Programmable Schottky Junctions Based on Ferroelectric Gated MoS$_{\mathrm{2}}$ Transistors.

We report a programmable Schottky junction based on MoS$_{\mathrm{2}}$ field effect transistors with a SiO$_{\mathrm{2}}$ back gate and a ferroelectric copolymer poly(vinylidene-fluoride-trifluorethylene) (PVDF) top gate. We fabricated mechanically exfoliated single layer MoS$_{\mathrm{2}}$ flakes into two point devices via e-beam lithography, and deposited on the top of the devices \textasciitilde 20 nm PVDF thin films. The polarization of the PVDF layer is controlled locally by conducting atomic force microscopy. The devices exhibit linear $I_{\mathrm{D}}$-$V_{\mathrm{D\thinspace }}$characteristics when the ferroelectric gate is uniformly polarized in one direction. We then polarized the gate into two domains with opposite polarization directions, and observed that the $I_{\mathrm{D}}$-$V_{\mathrm{D\thinspace }}$characteristics of the MoS$_{\mathrm{2}}$ channel can be modulated between linear and rectified behaviors depending on the back gate voltage. The nonlinear $I_{\mathrm{D}}$-$V_{\mathrm{D\thinspace }}$relation emerges when half of the channel is in the semiconductor phase while the other half is in the metallic phase, and it can be well described by the thermionic emission model with a Schottky barrier of \textasciitilde 0.5 eV. The Schottky junction can be erased by re-write the entire channel in the uniform polarization state. Our study facilitates the development of programmable, multifunctional nanoelectronics based on layered 2D TMDs..