Surface reactions of SiH, SiH4 and Si2H6 studied using molecular beam techniques

Molecular beams can be used in a variety of ways to obtain reactivity and mechanistic information about silicon hydride surface chemistry. This talk discusses two approaches to studying the reaction of silicon hydriges on a silicon surface. Molecular beam deposition of silicon from silane and disilane has shown a transition from the low temperature (600C) deposition with a 50 kcal/mole barrier, to the high temperature (1,000C) reaction which is not activated by surface temperature. At the highest temperature the reaction probability for silane colliding with the surface is .004. The reaction of SiH radicals at the surface of amorphous silicon was studied using a new technique (IRIS-Imaging of Radicals Interacting at Surfaces) in which a complex molecular beam generated from a plasma impinges on the surface of a deposition film. Laser induced fluorescence of SiH is imaged onto a diode array to obtain a spatial profile of the radicals approaching and leaving the surface. The SiH was found to react readily at the hydrogenated surface, but some (5% of incident SiH flux) was observed leaving the surface under steady state conditions