Selective growth of zinc oxide nanorods on inkjet printed seed patterns

This article appeared in a journal published by Elsevier. The attachedcopy is furnished to the author for internal non-commercial researchand education use, including for instruction at the authors institution

and sharing with colleagues.

Other uses, including reproduction and distribution, or selling orlicensing copies, or posting to personal, institutional or third party

websites are prohibited.

In most cases authors are permitted to post their version of thearticle (e.g. in Word or Tex form) to their personal website orinstitutional repository. Authors requiring further information

regarding Elsevier’s archiving and manuscript policies areencouraged to visit:

http://www.elsevier.com/copyright

http://www.elsevier.com/copyright

Author's personal copy

Selective growth of zinc oxide nanorods on inkjet printed seed patterns

Rungrot Kitsomboonloha a, Sunandan Baruah a, Myo Tay Zar Myint a,Vivek Subramanian b, Joydeep Dutta a,�

a Center of Excellence in Nanotechnology, School Of Engineering and Technology, ISE-Building, Asian Institute of Technology, Pathumthani 12120, Thailandb Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, CA 94720-1770, USA

a r t i c l e i n f o

Article history:

Received 28 October 2008

Received in revised form

8 February 2009

Accepted 17 February 2009

Communicated by R. FornariAvailable online 27 February 2009

PACS:

61.46.Hk

61.46.Km

62.23.St

81.16.Be

81.16.Dn

Keywords:

A2. Hydrothermal crystal growth

A2. Seed crystals

A3. Selective epitaxy

B1. Nanomaterials

B1. Zinc compounds

B2. Semiconducting II–VI materials

a b s t r a c t

A method for the selective patterning of zinc oxide (ZnO) nanorods is presented that combines inkjet

printing of zinc acetate precursors on a substrate used to form ZnO nanocrystallites that subsequently

grow into nanorods in a reaction bath containing zinc acetate and hexamethylamine during a

hydrothermal process. A total of 100mm patterns were formed on glass substrates kept at fixed

temperatures by printing dots that can also form lines, arrays and rectangular patterns through the use

of a 50mm printhead. Different concentrations of zinc acetate (0.1–1 M) ink-jetted onto the substrates

led to the growth of 100 nm to 1mm wide ZnO nanorods vertically out of the substrates. The length of

the ZnO nanorods could be controlled by the concentration of the precursor solution during the

hydrothermal process as well as the duration of growth process.

& 2009 Elsevier B.V. All rights reserved.

1. Introduction

Nanostructured zinc oxide (ZnO) materials have found theirway into many applications due to their remarkable properties[1]. With a bandgap of 3.37 eV for bulk material, ZnO is suitablefor short-wavelength optoelectronic applications. High excitonbinding energy of 60 meV in ZnO crystal ensures efficientexcitonic emission at room temperature. ZnO is transparent tovisible light and can be rendered conductive through doping. Italso exhibits photocatalytic properties whereby it can break upcomplex organic molecules into smaller organic or inorganicfragments in the presence of light [2]. Due to the high surface-to-volume ratios in nanostructures and also due to quantumconfinement effects [3], nano-crystalline materials exhibit differ-ent properties as compared to their bulk counterparts. Moreover,ZnO can be formed in varying morphologies, like nanotubes,nanorods, nanobelts, nanowires, nanoprisms, nanotowers, nano-volcanoes, nanorods, and nanoflowers [4–8].

ZnO nanowires and nanorods are of interest as they areattractive candidates for use in a wide variety of applications suchas in gas sensors [9,10], solar cells [11], piezoelectric devices [12],optoelectronics [13], etc. Different applications demand varyingsize and orientation of the nanorods and selectivity of growth.Vayssieres et al. [14] demonstrated a method of creating highlyoriented arrays of micro-rods based on liquid epitaxial growth ofZnO on a substrate. This process was further improved by fixingpre-synthesized ZnO particles on the substrate to act as seeds,resulting in an anisotropic epitaxial growth of ZnO nanorods/nanowires from the seeds [15,16]. Morphology of the hydrother-mally grown ZnO nanorods depends on the concentration of thereactants in the growth bath, the growth temperature andduration of growth. The orientation of the nanorods can becontrolled through different seeding techniques [16].

