Abstract
Density functional theory was used to investigate the effects of doping alkaline earth metal atoms (beryllium, magnesium, calcium and strontium) on graphene. Electron transfer from the dopant atom to the graphene substrate was observed and was further probed by a combined electron localization function/non-covalent interaction (ELF/NCI) approach. This approach demonstrates that predominantly ionic bonding occurs between the alkaline earth dopants and the substrate, with beryllium doping having a variant characteristic as a consequence of electronegativity equalization attributed to its lower atomic number relative to carbon. The ionic bonding induces spin-polarized electronic structures and lower workfunctions for Mg-, Ca-, and Sr-doped graphene systems as compared to the pristine graphene. However, due to its variant bonding characteristic, Be-doped graphene exhibits non-spin-polarized p-type semiconductor behavior, which is consistent with previous works, and an increase in workfunction relative to pristine graphene. Dirac half-metal-like behavior was predicted for magnesium doped graphene while calcium doped and strontium doped graphene were predicted to have bipolar magnetic semiconductor behavior. These changes in the electronic and magnetic properties of alkaline earth doped graphene may be of importance for spintronic and other electronic device applications.
Highlights
Theoretical research for alkaline earth dopants in graphene has had a relatively recent history beginning with studies on beryllium doping in graphenes.[1]
Binding and adsorption energies were used to evaluate the energetic feasibility of different alkaline earth dopants in graphene
Results for Ca-graphene have a consistent trend with results by Klain et al.[17] where they noted that calcium doping on graphene caused a work function lowering compared to pristine graphene
Summary
Be-graphene was further studied for tunability with concentration effects and co-doping with a view towards use as potential anodes for lithium-ion[3] and sodium-ion batteries.[4]. While theoretical studies have been conducted on alkaline earth doped graphene, there is still a knowledge gap with respect to how more precisely the interactions induced by alkaline earth dopants on graphene can be described and how it gives rise to electronic and magnetic properties predicted for or observed on the material. Theoretical study is needed to provide a more thorough probing of the chemical interactions between the alkaline earth atoms and the graphene substrate to determine the modi cations in the electronic and magnetic properties in these graphene based systems. This will allow for a more fundamental understanding of the patterns and a general description of the atomic interactions with a detailed analysis of the electronic properties. Examining alkaline earth element dopants as a group in this manner will elucidate trends which can guide future experiments and development of the utilization of these materials in graphene
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