  We investigate the work function (WF) variation of different Au
crystallographic surface orientations with carbon atom adsorption. Ab-initio
calculations within density-functional theory are performed on carbon deposited
(100), (110), and (111) gold surfaces. The WF behavior with carbon coverage for
the different surface orientations is explained by the resultant electron
charge density distributions. The dynamics of carbon adsorption at
sub-to-one-monolayer (ML) coverage depends on the landscape of the potential
energy surfaces. At higher ML coverage, because of adsorption saturation, the
WF will have weak surface orientation dependence. This systematic study has
consequential bearing on studies of electric-field noise emanating from
polycrystalline gold ion-trap electrodes that have been largely employed in
microfabricated electrodes.
