High-Electron-Mobility and Air-Stable 2D Layered PtSe2FETs

Two-dimensional crystals have emerged as a new class of materials with novel properties that may impact future technologies. Experimentally identifying and characterizing new functional two-dimensional materials in the vast material pool is a tremendous challenge, and at the same time potentially rewarding. In this work, we succeed in fabricating field-effect transistors based on few-layer black phosphorus crystals with thickness down to a few nanometers. Drain current modulation on the order of 10E5 is achieved in samples thinner than 7.5 nm at room temperature, with well-developed current saturation in the IV characteristics, both are important for reliable transistor performance of the device. Sample mobility is also found to be thickness dependent, with the highest value up to ~ 1000 cm2/Vs obtained at thickness ~ 10 nm. Our results demonstrate the potential of black phosphorus thin crystal as a new two-dimensional material for future applications in nano-electronic devices.

Preceding the current interest in layered materials for electronic applications, research in the 1960's found that black phosphorus combines high carrier mobility with a fundamental band gap. We introduce its counterpart, dubbed few-layer phosphorene, as a new 2D p-type material. Same as graphene and MoS2, phosphorene is flexible and can be mechanically exfoliated. We find phosphorene to be stable and, unlike graphene, to have an inherent, direct and appreciable band-gap that depends on the number of layers. Our transport studies indicate a carrier mobility that reflects its structural anisotropy and is superior to MoS2. At room temperature, our phosphorene field-effect transistors with 1.0 um channel length display a high on-current of 194 mA/mm, a high hole field-effect mobility of 286 cm2/Vs, and an on/off ratio up to 1E4. We demonstrate the possibility of phosphorene integration by constructing the first 2D CMOS inverter of phosphorene PMOS and MoS2 NMOS transistors.