Impact of Heat Treatment on a Hetero-Stacked MoS2/ ${h}$ -BN Field-Effect Transistor

We investigated device properties before and after heat treatment for a hetero-stacked two-dimensional field-effect transistor (FET). In dual-gated monolayer MoS
₂
FET using a top h-BN layer and bottom SiO
₂
substrate, careful but harsh heat treatment is implemented in high vacuum at 200 °C for 18 h. Under the top-gate bias sweep, the field-effect mobility increases by ~9 times, and the channel carrier density doubles after the treatment. The heat treatment effect is more noticeable in the top-transferred h-BN than in the bottom SiO
₂
layer, because it leads to homogeneous adhesion between the layers by diminishing the adverse effects of interfacial bubbles or adsorbates. A top-gate dielectric capacitance for h-BN of 55 fF is increased to ~70 fF after the treatment, which is comparable to the theoretical value. This indicates that strong capacitive coupling for the top gate is formed, as confirmed by the capacitance-voltage measurement.