Role of H Distribution on Coherent Quantum Transport of Electrons in Hydrogenated Graphene

Luca Parisi,Giuseppe Angilella,Ioannis Deretzis,Renato Pucci,Antonio La Magna

doi:10.3390/condmat2040037

Abstract

Using quantum mechanical methods, in the framework of non-equilibrium Green’s function (NEGF) theory, we discuss the effects of the real space distribution of hydrogen adatoms on the electronic properties of graphene. Advanced methods for the stochastic process simulation at the atomic resolution are applied to generate system configurations in agreement with the experimental realization of these systems as a function of the process parameters (e.g., temperature and hydrogen flux). We show how these Monte Carlo (MC) methods can achieve accurate predictions of the functionalization kinetics in multiple time and length scales. The ingredients of the overall numerical methodology are highlighted: the ab initio study of the stability of key configurations, on lattice matching of the energetic configuration relation, accelerated algorithms, sequential coupling with the NEGF based on calibrated Hamiltonians and statistical analysis of the transport characteristics. We demonstrate the benefit to this coupled MC-NEGF method in the study of quantum effects in manipulated nanosystems.

Highlights

Graphene’s (G) discovery [1] opened the breakthrough perspective to use materials made of a single atomic layer for nanotechnologies, including quantum technology (QT)
The final goal of this research is the use of a coupled methodology (MC-non-equilibrium Green’s function (NEGF)) to design the electronic features of hydrogenated graphene (HG) systems (NEGF application) using reliable predictions for the micro-structure of the HG sample after the hydrogenation process (LKMC application)
A prerequisite for the final goal is the derivation of a reliable energetic model to be implemented in the lattice kinetic Monte Carlo (LKMC) code for the simulations of interacting hydrogen adatoms

Summary

Introduction

Graphene’s (G) discovery [1] opened the breakthrough perspective to use materials made of a single atomic layer (i.e., two-dimensional materials) for nanotechnologies, including quantum technology (QT). This discovery has led to the discovery of a whole range of 2D materials [2], graphene still remains probably the most interesting one for applications, due to its intrinsic chemical and mechanical stability. The proposed applications usually need to modify the pristine electron structure of graphene by nano-structuring or functionalizing the material In this respect, probably the most direct method to achieve some of these goals is by using deposited hydrogen (H) adatoms to locally functionalize the graphene layer. Evidence of the modified electronic properties of graphene due to hydrogen adatoms or vacancies is already available from quantum-chemistry calculations for such impurities in large benzene-like molecules [4], as well as in their effect on the local density of states and conductivity of graphene [5]

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Conclusion