Probing the disilane adsorption kinetics: An alternative approach

The adsorption kinetics and subsequent dissociation of disilane during gas source molecular beam epitaxy on Si(001) surface is studied in situ using m odulated beam mass spectrometry, thermal desorption spectroscopy, reflectio n high. energy electron diffraction and growth of epitaxial layers involvin g repeated cycles of disilane adsorption and hydrogen desorption. The disso ciation of disilane molecules is found to occur sequentially and the major intermediate reaction products are SiH2 and SiH. At temperatures above 400 degrees C,disilane dissociates readily to give two Silicon atoms and all si x hydrogen atoms and forms the monohydride (2 x 1) + (lx 2) surface. The fo rmation of a Si-monohydride surface also passivates against further adsorpt ion and dissociation of disilane. The main reaction pathway for the decompo sition of SiH2 to SiH is identified and studied as a function of incident a ux and growth temperature, This process is found to be controlled by the nu mber of unsaturated dangling orbitals.