Thermal and catalytic decomposition of Si 2H 6 on a Ge(100)2 × 1 surface: Photoemission and LEED studies

Abstract

We present photoemission and LEED results concerning the thermal and catalytic decomposition of disilane Si 2H 6 on a monocrystalline Ge(100)2 × 1 surface. The catalytic decomposition of disilane was obtained with a hot tungsten filament. Germanium substrates were heated by the Joule effect in the 20–500°C temperature range and exposed to either catalytically decomposed or undecomposed disilane. The thicknesses of the Si deposited layers were estimated from X-ray photoelectron spectroscopy (XPS) measurements. The crystalline quality of the deposited films could be controlled by angle resolved ultraviolet photoelectron spectroscopy (ARUPS), X-ray photoelectron diffraction (XPD) and low energy electron diffraction (LEED). For a substrate temperature around 350°C, the exposures to undecomposed or catalytically decomposed disilane lead to deposition of well-ordered Si thin films. At this substrate temperature, the Si growth rate was found to be 2–3 times higher when disilane was catalytically decomposed. At substrate room temperature, while some authors claimed the adsorption of undecomposed disilane on a Ge(100)2 × 1 surface, our results seem to show that no reaction occurs between undecomposed disilane and a Ge(100)2 × 1 surface. For substrate temperature above 400°C, the decrease of the Si photoemission intensities can be explained by an indiffusion of Si into Ge.