SiH4 adsorption on SiGe(0Â 0Â 1)

The adsorption process of silane (SiH4) on a SiGe(0 0 1) surface has been investigated by using infrared absorption spectroscopy in a multiple internal reflection geometry. We have observed that SiH4 dissociatively adsorbs on a SiGe(0 0 1) surface at room temperature to generate Si and Ge hydrides. The dissociation of Si- and Ge-hydride species is found to strongly depend on the Ge concentration of the SiGe crystal. At a low Ge concentration of 9%, Si monohydride (SiH) and dihydride (SiH2) are preferentially produced as compared to the higher Si hydride, SiH3. At higher Ge concentrations of 19%, 36%, on the other hand, monohydrides of SiH and GeH and trihyderide SiH3 are favorably generated at the initial stage of the adsorption. We interpret that when SiH4 adsorbs on the SiGe surface, hydrogen atoms released from the SiH4 molecule stick onto Ge or Si sites to produce Si or Ge monohydrides and the remaining fragments of -SiH3 adsorb both on Si and Ge sites. The SiH3 species is readily decomposed to lower hydrides of SiH and SiH2 by releasing H atoms at low Ge concentrations of 0% and 9%, while the decomposition is suppressed by Ge in cases of 19% and 36%.