The interaction of hydrogen with silicon surfaces: A field ion microscope and pulsed-laser atom-probe study

Abstract

Field ion microscope and pulsed-laser atom-probe studies of silicon surfaces following various types of heat treatment in ultrahigh vacuum and in hydrogen have been carried out to identify any structural or compositional changes produced by the heating. In particular, the possibility of surface hydride formation due to hydrogen segregation from the bulk at moderate temperatures has been explored. Results from high purity whisker samples show no evidence of surface structural or compositional changes following vacuum heating up to temperatures of 625 K, unless gas phase hydrocarbons are present. At 700 K, thermal faceting, which indicates surface atom mobility, is observed. Results from samples prepared from 5-Ω-cm boules indicate that hydrogen segregation may occur along extended defects. Pulsed-laser heating of Si samples in molecular hydrogen is found to produce an amorphous overlayer on the surface, and the predominant species detected from this surface with the pulsed laser atom probe is SiH+3 . This observation suggests the presence of a silicon-trihydride surface phase.