| While traditional electronic components based on silicon technology are reaching the limit of miniaturization, researchers in both academia and industry are exploring novel materials and nanoscale devices based on new mechanisms. The first part of the dissertation will focus on electronic transport in graphene, a monolayer of carbon atoms proposed as the new promising material for carbon nanoelectronics. We observed electron ballistic transport phenomenon, proximity induced supercurrent and geometry-dependent minimum conductivity in graphene. In the ballistic transport regime, electrons propagate in graphene without any obstacle and scattering only happens on the interface of graphene and electrodes. This phenomenon can be realized by quantum interference of multiple reflected electronic waves between normal electrodes and multiple Andreev reflections from superconducting electrodes. Our discoveries may have important implications for graphene nanoelectronic devices, such as ballistic transistors.;The second part of the dissertation focuses on electrical transport in metal oxide based switches, which are promising candidates as the basis of next generation non-volatile random access memory and future nanoscale neuromorphic computation circuits. By performing the pressure-modulated conductance microscopy, for TiO2 based molecular devices with conductance between G Q and 2GQ (GQ is the conductance quantum), we observed oscillation of conductance with inter-electrode spacing at room temperature, which can be explained by quantum interference of electron waves between two partially transmitting electrodes. By performing the pressure-modulated conductance microscopy on TiO2 memristive nano-switches, AFM force modulation of tunnel gaps is realized and will also be discussed. |
