Probing the charge transfer and electron-hole asymmetry in graphene-graphene quantum dot heterostructure

journal article in Web of Science

English

In recent years, graphene-based van der Waals (vdW) heterostructures have come into prominence showcasing interesting charge transfer dynamics which is significant for optoelectronic applications. These novel structures are highly tunable depending on several factors such as the combination of the two-dimensional materials, the number of layers and band alignment exhibiting interfacial charge transfer dynamics. Here, we report on a novel graphene based 0D-2D vdW heterostructure between graphene and amine-functionalized graphene quantum dots (GQD) to investigate the interfacial charge transfer and doping possibilities. Using a combination of ab initio simulations and Kelvin probe force microscopy (KPFM) measurements, we confirm that the incorporation of functional GQDs leads to a charge transfer induced p-type doping in graphene. A shift of the Dirac point by 0.05 eV with respect to the Fermi level (E (F)) in the graphene from the heterostructure was deduced from the calculated density of states. KPFM measurements revealed an increment in the surface potential of the GQD in the 0D-2D heterostructure by 29 mV with respect to graphene. Furthermore, we conducted power dependent Raman spectroscopy for both graphene and the heterostructure samples. An optical doping-induced gating effect resulted in a stiffening of the G band for electrons and holes in both samples (graphene and the heterostructure), suggesting a breakdown of the adiabatic Born-Oppenheimer approximation. Moreover, charge imbalance and renormalization of the electron-hole dispersion under the additional influence of the doped functional GQDs is pointing to an asymmetry in conduction and carrier mobility.

graphene; graphene quantum dots; scanning probe microscopy; charge transfer; ab initio

ROY, R.; HOLEC, D.; KRATZER, M.; MUENZER, P.; KAUSHIK, P.; MICHAL, L.; KUMAR, G.; ZAJÍČKOVÁ, L.; TEICHERT, C.

6. 8. 2022

IOP Publishing Ltd

BRISTOL

0957-4484

NANOTECHNOLOGY

33

32

United Kingdom of Great Britain and Northern Ireland

325704-1

325704-9

9

https://iopscience.iop.org/article/10.1088/1361-6528/ac6c38