Asymmetric Schottky Contacts in van der Waals Metal-Semiconductor-Metal Structures Based on Two-Dimensional Janus Materials
(a) Scheme of asymmetric van der Waals metal-semiconductor-metal diode based on two-dimensional Janus MoSSe (scattering region) and 1T MoS2 (drain and source electrodes). The red squares indicate different contact interfaces with disparate Schottky barrier heights and band bending directions (S-S contact at source side with an n-type barrier and S-Se contact at drain side with a p-type barrier, marked as and , respectively). The violet, yellow, and green spheres represent Mo, S, and Se atoms, respectively. (b) The corresponding - characteristic curve at 300 K of this device. The illustrations are schematic band diagrams under negative (left) and positive (right) bias voltages, respectively. The purple curves represent the boundary of electrodes and bending of CB and VB. The blue arrows represent the primary transferring methods through contacts (tunneling and thermionic excitation under negative and positive voltages, respectively). The green dashed lines indicate the Fermi levels in two electrodes. The hollow and stuffed circles denote holes and electrons, respectively. (c) The current versus temperature from 200 to 300 K of the MSM structure under different bias voltages. The vertical dashed line represents the critical temperature where red and blue curves are crossed around 250 K. (d)-(f) The spatially resolved local density of states (LDOS) projected on the position of contact under , 0.40, and −0.40 V. The horizontal red dashed lines represent the chemical potentials () of electrodes. The red curves illustrate the boundaries of electrodes and theoretical band diagrams. The device configurations are depicted above LDOS graphs for references. The orange squares represent 1T MoS2, while the blue layer with one side flat and the other side fluctuant represents the Janus MoSSe semiconductor. The “S-S” and “S-Se” tags indicate and , respectively.