HYDROGEN STRETCHING VIBRATIONS AT GAAS(110) AND INP(110) SURFACES - AN ELECTRON-ENERGY-LOSS FINE-STRUCTURE STUDY

Hydrogen stretching vibrations at GaAs(110) and InP(110) surfaces were investigated by high-resolution electron energy-loss spectroscopy (HR EELS). With semi-insulating crystals, the linewidths were reduced such that the fine structure of the energy losses could be analysed. For G a-H stretching modes, two components at 1830 and 1860 cm(-1) (226.9 an d 230.6 meV) are found after low ex posure to atomic hydrogen. They ma y be explained by dipole-dipole interactions. Upon heavier hydrogenati on at third substructure at 1907 cm(-1) (236.5 meV) is observed. At H- covered InP(110) surfaces, the loss structure due to phosphorus-hydrog en stretching vibrations exhibits a double structure with components a t 2260 and 2300 cm(-1) (280.2 and 285.2 meV). The first is attributed to P-H monohydride and the second to P-H-2 dihydride vibrations. The r esults indicate that InP(110) surfaces are disrupted even after small H exposures.