The structural properties of Al doped ZnO films depending on the thickness and their effect on the electrical properties

In this study, the structural and electrical properties of AZO films with different film thickness deposited by r.f. magnetron sputtering were interpreted in relation with film growth process. The result shows that the grain size increases during film growth, which is accompanied by decrease of compressive stress, indicating the enhancement of crystallinity. The relationship between grain size and compressive stress follows the same tendency for the samples regardless of deposition temperature, which implies the strong dependencies between the grain size and the compressive stress. The XPS analysis shows that the defects such as chemisorbed oxygen and segregated Al2O3 cluster at grain boundary are reduced with increase of film thickness or deposition temperature, leading to increase of carrier concentration and mobility. The mobility increase is accompanied by grain size increase and compressive stress reduction, indicating the influences of grain boundary and crystallinity on the mobility.