Tunnelling induced photon emission from surface/interface systems of graphene on copper

Imaging with the smallest order of magnitude has always been an essential topic for researchers working in various areas. Especially with the invent of Nobel Prize winner scanning probe microscopy (SPM), investigations in nanoscopic scales have been performed in terms of topographic, electronic, magnetic and optical properties. In this thesis, we have focused on electronic and optical properties of surfaces using photon scanning tunnelling microscopy (pSTM). Light emission from a planar junctions such as Metal-Insulator-Metal systems attracted noticeable attention. These studies have indicated that surface plasmons are the dominant mechanism of this light emission. Surface plasmons has been defined as collective oscillations delocalised electrons which propagate electromagnetic waves along the conducting surfaces. There might occur different modes of surface plasmons e.g. surface plasmon polariton (SPP) and localised surface plasmon (LSP). SPP defines surface plasmons which are propagating electromagnetic waves along the surface. LSPs are the charge oscillations in the gap plasmons. However, it was also reported that SPPs might be arise by LSPs as well. With the invent of scanning tunnelling microscopy (STM), photon emission from tunnel junction was applied in nanoscopic scales as well. Photon emission investigations have been performed on surfaces such as noble metals, molecule adsorbed metals, thin film combinations etc.with pSTM systems. Although some allotropes of carbon have been investigated in pSTM studies, graphene has not been stated yet in these investigations. In our work, we have focused on photon emission characteristics of chemical vapour deposition (CVD) grown graphene/copper structure. Graphene is a promising two dimensional material having honeycomb lattice. Several studies have revealed its extraordinary electronic, mechanical and optical properties. On the other hand, graphene can protect where it covers like a shield against exposing to corrosion. In our study performed under ambient conditions, graphene protects copper substrate from oxidation. Certainly the electronic properties of copper has be considered in this investigation. In this work, photon emission from metal-tunnel junction-graphene/metal system under ambient conditions was first reported. It was clearly seen that crystal orientation of copper facets has a dominant role on this tunnelling induced luminescence from Graphene/Cu sample. Based on measurements, it was determined that the occurrence of free electron surface state of Cu(111) surfaces are decisive in photon emission.