Possible intermediate in H2S dissociation on GaAs (100)

The adsorption and dissociation of H2S on GaAs(100) has been studied using high-resolution electron energy loss spectroscopy, thermal desorption spectroscopy, and isotope exchange techniques. The dissociative adsorption of H2S at 100 K produces only H-As species with a vibrational frequency of 2072 cm(-1). Upon warming to 200 K, the vibration of H-As clearly shifts to 2105 cm(-1), corresponding to a free H-As species. In addition, the formation of H- Ga (1887 cm(-1)) is also observed upon thermal annealing. In coadsorption studies of H2S and D atoms, three main desorption features of H2S were observed at 135, 200, and 375 K, respectively. The peaks at 135 and 375 K can be attributed to the desorption of molecularly adsorbed H2S and the recombinative desorption of adsorbed H and HS, respectively. In addition to the 375 K peak, the desorption feature at 200 K also undergoes isotope exchange between coadsorbed D atoms and H2S . These observations strongly suggest that the dissociative adsorption of H2S on GaAs (100) involves an intermediate of Ga-HS-H-As. (C) 1998 American Institute of Physics. [S0003-6951(98)03845-5].