Electronic transport properties of graphene doped by gallium

Abstract

In this work we present the effect of low dose gallium (Ga) deposition (<4 ML) performed in UHV (10 Pa) on the electronic doping and charge carrier scattering in graphene grown by chemical vapor deposition. In situ graphene transport measurements performed with a graphene field-effect transistor structure show that at low Ga coverages a graphene layer tends to be strongly n-doped with an efficiency of 0.64 electrons per one Ga atom, while the further deposition and Ga cluster formation results in removing electrons from graphene (less n-doping). The experimental results are supported by the density functional theory calculations and explained as a consequence of distinct interaction between graphene and Ga atoms in case of individual atoms, layers, or clusters.

Investigation of carrier density and mobility variations in graphene caused by surface adsorbates

“…It should be noted that this trend has been exhibited for all the three exposures considered in this study, i.e. increase in majority carrier density leads to a strong decrease in mobility, which clearly indicates ionized impurity scattering as a major factor limiting mobility in these devices, which is commonly observed [25,27]. With mobility increasing more rapidly than the decrease in carrier concentration, the conductivity has a slightly increasing trend, contrary to expectations and observations for NO2 and NH3.…”

Advances and Trends in Chemically Doped Graphene

“…[41,49] Metals displaying different bonding states with graphene have also been reported, such as Fe and Cr. [50,51] Analogous to Si, Fe forms a divacancy planar or out-of-plane graphitic bonding system. Cr has demonstrated pyridinic and pyrrolic configurations, but the disruption caused by its doping is stronger (viz., the structural distortion is greater) because of the large size.…”

“…Some dopants present n-type doping (N in the graphitic state, P, Ga, Fe, etc. ), [50,[59][60][61] while others display p-type effect accompanied with a downshift of the Fermi level toward the Dirac point (e.g., N in the pyridinic state, B, S, Si, O, and halogens). [46,[62][63][64] It is generally thought that the opening of the bandgap is due to symmetry breaking induced by the doping atoms.…”

“…At low doping levels, the Ga-graphene interaction (adhesive bond) is dominant; while at higher doping level, the Ga-Ga interaction becomes more prominent, and so Ga clusters are formed and inhibit the n-type behavior. [41,50]…”

“…Thus, the exact relationships are difficult to extract. [ 50 ] The rational design and reproducible production of given electronic structures should greatly facilitate the commercialization of heterographene materials.…”