Gas adsorbates are Coulomb scatterers, rather than neutral ones, in a monolayer MoS2 field effect transistor

Abstract

Direct current (DC) and low-frequency (LF) noise analyses of a chemical vapor deposition (CVD)-grown monolayer MoS2 field effect transistor (FET) indicate that time-varying carrier perturbations originate from gas adsorbates. The LF noise analysis supports that the natural desorption of physisorbed gas molecules, water and oxygen, largely reduces the interface trap density (N-ST) under vacuum conditions (approximate to 10(-8) Torr) for 2 weeks. After a longer period of 8 months under vacuum, the carrier scattering mechanism alters, in particular for the low carrier density (N-acc) region. A decrease of both N-ST and the scattering parameter (SC) with desorption of surface adsorbates from MoS2, explains the enhanced carrier mobility and the early turn-on of the device. The stabilized carrier behavior is verified with = 0.5 in the formula (SC) N-acc(-), as in Si-MOSFETs. Our results support that the gas adsorbates work as charged impurities, rather than neutral ones © The Royal Society of Chemistry 2018