View
3
Download
0
Category
Preview:
Citation preview
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. ☺
Recommended