Mechanisms of disilane decomposition on Si(111)-7 × 7

Abstract

The mechanisms of disilane surface decomposition on Si(111)-7 × 7 have been studied for surface temperatures ( T s) from 80 to 500°C using temperature programmed desorption (TPD), static secondary ion mass spectrometry (SSIMS), and low energy electron diffraction (LEED). Below 400°C, the surface becomes passivated when covered by SiH x species after Si 2H 6 exposure and Si 2H 6 decomposition reactions do not proceed beyond the monolayer level. Near 80°C, both Si 2H 2 and SiH species are detected by SSIMS after 5000 monolayers exposure to disilane, while above 350°C only SiH is detected. Between 80 and 400°C, the total H coverage measured by TPD after this exposure increases with increasing T s. Between 400 and 500°C, when the surface is covered with SiH, an ordered hydrogenated film exhibiting a 1 × 1 LEED pattern is detected after Si 2H 6 exposure. At 500°C and above, epitaxial growth (7 × 7 LEED pattern) is observed. Observations are reported here which support reaction mechanisms proposed in the preceding paper (S.K. Kulkarni et al., Surf. Sci. 239 (1990) 13, ref. [1]). The slow desorption of H 2 wish a desorption time constant on the order of 1 s at H coverage of 0.05 H/Si or less, and T s up to 800°C is confirmed here. Removal of pre-adsorbed D atoms by Si 2H 6 exposure at T s = 490°C is also observed.