrate





100

25

00 25 50 75 100

50nm

25nm

00nm

(120583m)

(120583m

)

(a)

650∘C

x 2000 120583mdivz 500 nmdiv

24

68

(120583m)(120583m)

(b)

5002500

500

250

0

100nm

50nm

00nm

(120583m)

(120583m

)

(c)

800∘C

x 1000 120583mdivz 10000 nmdiv

12

34

200

(120583m)

(120583m)

(d)

100

75

50

25

01007550250

100nm

50nm

00nm

(120583m

)

(120583m)

(e)

900∘C

x 2000 120583mdivz 10000 nmdiv

24

68

200

(120583m)

(120583m)

(f)






(a)

8

7

6

5

4

3

2

times104

0 100 200 300 400 500 600


tens

ity (a

u)

(b)


3


(a) (b)

Cu

CuFe

Fe

BIBI

6 8 10 12 14

B

(c)


3nanotubes (c)



33


33at






2120583m

(a)

1120583m

(b)

03 120583m

(c)

2120583m

(d)

1120583m

(e)

03 120583m

(f)



2

1

0

minus1


2

1

0

0 100 200 300

M(e

mu

g)

M(e

mu

g)

Size (nm)

H (kOe)

14nm41nm51nm75nm

95nm245nmBulk

(a)

M(e

mu

g)

M(e

mu

g)

H (Oe)

14nm41nm51nm75nm

95nm

14nm41nm51nm

75nm95nm

245nmBulk

03

00

minus03

minus2500 0 2500 5000

18

12

06

00

0 2 4 6 8


(b)


3



50

40

30

20

10

0

minus10

minus20


FilmIsland

Piez

ores

pons

e (pm

V)

Applied bias (V)


0018

0016

0014

0012

0010

0008

0006

0004

00020 50 100 150 200 250 300 350 400

M(e

mu

g)

T (K)

ZFC

ZFC

FC

FC

Tf

(a)

M(e

mu

g)

H (Oe)

015

010

005

000

minus005

minus010

minus015


300K5K

(b)







3




60

40

20

0

minus20

minus40

minus60


Pola

rizat

ion

(120583C

cm2)


(a)

600

500

400

300

200

100

0

1000 10000 100000 1000000

12

10

08

06

04

02

00

Die

lect

ric co

nsta

nt (120576

)

Frequency (Hz)

Die

lect

ric lo

ss (t

an 120575)

(b)


3nanowires

02

01

00

minus01

minus02

minus03


Piez

ores

pons

e (au

)

DC bias (V)

(a)

400

350

300

250

200

150

100

501000 10000 100000 1000000

10

05

00

minus05

Die

lect

ric co

nsta

nt

Frequency (Hz)

tan 120575

(b)










3substrateswith




3000

2000

1000

0

minus1000

minus2000


Pola

rizat

ion

(120583C

cm2)

Voltage (V)

1kHz2kHz

10kHz20kHz

(a)

3

2

1

0

minus1

minus2


J sc

(mA

cm

2)

Voltage (V)



(b)

12

10

8

6

4

2

0

200 300 400 500 600 700

Wavelength (nm)

Exte

rnal

qua

ntum

effici

ency

()

6 5 4 3 2

Photon energy (eV)

(c)



6 Conclusions






Acknowledgments


References




















3rdquo Applied



3- CoFe





















3nanoparticlesrdquo



















3nano-



3multiferroic nano-




3nan-




















062909 3 pages 2009








CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




100

25

00 25 50 75 100

50nm

25nm

00nm

(120583m)

(120583m

)

(a)

650∘C

x 2000 120583mdivz 500 nmdiv

24

68

(120583m)(120583m)

(b)

5002500

500

250

0

100nm

50nm

00nm

(120583m)

(120583m

)

(c)

800∘C

x 1000 120583mdivz 10000 nmdiv

12

34

200

(120583m)

(120583m)

(d)

100

75

50

25

01007550250

100nm

50nm

00nm

(120583m

)

(120583m)

(e)

900∘C

x 2000 120583mdivz 10000 nmdiv

24

68

200

(120583m)

(120583m)

(f)






(a)