For most electronic applications, selective growth of nanowiresinto arrays is important to reduce series resistance and to improvethe effective transport of electrons in the nanostructures to thecollecting electrodes. Many methods for the patterned growth ofsemiconductor nanowires have been reported [17], but fewreports on the selective growth of ZnO nanorods have appearedin the literature. Generally, the technique utilized to achieve a

ARTICLE IN PRESS

Contents lists available at ScienceDirect

journal homepage: www.elsevier.com/locate/jcrysgro

Journal of Crystal Growth

0022-0248/$ - see front matter & 2009 Elsevier B.V. All rights reserved.

doi:10.1016/j.jcrysgro.2009.02.028

�Corresponding author. Tel.: +66 2 5245680; fax: +66 2 5245697.

E-mail address: [email protected] (J. Dutta).

Journal of Crystal Growth 311 (2009) 2352–2358


site-specific growth of ZnO nanorods or nanowires involvespatterning and selective growth. The patterns were createdthrough a combination of photolithography [18] or electron-beamlithography [19] and subsequent deposition of zinc metal bysputtering [20] followed by selective etching, or by deposition viametal organic chemical vapor deposition (MOCVD) [21,22].Hydrophobic/hydrophilic interactions for self-assembled mono-layer assembly [23], microsphere self-assembled monolayerformation [24], atomic layer epitaxy (ALE) combined with softlithography [25], and micro-contact printing [26] have also beenreported in recent times for the formation of the seed layers.Nanostructures were then grown from the patterned zinc oroxidized zinc layer by the thermal oxidation of metallic zincprecursors [27,28], thermal evaporation [29] or through hydro-thermal methods [18,20,30]. These techniques for the selectivegrowth of ZnO nanorods have varying disadvantages, e.g. therequirements of highly sophisticated equipment and time-consuming processes, small sample sizes, severe fabricationconditions (high pressure and temperature), spilling out thegrowth from the planned patterned areas, etc.

Here we report, a novel method to pattern ZnO nanorods ontoa substrate that is seeded through a simple, inexpensive, versatile,and low-temperature patterning process using an inkjet printerfollowed by the subsequent growth of the nanorods through thehydrothermal process. The process includes inkjet printing ofprecursor patterns that form the seed layer which allows theselective growth of ZnO nanorods upon the subsequent hydro-thermal process. Inkjet printing is a direct-writing techniqueknown to have potential for use in low-cost and large areacoverage [31], and was used to pattern the substrate with the seedlayer of ZnO.

Inkjet printing of the seed layer and the subsequent hydro-thermal growth of the nanorods are additive processes and assuch wastage of chemicals is minimum. The whole process,starting from seed patterning to the nanorod growth process, usesaqueous solutions and is thus environment friendly. Anotherattractive feature of this method is the low growth temperatures(maximum temperature of 300 1C during seed crystallization) andthat the process is carried out in atmosphere, thereby avoiding theneed of expensive high-pressure or high-vacuum systems. Thiswork is aimed at developing a simple yet effective system forgrowing patterned ZnO nanorods.

2. Experimental

2.1. Materials used

Analytical grade zinc acetate dihydrate and hexamethylenete-tramine from Merck and Carlo erba reagents, respectively, wereused without further purification. Fluorine tin-oxide-coated glasssheets were supplied by Kintec, Japan. The substrates werecleaned before printing with acetone and deionized water (DI)in an ultrasonic bath for 20 min, respectively. Zinc acetate wasdissolved in DI water with different concentrations and used asinks for designing the patterns for the seed growth.

