High-Performance, Air-Stable, Top-Gate, p-Channel WSe₂ Field-Effect Transistor with Fluoropolymer Buffer Layer

High-performance, air-stable, p-channel WSe₂ top-gate field-effect transistors (FETs) using a bilayer gate dielectric composed of high- and low-k dielectrics are reported. Using only a high-k Al₂O₃ as the top-gate dielectric generally degrades the electrical properties of p-channel WSe₂, therefore, a thin fluoropolymer (Cytop) as a buffer layer to protect the 2D channel from high-k oxide forming is deposited. As a result, a top-gate-patterned 2D WSe₂ FET is realized. The top-gate p-channel WSe₂ FET demonstrates a high hole mobility of 100 cm² V^-1 s^-1 and a I_ON/I_OFF ratio > 10⁷ at low gate voltages (V_GS ca. -4 V) and a drain voltage (V_DS) of -1 V on a glass substrate. Furthermore, the top-gate FET shows a very good stability in ambient air with a relative humidity of 45% for 7 days after device fabrication. Our approach of creating a high-k oxide/low-k organic bilayer dielectric is advantageous over single-layer high-k dielectrics for top-gate p-channel WSe₂ FETs, which will lead the way toward future electronic nanodevices and their integration.