8

7

6

5

4

3

2

times104

0 100 200 300 400 500 600


tens

ity (a

u)

(b)


3


(a) (b)

Cu

CuFe

Fe

BIBI

6 8 10 12 14

B

(c)


3nanotubes (c)



33


33at






2120583m

(a)

1120583m

(b)

03 120583m

(c)

2120583m

(d)

1120583m

(e)

03 120583m

(f)



2

1

0

minus1


2

1

0

0 100 200 300

M(e

mu

g)

M(e

mu

g)

Size (nm)

H (kOe)

14nm41nm51nm75nm

95nm245nmBulk

(a)

M(e

mu

g)

M(e

mu

g)

H (Oe)

14nm41nm51nm75nm

95nm

14nm41nm51nm

75nm95nm

245nmBulk

03

00

minus03

minus2500 0 2500 5000

18

12

06

00

0 2 4 6 8


(b)


3



50

40

30

20

10

0

minus10

minus20


FilmIsland

Piez

ores

pons

e (pm

V)

Applied bias (V)


0018

0016

0014

0012

0010

0008

0006

0004

00020 50 100 150 200 250 300 350 400

M(e

mu

g)

T (K)

ZFC

ZFC

FC

FC

Tf

(a)

M(e

mu

g)

H (Oe)

015

010

005

000

minus005

minus010

minus015


300K5K

(b)







3




60

40

20

0

minus20

minus40

minus60


Pola

rizat

ion

(120583C

cm2)


(a)

600

500

400

300

200

100

0

1000 10000 100000 1000000

12

10

08

06

04

02

00

Die

lect

ric co

nsta

nt (120576

)

Frequency (Hz)

Die

lect

ric lo

ss (t

an 120575)

(b)


3nanowires

02

01

00

minus01

minus02

minus03


Piez

ores

pons

e (au

)

DC bias (V)

(a)

400

350

300

250

200

150

100

501000 10000 100000 1000000

10

05

00

minus05

Die

lect

ric co

nsta

nt

Frequency (Hz)

tan 120575

(b)










3substrateswith




3000

2000

1000

0

minus1000

minus2000


Pola

rizat

ion

(120583C

cm2)

Voltage (V)

1kHz2kHz

10kHz20kHz

(a)

3

2

1

0

minus1

minus2


J sc

(mA

cm

2)

Voltage (V)



(b)

12

10

8

6

4

2

0

200 300 400 500 600 700

Wavelength (nm)

Exte

rnal

qua

ntum

effici

ency

()

6 5 4 3 2

Photon energy (eV)

(c)



6 Conclusions






Acknowledgments


References




















3rdquo Applied



3- CoFe





















3nanoparticlesrdquo



















3nano-



3multiferroic nano-




3nan-




















062909 3 pages 2009








CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




(a)

8

7

6

5

4

3

2

times104

0 100 200 300 400 500 600


tens

ity (a

u)

(b)


3


(a) (b)

Cu

CuFe

Fe

BIBI

6 8 10 12 14

B

(c)


3nanotubes (c)



33


33at






2120583m

(a)

1120583m

(b)

03 120583m

(c)

2120583m

(d)

1120583m

(e)

03 120583m

(f)



2

1

0

minus1


2

1

0

0 100 200 300

M(e

mu

g)

M(e

mu

g)

Size (nm)

H (kOe)

14nm41nm51nm75nm

95nm245nmBulk

(a)

M(e

mu

g)

M(e

mu

g)

H (Oe)

14nm41nm51nm75nm

95nm

14nm41nm51nm

75nm95nm

245nmBulk

03

00

minus03

minus2500 0 2500 5000

18

12

06

00

0 2 4 6 8


(b)


3



50

40

30

20

10

0

minus10

minus20


FilmIsland

Piez

ores

pons

e (pm

V)

Applied bias (V)


0018

0016

0014

0012

0010

0008

0006

0004

00020 50 100 150 200 250 300 350 400

M(e

mu

g)

T (K)

ZFC

ZFC

FC

FC

Tf

(a)

M(e

mu

g)

H (Oe)

015

010

005

000

minus005

minus010

minus015


300K5K

(b)







