Electrochemical Deposition of Iron Nanoparticles on PPY and H terminated Si substrates. Karan Sukhija Co-op Term # 1 April 28 th, 2005

Transcription

1 Electrochemical Deposition of Iron Nanoparticles on PPY and H terminated Si substrates Karan Sukhija Co-op Term # 1 April 28 th, 2005

2 Future Suggested Experiments Acknowledgments Presentation 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 FeCl 3 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

3 Background Research 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 Tunneling Microscopy (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 Fe 2 O 3 source

4 Determine the effects of a magnetic field on deposition of iron nanoparticles Deposit Iron nanoparticles on PPY and H terminated Si wafers using electrochemical methods Determine the effects of deposition in an Ar (g) environment and N 2(g) environment. Determine the effects of aging of solution Determine the effects of solution concentration (FeCl 3 ) and Applied Potential on Number Density

5 The solution is first aired out with either Ar (g) or N 2(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. General Procedure for Iron deposition The cell contains a solution of Iron III Chloride (of typically 10mM) and 0.1mM Sodium Perchloride. (Solution is initially bubbled with N 2 gas for 20 minutes) A potential (of typically 0.8v) is applied This current supplied works the reaction: Fe e- = Fe(S) The Fe (S) is deposited at the working electrode on the substrate used, as nanoparticles.

6 General Procedure for 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.

7 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 mbar, which was operated with a monochromatic AlKα X-ray source (1486.6eV). General Procedure for analysis of samples The analyzer pass energy was fixed at 40eV for the survey spectra and 20eV for core shell spectra.

8 PART 1: PARAMETRIC STUDY

9 Parameters for Electrodepostion Electrochemical depositions were performed under two different parameters (Solution age, Gas environment, FeCl 3 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.

10 Effects of Solution Age Solution of 10 mm Iron III Chloride aged for thirteen days Solution of 10 mm Iron III Chloride freshly prepared Parameters: Applied Potential: V Fixed Charge: 2.5e-4 C

11 Effects of airing the solution with Argon vs. Nitrogen Aired With Ar gas Aired With N2 gas Parameters: Applied Potential: V Fixed Charge: 2.5e-4 C

12 Effects of FeCl 3 Concentration Spherical particles a) Deposition of 0.1 mm FeCl 3 Parameters: b) Deposition of 1 mm FeCl 3 Applied Potential: -0.8 V Fixed Charge: 2.5e-4 C c) Deposition of 10 mm FeCl 3 d) Deposition of 20 mm FeCl 3 Depositions of various concentrations of FeCl 3 and 0.1 M NaClO 4 on H-terminated Si waifers.

13 800 Effects of Iron III Chloride Concentration (in mm) on Number Density Number Density Iron III Chloride Concentration FeCl 3 Concentration (in mm) Number Density of Rice Structures

14 Effects of Applied Potential a) At -0.4 V b) At -0.6 V c) At -0.8 V d) At -1.0 V a) At -1.2 V f) At -1.4 V Parameters: FeCl 3 Concentration: 10mM Fixed Charge: 2.5e-4 C Depositions of 10mM FeCl 3 and 0.1 M NaClO 4 on H-terminated Si wafers at different applied potentials.

15 Effects of Applied Potential (in V) on Number Density Number Density Applied Potential (in V) Applied Potential (in V) Number Density of Rice Structures

16 Conclusion and Discussion Effects of Solution Age: Depositions with aged FeCl 3 solutions have more iron rice structures, less dot particles, and are generally more visible under 100,000 magnification, as compared to depositions performed with freshly prepared 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 FeCl 3 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.

17 PART 2: Effects of a Magnetic Field

18 Effects of a Magnetic Field during Depostion Procedures (preparation of wafers): Si wafers are first coated with Ni using the Coating Machine. ( 50 mt, 20 ma 4 x 120 seconds) Then, these wafers are coated with Au using the same Machine. ( 50 mt, 20 ma 3 x 120 seconds) Finally, the Ppy is electrochemically deposited on these wafers. (0.05 M pyrole M NaClO4 solution.)

19 Effects of a Magnetic Field during Depostion Procedures (experimental setup): For Dimagnetizing field: The cell is placed in a demagnetizer, and the deposition is performed as outlined in General Procedures

20 Effects of a Magnetic Field For Magnetic Field: during Depostion Procedures (experimental setup): 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.

21 Effects of a Magnetic Field during Depostion a) 100,000 magnification a) 200,000 magnification 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.

22 Effects of a Demagnetizer during Depostion a) With Demagnetizer b) Without Demagnetizer 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 Using a demagnetizer, the iron particles seem more randomly spread out than as compared to deposition without a demagnetizer.

23 Conclusion 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.

24 PART 3: Structure of Iron Nanoparticles

25 Structure of the Rice Iron Nanoparticle: Data Analysis Fe deposited on Si wafer Etch time=25s Etch time=40s Etch time=90s Etch time=180s Etch time=300s Etch time=600s

26 Structure of the Rice Iron Nanoparticle: Data Analysis (continued )

27 Structure of the Rice Iron Nanoparticle: Data Analysis (continued ) Etch time (s) Si 2p3/2 Fe2p O1s Cal. FeOOH Fe3O4 FeO Fe SiO2 OH O Cal. Cal. Cal. Cal. Cal. Cal. Cal / / / / / / / / / / / / / / / /

28 Structure of the Rice Iron Nanoparticle: Data Analysis (continued ) 1.2 FeOOH FeO Fe C Ratio of Peak Intensity to Si 2p Etch time (s)

29 Structure of the Dot Iron Nanoparticle: Data Analysis Fe deposited on Si wafer Etch time=5s Etch time=10s Etch time=15s Etch time=20s Etch time=30s Etch time=45s Etch time=75s Etch time=135s Etch time=235s Etch time=285s Etch time=375s

30 Structure of the Dot Iron Nanoparticle: Data Analysis (continued )

31 Structure of the Dot Iron Nanoparticle: Data Analysis (continued ) Etch time (s) Si2p3/2 Fe2p Fe2O3 FeO Fe SiO2 O O1s Cal. Cal. Cal. Cal. Cal. Cal / / / / / / / / / / / / / / / / / / / / / / / / / / / /

32 Structure of the Dot Iron Nanoparticle: Data Analysis (continued ) 0.8 Fe2O3 FeO Fe C Ratio of Peak Intensity to Si 2p Etch time (s)

33 Conclusions and Discussions Structure of the Rice 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 Fe 3 O 4 mixture, with an Fe (s) core. FeOOH and Fe 3 O 4 mixture Fe (s) core

34 Conclusions and Discussions Structure of the Dot 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 Fe 2 O 3 mixture, with an Fe (s) core. FeOOH and Fe 3 O 4 mixture Fe (s) core

35 Future Suggested Experiments Effects of Magnetic Field on deposition using a strong magnet Effects of Applied Potential for solutions 0.1 mm FeCl 3 Determine the Effects of Applied Potential on Dot Iron Nanoparticles.

36 Acknowledgments K. T. Leung Thank you for this project and all the support provided throughout this term. Liyan Zhao Thank 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.