Opto-electrical properties and internal stress in Al:ZnO thin films deposited by direct current reactive sputtering

Abstract

In this work we study the effect of the oxygen concentration, deposition temperature, and post-deposition annealing on the optical and electrical properties of Al:ZnO thin films deposited by direct current (DC) reactive sputtering. The internal stress in the thin film is also monitored in-situ during growth with a multi-beam optical stress sensor. This latter technique allows to have an insight on the growth mechanisms. Coupled with an analysis of the discharge curve, the optical transparency, the electrical conductivity, and the chemical composition of the films as a function of the oxygen concentration and temperature during deposition, it allows to estimate what are the optimal deposition conditions to minimize the resistivity and maximize the transparency. The analysis of the internal stress is also of interest because it can be a source of premature fracture or delamination of thin films. The internal stress can also change the intrinsic properties of a thin film. The influence of the stress on the resistivity is therefore studied for samples deposited in the different sputtering regimes.