The effects of chemical etching and mechanochemical polishing on p-type silicon have been studied using capacitance measurements. The flatband potential VFB, as determined from Mott-Schottky plots, was found to be unrealistically large and very sensitive to the surface preparations used. The positive shifts of VFBare explained in terms of a compensating effect from the silicon bulk. This compensating effect is partially suppressed by annealing. Elemental analysis of the surface using secondary ion mass spectroscopy and x-ray photoelectron spectroscopy indicates that the most likely cause of the compensating effect is hydrogen. The source of hydrogen is the aqueous media used in the surface treatment processes. copyright. © 1990, The Electrochemical Society, Inc. All rights reserved.