The morphology of ZnGa2O4:Cr3+ phosphors is studied by SEM. Fig. 3(a) illustrates that the particles of ZnGa2O4:Cr3+ powder are irregularly
shaped. As shown in Fig. 3(b) and (c), then variation in surface morphology is evident for the ZnGa2O4:Cr3+ films deposited at the two different oxygen pressures. The shape of grains at 0 and 1 Pa is mixed and rod types, respectively. The SEM images confirm that ZnGa2O4:Cr3+ films exhibit preferred orientation. The average
grain size of ZnGa2O4:Cr3+ film deposited at an oxygen pressure of 0 Pa is about 130 nm, much larger than that of about 70 nm at an oxygen
pressure of 1 Pa.