We report on the nanosheet-thickness effects on the performance of top-gate MoS2 field-effect transistors (FETs), which is directly related to the MoS2 dielectric constant. Our top-gate nanosheet FETs with 40 nm thin Al2O3 displayed at least an order of magnitude higher mobility than those of bottom-gate nanosheet FETs with 285 nm thick SiO 2, benefiting from the dielectric screening by high-k Al 2O3. Among the top-gate devices, the single-layered FET demonstrated the highest mobility of ∼170 cm2 V-1 s-1 with 90 mV dec-1 as the smallest subthreshold swing (SS) but the double- and triple-layered FETs showed only ∼25 and ∼15 cm2 V-1 s-1 respectively with the large SS of 0.5 and 1.1 V dec-1. Such property degradation with MoS2 thickness is attributed to its dielectric constant increase, which could rather reduce the benefits from the top-gate high-k dielectric.
All Science Journal Classification (ASJC) codes
- Materials Science(all)