UBC Theses and Dissertations
X-ray diffraction and raman spectroscopy of pulsed light irradiated nanocrystalline silicon Patel, Bhavesh
A series of experiments is performed on a number of hydrogenated nanocrystalline silicon samples prepared through pulsed xenon light irradiation. These samples are then subjected to XRD and Raman spectroscopic analyzes. The mean crystalline size, corresponding to one of the pulsed hydrogenated nanocrystalline silicon sample, was determined from the XRD results through the use of Scherrer's equation. This yielded a mean crystallite size of 3.8 ± 1.1 nm, which is much less than that typically found in hydrogenated nanocrystalline silicon prepared through conventional means. The Raman spectra, corresponding to all of the samples, is determined using two different Raman excitation sources, 442 and 633 nm. Through a process of peak decomposition, the crystalline volume fraction is determined corresponding to each sample and each Raman excitation source. Five key observations are made from this analysis. First, it is observed that pulsing seems to enhance the crystalline volume fraction. Second, it is noted that the substrate holder temperature plays a relatively minor role, if at all, in shaping the crystalline volume fraction. Third, the crystalline volume fraction of the samples considered in this study is representative of that found in other forms hydrogenated nanocrystalline silicon. Fourth, the dependence of the crystalline volume fraction on the mean crystallite size seems to follow the general trend observed in the literature, i.e., that smaller mean crystallite sizes correspond to greater crystalline volume fractions, although further data would be required in order to confirm this trend. Fifth and finally, it is observed that the crystalline volume fractions determine from the 633 nm Raman excitation source are less than those found from the 442 nm Raman excitation source. This suggests an inhomogeneity in the material structure, with deeper materials from the surface having a reduced crystalline content. The reasons for this remain unknown at the present time. Some recommendations further study are then made.
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