Tunable quasiparticle band gap in few-layer GaSe/graphene van der Waals heterostructures

Abstract

Two-dimensional few-layered materials exhibit unique and exotic electronic properties when compared to their bulk counterparts. Here, the authors report the role of dimensionality on the electronic properties of a van der Waals GaSe/graphene heterostructure. The strong thickness dependence of the GaSe band gap is demonstrated experimentally using scanning tunneling spectroscopy. The GaSe band gap decreases as the number of layers increases due to quantum confinement effects. The particular GaSe `Mexican hat' band structure is further explored by angle-resolved photoemission spectroscopy and by theoretical calculations. Interestingly, an electron transfer from graphene to GaSe has also been detected. It results in $n$-type doped thin GaSe films, opposite to the $p$-type character GaSe bulk.