Nonlinear optical spectroscopy of diamond surfaces
- Univ. of California, Berkeley, CA (United States)
Second harmonic generation (SHG) and infrared-visible sum frequency generation (SFG) spectroscopies have been shown to be powerful and versatile for studying surfaces with submonolayer sensitivity. They have been used in this work to study bare diamond surfaces and molecular adsorption on them. In particular, infrared-visible SFG as a surface vibrational spectroscopic technique has been employed to identify and monitor in-situ surface bonds and species on the diamond (111) surface. The CH stretch spectra allow us to investigate hydrogen adsorption, desorption, abstraction, and the nature of the hydrogen termination. The C(111) surface dosed with atomic hydrogen was found to be in a monohydride configuration with the hydrogen atoms situated at top-sites. The ratio of the abstraction rate to the adsorption rate was appreciable during atomic hydrogen dosing. Kinetic parameters for thermal desorption of H on C(111) were determined showing a near first-order kinetics. For the fully H-terminated (111) surface, a large (110 cm-1) anharmonicity and ~19 psec lifetime were measured for the first-excited CH stretch mode. The bare reconstructed C(111)-(2 x l) surface showed the presence of CC stretch modes which were consistent with the Pandey π-bonded chain structure. When exposed to the methyl radical, the SFG spectra of the C(111) surface showed features suggesting the presence of adsorbed methyl species. After heating to sufficiently high temperatures, they were converted into the monohydride species. Preliminary results on the hydrogen-terminated diamond (100) surface are also presented.
- Research Organization:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
- Sponsoring Organization:
- USDOE, Washington, DC (United States); Natural Sciences and Engineering Research Council of Canada, Ottawa, ON (Canada)
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 93466
- Report Number(s):
- LBL--37110; ON: DE95014834
- Country of Publication:
- United States
- Language:
- English
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