Ultra-sharp lateral $p\text{-}n$ junctions in modulation-doped graphene

TL;DR

This paper reports the creation of ultra-sharp lateral p-n junctions in graphene, achieved through proximity doping with $ ext{RuCl}_3$, with junction widths less than 10 nm, verified by multiple experimental and theoretical methods.

Contribution

The study demonstrates a novel method to fabricate ultra-sharp graphene p-n junctions using crystalline edge proximity doping, achieving boundary widths below 10 nm.

Findings

Junction width less than 10 nm achieved

Charge doping decays sharply over nanometers

Potential variations observed on sub-10 nm scale

Abstract

We demonstrate ultra-sharp (${\lesssim}\,10\text{ nm}$) lateral $p\text{-}n$ junctions in graphene using electronic transport, scanning tunneling microscopy, and first principles calculations. The $p\text{-}n$ junction lies at the boundary between differentially-doped regions of a graphene sheet, where one side is intrinsic and the other is charge-doped by proximity to a flake of $\alpha$-RuCl$_3$ across a thin insulating barrier. We extract the $p\text{-}n$ junction contribution to the device resistance to place bounds on the junction width. We achieve an ultra-sharp junction when the boundary between the intrinsic and doped regions is defined by a cleaved crystalline edge of $\alpha$-RuCl$_3$ located 2 nm from the graphene. Scanning tunneling spectroscopy in heterostructures of graphene, hexagonal boron nitride, and $\alpha$-RuCl$_3$ shows potential variations on a sub-10 nm length scale. First principles calculations reveal the charge-doping of graphene decays sharply over just nanometers from the edge of the $\alpha$-RuCl$_3$ flake.