Thickness study of AZO films by RF sputtering in Ar + H2 atmosphere at room temperature

Abstract

AbstractAl‐doped ZnO (AZO) films were prepared on glass substrates by RF magnetron sputtering in an Ar + 5%H2 ambient at room temperature. The influence of film thickness (85–1101 nm) on the structural, electrical, and optical properties of the films was investigated. With increasing film thickness, it is found that the crystallinity of the films is improved and the surface roughness of the films increases. The decrease of resistivity is accompanied by an increase of carrier concentration and mobility. At the film thickness of 583–1101 nm, larger figures of merit (FOM) of the films can be obtained, in which the film with a thickness of 803 nm has the lowest resistivity of 3.13 × 10−4 Ω cm, a sheet resistance of 3.90 Ω/sq, and an average optical transmittance in the visible range of 80%. With increasing film thickness, the crystallite size, carrier concentration, and mobility of the films increase simultaneously, implying that the main scattering mechanism is the intercrystallite boundary scattering. It is found that the optical bandgap (Eg) increases from 3.50 to 3.72 eV with film thickness, and this increase can be ascribed to the Burstein–Moss (BM) effect after considering all possible effect factors. The results demonstrate that AZO films deposited in an Ar + H2 atmosphere at room temperature are suitable for application in thin‐film solar cells as transparent conductive electrode layers.