Adsorption mechanisms of Si2H6 and GeH4 on Si(100)2x1 surfaces

We studied the adsorption mechanisms of Si2H(6) and GeH4 on Si(100)2 x 1 surfaces by investigating the gas-exposure dependence of surface-hydrogen coverage at room temperature. In Si2H6 adsorption there are two distinct adsorption mechanisms depending on surface-hydrogen coverage. At low coverage below 1 monolayer, dissociative adsorption of Si2H6 to dangling bands (Si2H6 + 2db --> 2SiH(3)(ad)) is rate limiting, while adsorption to a dimer bond (Si2H6(ad) + Si-Si --> SiH3(ad)) dominates at high coverage (ad and db denote an adsorbate and a dangling bond, respectively). Adsorption of GeH, is characterized as four-site adsorption, which is independent of surface-hydrogen coverage. Based on these results, we discuss a possible adsorption model of SiGe growth using Si2H6 and GeH4.