Optical and electronic properties of cobalt-doped zinc oxide films prepared by the sputtering method

Abstract

In-doped ZnO, Co-doped ZnO and Li-doped NiO are successively deposited on quartz by the sputtering method. A current versus voltage curve of the three-layer device, in which the Indoped ZnO and Li-doped NiO are used as electrodes, reveals that the In-doped ZnO is an ohmic electrode and the Li-doped NiO is a blocking electrode with respect to electron injection. In photocurrent spectra of the three-layer device, there are two distinct peaks around 410 and 640 nm. The former is ascribed to the photoionization caused by the electric-dipole transition from the ground states,⁴A₂(F), to the conduction band, and the latter to the thermal emission from electronic excited states of Co²⁺,⁴T₁(P).