Probing the disilane adsorption kinetics: An alternative approach

Abstract

The adsorption kinetics and subsequent dissociation of disilane during gas source molecular beam epitaxy on Si(001) surface is studied in situ using modulated beam mass spectrometry, thermal desorption spectroscopy, reflection high energy electron diffraction and growth of epitaxial layers involving repeated cycles of disilane adsorption and hydrogen desorption. The dissociation of disilane molecules is found to occur sequentially and the major intermediate reaction products are SiH2 and SiH. At temperatures above 400°C, disilane dissociates readily to give two silicon atoms and all six hydrogen atoms and forms the monohydride (2×1)+(1×2) surface. The formation of a Si-monohydride surface also passivates against further adsorption and dissociation of disilane. The main reaction pathway for the decomposition of SiH2 to SiH is identified and studied as a function of incident flux and growth temperature. This process is found to be controlled by the number of unsaturated dangling orbitals. ©1999 The American Physical Society.