Tunable Quasiparticle Band Gap in Few Layer GaSe/graphene Van der Waals Heterostructures

Abstract

Two-dimensional (2D) materials have recently been the focus of extensive research. By following a similar trend as graphene, other 2D materials including transition metal dichalcogenides (MX2) and metal mono-chalcogenides (MX) show great potential for ultrathin nanoelectronic and optoelectronic devices. Despite the weak nature of interlayer forces in semiconducting MX materials, their electronic properties are highly dependent on the number of layers. Using scanning tunneling microscopy and spectroscopy (STM/STS), we demonstrate the tunability of the quasiparticle energy gap of few layered gallium selenide (GaSe) directly grown on a bilayer graphene substrate by molecular beam epitaxy (MBE). Our results show that the band gap is about 3.50 +/-0.05 eV for single-tetralayer (1TL), 3.00 +/-0.05 eV for bi-tetralayer (2TL) and 2.30 +/-0.05 eV for tri-tetralayer (3TL). This band gap evolution of GaSe, in particularly the shift of the valence band with respect to the Fermi level, was confirmed by angle-resolved photoemission spectroscopy (ARPES) measurements and our theoretical calculations. Moreover, we observed a charge transfer in GaSe/graphene van der Waals (vdW) heterostructure using ARPES. These findings demonstrate the high impact on the GaSe electronic band structure and electronic properties that can be obtained by the control of 2D materials layer thickness and the graphene induced doping.

References in corpus (5)

• Observation of giant bandgap renormalization and excitonic effects in a monolayer transition metal dichalcogenide semiconductor
• Tunable Magnetism and Half-Metallicity in Hole-doped Monolayer GaSe
• Bandgap and doping effects in MoS2 measured by Scanning Tunneling Microscopy and Spectroscopy
• Observation of the quantum Hall effect in epitaxial graphene on SiC(0001) with oxygen adsorption
• Magnetisms in $p$-type monolayer gallium chalcogenides (GaSe, GaS)

Cited by in corpus (4)

• Indirect to direct gap crossover in two-dimensional InSe revealed by ARPES
• Spin-orbit coupling, optical transitions, and spin pumping in mono- and few-layer InSe
• Strong Modulation of Optical Properties in Rippled 2D GaSe via Strain Engineering
• Evidence of Direct Electronic Band Gap in two-dimensional van der Waals Indium Selenide crystals