Electrochemical Deposition of Iron Nanoparticles on PPY and

H – terminated Si substrates

Karan SukhijaCo-op Term # 1April 28th, 2005

Presentation OutlinePresentation Outline• Background• General Procedures• Part 1: Parametric Study

– Parameters for Electrodeposition – Effects of Solution Age– Effects of Airing the solution with Argon vs. Nitrogen– Effects of FeCl3 Concentration– Effects of Applied Potential– Conclusions and Discussion

• Part 2 : Effects of a Magnetic Field– Procedures– Effects of a Magnetic Field on deposition– Effects of a Demagnetizer during deposition– Conclusions and Discussion

• Part 3: Structure of the Iron Nanoparticles– Structure of ‘Rice’ Iron Nanoparticles– Structure of ‘Dot’ Iron Nanoparticles– Conclusions and Discussion

• Future Suggested Experiments• Acknowledgments

BackgroundBackgroundResearch of magnetic nanoparticles is of significant interest due to the potential application in magnetic

recording media.

S. Gangopadhyay et al. developed a method for synthesizing ultrafine particles of Fe by evaporation and condensation of the bulk metal in an inert atmosphere

Y. Li et al. used Scanning TunnelingMicroscopy (STM) assisted by chemical vapor deposition

to grow in high precision alignment

S. Jain et al. present a new method for synthesizing Fe nanoparticles with electron beam deposition from Fe2O3

source

Deposit Iron nanoparticles on PPY and H –terminated Si wafers using electrochemical methods

Determine the effects of deposition in an Ar(g)environment and N2(g) environment.

Determine the effects of aging of solution

Determine the effects of solution concentration (FeCl3) and Applied Potential on Number Density

Determine the effects of a magnetic field on deposition of iron nanoparticles

General ProcedureGeneral Procedurefor Iron depositionfor Iron deposition

• The solution is first aired out with either Ar(g) or N2(g) for 20 minutes.

• Deposition occurs in an 3-electrode cell where the current is passed between the Working Electrode and Counter electrode.

• The Counter Electrode is either an H –terminated Si wafer, or Si wafer with gold and Ppy deposited on it.

• The cell contains a solution of Iron III Chloride (of typically 10mM) and 0.1mM Sodium Perchloride. (Solution is initially bubbled with N2gas for 20 minutes)

• A potential (of typically 0.8v) is applied

• This current supplied works the reaction:Fe3+ + 3e- = Fe(S)

• The Fe(S) is deposited at the working electrode on the substrate used, as nanoparticles.

General ProcedureGeneral Procedurefor analysis of samplesfor analysis of samples

• The samples were all analyzed using the Scanning Electron Microscope (SEM).

• The samples were observed with the In-Lens Detector. The In-lens detector gave optimum resolution of the samples under magnifications upto 200,000.

General ProcedureGeneral Procedurefor analysis of samplesfor analysis of samples

The chemical state of the deposited iron nanoparticles on the film was analyzed by depth profiling X-ray Photoelectron spectroscopy, which alternating XPS analysis and low energy argon ion sputtering.

The experiment was performed on a VG Scientific ESCALab 250 photoelectron spectrometer with basic pressure in the analysis chamber of 1.5×10-8 mbar, which was operated with a monochromatic AlKα X-ray source (1486.6eV).

The analyzer pass energy was fixed at 40eV for the survey spectra and 20eV for core shell spectra.

PART 1: PART 1: PARAMETRIC STUDYPARAMETRIC STUDY

Parameters for ElectrodepostionParameters for Electrodepostion

Electrochemical depositions were performed under two different parameters (Solution age, Gas environment, FeCl3 concentration, Applied Potential) to determine the effects of these parameters on deposition results.

Although the experiments were performed several times, the results varied due to aging of solution. However, the pattern in the number density remain reproducible.

Due to the structure of the nanoparticles formed (discussed later), the size of the nanoparticles were not focused on.

