Where Does the Current Flow in Two-Dimensional Layered Systems?

In this Letter, we map for the first time the current distribution among the individual layers of multilayer two-dimensional systems. Our findings suggest that in a multilayer MoS2 field-effect transistor the "HOT-SPOT" of the current flow migrates dynamically between the layers as a function of the applied back gate bias and manifests itself in a rather unusual "contact resistance" that cannot be explained using the conventional models for metal-to-semiconductor contacts. To interpret this unique, contact resistance, extracted from a channel length scaling study, we employed a resistor network model based on Thomas-Fermi charge screening and interlayer coupling. By modeling our experimental data we have found that the charge screening length for MoS2 is rather large (lambda(MoS2) = 7 nm) and translates into a current distribution in multilayer MoS2 systems, which is distinctly different from the current distribution in multilayer graphene (lambda(graphene) = 0.6 nm). In particular, our experimental results allow us to retrieve for the first time fundamental information about the carrier transport in two-dimensional layered systems that will likely play an important role in the implementation of future electronics components but that have not been evaluated in the past.