Chemical doping effects of gas molecules on black phosphorus field-effect transistors

Black phosphorus (BP) is a recently rediscovered layered material with outstanding optical and electrical properties. Its large adsorption energy and high surface-to-volume ratio have motivated chemical sensing and doping applications. We analyzed the charge transport properties as BP-based field-effect transistors (FETs) were chemically doped by adsorption of gas molecules. The electron-withdrawing NO₂ and the electron-donating NH₃ molecules were applied to observe p-doping and n-doping behaviors, respectively, in BP channel layer. Y-function method was used to extract the device parameters, allowing us to elucidate the chemical doping effects of different types of gas molecules in BP FETs. Excellent sensing ability of BP-based devices to gas molecules was also demonstrated. Our results provide a facile method to control the device properties of BP-based FET via the chemical doping.