Dielectric Properties of Amorphous SrTiO3 Thin Films

In this work, the effects of deposition and annealing conditions on the dielectric properties and dc conductivity were investigated on the thin amorphous SrTiO3 films prepared by a sputtering method using neutralized argon-ion beams. It was demonstrated that the dielectric constant and dc conductivity increased markedly by vacuum annealing and by increasing the target-substrate distance during deposition. The amorphous SrTiO3 films have the optical band gap of about 2.5eV, accompanying with rather wide band tails. This suggests the existence of structural defects which may be caused by oxygen deficiency in the amorphous structure. The amounts of the oxygen deficiency were considered to be dependent on the annealing atmosphere as well as the target-substrate spacing. It is supposed that the ionization of oxygen vacancies, Vo→Vo¨+2e', plays an important role for the dielectric properties and dc conductivity of the amorphous SrTiO3 thin flms. The relative dielectric constants obtained ranged from 20 to 550.