Substrate-induced phase control of In2Se3 thin films

Two-dimensional In2Se3 crystal is a promising candidate for optoelectronics, phase-change memories and ferroelectrics. However, due to its polymorphic crystal structures, the controlled growth of pure monophasic In2Se3 poses a huge challenge for the fundamental physical exploration and practical applications. Here, we demonstrate a substrate-directed method to prepare β- and γ-phase In2Se3 thin films on Al-doped ZnO (AZO) and F-doped SnO2 (FTO) substrates, respectively. Aliovalent ion dopant with Zn element is responsible for stabilizing the metastable β-In2Se3. Owing to its narrow bandgap, the β-In2Se3 photodetector exhibits a wide spectral photoresponse. In addition, the as-grown layered β-In2Se3 thin films can be exfoliated to few atomic layers and exhibit n-type behavior. This work demonstrates that directed phase-engineering on different substrates may be an important breakthrough towards large-scale preparation of the desired phase In2Se3 atomic crystals.