H-induced surface restructuring on Si(100): Formation of higher hydrides

Abstract

H-induced surface structures on Si(100) were studied using temperature-programmed-desorption mass spectroscopy and low-energy electron diffraction. It is shown that the (3\ifmmode\times\else\texttimes\fi{}1) phase consists of mainly monohydride and dihydride structures, while the (1\ifmmode\times\else\texttimes\fi{}1) phase is composed of a mixture of monohydride, dihydride, and trihydride surface species. The trihydride surface species is associated with the phase transition between the (3\ifmmode\times\else\texttimes\fi{}1) and (1\ifmmode\times\else\texttimes\fi{}1) surface phases, and liberates ${\mathrm{SiH}}_{4}$ and ${\mathrm{\ensuremath{\beta}}}_{3\mathrm{\ensuremath{-}}}$${\mathrm{H}}_{2}$ during thermal desorption, beginning at \ensuremath{\sim}200 K. For the fully saturated Si(100) surface, a saturation surface coverage of 1.9 monolayers (ML) H has been established at a Si(100) adsorption temperature of 210\ifmmode\pm\else\textpm\fi{}10 K. These results suggest that the 1.9-ML saturation coverage of H on Si(100) involves the presence of ${\mathrm{SiH}}_{3}$(a) species, which leads to a (3\ifmmode\times\else\texttimes\fi{}1)\ensuremath{\rightarrow}(1\ifmmode\times\else\texttimes\fi{}1) LEED pattern change. This is contrary to a model for the (1\ifmmode\times\else\texttimes\fi{}1) surface involving a uniform ${\mathrm{SiH}}_{2}$(a) overlayer.