Role of hexagonal boron nitride configuration in gate-induced hysteresis of WSe2 field-effect transistors

Environmental sensitivity of layered materials necessitates investigating the impact of surrounding materials like hexagonal boron nitride (hBN) on their electrical properties. We investigate the effects of hBN on gate-induced hysteresis in multilayer WSe₂ field-effect transistors (FETs) with four configurations: bare WSe₂, WSe₂ on bottom hBN (b-hBN), WSe₂ under top hBN (t-hBN), and WSe₂ encapsulated with hBN. The presence of b-hBN greatly improves the electrical properties of the two corresponding WSe₂ FETs, leading to a more than tenfold increase in channel currents and a significant reduction in hysteresis. In contrast, the effect of t-hBN is weaker than that of b-hBN. When the environment changes from vacuum to atmospheric conditions, the hysteresis of the two WSe₂ FETs without b-hBN increases substantially, while the change is small for those with b-hBN. Our observations support that pressure-dependent hysteresis originates from gas molecule adsorptions at the WSe₂/SiO₂ interface, not directly on the WSe₂ surface.