Electronic and Transport Properties of Covalent Functionalized Monolayer MoS2 by Ferrocene Derivatives

We have investigated the electronic and transport properties of a series of 2D Fc(X)(n)-MoS2 (Fc=Fe(Cp)(2); X=SiH2, CH2, CH=CH, or C equivalent to C; n = 1 or 2) systems by using ferrocene derivatives Fc(X)(n) to be grafted onto a MoS2 surface. Calculations have been carried out by density functional theory (DFT) and nonequilibrium Green's function (NEGF) methods. All these Fc(X)(n)-MoS2 give type-II heterostructures, and the grafted Fc(X)(n) behaves as a quantum dot-like group. No matter which Fc(X)(n) group is introduced, the conductivity is improved. The current magnitudes at a certain bias voltage follow the sequence of Fc(C equivalent to C)-MoS2 approximate to Fc(CH=CH)-MoS2 > Fc(SiH2)(2)-MoS2 approximate to Fc(SiH2)-MoS2 > Fc(CH2)(2)-MoS2 approximate to Fc(CH2)-MoS2, corresponding well to the abilities of supplying electrons from the (X)(n) group to MoS2. The armchair direction exhibits a larger current by about 4 times compared to the zigzag direction. A distinct NDR behavior is found for the Fc(C equivalent to C)-MoS2, meaning that the transport channel can be electrically switched from the off state to the on state, and again turned to the off state.