Effects of Solution AgeEffects of Solution Age

Solution of 10 mM Iron III Chloride freshly prepared

Solution of 10 mM Iron III Chloride aged for thirteen days

Parameters: Applied Potential: - 0.8 VFixed Charge: 2.5e-4 C

Effects of airing the solution Effects of airing the solution with Argon vs. Nitrogenwith Argon vs. Nitrogen

Parameters: Applied Potential: - 0.8 VFixed Charge: 2.5e-4 C

Aired With N2 gas Aired With Ar gas

Effects of FeClEffects of FeCl33 ConcentrationConcentration

a) Deposition of 0.1 mM FeCl3 b) Deposition of 1 mM FeCl3

c) Deposition of 10 mM FeCl3 d) Deposition of 20 mM FeCl3

Depositions of various concentrations of FeCl3 and 0.1 M NaClO4 on H-terminated Si waifers.

Parameters: Applied Potential: -0.8 VFixed Charge: 2.5e-4 C

Spherical particles

FeCl3Concentration

(in mM)

Number Density of ‘Rice’ Structures

0.1 0

1 1

10 256

20 752

Effects of Iron III Chloride Concentration (in mM) on Number Density

-100

0

100

200

300

400

500

600

700

800

0 5 10 15 20 25Iron III Chloride Concentration

Num

ber

Den

sity

Effects of Applied PotentialEffects of Applied Potential

a) At -0.4 V

Depositions of 10mM FeCl3 and 0.1 M NaClO4 on H-terminated Si wafers at different applied potentials.

Parameters: FeCl3 Concentration: 10mM Fixed Charge: 2.5e-4 C

c) At -0.8 V

d) At -1.0 V f) At -1.4 V

b) At -0.6 V

a) At -1.2 V

Applied Potential

(in V)

Number Density of ‘Rice’ Structures

-0.4 229

-0.6 152

-0.8 101

-1.0 55

Effects of Applied Potential (in V) on Number Density

0

50

100

150

200

250

-1.6 -1.4 -1.2 -1 -0.8 -0.6 -0.4 -0.2 0Applied Potential (in V)

Num

ber

Den

sity

-1.2 39

-1.4 128

Conclusion and DiscussionConclusion and Discussion• Effects of Solution Age:

– Depositions with aged FeCl3 solutions have more iron ‘rice’ structures, less dot particles, and are generally more visible under 100,000magnification, as compared to depositions performed with freshlyprepared solution.

• Effects of Airing the solution with Argon vs. Nitrogen:– Two depositions, under same parameters, with the exception of the gas

used to air out the solution, yield same results. – This suggests that the oxidation of iron nanoparticles on the substrate

does not occur within the solution during the deposition.

• Effects of FeCl3 Concentration:– At 0.1mM, there are no ‘rice’ shaped structures, but spheres of iron

nanoparticles of roughly 4-10 nm.– At concentration ≥ 1mM, there are ‘rice’ shaped structures deposited.

The number density increases with increasing concentration.

• Effects of Applied Potential:– As the Applied Potential goes more negative, the number density

decreases, except at potentials more negative than -1.2 V.– At potentials more negative than -1.2 V, the number density starts to

increase.

PART 2:PART 2:Effects of a Magnetic Effects of a Magnetic

FieldField

Effects of a Magnetic Field Effects of a Magnetic Field during Depostionduring Depostion

Procedures (preparation of wafers):• Si wafers are first coated with Ni using the

Coating Machine.

• Then, these wafers are coated with Au using the same Machine.

• Finally, the Ppy is electrochemically deposited on these wafers.

( 50 mT, 20 mA4 x 120 seconds)

( 50 mT, 20 mA3 x 120 seconds)

(0.05 M pyrole + 0.1 M NaClO4 solution.)

