Internal current amplification induced by dielectric hole trapping in monolayer MoS transistor.

Carrier transport in layered transition-metal dichalcogenides is highly sensitive to surrounding charges because of the atomically thin thickness. By exploiting this property, we report a new internal current amplification mechanism through positive feedback induced by dielectric hole trapping in a MoS back-gate transistor on a tantalum oxide substrate. The device exhibits an extremely steep subthreshold slope of 17 mV/decade, which is strongly dependent on the substrate material and drain bias.

Optically initialized robust valley-polarized holes in monolayer WSe2.

A robust valley polarization is a key prerequisite for exploiting valley pseudospin to carry information in next-generation electronics and optoelectronics. Although monolayer transition metal dichalcogenides with inherent spin-valley coupling offer a unique platform to develop such valleytronic devices, the anticipated long-lived valley pseudospin has not been observed yet. Here we demonstrate that robust valley-polarized holes in monolayer WSe2 can be initialized by optical pumping.