2.2. Customized inkjet printer setup

The customized inkjet printer consists of a stage on which theheated substrate is put and the inkjet nozzle that deposits the inkon the substrates. The movement system (Intellidrives Inc., USA)of the custom inkjet printer used consists of mechanical actuatorsand electronic controllers [32]. By utilizing linear micro-steppingtechnology, a theoretical resolution as high as 1mm can be

achieved with our system. The limitation of resolution comesbasically from the droplet size jetted through the printhead andthe landing accuracy of droplet placement. The dispensing systemconsists of an adjustable pressure system (very fine adjustmentpossible), a piezoelectric printhead, and its electronic driver thatis commanded by a host computer for synchronous motion. Thenozzle diameter of the printhead used in this work was 50mm,which can provide dots with a diameter of 100mm on thesubstrate. The sample is placed below the nozzle on the heatedsubstrate holder kept at a distance of about 500mm from theprinthead [33]. In order to keep a constant optimized waveformfor the printheads, a stroboscope was used to qualify the dropletejection process prior to each set of experiments by observingdroplet formation and traveling velocity. In addition, an integrat-ing station was added to reduce printing errors arising fromheight variations between the nozzle and the substrate, printheadposition variations related to the XY stage, vibrations, etc. Thedesign patterns can be loaded to the printer by a user via the hostcomputer. Moreover, the substrate temperature, which signifi-cantly affects the evaporation rate of printed dots on thesubstrate, can be controlled with accuracy of 70.5 1C. Digitalpatterns were printed on commercial float glass or fluorine-dopedtin-dioxide (FTO) coated glass substrates (Kintec, Japan), formingthe template for the subsequent selective growth of ZnOnanocrystallites. Hydrothermal growth of the ZnO nanorods wasthen carried out in aqueous solution at temperatures less than theboiling point of water (o95 1C) in a reaction bath containing20 mM quantities of zinc acetate dihydrate and hexamethylenete-tramine [16].

2.3. Patterning and growth of ZnO nanorods

In Fig. 1, we schematically represent the procedure followed forthe patterned growth of ZnO nanorods. It consists of three mainsteps: (a) patterning with zinc acetate precursors, (b) oxidation ofprecursor to form ZnO crystallites, and (c) growth of ZnOnanorods using hydrothermal means. A simple array patternwas printed on the substrate with varying concentrations of zincacetate to study the effect of precursor concentration in theseeding solution on the final morphology of the ZnO nanorodsobtained. An optimized condition for the seeding process wasselected for further experiments regarding the patterned growthof ZnO nanorods. In order to create complex structures, each dotsact as a building block of the microstructures and the spacingbetween dots was varied to create the desired patterns.

2.3.1. Patterning using the inkjet printer

The line resolution is affected by the size of the drop, spreadingof the drop on the substrate, and convolution/interaction betweenthe neighboring drops as deposited (for lines). The evaporationrate, viscosity, and surface tension of the solvent affect both theinitial drop ejection and the interaction on the substrate. Thesecombined with the properties of the hydraulic transient influencethe ejection behavior. Ideally, one wants to minimize the above-mentioned properties of the solvent to form smaller drop size.However, once the droplet impacts the substrate, the undesirablespreading of the drop occurs if these parameters are low [34]. Thecustomized inkjet printer discussed above, consisting of adispensing system and a precision positioning system wasemployed to pattern seed layers using analytical grade zincacetate dihydrate. Zinc acetate was dissolved in deionized waterat different concentrations ranging from 0.1 to 1 M to change theviscosity of the precursor solution. This solution was then utilizedas ink for the printer without further purification for the seedpattern deposition. Substrates were carefully cleaned through

ARTICLE IN PRESS

R. Kitsomboonloha et al. / Journal of Crystal Growth 311 (2009) 2352–2358 2353


ultrasonication in acetone and DI water for 20 min, respectively,followed by drying in an oven at 90 1C for about 30 min. Duringthe patterning process, the inkjet printer was kept in the ambientenvironment at room temperature (�25 1C), but the printing areawas maintained at a temperature of 45 1C, to shorten theevaporation time of solvent in order to obtain the finest patternspossible with this system.