Effects of a Magnetic Field Effects of a Magnetic Field during Depostionduring Depostion

Procedures (experimental setup):

• For Dimagnetizing field:

– The cell is placed in a demagnetizer, and the deposition is performed as outlined in General Procedures

Effects of a Magnetic Field Effects of a Magnetic Field during Depostionduring Depostion

• For Magnetic Field:

– The Ni-Au-Ppy wafers are placed on a magnet (with alignment of E – W) for 20 minutes to magnetize and align all Ni particles.

– Depostion is performed as outlined in General Procedures.

Procedures (experimental setup):

Effects of a Magnetic Field Effects of a Magnetic Field during Depostionduring Depostion

Deposition of Iron III Chloride on waifer layered with Nickel, Gold, and Polypyrrole, and then magnetized.

Depositions under a magnetic field assorts the iron nanoparticles into groups of structures of three or more pointing in a specific direction.

a) 100,000 magnification a) 200,000 magnification

Effects of a Demagnetizer during Effects of a Demagnetizer during DepostionDepostion

Deposition of Iron III Chloride on waifer layered with Nickel, Gold, and Polypyrrole, a) under a demagnetizer, and b) without a demagnetizer, at

100,000 magnification

a) With Demagnetizer b) Without Demagnetizer

Using a demagnetizer, the iron particles seem more randomly spread out than as compared to deposition

without a demagnetizer.

Conclusion and DiscussionConclusion and Discussion

• Effects of a Magnetic Field

– Deposition in the presence of a magnetic field results in iron nanoparticles lying parallel to the surface of the substrate, and in groups pointing in one direction

– Deposition in the presence of a demagnetizer results in more randomization as compared to deposition without a demagnetizer.

PART 3:PART 3:Structure of Iron Structure of Iron NanoparticlesNanoparticles

Structure of the ‘Rice’ Iron Structure of the ‘Rice’ Iron Nanoparticle: Data AnalysisNanoparticle: Data Analysis

Fe deposited on Si wafer Etch time=25s Etch time=40s Etch time=90s

Etch time=300s Etch time=600sEtch time=180s

Structure of the ‘Rice’ Iron Nanoparticle: Data AnalysisStructure of the ‘Rice’ Iron Nanoparticle: Data Analysis(continued…) (continued…)

Si 2p3/2 Fe2p O1s

FeOOH Fe3O4 FeO Fe SiO2 OH O

Cal. Cal. Cal. Cal. Cal. Cal. Cal.

0 99.75

99.07

712.47

711.79 710.90 710.22

/ / / / 532.21 532.53 531.63 530.95 530.07 529.39

25 99.30

99.07

711.44

711.11 / / 709.59 709.36 707.34 707.11 532.08 531.85 530.42 530.19

40 99.29

99.07

711.54

711.32 / / 709.54 709.32 707.40 707.18 531.80 531.58 530.40 530.18

90 99.23

99.07

711.43

711.27 / / 709.44 709.28 707.33 707.17 532.23 532.1 530.64 530.51

180 99.20

99.07

711.41

711.28 / / 709.27 709.14 707.30 707.17 532.23 532.1 530.66 530.53

300 99.19

99.07

711.32

711.20 / / 709.32 709.2 707.32 707.2 532.14 532.02 530.54 530.42

600 99.20

99.07

/ / 707.40 707.27

Cal.

Etch time(s)

Structure of the ‘Rice’ Iron Nanoparticle: Data AnalysisStructure of the ‘Rice’ Iron Nanoparticle: Data Analysis(continued…) (continued…)

0 200 400 600 800 1000

0.0

0.2

0.4

0.6

0.8

1.0

1.2

Rat

io o

f Pea

k In

tens

ity to

Si 2

p

Etch time (s)

FeOOH FeO Fe C

Structure of the ‘Rice’ Iron Nanoparticle: Data AnalysisStructure of the ‘Rice’ Iron Nanoparticle: Data Analysis(continued…) (continued…)

