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SYNTHESIS AND CHARACTERIZATION OF SILICA THIN FILMS

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Presentation on theme: "SYNTHESIS AND CHARACTERIZATION OF SILICA THIN FILMS"— Presentation transcript:

1 SYNTHESIS AND CHARACTERIZATION OF SILICA THIN FILMS
Department of Chemistry and Biochemistry North Dakota State University Mindika Tilan Nayakasinghe

2 Objective To deposit Mo clusters on synthesized 2D-Zeolite like thin film to study Hydrodesulfurization

3 Hydrodesulfurization
Motivation Hydrodesulfurization Hydrodesulphurization is the process of removing sulfur compounds form natural gas and form refined petroleum products. Example: C2H5SH + H C2H6 + H2S Catalyst

4 Main HDS catalysts are based on MoS2 (Molybdenum Disulfide)
Other catalysts RhS2 Binary combinations of Co and Mo (Cobalt modified MoS2 catalyst) Metal disulfides are supported on materials with high surface area. Support allows the catalyst to be more widely distributed. Zeolite structure Ref: M. M. J. Treacy , C. J. Dawson , V. Kapko , I. Rivin , Flexibility mechanisms in ideal zeolite frameworks , DOI: /rsta

5 Project Structure Synthesis of crystalline Silica films
Thiophene adsorption of Silica thin films Synthesis of 2D Zeolite like thin films and characterization by LEED, AES, XPS and XRD Deposition of Mo clusters on 2D Zeolite like films Thiophene adsorption on Silica supported Mo model catalyst

6 Preparation of Thin Silica Films on Mo(112)

7 Synthesis of crystalline Silica films
Clean Mo(112) substrate Do several cycles of Ar ion sputtering followed by annealing Oxidize the substrate Oxygen anneal for 10 minutes with the surface at 850 K (PO2= 1x10-8 mbar) Dose Silicon on oxidized substrate P= 3-5 x mbar Ultra high vacuum chamber Oxidize Si dosed substrate to form Silica thin films

8 Step1: Cleaning process- AES Results
Auger process Ionization of the atom Vacuum level hole Relaxation and Auger electron emission Vacuum level Auger electron Auger electron spectrum of Mo(112) substrate as received Auger electron spectrum of Mo(112) substrate after cleaning hole

9 Top view of Mo(112) surface
LEED….. Electron diffraction by a layer of atoms LEED pattern of Mo(112) as received Top view of Mo(112) surface LEED pattern of Mo(112) after cleaning Ref: (1) Tetsuhiro Kinoshita, Seigi Mizuno, Surface Science 605 (2011) 1209–1213

10 Step2: Oxidation of Mo(112) Substrate
LEED pattern of Mo(112) after cleaning LEED pattern of Mo(112) after oxidation Auger electron spectrum of Mo(112) substrate after oxidation

11 X-ray photoelectron spectra obtained for Oxidized Mo(112)
XPS Results (a) (b) Binding energy/ eV X-ray photoelectron spectra of, (a) Oxygen and (b) Mo Ref: Moulder J,F; Stickle W,F; Sobol P,E; Bomben K,D; Hand Book of X-ray Photoelectron Spectroscopy. X-ray photoelectron spectra obtained for Oxidized Mo(112)

12 Step 3: Si dosing and Oxidation
Metal Doser Dose Si by home made metal doser. Take AES to confirm the presence of Silicon. Oxygen annealing. Take AES and calculate Si/Mo ratio. Repeat the procedure until a monolayer or slightly less than a monolayer of silica layer is obtained.

13 Characterization by XPS
X-ray photoelectron spectra of Silicon Ref: Moulder J,F; Stickle W,F; Sobol P,E; Bomben K,D; Hand Book of X-ray Photoelectron Spectroscopy.

14 Si/Mo ratio and Coverage
AES results Silica Mo (f) (e) (d) (c) Si/Mo ratio and Coverage (b) Curve Si/ Mo ratio Coverage Mo(112) - (a) 0.1175 0.26 ML (b) 0.2463 0.54 ML (c) 0.3042 0.66 ML (d) 0.3775 0.82 ML (e) 0.4235 0.92 ML (f) 0.4594 1.00 ML (a) Mo(112) substrate 50 100 150 200 First dose of Silicon after oxidation electron energy (eV) AES spectra of SiO2 films on Mo(112) with different SiO2 coverages

15 Characterization of thin silica films by LEED
Top view and side view of (A) Mo(112), (B) Mo(112)-c(2 × 2)-[SiO4] surface Ref: M. S. Chen, A. K. Santra, and D. W. Goodman; J. Phys. Chem. B 2004, 108, LEED pattern obtained for Mo(112) Oxidized Mo(112) LEED pattern for silica thin film on Mo(112)

16 Future Work…… Experiment with Water Experiment with CO
Experiment with Thiophene Mo(112)-c(2X2)- [SiO4] Zeolite thin film on Mo(112) Mo deposited Zeolite thin film

17 Acknowledgements Dr.Uwe Burghaus Dr. Ashish Chakradhar
Nilushni Sivapragasam The donors of the American Chemical Society and Petroleum Research Fund are acknowledged for the support of this research


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