2.3.2. ZnO nanoparticle seed formation and hydrothermal nanorod

growth

After jetting zinc acetate in desired patterns, the samples wereannealed at 300 1C for 1 h in atmosphere to form preferentiallyoriented ZnO nanoparticle seeds on the substrates that serve asnucleation sites for the growth of the ZnO nanorods during thehydrothermal growth process [16]. The sample side to be coatedwas placed face down in a reaction bath containing equimolar(20 mM) quantities of zinc acetate and hexamethylenetetraminemaintained at a temperature of 95 1C and the growth was carriedout for 20 h. The depleted reaction bath was replenished withfresh reactants every 5 h to maintain a high growth rate [35]. Afterthe completion of the ZnO nanorod growth, the samples wererinsed carefully with DI water and then annealed at 450 1C for 2 hto eliminate any organic residues.

2.4. Characterization

Field emission scanning electron microscope (FESEM) [JEOLJSM-6301F] and optical microscopy was employed to investigatethe morphology of the microstructures. Transmission electronmicroscope (TEM) [JEOL JEM 2010] operated at 120 kV was used

on samples grown on a carbon-coated TEM copper grid to checkthe crystalline structure of the seed layer from the micrographs.Measurements on FESEM and TEM images were done using ScionImage processing software.

3. Results and discussion

Fig. 1(a) shows the optical image of an array of zinc acetatedots printed using the inkjet printer. The color of the printed dotschanged after annealing, from transparent to white, the char-acteristic color of ZnO, as shown in Fig. 1(a). Zinc acetate is knownto decompose at a temperature of 237 1C [36,37] through theformation of basic zinc acetate arising from the loss of aceticanhydride (Eq. (1)).

4ZnðCH3COOÞ2 �!237�C

Zn4OðCH3COOÞ6 þ ðCH3COÞ2O (1)

Acetic anhydride further hydrolyses to form acetic acid asshown in Eq. (2)

ðCH3COÞ2OþH2O! 2CH3COOH (2)

Basic zinc acetate hydrolyses in presence of residual watervapor forming ZnO crystallites following the reaction shown inEq. (3).

Zn4OðCH3COOÞ6 þ 3H2O! 4ZnOþ 6CH3COOH (3)

When the temperature of the sample is increased to about300 1C, decarboxylation occurs and basic zinc acetate decomposesto its oxide leading to the formation of ZnO nanocrystallites, asshown in Eq. (4).

Zn4OðCH3COOÞ6 �!300�C

4ZnOþ 3CH3COCH3þ3CO2 (4)

Details of the reactions that take place during the hydrolysis ofzinc acetate are available elsewhere [38]. A series of experimentswere conducted at different preheating and post-annealingtemperatures to study the effect of these parameters on thenanocrystallite sizes of the seed layers and preferential orienta-tion of the planes, details of which will be presented in a separatereport. Based on these results, the annealing temperature for theseeding using the inkjet printer was set at 300 1C for 1 h. Thescanning electron micrograph (SEM) of ZnO nanoparticles formedafter annealing zinc acetate precursor at 300 1C for 1 h is shown inFig. 2(b). Quasi-spherical particles between 20 and 30 nm in sizeare formed very similar to the observations made by Paraguayet al. [37].

In Fig. 3, we have shown TEM images of a typical sample of theZnO nanocrystallites where the clearly visible lattice fringes showthe crystallinity of the material. Measurement done at differentsections of the micrograph using Scion Image processing softwarerevealed identical lattice fringes with a separation of 0.26 nmindicating highly oriented crystallites of a wurtzite structure withthe (0 0 2) face perpendicular to the substrate [38,39]. As ZnO doesnot dissolve readily in water or neutral solution (pH 7), the dotsprinted on the substrates consisting of the ZnO nanocrystallitescan be preserved effectively during the hydrothermal growthprocess, since the growth solution has an initial pH of about6.6 gradually shifting to 7.3 during the growth process [35,40].

