Surface chemical processes of CH 2 =CCl 2 on Si(111) 7 7 mediated by low-energy electron and ion irradiation*

Transcription

1 Surface chemical processes of CH 2 =CCl 2 on Si(111) 7 7 mediated by low-energy electron and ion irradiation* Z. He, X. Yang and K. T. Leung Department of Chemistry University of Waterloo Waterloo, Ontario N2L 3G1, Canada Work supported by NSERC

2 Outline Objective Background Si(111) 7 7 Basics Halo Silicon Surface Chemistry Experiment Results Summary Acknowledgement

3 Objective Adsorption of the dichloroethylene on Si(111) 7 7 surface: Surface states and thermal evolution The surface reaction induced by electron irradiation The surface reaction induced by ion irradiation

4 Crystal Structure of Silicon

5 Dimer-Adatom-Stacking fault (DAS) model of Si(111)7 7. (A) Top view. (B) Side view. (C) Structure and bonding.

6 Clean Si(111)7x7 Si(111)7x7 Introduction DAS model: 12 adatoms, 6 rest atoms, 19 dangling bonds Cleaning: Repeated cycles of Ar sputtering and annealing to 1200 K SiCl x Vibrational feature at cm -1 corresponding to Si Cl ing mode C/Si Randomly located, Si C at cm -1 C=CH 2 /Si C-H ing: ~ 2910 cm -1 CH 2 scissoring: ~ 1387 cm -1 C=C ing: ~ 1510 cm -1 Si-H ing: ~ 2075 cm -1

7 Some vibration modes SiCl x related peaks: (1meV=8.065cm -1 ) Si-Cl ing: ~ cm -1 Si-C ing: ~ cm -1 CCl x related peaks: ing: ~ 720 cm -1 Hydrocarbon related peaks: C-H ing: ~ 2910 cm -1 CH 2 scissoring: ~ 1387 cm -1 Si-H ing: ~ 2075 cm -1 C=C ing: ~ 1510 cm -1

8 Research Approach Spectroscopy EELS, TDS, LEED, Auger Reactions Surface Reactions Applications Etching Process, Film growth

9 Surface analysis techniques involved EELS Electron Energy Loss Spectroscopy Detecting vibrational excitations TDS Temperature Desorption Spectroscopy Determining desorbed species and features LEED Low Energy Electron Diffraction Determining long range order of the surfaces

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11 Surface analysis techniques

12 H. Yu, PhD thesis, 1998 EELS

13 TDS Order of desorption Identify the products of surface reaction The nature and strength of lateral adatom interactions Relative surface coverage of adsorbate Xiang Yang, Chem794

14 LEED Clean Si(111) 7 7 After 50 L DCE

15 Adsorption of 1,1-DCE on Si(111) Si-Cl or C-Cl Si(111) 7x7 1,1-DCE 530 Si-Cl or C-Cl Si(111) 7x7 1,1-DCE Relative Intensity (abitrary units) 1050 C-C C-H 2 scissor Si-H 3650 O-H 2910 C-H (c) 5 L (b) 2 L Relative Intensity (abitrary units) Si-C 850 C-H 2 scissor 1360 Si-H C-H (c) 900 K (b) 550 K (a) 1 L 1510 (a) 2 L 1510 C=C C=C Energy Loss (cm -1 ) Energy Loss (cm -1 )

16 Adsorption of Cl 2 C=CCl 2 Si(111) 7x7 FCE Relative Intensity (abitrary units) Si-Cl or C-Cl 530 C-Cl 780 C=C 1510 (e) 850 K (d) 750 K (c) 530 K (b) 410 K Relative Intensity 820 inten0 inten (a) 40 L Loss (cm -1 ) Energy Loss (cm -1 )

