Transport and optical studies on individual nanostructures

Nanotechnology is considered a very important scientific discipline. It probably will offer tremendous growth opportunities to many industries. Numerous nanostructures showing interesting and practical properties have been synthesized. In order to fully understand and assemble these nanostructures into useful "nano-machines", investigations on individual nanostructures are needed. This thesis will present electron transport studies on individual organic molecules, a new method of fabricating asymmetric junctions to contact individual nanostructures, and synthesis, electrical and optical characterizations on single vanadium dioxide nanobeams.; Chapter 1 serves as a brief introduction to the progress and challenges in nanotechnology.; Chapter 2 first introduces single charge tunneling theory, and then discusses in detail the fabrication of single molecule transistors. Finally, this chapter presents a novel electrodeposition-based method to fabricate electrode pairs of dissimilar metals with a nanometer-sized gap between them. This electrodeposition-based method prevents cross-contamination of the different metals and enables simultaneous fabrication of multiple electrode pairs in a self-limiting manner.; Chapter 3 presents electron transport studies on single molecule transistors based on individual ferrocene and nickelocene molecules. These devices show clean Coulomb blockade and energy quantization at liquid helium temperature. Low energy excited states are attributed to ring-torsion and center-of-mass vibrational modes of these molecules.; Chapter 4 discusses electron transport properties of single molecule transistors based on individual [W6CCl18]n- molecules. Besides Coulomb blockade and energy quantization, these transistors demonstrate that tunneling electrons change the vibrational spectrum of [W 6CCl18]n- molecules and the vibrational modes in turn affect electron tunneling.; Chapter 5 presents a vapor transport synthetic method of single crystalline vanadium dioxide nanobeams and tungsten doped vanadium dioxide nanobeams.; Chapter 6 discusses a combined electrical, scanning probe, and optical characterizations of vanadium dioxide nanobeams. This study reveals that strain significantly alters the metal-insulator phase transition in this material. Phase ordering in the nanobeam is caused by a simple, non-directional adhesion to a substrate because of the nanobeam growth direction and its morphology.; Chapter 7 demonstrates oscillator and inverter functions of simple two-probe devices based on tungsten doped vanadium dioxide nanobeams. These functions are a result of the morphology and material properties of these nanobeams.