3




60

40

20

0

minus20

minus40

minus60


Pola

rizat

ion

(120583C

cm2)


(a)

600

500

400

300

200

100

0

1000 10000 100000 1000000

12

10

08

06

04

02

00

Die

lect

ric co

nsta

nt (120576

)

Frequency (Hz)

Die

lect

ric lo

ss (t

an 120575)

(b)


3nanowires

02

01

00

minus01

minus02

minus03


Piez

ores

pons

e (au

)

DC bias (V)

(a)

400

350

300

250

200

150

100

501000 10000 100000 1000000

10

05

00

minus05

Die

lect

ric co

nsta

nt

Frequency (Hz)

tan 120575

(b)










3substrateswith




3000

2000

1000

0

minus1000

minus2000


Pola

rizat

ion

(120583C

cm2)

Voltage (V)

1kHz2kHz

10kHz20kHz

(a)

3

2

1

0

minus1

minus2


J sc

(mA

cm

2)

Voltage (V)



(b)

12

10

8

6

4

2

0

200 300 400 500 600 700

Wavelength (nm)

Exte

rnal

qua

ntum

effici

ency

()

6 5 4 3 2

Photon energy (eV)

(c)



6 Conclusions






Acknowledgments


References




















3rdquo Applied



3- CoFe





















3nanoparticlesrdquo



















3nano-



3multiferroic nano-




3nan-




















062909 3 pages 2009








CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




2120583m

(a)

1120583m

(b)

03 120583m

(c)

2120583m

(d)

1120583m

(e)

03 120583m

(f)



2

1

0

minus1


2

1

0

0 100 200 300

M(e

mu

g)

M(e

mu

g)

Size (nm)

H (kOe)

14nm41nm51nm75nm

95nm245nmBulk

(a)

M(e

mu

g)

M(e

mu

g)

H (Oe)

14nm41nm51nm75nm

95nm

14nm41nm51nm

75nm95nm

245nmBulk

03

00

minus03

minus2500 0 2500 5000

18

12

06

00

0 2 4 6 8


(b)


3



50

40

30

20

10

0

minus10

minus20


FilmIsland

Piez

ores

pons

e (pm

V)

Applied bias (V)


0018

0016

0014

0012

0010

0008

0006

0004

00020 50 100 150 200 250 300 350 400

M(e

mu

g)

T (K)

ZFC

ZFC

FC

FC

Tf

(a)

M(e

mu

g)

H (Oe)

015

010

005

000

minus005

minus010

minus015


300K5K

(b)







3




60

40

20

0

minus20

minus40

minus60


Pola

rizat

ion

(120583C

cm2)


(a)

600

500

400

300

200

100

0

1000 10000 100000 1000000

12

10

08

06

04

02

00

Die

lect

ric co

nsta

nt (120576

)

Frequency (Hz)

Die

lect

ric lo

ss (t

an 120575)

(b)


3nanowires

02

01

00

minus01

minus02

minus03


Piez

ores

pons

e (au

)

DC bias (V)

(a)

400

350

300

250

200

150

100

501000 10000 100000 1000000

10

05

00

minus05

Die

lect

ric co

nsta

nt

Frequency (Hz)

tan 120575

(b)










3substrateswith




3000

2000

1000

0

minus1000

minus2000


Pola

rizat

ion

(120583C

cm2)

Voltage (V)

1kHz2kHz

10kHz20kHz

(a)

3

2

1

0

minus1

minus2


J sc

(mA

cm

2)

Voltage (V)



(b)

12

10

8

6

4

2

0

200 300 400 500 600 700

Wavelength (nm)

Exte

rnal

qua

ntum

effici

ency

()

6 5 4 3 2

Photon energy (eV)

(c)



6 Conclusions






Acknowledgments


References




















3rdquo Applied



3- CoFe





















3nanoparticlesrdquo



















3nano-



3multiferroic nano-




3nan-




















062909 3 pages 2009








CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




50

40

30

20

10

0

minus10

minus20


FilmIsland

Piez

ores

pons

e (pm

V)

Applied bias (V)


0018

0016

0014

0012

0010

0008

0006

0004

00020 50 100 150 200 250 300 350 400

M(e

mu

g)

T (K)