17 Adsorption of 1,1-DCE: Saturation x25 Si-Cl or C-Cl Si(111) 7x7 1,1-DCE x Si-C Si(111) 7x7 1,1-DCE Relative Intensity (abitrary units) C-C 1360 C-H 2 scissor 1510 Si-H C=C 2970 C-H 3650 O-H (c) 5 L Electronirradiated 226 microa 300 ev 10 mins (b) 1 kl (a) 5 L Relative Intensity (abitrary units) 135 C-H 2 scissor 1360 Si-H C-C 1510 C=C C-H 2910 (i) 850 K (h) 790 K (g) 740 K (f) 670 K (e) 620 K (d) 570 K (c) 520 K (b) 410 K (a) 1 kl Loss (cm -1 ) Energy Loss (cm -1 )

18 Mass spectrum of 1,1-dichloroethylene NIST Chemistry WebBook (

19 TDS results L 1,1-DCE on Si(111) 7x7 Relative Intensity (f) mass 61 (e) mass 62 (d) mass 96 (c) mass 35 (b) mass 63 (a) mass Temperature (K)

20 TDS results L 1,1-DCE on Si(111) 7x7 8 Relative Intensity mass Temperature (K)

21 Proposed Adsorption Configuration

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23 Summary H 2 C=CCl 2 chemisorb on Si(111) 7 7 dissociatively at room temperature ~ 5 L exposure of H 2 C=CCl 2 can saturate the surface Successive annealing of the H 2 C=CCl 2 adsorbed surface causes dissociation and desorption of the adsorbates Around K, the SiH m surface species are formed due to dehydrogenation of part of CH n surface species During 700 K- 780 K, most of SiH m and CH n desorb from surface During 780 K K, part of SiCl x come off from surface Beyond 900 K, only SiC species left on the surface The ion-irradiation of Si(111) 7 7 in H 2 C=CCl 2 generates more surface species The effect of low-energy electron irradiation was demonstrated on H 2 C=CCl 2 adsorbed Si(111) 7 7

24 Acknowledgment Supervisor: Dr. K. T. Leung Colleagues: Xiang Yang Hui Yu Qiang Li Sergey Milton Xiaojing Zhou Committee:

25 Surface processes Surface adsorption, co-adsorption, surface reaction Electron and ion induced surface processes Ion gun Xiang Yang, Chem 794 H. Yu, PhD thesis, University of Waterloo, 1998 Electron gun

26 Si(111)7 7 ion-irradiated in 1,1-DCE dependence on exposure, impact energy and temperature Relative Intensity (abitrary units) x Si-Cl or C-Cl C-C C-H 2 scissor 2060 Si-H 1510 C=C Si(111) 7x7 1,1-DCE (a) 5 L (b) 5 L at 200 ev (c) 100 L at 200 ev (d) 1 kl at 200 ev (e) 1 kl at 500 ev 2910 C-H (e) (d) (c) (b) (a) Relative Intensity (abitrary units) x Si-C 1360 C-H 2 scissor Si-H 2060 C-C C=C 3650 O-H 2910 C-H Si(111) 7x7 1,1-DCE (j) 950 K (i) 900 K (h) 850 K (g) 800 K (f) 750 K (e) 700 K (d) 620 K (c) 530 K (b) 400 K (a) 1 kl at 500 ev Energy Loss (cm -1 ) Loss (cm -1 )

27 The effect of electron irradiation dependence on current, impact energy, exposure and temperature Relative Intensity (abitrary units) 135 x25 Si-Cl or C-Cl C-C C-H 2 scissor Si(111) 7x7 1,1-DCE (a) 5 L (b) 10 microa, 50 ev, 5 mins (c) 40 microa, 100 ev, 10 mins (d) 100 microa, 200 ev, 10 mins (e) 226 microa, 300 ev, 10 mins Si-H C=C C-H 2910 (e) (d) (c) (b) (a) Relative Intensity (abitrary units) x Si-C C-H 2 scissor 1360 Si-H 2060 C-C C=C 3650 O-H (g) 900 K C-H 2910 Si(111) 7x7 1,1-DCE (f) 850 K (e) 800 K (d) 700 K (c) 600 K (b) 500 K (a) EI after 5 L Energy Loss (cm -1 ) Energy Loss (cm -1 )

28 Isometric view of ultra vacuum chamber developed at Waterloo