In2Se3/Bi2Se3 is a promising topological insulator (TI) device structure. However, the (Bi1-xInx)(2)Se-3 thin film system undergoes a transition from TI to band insulator as a function of In concentration, so an investigation of interdiffusion and its influence on transport properties of this system is important. We have grown Bi2Se3 thin films on sapphire (Al2O3) using molecular beam epitaxy followed by In2Se3 thin film growth at three different temperatures. Medium energy ion scattering measurements of those films showed that the 50 degrees C growth temperature resulted in less In diffusion and an amorphous In2Se3 structure. At higher growth temperatures In diffusion was more significant and better In2Se3 crystallinity was observed. Our transport measurements showed that the mobility decreases with increasing In diffusion into Bi2Se3. (C) 2014 Elsevier B. V. All rights reserved.