We have prepared thin indium oxide films by the autowave oxidation reaction. Measurements of temperature dependence of resistivity, Hall carrier concentration and Hall mobility have been conducted in the temperature range 5-272 K. Before ultraviolet (UV) irradiation, the indium oxide film had a semiconductor-like temperature dependence of resistivity ρ and the ratio of ρ (5 K)/ρ(272 K) was very limited (∼1.2). It was found that after UV irradiation of the In 2 O 3 film, the metal-semiconductor transition (MST) was observed at ∼100 K. To show that this MST is reversible and repeatable, two full cycles of 'absence of MST-presence of MST' have been done using UV irradiation (photoreduction) as the induced mechanism and exposure to an oxygen environment as the reversible mechanism, respectively. MST in transparent conducting oxide (TCO) is possibly associated with the undoped structure of metal oxide, which has some disorder of oxygen vacancies. It was suggested that reversible UV induced metal-semiconductor transition would occur in other TCOs.

The influences of ultraviolet (UV) irradiation and temperature on the electrical and optical properties in