Oxygen-plasma induced hydrogen desorption from hydrogen (H)-terminated Si(100) and (111) surfaces is investigated using infrared absorption spectroscopy (IRAs) in the multiple internal reflection (MIR) geometry. When a hydrofluoric (HF)-treated Si(100) surface is exposed to oxygen-plasma without sample heating, silicon hydride species rapidly decrease in density and SiH2 species are removed rapidly as compared with SiH species. On the other hand, when a NH4F-treated Si(111) surface is exposed to oxygen-plasma without sample heating, all the hydride species rapidly perish. SiH species resides on the terrace of the H-terminated Si(111) surface, while SiH2 species resides on the terrace of the H-terminated Si(100) surface. Oxygen-plasma induced hydrogen desorption from H-terminated Si surfaces does not depend on the type of hydride species, but on their positions; that is, hydrogen of hydride species at upper sites is desorbed at high rates by oxygen-plasma exposure. (C) 2004 Elsevier B.V. All rights reserved.