Fe deposited on Si wafer Etch time=5s Etch time=10s Etch time=15s

Etch time=30s Etch time=45s Etch time=75s

Etch time=135s Etch time=235s Etch time=285s

Etch time=20s

Etch time=375s

Structure of the ‘Dot’ Iron Nanoparticle: Structure of the ‘Dot’ Iron Nanoparticle: Data AnalysisData Analysis

Structure of the ‘Dot’ Iron Nanoparticle: Data AnalysisStructure of the ‘Dot’ Iron Nanoparticle: Data Analysis(continued…) (continued…)

Fe2p O1s

Fe2O3 FeO Fe SiO2 O

Cal. Cal. Cal. Cal. Cal. Cal.

0 99.72 99.11 711.47 710.86 / / / / 532.99 532.38 530.42 529.81

5 99.34 99.11 711.10 710.87 709.60 709.37 707.35 707.20 532.63 532.4

10 99.33 99.11 711.10 710.88 709.60 709.38 707.37 707.24 532.42 532.2

15 99.30 99.11 / / 709.62 709.43 707.46 707.27 532.36 532.17

20 99.29 99.11 / / 709.60 709.42 707.48 707.30 532.25 532.07

30 99.28 99.11 / / 709.50 709.33 707.48 707.31 532.12 531.95

45 99.31 99.11 / / 709.60 709.4 707.48 707.28 531.96 531.76

75 99.30 99.11 / / 709.60 709.41 707.47 707.27 531.80 531.61

135 99.25 99.11 / / 709.68 709.54 707.42 707.31 531.70 531.56

235 99.19 99.11 / / / / 707.44 707.31 531.77 531.69

285 99.15 99.11 / / / / 707.46 707.36 531.89 531.85

375 99.15 99.11 / / / / 707.42 707.31 532.01 531.97

Si2p3/2

Etch time(s)

Structure of the ‘Dot’ Iron Nanoparticle: Data AnalysisStructure of the ‘Dot’ Iron Nanoparticle: Data Analysis(continued…) (continued…)

0 200 400

0.0

0.2

0.4

0.6

0.8

Rat

io o

f Pea

k In

tens

ity to

Si 2

p

Etch time (s)

Fe2O3 FeO Fe C

Structure of the ‘Dot’ Iron Nanoparticle: Data AnalysisStructure of the ‘Dot’ Iron Nanoparticle: Data Analysis(continued…) (continued…)

Conclusions and DiscussionsConclusions and DiscussionsStructure of the ‘Rice’ Structure of the ‘Rice’ Iron Nanoparticle: Iron Nanoparticle:

• As discussed, at concentration ≥ 1mM, ‘rice’ shaped particles are deposited.

• Through XPS results, these structures were deduced to be a shell of FeOOH and Fe3O4 mixture, with an Fe(s) core.

FeOOH and Fe3O4 mixtureFe(s) core

Conclusions and DiscussionsConclusions and DiscussionsStructure of the ‘Dot’ Structure of the ‘Dot’ Iron Nanoparticle: Iron Nanoparticle:

• As discussed, at concentration ≤ 0.1mM, ‘dot’ shaped particles are deposited.

• Through XPS results, these structures were deduced to be a shell of FeOOH and Fe2O3 mixture, with an Fe(s) core.

FeOOH and Fe3O4 mixture

Fe(s) core

Future Suggested Future Suggested ExperimentsExperiments

• Effects of Magnetic Field on deposition using a strong magnet

• Effects of Applied Potential for solutions ≤ 0.1 mM FeCl3– Determine the Effects of Applied

Potential on ‘Dot’ Iron Nanoparticles.

AcknowledgmentsAcknowledgmentsK. T. LeungThank you for this project and all the support provided throughout this

term.Liyan ZhaoThank you for

training me for this project, and

mentoring me during the course

of this project. Nina Heinig Thank you for your

training with the machines, your

‘technical support’ and your help magnetizing

the iron particles.

...and everyone for their help and interest in this project. ☺