Modulation doping in van der Waals materials: Fabrication of high quality α-RuCl₃/graphene heterostructures

2d devices made from van der Waals materials require clean and uniform doping. However, most common techniques used to dope 2d materials either are limited in the carrier densities they can induce, or can degrade sample quality. Recently we discovered that the layered Mott insulator α-RuCl₃ can strongly charge dope graphene, inducing a large population of holes of order a few 10¹³ cm^-2 when placed in direct contact. Fortuitously, the graphene is found to maintain a high mobility, achieving the highest reported value at such large induced densities. However, due to the short-ranged nature of this charge transfer, α-RuCl₃/graphene heterostructures require careful fabrication procedures to induce uniform doping across typical device scales. In this talk, we discuss particulars of α-RuCl₃/graphene device fabrication essential for producing high quality, uniformly doped devices, including using Raman spectroscopy to quantify and pre-screen sample homogeneity, and methods of making low-resistance electrical contact to graphene layers within the stack without degrading sample quality.