Graphene is a two-dimensional single sheet of carbon atoms and has unique crystal and electronic structure, physical properties such as ambipolar electric field effect, flexibility, transparency (97.7% for single layer), very high charge carrier mobility, anomalous quantum Hall effect, thermal conductivity, and much more that is yet to be discovered. These properties have generated tremendous excitement in the scientific community and make graphene ap­ propriate for many applications, including flexible electronic and optoelectronic devices, supercapacitors, transparent conducting electrodes, and chemical, and bio sensors. There has been great interest in charge carrier modulation of graphene because it tuned the Fermi level of graphene. The tuning of graphene’s Fermi level is an important factor in determining the successful operation of electronic/optoelectronic devices. The Fermi level of graphene can be easily tuned by the modulation of charge carriers in graphene.
The electrical properties of graphene are very sensitive to the charge impurities, doping level, and defects. Recently, several approaches have been applied to modulate the electronic properties of graphene. For example, depositing dopant atoms on a graphene surface induces interstitial doping, chemical modification by absorp­ tion of gas molecules or by aromatic compounds and by electrostatic field tuning. Doped graphene has attracted considerable atten­ tion due to their exciting electronic properties and demonstrate immense potential for various applications such as transparent conducting electrodes, light-emitting diodes, photovoltaic devices, and supercapacitors. Therefore, it is necessary to tune the Fermi level of graphene for high performance of devices. This book covers all aspects of graphene.