Controlling the activation energy of graphene-like thin films through disorder induced localization

Abstract

The influence of disorder on the activation energy in few layer graphitic films is demonstrated through combined Raman and temperature dependent transport studies. A laser ablation technique is employed which allows the level of disorder in the sp2-C phase to be controlled and conditions for minimizing the level of disorder are determined. As conditions vary from optimal, Raman measurements show increasing D and G bandwidths while the activation energy, negligible for optimal growth conditions, can be correlated with the level of disorder. This laser ablation technique allows the specific effects of structural disorder in the sp2 phase to be probed while defects act as effective barriers resulting in localization of charge carriers. Electron transmission spectra, calculated with a tight-binding model, account for the change of localization length as a result of disorder in the sp2 hybridized phase. This tandem experimental and theoretical approach shows that the localization length of the thin graphitic films can be tuned with the level of disorder which is controlled through synthesis parameters. This study, which addresses the role of disorder in graphene-like materials, is a prerequisite for device applications.