In Fig. 4, the SEM images of ZnO nanorods grown in individualpatterned dots deposited with varying concentrations of the zincacetate precursor by the inkjet printer. The concentration of theacetate precursor is crucial for obtaining a well-defined anduniform seed pattern. A typical dot highlighted in Fig. 4(a), using a0.1 M concentrated ink, is not perfectly circular as the precursorsolution does not have appropriate viscosity and hence form acoffee ring upon contact with the substrate [41]. Coffee-ring

ARTICLE IN PRESS

FTO

Printed zinc acetate

ZnO Nanocrystallites

ZnO Nanorods

Hydrothermal growth

SiO2

Baked at 300°C

SiO2

SiO2

Fig. 1. Schematic representation of selective growth of ZnO nanorods by printing

zinc acetate on a fluorine-doped tin-oxide (FTO)-coated glass substrate; (a) printed

zinc acetate patterns, (b) ZnO nanocrystallites formed after annealing at 300 1C,

and (c) ZnO nanorod growth at 95 1C by the hydrothermal method.

R. Kitsomboonloha et al. / Journal of Crystal Growth 311 (2009) 2352–23582354


formation of zinc acetate on the substrate cause non-uniformconcentration gradient in the deposited dots that lead to a broadersize distribution of ZnO nanocrystals upon subsequentdecarboxylation. This result in a wider variation in length andwidth of the nanorods and a non-uniform growth of nanorodsformed (inset: Fig. 4(a)). The 0.25 M and 0.5 M seeding solutionsgave excellent patterns (Fig. 4(b) and (c)) and the individual spotsare almost circular. The ZnO nanorods grown on the printedpattern with 0.5 M precursor solution have the most uniformdiameter of nanorods (�500–600 nm), while the patterns using0.1 M and the 0.25 M precursors led to wide variations in nanoroddiameters upon subsequent hydrothermal growth of the nanorods

on the patterned substrates. Upon printing with 1 Mconcentration zinc acetate solution, the dense precursor solutionled to the formation of an uneven deposit onto the substrate thatresulted in non-uniform thickness of ZnO nanocrystallite layers onthe patterned dots upon annealing, resulting in the growthof nanorods exhibiting a coral reef like formation (Appendix A).Fig. 4(d) shows the pattern formed using a 1 M concentrated zincacetate precursor. The nanorods grown by this technique aredensely populated in each patterned dot which is primarily due tothe availability of higher number of nucleation sites on eachpatterned area for the liquid epitaxial growth of the nanorods tooccur during the hydrothermal process. Increase in the density of

ARTICLE IN PRESS

Fig. 2. (a) Array of ZnO dots formed by the oxidation of zinc acetate at 300 1C and (b) scanning electron micrograph of one individual dot showing typical image of the

ZnO nanoparticles grown as seeds for subsequent nanorod growth (approximately 20–30 nm agglomerates).

Fig. 3. (a) Transmission electron microscope (TEM) image of the nanocrystalline ZnO seed layer formed after post oxidizing the printed zinc acetate precursor at 350 1C

for 1 h. (b), (c), and (d) lattice spacing measured on different areas of the HRTEM micrograph shown in (a) suggests wurtzite a structure of ZnO with the (0 0 2) facing up.



nanocrystallites on the same surface area resulted in the growthof thinner rods with average diameter around 100 nm. This can beattributed to arise due to slower diffusion of zinc ions through thedense growth during the hydrothermal process (bottom inset:Fig. 4(d)). The length of the nanorods does not depend on theconcentration of the precursor used for seeding, butunderstandably depends on the concentration of the growthreactants used for the hydrothermal process and the duration ofgrowth, e.g. a growth duration of 20 h in a 20 mM concentratedchemical bath yielded nanorods with lengths of approximately10mm (Fig. 5(c)). However, it was observed that the use ofconcentrated precursor (1 M) during patterning process resultedin the growth of smaller ZnO nanorods in the unpatterned areasprobably due to the displacement of loosely bondednanocrystallites on the substrate surface at the onset ofhydrothermal growth process that act as seeds for the growth innon-patterned areas (top inset: Fig. 4(d)). The average diameter ofthe dot boundary in all conditions studied in this work was foundto increase during the hydrothermal growth due to some non-vertical (slanted) growth of the nanorods at the edge of thedroplets where the concentration of zinc acetate should bemaximum during the drying process, because of theaforementioned coffee-ring formation, which is a knownproblem with inkjet printing [41–43].

