VIBRATIONAL SUM-FREQUENCY GENERATION SPECTROSCOPY OF A HOMOEPITAXIALLY-GROWN DIAMOND C(100) SURFACE

Vibrational sum-frequency generation (VSFG) spectroscopy was applied to a study of the CH bonds on a homoepitaxially-grown diamond C(100) surface. The VSFG spectrum taken under the (p,p) polarization combination of visible and infrared excitation beams gave vibrational resonance peaks at 2910 and 2960 cm(-1) along with a significant background (BG) signal, and the spectrum taken under the (s,p) combination had a peak at 2910 cm(-1) and a negligibly weak BG signal. From analyses of the spectral features and polarization characteristics, the 2910 cm(-1) band was assigned to the CH stretching vibration of the monohydride (CH) groups on a reconstructed C(100) 2 x 1 surface, and the 2960 cm(-1) band to the anti-symmetric CH stretching vibration of the dihydride (CH2) groups located at either the unreconstructed C(100) 1 x 1 island surface or step sites. The tilt angle of the CH group was estimated to be in the range of 30-60 degrees, the large uncertainty originating from the lack of data on the Raman depolarization ratio. The tilt angle of the CH2 group was estimated to be less than 40 degrees.