Synchrotron Radiation X-ray Absorption Study and Related Optical Characterization on GaN and CdZnTe
Date Issued
2009
Date
2009
Author(s)
Li-Wu, Yu
Abstract
During the past decade, synchrotron light sources have become indispensable tools for advanced scientific research. Synchrotron light is used widely in basic and applied research throughout the fields of materials science, biology, medicine, physics, chemistry, chemical engineering, geology, archeology, environmental science, energy, electronics, micro-mechanical engineering, and nanotechnology. For this reason synchrotron light sources have been coined "magic lamps of science". his thesis will focus on synchrotron radiation technology studies of semiconductors and heterostructures. It consists of five chapters: in chapter one, we introduce the synchrotron radiation, including the explanation, history, sources, properties, production and applications of synchrotron radiation. In chapter two, the experimental instruments and the theoretical backgrounds have been introduced, including Raman scattering, X-ray diffraction (XRD), and X-ray absorption spectroscopy (XAS). The data treatment of X-ray absorption spectroscopy will be introduced in chapter three.OCVD grown Si-doped GaN and MBE grown undoped GaN have been studied by combined Raman scattering, X-ray absorption fine structure and XRD techniques in chapter four. Polarization-dependent X-ray absorption fine structure has been employed to study the bond length around the Ga atom and the strain in the GaN films can be further obtained. In-plane strain can also be measured with a lateral spatial resolution of 1 mm with micro-Raman spectroscopy using shifts of the E2 phonon. Therefore, by combining Raman measurement and polarization-dependent extended X-ray absorption fine structure (EXAFS) analysis, both techniques can provide complementary information to reveal the residual stress in GaN films grown by different growth condition. In chapter five, Raman spectroscopy was also used to induce areas of Te secondary phases on the surfaces of the CZT crystals. These secondary phases may affect spectrometer performance. Therefore, to discuss the reasons that cause the secondary phase happen is the main purpose in this chapter.
Subjects
X-ray absorption spectroscopy
Raman spectroscopy
GaN
CdZnTe
Type
thesis
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