Nanosheet thickness-modulated MoS2 dielectric property evidenced by field-effect transistor performance.

We report on the nanosheet-thickness effects on the performance of top-gate MoS(2) field-effect transistors (FETs), which is directly related to the MoS(2) dielectric constant. Our top-gate nanosheet FETs with 40 nm thin Al(2)O(3) 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(2)O(3). Among the top-gate devices, the single-layered FET demonstrated the highest mobility of ∼170 cm(2) 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 cm(2) V(-1) s(-1) respectively with the large SS of 0.5 and 1.1 V dec(-1). Such property degradation with MoS(2) thickness is attributed to its dielectric constant increase, which could rather reduce the benefits from the top-gate high-k dielectric.