In order to print a line, droplets can be overlapped and hence aline pattern can be constructed by adding up dots. Systematicexperiments were designed with different dot spacing and time-delays in jetting subsequent droplets in order to control theintermixing of the liquid droplets leading to uniform lines. The

structures shown in Figs. 5(a) and (b) were drawn by printingdroplets with spacing of 50 and 100mm, respectively, with a time-delay in the jetting period of �100 ms. The 50mm line is anexample of continuous line created by joining the seedingdroplets (of zinc acetate) during the printing process while the100-mm-line spacing does not lead to the fusion of the drops whenprinted, but during the hydrothermal process a continuous lineevolves due to the spreading of the nanocrystal seeds andeventually the nanorod growth between two distinct droplets.In Fig. 5(b), a typical micrograph shows the original dropletsextends and finally touching with the next droplet creating acontinuous line. In the case of 50-mm spacing between the dots,the width of the continuous line of nanorods was approximatelythe same as the 100mm dot size. Due to the high concentration ofthe seeds in the dots printed using higher molarity of precursors,or in the case of the intermixing of adjoining printed dots the fastdrying of the precursors lead to a ripple like surface on the dots.This promotes a non-vertical (slanted) growth of the nanorods atthe edge of each of these undulations (in Appendix A). Moreover,in the case of a 100-mm spacing, we could clearly observe theimpact of the coffee-ring effect [41–43], resulting in non-uniformgrowth of the ZnO nanorods, with the density of growth higherat the center than at the sides. Although there are nanorodsgrowing outside the patterned areas under certain conditions, themajor concentration of the nanorods can be concentrated withinthe patterned areas. Programmable patterns have also beenformed and ZnO nanorods have been selectively grown onthese patterns showing the flexibility of this process for futureapplications.

ARTICLE IN PRESS

Fig. 4. Scanning electron microscope (SEM) image of ZnO nanorods grown after seeding using inkjet printing: (a) 0.1 M, (b) 0.25 M, (c) 0.5 M, and (d) 1 M. Inset:

magnifications of the squared areas.



4. Conclusions

A novel method to selectively grow ZnO nanorods has beendemonstrated by utilizing inkjet printing for pattern creation withsubsequent liquid epitaxial growth of ZnO nanorods. It waspossible to selectively grow oriented nucleation sites attached tothe substrate through the decomposition of zinc acetate at 300 1Cfor a subsequent liquid phase epitaxial growth of ZnO nanorods.A total of 100 nm to 1mm wide ZnO nanorods could be obtainedsimply by controlling the concentration from 0.1 to 1 M of the zincacetate precursor used during the seeding process. The length canbe controlled by the concentration of the precursor during thenanorod growth as well as the duration of growth, e.g. the lengthof the nanorods obtained after a 20 h growth in a 20 mM reactionbath, was about 10mm and was uniform over the whole patterneddot. Rapid advances have been achieved in inkjet technology withreports of nanoliter and picoliter non-contact liquid dispensingsystems [44]. Sekitani et al. have recently demonstrated state ofthe art inkjet technology with sub-femtoliter accuracy, where onemicrometer-line resolution was realized [45]. With the availabilityof picoliter dispensing systems [44], resolutions as low as 1mmcan potentially be perceived which could lead to the lithography-free patterning of ZnO nanorods on substrates [45]. Low-costnanofabrication process for selective growth of ZnO nanorods canbe achieved. Since this method selectively grows ZnO nanorods

without the utilization of other metal catalysts, any metalcontamination from the growth process can be avoided.

