Possible intermediate in H2S dissociation on GaAs(100)

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Abstract
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.