The invention provides a temperature switch material capable of detecting a very low temperature not higher than 150 K. It also provides a light switch material for detecting light in the ultraviolet region. It further provides a switch material suited for use as a substrate for thin oxide layer formation thereon. The switching material utilizes an abrupt change in photoelectric current as produced upon phase transition of SrTiO3 at a low temperature. The photoelectric switch or temperature switch utilizes the change in photoconduction spectrum upon irradiation of SrTiO3 with light in the 3 eV-5 eV ultraviolet region. A switch is available by varying the intensity of irradiating light thereby controlling the transition temperature.
