SnSe ambipolar thin film transistor arrays with copper-assisted exfoliation

Abstract

SnSe is a layered metal chalcogenide with potential ambipolar applications. However, the scale of devices is subject to limitation of milli/centi-meter-sized two-dimensinal (2D) flakes. Here, we demonstrate the preparation of wafer-scale SnSe ambipolar thin film transistor (TFT) arrays. The a-axis-oriented SnSe thin films were prepared via atomic layer deposition. The processes of lithography and copper-assisted exfoliation help to peel off unnecessary films to form isolated SnSe flakes. After evaporating nickel as contact electrodes, TFT arrays were successfully fabricated. The on/off current ratios are upgraded from 103 to 104 through annealing at 500 °C to improve the crystalline quality of SnSe, and both hole and electron mobilities increase fivefold to 41.29 and 34.99 cm2 V−1 s−1, respectively. The devices exhibit from symmetric ambipolar to hole-dominated behaviors as SnSe channel thickness increases to 50 nm. The copper-assisted exfoliation method provides an etching technique to make patterned 2D devices.