Engineering two-dimensional electron gases at the (001) and (101) surfaces ofTiO2anatase using light

Angle-resolved photoemission shows the existence of two-dimensional metallic states of confined itinerant electrons at the (001) and (101) surfaces of insulating TiO₂ anatase. This is a material of much current interest, as a photocatalyst or a transparent conducting oxide, for instance. The 2D electron gases come from the formation of oxygen vacancies in the near-surface region, created by exposure to ultraviolet irradiation. The results here open a route to nano-engineering these confined electronic states using ultraviolet light, controlling their metallic or insulating nature.