Tunability of Doping in 2D Material Heterostructures using High Work Function RuCl₃: A First Principles Study

The facile formation of heterostructures based on two-dimensional (2D) materials permits controling the electronic properties of the resulting systems [1,2,3,4]. In particular, charge transfer between adjacent layers may be exploited to dope layers that improve charge carrier injection and engineer band alignments [3,4,5,6,7]. Here we quantify how large work function RuCl₃alters the electronic properties of heterostructures formed with various 2D materials: semiconducting transition metal dichalcogenides (TMDs), and few layer graphene structures. To this end we produce first principles calculations within the density functional theory (DFT) accounting for the on-site Coulomb interaction and spin-orbit. In the proximity of RuCl₃, TMD and graphene layer(s) become heavily p-doped with carrier densities of ~ 5 × 10¹³cm^-2, in agreement with prior experiments on RuCl₃ on graphene and WSe₂ [7]. We successfully rationalize our first principles results employing an analytical model based on properties of individual constituents. Study of the structural and electronic properties of the heterostructure upon application of vertical strain on these systems reveals that strain barely alters charge transfer but yields a stronger hybridization between layers. Additionally, accounting for the magnetic order in the RuCl₃ also results in similar doping when adjacent to semiconducting TMDs or graphene layers. The results of this work show that 2D material heterostructures may improve charge injection efficiency and band engineering in these systems.<br/>The authors gratefully acknowledge the support from the National Science Foundation (NSF) through Grant No. NSF-1848344.<br/><br/><br/>1. Novoselov et al., “2D materials and van der Waals heterostructures”, Science 353, aac9439 (2016).<br/>2. Geim et al. “Van der Waals heterostructures”, Nature 499, (2013).<br/>3. Zutic et al., “Proximitized materials”, Materials Today 22, (2019)[MK1] .<br/>4. Lotsch “Vertical 2D Heterostructures”, Annual Review ofMaterials Research 45, (2015)[MK2] .<br/>5. Solís-Fernándezet al., “Synthesis, structure and applications of graphene-based 2D heterostructures”, Chemical Society Reviews 46, (2017)<br/>6. Yoo et al., “Recent Advances in Electrical Doping of 2D Semiconductor Materials: Methods, Analyses, and Applications”, Nanomaterials 832, (2021).<br/>7.Wang et al., “Modulation Doping via a Two-Dimensional Atomic Crystalline Acceptor”, Nano<br/>Letters 20, 8446 (2020).