2D MoSe₂ Transistor with Polymer-Brush/Channel Interface

Toward any practical applications of 2D transition metal dichalcogenide (TMD) transistors, two issues are often met. First, threshold voltage (V_th) of usual TMD 2D field effect transistors (FETs) is located quite away from 0 V, making the device already on and less practical. Second, a large hysteresis exists during transistor operation. Here, hysteresis-minimized n-TMD FETs are fabricated using polymer-brush/channel interface, to extend the 2D FET study to a sensor application. Gated by piezoelectric P(VDF-TrFE) touch pad that allows dipole switching and instantaneous voltages of +5 and -5 V, n-MoSe₂ FET operates well in its ON/OFF drain current behavior, due to its properly small V_th of −5 V. However, n-MoS₂ FET with a relatively high V_th of more than −8 V cannot be suitably switched off. To minimize the gate hysteresis, ultrathin polystyrene-brush layer is applied between TMD channel and 50 nm thin Al₂O₃ dielectric. n-Channel MoS₂ and MoSe₂ FETs exhibit a minimum voltage hysteresis of 1 and 0.5 V, respectively. It is regarded that V_th and hysteresis issues are uneasy to resolve but still possible to circumvent by using proper TMD channel and channel/dielectric interface materials.