Acknowledgements

The authors would like to acknowledge partial financialsupport from the National Nanotechnology Center, belonging tothe National Science & Technology Development Agency (NSTDA),Ministry of Science and Technology (MOST), Thailand and theCentre of Excellence in Nanotechnology at the Asian Institute ofTechnology.

Appendix A

See Fig. A1.

References

[1] J. Zhang, L. Sun, H. Pan, C. Liaoa, C. Yan, New Journal of Chemistry 26 (2002) 33.[2] S. Baruah, R.F. Rafique, J. Dutta, NANO 3 (2008) 399.[3] G.L. Hornyak, J. Dutta, H.F. Tibbals, A.K. Rao, Introduction to Nanoscience,

third ed., Taylor & Francis Group, New York, 2008.[4] Y. Huang, K. Yu, Z. Zhu, Current Applied Physics 7 (2007) 702.[5] Y. Zhang, K. Yu, S. Ouyang, Z. Zhu, Physica B: Condensed Matter 382 (2006) 76.

ARTICLE IN PRESS

Fig. 5. Scanning electron micrographs showing line patterns using different spacing between dots (a) 50mm spacing, (b) 100mm spacing, and (c) cross-sectional view of the

ZnO nanorods.

Fig. A1. Scanning electron micrograph showing (a) a wrinkled surface and (b) its magnified image. The nanorods grown on the seed patterns created using 1 M zinc acetate

solution were very dense due to availability of increased nucleation sites in the form of ZnO nano-crystallites. The nanorod growth shown in the above figure was wrinkled

and appeared like a nano coral reef.



[6] Y. Tong, Y. Liu, L. Dong, D. Zhao, J. Zhang, Y. Lu, D. Shen, X. Fan, Journal ofPhysical Chemistry B 110 (2006) 20263.

[7] U. Pal, P. Santiago, Journal of Physical Chemistry B 109 (2005) 15317.[8] S. Baruah, J. Dutta, Science and Technology of Advanced Materials 10 (2009)

013001.[9] J. Xu, Y. Chen, Y. Li, J. Shen, Journal of Materials Science 40 (2005) 2919.

[10] M.K. Hossain, S.C. Ghosh, Y. Boontongkong, C. Thanachayanont, J. Dutta,Journal of Metastable and Nanocrystalline Materials 23 (2005) 27.

[11] M. Law, L.E. Greene, J.C. Johnson, R. Saykally, P. Yang, Nature Materials 4(2005) 455.

[12] X. Wang, J. Song, J. Liu, L.W. Zhong, Science 316 (2007) 102.[13] C.J. Chang, M.H. Tsai, Y.H. Hsu, C.S. Tuan, Thin Solid Films 516 (2008) 5523.[14] L. Vayssieres, K. Keis, S.E. Lindquist, A. Hagfeldt, Journal of Physical Chemistry

B 105 (2001) 3350.[15] L.E. Greene, M. Law, J. Goldberger, F. Kim, J.C. Johnson, Y. Zhang, R.J. Saykally,

P. Yang, Angewandte Chemie, International Edition 42 (2003) 3031.[16] A. Sugunan, H.C. Warad, M. Boman, J. Dutta, Journal of Sol–Gel Science and

Technology 39 (2006) 49.[17] H.J. Fan, P. Werner, M. Zacharias, Small 2 (2006) 700.[18] D. Palms, C. Priest, R. Sedev, J. Ralston, G. Wegner, Journal of Colloid and

Interface Science 303 (2006) 333.[19] H.L. Zhou, A. Chen, L.K. Jian, K.F. Ooi, G.K.L. Goh, K.Y. Zang, S.J. Chua, Journal of

