Zinc oxide nanowires are excellent candidates as building blocks for future functional nanoscale devices for applications ranging from electronics and sensing to optoelectronics, due to their wide direct band gap energy (~ 3.4 eV) and a high exciton-binding energy (~ 60 meV). During this research project, the electrical and optical properties of zinc oxide nanowire field effect transistors were studied with emphasis on the near-ultraviolet photodetector and non-volatile memory device applications. Furthermore, tuning of the electrical properties of transistors was investigated through nanowire surface passivation with a wide range of dielectric materials and the mechanisms behind the inherent threshold voltage instability of zinc oxide nanowire field effect transistors were elucidated.
Full Name: Stanko Nedic & Nikhil Tiwale & Mark Welland
Institution: University of Cambridge
Department: The Nanoscience Centre
Position: Engineering PhD Student
Bottom up growth of nanostructures is a fascinating area of nanoscience. The growth of nanowires typically takes place by a vapour-liquid-solid mechanism whereby molten metal catalyst particles on the substrate catalyse the growth process. Equal weight ratio of ZnO and graphite powders is often used as precursor, whereby the graphite powder assists in reducing the required reaction temperature and maintains a steady nanowire growth rate. During this process, ZnO nanowire growth also sometimes occurs on the graphite flakes themselves. The presented scanning electron microscope image depicts ZnO nanowires grown on a graphite flake during thermal chemical vapour deposition. The image (originally grayscale) has been coloured using Adobe Photoshop. Our research group at the Nanoscience Centre has been exploring the use of the high performance ZnO nanowire based field effect transistors for memory, logic and sensor device applications.