Transforming a Two-Dimensional Layered Insulator into a Semiconductor or a Highly Conductive Metal through Transition Metal Ion Intercalation

Atomically thin two-dimensional (2D) materials are the building bricks for next-generation electronics and optoelectronics, which demand plentiful functional properties in mechanics, transport, magnetism and photoresponse. For electronic devices, not only metals and high-performance semiconductors but also insulators and dielectric materials are highly desirable. Layered structures composed of 2D materials of different properties can be delicately designed as various useful heterojunction or homojunction devices, in which the designs on the same material (namely homojunction) are of special interest because preparation techniques can be greatly simplified and atomically seamless interfaces can be achieved. We demonstrate that the insulating pristine ZnPS_3, a ternary transition-metal phosphorus trichalcogenide, can be transformed into a highly conductive metal and an n-type semiconductor by intercalating Co and Cu atoms, respectively. The field-effect-transistor (FET) devices are prepared via an ultraviolet exposure lithography technique. The Co-ZnPS_3 device exhibits an electrical conductivity of 8\times10^4 S/m, which is comparable to the conductivity of graphene. The Cu-ZnPS_3 FET reveals a current ON/OFF ratio of 10^5 and a mobility of 3\times10^-2 cm^2\cdotV^-1\cdots^-1. The realization of an insulator, a typical semiconductor and a metallic state in the same 2D material provides an opportunity to fabricate n-metal homojunctions and other in-plane electronic functional devices.