The state of the surface of standard phosphorus-doped n-Si(111) and n-Si(100) (KEF grade) and boron-doped p-Si(111) (KDB grade) single-crystal wafers treated in a 50% HF-70% HNO3 (1: 3, v/v) polishing solution has been studied using soft X-ray reflection spectroscopy. The fine structure of the reflection spectra in the region of the Si L 2,3 ionization threshold has been analyzed. The dependence of the natural oxide thickness on the orientation of a silicon single crystal surface is established. © 2009 Pleiades Publishing, Ltd.