New ESR Investigation of the Cleaved-Silicon Surface

In situ electron-spin-resonance measurements have been performed on silicon crystals cleaved under ultrahigh-vacuum conditions. Our observations are in conflict with existing publications which report a surface signal ($g=2.0055\mathrm{}$) corresponding to a spin density of the order of ${10}^{14}$/${\mathrm{cm}}^2$. No signal which could be ascribed to the cleaved surface was detected although the minimum detectable surface spin density was less than ${10}^{13}$/${\mathrm{cm}}^2$. In view of this result we comment on the origin of the ESR observed in powders and amorphous films.