Possible intermediate in H2S dissociation on GaAs(100)

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.

Quantum Chemical Study of Adsorption and Dissociation of H2S on the Gallium-Rich GaAs (001)-4 × 2 Surface

“…More recently, Chuang and co-workers employed HREELS, LEED, and temperature programmed desorption (TPD) to investigate the surface chemistry of H 2 S on the GaAs (001)-4 × 2 surface. ,− Their experimental evidence supported the fact that H 2 S initially adsorbs dissociatively to HS and H species on the GaAs (001)-4 × 2 surface with the hydrogen selectively bonded to As at 100 K. As a result, only the H−S and As−H stretching modes were monitored in their HREEL spectra, while the Ga−H stretching mode was not observed. On the other hand, the sulfur from HS dissociation is predominantly bonded to Ga after annealing to 700 K. Their results were confirmed by Wei et al who found that the dissociative adsorption of H 2 S at 100 K produces only As−H species with a vibrational frequency of 2072 cm -1 . , Furthermore, the formation of Ga−H was also observed upon thermal annealing. Then they suggested that an energy barrier may exist between the two adsorption states of H atoms and the dissociative adsorption of H 2 S on the GaAs (100) surface involves an intermediate of Ga−HS−H−As.…”

“…On the other hand, the sulfur from HS dissociation is predominantly bonded to Ga after annealing to 700 K. Their results were confirmed by Wei et al who found that the dissociative adsorption of H 2 S at 100 K produces only As-H species with a vibrational frequency of 2072 cm -1 . 27,28 Furthermore, the formation of Ga-H was also observed upon thermal annealing. Then they suggested that an energy barrier may exist between the two adsorption states of H atoms and the dissociative adsorption of H 2 S on the GaAs (100) surface involves an intermediate of Ga-HS-H-As.…”

Stereo-selective binding of chlorobenzene on Si(111)-7×7

“…15 The vacuum chamber is equipped with a high resolution electron spectrometer ͑LK-2000-14R͒ for HREELS and a quadrupole mass spectrometer ͑UTI-100͒ for TDS and gas analysis. The EEL spectrometer consists of a double-pass 127°cylindrical deflector analyzer ͑CDA͒ for the monochromator and a single-pass 127°CDA for the analyzer.…”