Trends in Graphene Conductivity-change upon Gas-adsorption: the Relevance of Orbital Distortion.

The experimental ability to alter graphene (G) conductivity by single gas-molecule adsorption is promoting the development of ultra high-sensitivity gas detectors, and could ultimately provide novel playground for future nanoelectronics devices. Presently, the underpinning effect is broadly attributed to a variation of G carrier concentration, caused by adsorption-induced Fermi-level shift. By means of first-principle Kubo-Greenwood calculations, here we demonstrate that adsorbate-induced orbital distortion could also lead to small but finite G conductivity changes, even in the absence of Fermi-level shifts. This mechanism enables sound physical interpretation of observed variable sensitivity of G devices to different chemical moieties, and it can be strongly enhanced by means of a suitable Ni substrate, thereby opening new pathways for optimal design of operational nanoscale detectors.