(622b) Permanent and Patterned Adjustment of the Surface Potential of Graphene-Like Carbon through Chemical Functionalization

The potential use of graphene in electronics requires reliable and pattern-controlled methods to inject or remove electron density from the two-dimensional carbon honeycomb lattices. Combining well established radical chemistry at ambient conditions and classical lithography, we find that the structure of graphene layers can be permanently altered through covalent chemical functionalization. We further demonstrate how the classic Hammett concept and the Linear Free Enthalpy Relationship from organic chemistry can be used to predict the surface potential shifts in graphene-like carbon surfaces. Our study (1) reveals an astonishingly simple yet accurate method to adjust the surface potential in graphene layers. Next to the direct application of such patterning in device fabrication, the here shown covalent attachment introduces a third dimension in the two-dimensional graphene base. Such functionalization can ultimately lead to covalent attachment of molecular electronics, circuitry incorporated chemical sensors or actuators and offers an alternative approach to address the contacting problem in the nm range. The possibility to print a potential pattern onto a graphene sheet was only conceptually shown at present, but this approach offers a permanent polarization of the graphene sheets as in the case of gate-induced changes in conductivity. Latter will be of crucial importance when using a larger graphene sheet as a starting material in device fabrication (3D analogy: native Si wafer), which is then doped and partially oxidized (3D analogy: insulating silicon oxide). One might envision that for graphene, doping or oxidation to an insulating state could therefore be achieved through simple chemical processing and classical or dip-pen lithography.