ZFC

ZFC

FC

FC

Tf

(a)

M(e

mu

g)

H (Oe)

015

010

005

000

minus005

minus010

minus015


300K5K

(b)







3




60

40

20

0

minus20

minus40

minus60


Pola

rizat

ion

(120583C

cm2)


(a)

600

500

400

300

200

100

0

1000 10000 100000 1000000

12

10

08

06

04

02

00

Die

lect

ric co

nsta

nt (120576

)

Frequency (Hz)

Die

lect

ric lo

ss (t

an 120575)

(b)


3nanowires

02

01

00

minus01

minus02

minus03


Piez

ores

pons

e (au

)

DC bias (V)

(a)

400

350

300

250

200

150

100

501000 10000 100000 1000000

10

05

00

minus05

Die

lect

ric co

nsta

nt

Frequency (Hz)

tan 120575

(b)










3substrateswith




3000

2000

1000

0

minus1000

minus2000


Pola

rizat

ion

(120583C

cm2)

Voltage (V)

1kHz2kHz

10kHz20kHz

(a)

3

2

1

0

minus1

minus2


J sc

(mA

cm

2)

Voltage (V)



(b)

12

10

8

6

4

2

0

200 300 400 500 600 700

Wavelength (nm)

Exte

rnal

qua

ntum

effici

ency

()

6 5 4 3 2

Photon energy (eV)

(c)



6 Conclusions






Acknowledgments


References




















3rdquo Applied



3- CoFe





















3nanoparticlesrdquo



















3nano-



3multiferroic nano-




3nan-




















062909 3 pages 2009








CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




60

40

20

0

minus20

minus40

minus60


Pola

rizat

ion

(120583C

cm2)


(a)

600

500

400

300

200

100

0

1000 10000 100000 1000000

12

10

08

06

04

02

00

Die

lect

ric co

nsta

nt (120576

)

Frequency (Hz)

Die

lect

ric lo

ss (t

an 120575)

(b)


3nanowires

02

01

00

minus01

minus02

minus03


Piez

ores

pons

e (au

)

DC bias (V)

(a)

400

350

300

250

200

150

100

501000 10000 100000 1000000

10

05

00

minus05

Die

lect

ric co

nsta

nt

Frequency (Hz)

tan 120575

(b)










3substrateswith




3000

2000

1000

0

minus1000

minus2000


Pola

rizat

ion

(120583C

cm2)

Voltage (V)

1kHz2kHz

10kHz20kHz

(a)

3

2

1

0

minus1

minus2


J sc

(mA

cm

2)

Voltage (V)



(b)

12

10

8

6

4

2

0

200 300 400 500 600 700

Wavelength (nm)

Exte

rnal

qua

ntum

effici

ency

()

6 5 4 3 2

Photon energy (eV)

(c)



6 Conclusions






Acknowledgments


References




















3rdquo Applied



3- CoFe





















3nanoparticlesrdquo



















3nano-



3multiferroic nano-




3nan-




















062909 3 pages 2009








CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




3000

2000

1000

0

minus1000

minus2000


Pola

rizat

ion

(120583C

cm2)

Voltage (V)

1kHz2kHz

10kHz20kHz

(a)

3

2

1

0

minus1

minus2


J sc

(mA

cm

2)

Voltage (V)



(b)

12

10

8

6

4

2

0

200 300 400 500 600 700

Wavelength (nm)

Exte

rnal

qua

ntum

effici

ency

()

6 5 4 3 2

Photon energy (eV)

(c)



6 Conclusions






Acknowledgments


References




















3rdquo Applied



3- CoFe





















3nanoparticlesrdquo



















3nano-



3multiferroic nano-




3nan-




















062909 3 pages 2009








CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




Acknowledgments


References




















3rdquo Applied



3- CoFe





















3nanoparticlesrdquo



















3nano-



3multiferroic nano-




3nan-




















062909 3 pages 2009








CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials





3nan-




















062909 3 pages 2009








CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials










CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials



Documents

Review Article Fabrication, Characterization, Properties ...downloads.hindawi.com/journals/jnm/2014/471485.pdfReview Article Fabrication, Characterization, Properties, and Applications