c-Axis oriented SrMoO4 thin films by chemical solution deposition: Self-assembled orientation, grain growth and photoluminescence properties

In this study, SrMoO4 thin films have been prepared by chemical solution deposition using rapid thermal annealing. The results show that the thus-derived thin films are c-axis oriented, irrespective of the annealing temperature or the substrate orientation, indicating the self-assembled nature of the c-axis orientation, which is attributed to the combined effects of rapid thermal annealing, the lowest surface energy of the (0 0 1) plane, and the large anisotropic thermal expansion coefficient between the ab-plane and along the c-axis orientation in SrMoO4. Abnormal grain growth in thin films annealed under high temperatures or on substrates with large lattice/thermal expansion coefficient mismatch is observed and can be attributed to “strain-induced secondary recrystallization” or “strain annealing”. Bimodal-like rocking curves that are observed in some of the present thin films are attributed to the different interface structures, as confirmed by transmission electron microscopy observations. The photoluminescence properties show different characteristics due to the variations in the degree of orientation, the microstructure and the strain. The results will provide an instructive route to optimizing the properties of scheelite-structured molybdate thin films.