Effects of in content on the microstructure and the roughness of ZnO:In films

We investigated the changes in the preferred orientation and microstructure of ZnO:In films with increasing In content. ZnO and ZnO:In films with In contents of up to 50 at.% were deposited on Si (111) substrates by using pulsed laser deposition and were subsequently characterized using X-ray diffraction (XRD), atomic force microscopy (AFM), and transmission electron microscopy (TEM). The structural analysis of the films revealed that as the In content was increased, the preferred orientation of the films changed from a c-axis to a random orientation at In content of 10 at.% and finally became a a-axis orientation at In content of 20 at.%. The column grain size and values of root-mean-square (RMS) roughness showed a gradual decrease with increasing In content. As the In content was increased to 10 at.%, the initial orientation of the nuclei changed from a c-axis to a random orientation; nuclei with a preferred an a-axis orientation were dominant for an In content of 20 at.%, reflecting a deterioration in the tetrahedral coordination of ZnO. Consequently, the growth direction of the grains changed, and the preferred orientation of the grains affected the microstructure.