| Scientific and technological interest in graphene has rapidly grown because of the outstanding physical and electronic properties of this two-dimensional material. To fully realize its technological potential, it is important to engineer a band gap as well as the charge carrier concentration through doping. In this thesis, we present routes to address both these aspects.;Graphene is a semimetal and therefore it does not have a technologically relevant band gap. To address this problem, it has been shown that sub-20 nm patterning can be used to open up a band gap in graphene through the quantum confinement effect. We present approaches for creating semiconducting nanoperforated graphene and graphene nanoribbons using block copolymer lithography, which addresses all of the following challenges simultaneously: (i) scalability, (ii) compatibility with the current manufacturing processes, (iii) high resolution, and (iv) pattern fidelity. By developing the materials and processes for the fabrication of sub-10 nm features over large areas, we study the structure-property relationships in nanopatterned graphene as a function of constriction width. We examine the limitations of top-down etching based fabrication methods in detail by examining the edge defect structures through Raman spectroscopy and electronic transport characterizations. These studies underline the importance of edge structure engineering in combination with patterning techniques to attain high quality semiconducting graphene.;In the second part of the thesis, we demonstrate a strategy to effectively control doping in graphene without degradation of the electronic properties. We do so by noncovalently latching a photoisomerizable dipolar azobenzene derivative to graphene via pi-pi interaction to create stable chromophore/graphene hybrids. A reversible molecular transformation triggered by light was used as an additional handle to reversibly modulate charge carrier concentration while retaining high mobility of pristine graphene. As the molecules switch reversibly from trans to cis upon UV light illumination, the dipole moment changes, hence the extent of doping in graphene. Through experimental and theoretical studies, we develop mechanistic insight into the observed enhancement of Raman intensity from the chromophore attached to graphene. |
