Wafer-scale metal chalcogenide thin films via ion exchange approach

Developing facile and controllable ways to tune the optoelectronic properties of two dimensional (2D) metal chalcogenide semiconductors via chemical composition is of significant importance for boosting their application in various functional devices. However, it is still great challenge for present approaches of synthesis to tailor the chemical composition of metal chalcogenide and keep high quality 2D thin film structure, especially for solution based methods. Here, we demonstrate a versatile and scalable ion exchange method for the fabrication of metal chalcogenide thin films on substrate. Based on this method, high quality continuous CdS and CdSe thin film on 2 inch sapphire have been successfully prepared and deliver excellent performances in photodetector. Meanwhile, Cu2S and Cu2Se thin films exhibit great electrical properties with comparable conductivities (75 S/cm for Cu2S and 663 S/cm for Cu2Se) and extremely high mobilities (536.9 cm2/(V*s)for Cu2S and 1411.8 cm2/(V*s)for Cu2Se). Furthermore, our strategy can be easily extended not only to other metal chalcogenides to modulate their composition and properties, but also to the establishment of in-plane heterostructures via spatially controlled ion exchange by using photolithography.