Ambipolar transport based on CVD-synthesized ReSe₂

Control of the carrier type in two dimensional (2D) materials is a serious issue for the realization of logic devices. The carrier type control of 2D semiconducting materials such as MoTe₂, WSe₂ and black phosphorus have been studied for this purpose. However, the systematic study on the polarity control of transistors based on ReSe₂, a new member of 2D materials, has remained unexplored despite the intriguing anisotropic optical and electrical properties deriving from the exotic crystal structure. Here, we report the electrical characterization of field effect transistors (FETs) of single crystalline ReSe₂ grown by a chemical vapor deposition. In contrast to a previous report of unipolar p-type exfoliated crystals, synthesized ReSe₂ FETs on SiO₂ with Au contact exhibit highly symmetric ambipolar behaviors with the current on/off ratios of ∼10⁴ for both of hole and electron injection. The carrier type could be controlled via the metal contact. With Al contacts, ReSe₂ FETs display perfect transition to pure n-type unipolar behavior. It is found that carrier type of ReSe₂ via thickness variation was hardly modulated because the ReSe₂ bandgap has little dependence on its thickness. We successfully achieved the fabrication of a logic inverter by using only ambipolar ReSe₂ FETs on SiO₂/Si without electrostatic doping or chemical treatments. These results demonstrate that ReSe₂ is a promising candidate for future low power logic devices and functional nano electronic applications. (paper)