First observation of photoconductivity in the semiconducting phase of VO2

We report in this paper the first successful measurements of photoconductivity in the semiconducting phase of VO₂ single crystals. At low temperatures the frequency dependence of the photosensitivity (ps) exhibits an edge which gradually flattens at higher temperatures. The resulting mobility gap at 4.2 K amounts to 0.95 eV and thus differs from the optically determined band gap (0.65–0.75 eV).¹ These measurements, together with other known data suggest a “quasi-amorphous” electronic behavior of crystalline and semiconducting VO₂.