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<p>The goals of this thesis are to demonstrate the operation of a near-field scanning microscope (NSOM) inside  a scanning electron microscope (SEM) to collect spatially resolved luminescence and to image transport on nano-scale  structures, particularly nanowires. The SEM is used to generate localized charge and the NSOM is used to observe the  motion of the excess charge due to diffusion and/or drift via its recombination emission. This will allow direct  determination of transport parameters, such as minority carrier mobility and lifetime, that are key to the performance of  LEDs, lasers and bipolar devices.  For nano-structures such as nanowires, device sizes are commonly less than 100 nm. The resolution in a  standard optical microscope is diffraction limited and hence resolution of luminescence from individual devices requires  collection of light in the near field limit. An atomic force microscope (AFM/NSOM) has been installed in the SEM to  allow for simultaneous near-field optical collection with an electron beam for charge generation. The work in this thesis  has observed CL luminescence from ZnO nanowires using normal SEM-OM and anaylzed the spectra. In addition, the  work has demonstrated successful AFM/NSOM operation within the SEM. Light is collected from both GaAs  heterostructures and single ZnO nanowires and control experiments have been performed. Challenges for transport  imaging in SEM have been identified  Finally, a suggestion for further work is to specifically image charge motion along a single wire, including  electric field mapping in these nanoscale, low dimensional structures. These nanoscale wires are poised to  revolutionize solid state devices in the near future and direct measurements of key electronic parameters will be  required.
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<br>Subjects: Nanowires; Nanostructured materials; Atomic force microscopy; Near-field microscopy; Imaging systems; Scanning electron microscopes; Zinc oxide; Transport properties</div>
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Ang, Goon Hwee</div>
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