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

Rajarshi Roy, David Holec, Markus Kratzer, Philipp Münzer, Preeti Kaushik, Lukas Michal, Gundam Sandeep Kumar, Lenka Zajíčková, Christian Teichert

Publikation: Beitrag in FachzeitschriftArtikelForschungBegutachtung


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.

PublikationsstatusVeröffentlicht - 20 Mai 2022

Bibliographische Notiz

Funding Information:
RR would like to acknowledge funding by European Regional Development Fund-Project ‘MSCAfellow2@MUNI’ (No. CZ.02.2.69/0.0/0.0/18_070/0009846). We acknowledge CzechNanoLab Research Infrastructure supported by MEYS CR (LM2018110) to carry out this research. The authors would like to acknowledge Subhajit Saha, from Institute of Biomedical Engineering, National Tsing Hua University, Hsinchu, Taiwan and Saikat Sarkar, Dept. of Physics, Jadavpur University for helpful discussions during this work. The computational results presented have been achieved using the Vienna Scientific Cluster (VSC).

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© 2022 IOP Publishing Ltd.

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