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We present a novel method of modeling the contact between a metal and a two-dimensional semiconductor. Using Au on MoS 2 as an example, we self-consistently solve the Schrödinger and Poisson equations and obtain the charge density in the contact. We consider open boundary conditions using the quantum transmitting boundary method and model the electron current through the contact region. We then investigate the effect of effective Schottky barrier height, electrostatic doping, and length of the overlap region on the contact resistance in a top contact geometry. By using data from experiments or from ab initio calculations for the fitting of parameters, such as the effective Schottky barrier height, the model can be used to efficiently obtain the contact resistance and, therefore, the quality of the contact. Furthermore, we investigate the effect of sampling of the Brillouin zone in the transverse direction on the numerical calculation of key quantities, such as contact resistance and free charge density. Additionally, we show that the boundary conditions applied to the Poisson equation during the calculation of the free charge density have a significant impact on the calculated contact resistance and that the impact is more pronounced in heterostructures with a larger Schottky barrier. We found that the contact resistance may be significantly underestimated, by up to one order of magnitude, when the height of the simulation domain is not large enough. [ABSTRACT FROM AUTHOR]

We investigate theoretically the impact of the dielectric environment on electronic transport in transition metal dichalcogenide monolayers. The low-field carrier mobility in free-standing layers is calculated using well-known ab initio methods, and the study is extended to layers in double-gate structures using the dielectric continuum approximation. In particular, we account for the screening of the electron–phonon interaction by the free carriers in the layer and by the dielectric environment. In addition, we include scattering with the hybrid interface optical-phonon/plasmon excitations ("remote phonons"). We find that whereas the presence of insulators with a high dielectric constant may increase the carrier mobility when ignoring the latter process, scattering with the hybrid interface excitations negates this beneficial effects and depresses the mobility significantly below its value in free-standing monolayers. [ABSTRACT FROM AUTHOR]

We study the magnetic properties of platinum diselenide (PtSe2) intercalated with Ti, V, Cr, and Mn, using first-principle density functional theory (DFT) calculations and Monte Carlo (MC) simulations. First, we present the equilibrium position of intercalants in PtSe 2 obtained from the DFT calculations. Next, we present the magnetic groundstates for each of the intercalants in PtSe 2 along with their critical temperature. We show that Ti intercalants result in an in-plane AFM and out-of-plane FM groundstate, whereas Mn intercalant results in in-plane FM and out-of-plane AFM. V intercalants result in an FM groundstate both in the in-plane and the out-of-plane direction, whereas Cr results in an AFM groundstate both in the in-plane and the out-of-plane direction. We find a critical temperature of <0.01 K, 111 K, 133 K, and 68 K for Ti, V, Cr, and Mn intercalants at a 7.5% intercalation, respectively. In the presence of Pt vacancies, we obtain critical temperatures of 63 K, 32 K, 221 K, and 45 K for Ti, V, Cr, and Mn-intercalated PtSe 2 , respectively. We show that Pt vacancies can change the magnetic groundstate as well as the critical temperature of intercalated PtSe 2 , suggesting that the magnetic groundstate in intercalated PtSe 2 can be controlled via defect engineering. [ABSTRACT FROM AUTHOR]