Charge Transfer and Photocurrent in Interfacial Junctions between Bismuth and Graphene

Abstract

Graphene, the two dimensional monolayer of carbon, is an essential building block for advanced electronic applications. Graphene is often integrated with bulk conductors, metals and semiconductors, for optoelectronic applications. The semimetal bismuth, that shares many electronic properties with these other conductors, is interesting because like graphene, it is a gapless conductor of high electronic mobility with linear dispersion relations and low electronic density. We studied the doping of graphene by Bi and the interfacial electric dipole.Graphene Raman spectroscopy results show that there is a very large charge transfer between graphene and bismuth. This doping is larger than in the interfaces of graphene with metals such as Cu and semiconductors such as Si. Our findings are in good agreement with recent theoretical results for graphene bismuth interfaces. We also present a demonstration of zerobias photocurrent generation that is enabled by the electric dipole at the graphene bismuth interface.

Quantum materials interfaces: graphene/Bismuth (111) heterostructures

“…Hence, the charge should flow from Bi to graphene, generating a considerable electric field. Thus, our results favor the view of Huber et al [8] that the photocurrent generated in graphene/bismuth nanowire heterostructures is mostly of photovoltaic nature.…”

“…We performed first-principle calculations using the projector-augmented wave method [17] as implemented in the Vienna ab-initio simulation package (VASP) [18]. Considering that the diameter of nanowires used in the experiments [7,8] is large (200-250 nm), their interaction with a graphene layer can be understood by studying an interface between graphene and a bismuth thinfilm. In our study, we used a Bi (111) surface as it is known to be the most important Bi surface for practical applications [13].…”

“…The ability to absorb light over a wide range of frequencies also makes graphene/Bi interfaces ideal for use in photodetectors. In this context, a particular composite structure -bismuth nanowire arrays capped by graphene -was found to be especially promising as it exhibited an enhanced, fast and broadband photoresponse [7,8].…”

“…These theoretical works, although instructive, cannot be used to understand and explain the photoresponse of graphene-bismuth interfaces that were investigated in the aforementioned experiments. Motivated by the lack of an understanding of the physics of the system at the atomistic level and the experimental works on this heterostructure [7,8], here we study graphene/Bi interface. We address several unresolved questions: (a) What is the most stable crystal structure of the interface?…”

“…This phenomenon was interpreted differently in Refs. [7] and [8]. According to Jin et al, the major player here is graphene, and its improved light absorption is due to the opening of a band gap.…”