Electronic transport properties monitored by selective functionalization in Bernal bilayer graphene

Jouda Jemaa Khabthani, Ahmed Missaoui, Didier Mayou, Guy Trambly de Laissardière

Published 2021-05-06Version 1

Monitoring electronic properties of 2D materials is an essential challenge to open a way for applications such as electronic devices and sensors. From that perspective, Bernal's bilayer graphene (BLG) is a fairly simple system that offers great possibilities for tuning electronic gap and charge carriers mobility. The BLG cell contains non-equivalent carbon atoms, which opens up many possibilities for selective functionalization. It has been shown that its functionalization by selective adsorptions of atoms or molecules of one layer created midgap states that can strongly modify both the electronic structure and the diffusion of charge carriers. Here, we present a detailed numerical study of BLG electronic properties when two types of adsorption are present together. We focus on realistic cases that should be able to be performed experimentally. We show a wide range of behaviors, such as gap opening or abnormal conductivity, depending on the adsorbate positions, their concentrations, the doping, and eventually the coupling between midgap states which can create a midgap band. These behaviors are understood by simple arguments based on the fact that BLG lattice is bipartite. We also analyze the conductivity in regimes where the quantum effects cannot be ignored. This occurs at low temperature for values which depend on the type of functionalization. Moreover when the Fermi energy lies in the band of midgap states for which the average velocity cancels but which can conduct thanks to quantum fluctuations of the position.