Relaxation and H coverage of ammonium fluoride treated Si(111)

Using medium energy ion scattering and elastic recoil detection, we have studied silicon surfaces prepared by ex situ NH4F wet etching. We report direct measurements of relaxation and hydrogen coverage of the passivated Si(111)-(1×1) surface. For Si(111), nearly ideal, unreconstructed surfaces are obtained, terminated by a single atomic layer of hydrogen. Silicon backscatter yields agree closely with simulations of a bulk truncation, with an inward relaxation of the outermost layer of 0.075±0.03 Å. On the other hand, Si(001) prepared by NH4F solution shows severe roughening.