Effective work function lowering of multilayer graphene films by subnanometer thick AlOx overlayers

A simple method for controlling the effective work function (WF) of conductive multilayer graphene (MLG) film, synthesized by using chemical vapor deposition and transferred to a dielectric substrate, was developed. The WFs of the MLG during the step-by-step deposition of aluminum (Al) were measured using in situ ultraviolet photoelectron spectroscopy. Core-level spectra were also collected to investigate the chemical reaction that occurred when a small amount of Al was deposited onto MLG in a stepwise manner. The measurements revealed that the effective WF of the conductive MLG film could be controlled from 3.77 to 4.40 eV by the deposition of an Al layer less than 0.6 nm thick. (c) 2011 American Institute of Physics. [doi:10.1063/1.3534795]