Crystal Growth 310 (2008) 3626.[20] S.H. Jung, S.H. Jeong, Materials Letters 62 (2008) 3673.[21] Y. Tak, K. Yong, C. Park, Journal of Crystal Growth 285 (2005) 549.[22] S. Muthukumar, H. Sheng, J. Zhong, Z. Zhang, N.W. Emanetoglu, Y. Lu, IEEE

Transactions on Nanotechnology 2 (2003) 50.[23] X. Wang, C.J. Summers, Z.L. Wang, Nano Letters 4 (2004) 423.[24] D.F. Liu, Y.J. Xiang, X.C. Wu, Z.X. Zhang, L.F. Liu, L. Song, X.W. Zhao, S.D. Luo, W.J.

Ma, J. Shen, W.Y. Zhou, G. Wang, C.Y. Wang, S.S. Xie, Nano Letters 6 (2006) 2375.[25] M. Yan, Y. Koide, J.R. Babcock, P.R. Markworth, J.A. Belot, T.J. Marks, R.P.H.

Chang, Applied Physics Letters 79 (2001) 1709.[26] H. Shao, X. Qian, B. Huang, Materials Science in Semiconductor Processing 10

(2007) 68.

[27] D. Nezaki, M. Yasuda, T. Yasui, M. Takata, Solid State Ionics 172 (2004)353.

[28] T.W. Kim, T. Kawazoe, S. Yamazaki, M. Ohtsu, T. Sekiguchi, Applied PhysicsLetters 84 (2004) 3358.

[29] J.S. Lee, M.I. Kang, S. Kim, M.S. Lee, Y.K. Lee, Journal of Crystal Growth 249(2003) 201.

[30] Y.W. Koh, M. Lin, C.K. Tan, Y.L. Foo, K.P. Loh, Journal of Physical Chemistry B108 (2004) 11419.

[31] K. Cheng, M.H. Yang, W.W.W. Chiu, C.Y. Huang, J. Chang, T.F. Ying, Y. Yang,Macromolecular Rapid Communications 26 (2005) 247.

[32] S.N. Jayasinghe, M.J. Edirisinghe, Journal of Aerosol Science 35 (2004) 233.[33] C. Yang, K.C. Leong, Experiments in Fluids 33 (2002) 728.[34] S. Maenosono, C.D. Dushkin, S. Saita, Y. Yamaguchi, Langmuir 15 (1999)

957.[35] S. Baruah, C. Thanachayanont, J. Dutta, Science and Technology of Advanced

Materials (2008) 9.[36] M. Wei, D. Zhi, J.L. MacManus-Driscoll, Nanotechnology 16 (2005) 1364.[37] F. Paraguay D, W. Estrada L, D.R. Acosta N, E. Andrade, M. Miki-Yoshida, Thin

Solid Films 350 (1999) 192.[38] S. Baruah, J. Dutta, Journal of Sol–Gel Science and Technology (2009),

in press, doi:10.1007/s10971-009-1917-2.[39] A. Sugunan, H. Warad, M. Boman, J. Dutta, Journal of Sol–Gel Science and

Technology 39 (2006) 49.[40] S. Baruah, J. Dutta, Journal of Crystal Growth (2009), in press, doi:10.1016/

j.jcrysgro.2009.01.135.[41] D. Soltman, V. Subramanian, Langmuir 24 (2008) 2224.[42] S.B. Fuller, E.J. Wilhelm, J.M. Jacobson, Journal of Microelectromechanical

Systems 11 (2002) 54.[43] N. Stutzmann, R.H. Friend, H. Sirringhaus, Science 299 (2003) 1881.[44] P. Koltay, R. Zengerle, in: Solid-State Sensors, Actuators and Microsystems

Conference, 2007. TRANSDUCERS 2007, International (2007) 165.[45] T. Sekitani, Y. Noguchi, U. Zschieschang, H. Klauk, T. Someya, Proceedings of

the National Academy of Sciences of the United States of America 105 (2008)4976.

ARTICLE IN PRESS


Documents

Selective growth of zinc oxide nanorods on inkjet printed seed patterns