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Thesis (M.S.)--Oregon State University, 2008. / Printout. Includes bibliographical references (leaves 90-92). Also available on the World Wide Web.

Thesis (Ph.D.)--University of Nebraska-Lincoln, 2008. / Title from title screen (site viewed Apr. 9, 2009). PDF text: xvii, 113 p. : ill. (some col.) ; 3 Mb. UMI publication number: AAT 3339351. Includes bibliographical references. Also available in microfilm and microfiche formats.

We have determined that the temperature for desorption of gallium oxide from GaAs increases linearly with oxide thickness, for oxide layers between about 6Å and 26Å thick. The temperature for the oxide desorption ranged from 580°C to 630°C. The wafer temperature was determined from the optical band-gap measured from the diffuse reflectivity of the sample, which was polished on the front surface and textured on the back surface. Different thicknesses of oxide layers were created by varying the exposure time of the GaAs wafers to a low pressure oxygen plasma. The oxide thicknesses were determined by XPS analysis. Desorption experiments were carried out in a VG V80H MBE system under a As4 beam equivalent pressure of 1.5 x 10⁻⁵ ton. Measurement of diffuse light scattering using a HeNe laser shows an abrupt and non-reversible increase in the scattered light intensity during the oxide desorption. This suggests the surface is macroscopically roughened due to inhomogeneous desorption of the oxide. The oxide desorption was also studied by monitoring the secondary electrons produced by the high energy electrons from the RHEED gun. After the gallium oxide desorption there is a reversible, order of magnitude, increase in the number of scattered electrons produced by the incoming primary beam. We interpret this result as evidence for some form of microscopic roughening. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

A novel laser desorption system, with improved signal stability and extraordinary long lifetime, is presented for the study of jet cooled biomolecules in the gas phase using vibrationally resolved photoionisation spectroscopy. Tryptophan (Trp) is used as the test substance to characterize this desorption source. Here, the surface of a moving and rotating rod (graphite/Trp, 3mm diameter and 6 mm length) is exposed to a pulsed desorption beam from a Nd:YAG (1064 nm) laser running at 20Hz (Continuum Minilite).The characteristics of the source developed here and its properties with respect to cooling and stability have been investigated. Good control over the rod movement and the delivery of the IR beam result in a highly stabilized source with no noticeable fragmentation products.The combination of premixing within the source and using a pellet has made it possible to produce a stable jet-cooled beam of Trp, which lasts for several weeks without changing the sample. Additionally, the stability and signal to noise ratio has been improved by averaging the signal over the entire sample pellet by synchronizing the data acquisition with the rotation of the sample rod. The results demonstrate how a combination of the above helps to produce stable time of flight (TOF) signal and good quality one- and two-colour resonant two-photon ionisation (R2PI), photoionisation efficiency (PIE) and mass analyzed threshold ionization (MATI) spectra of Trp. The existence of six low-lying conformers of Trp in the gas phase has been confirmed. The first MATI spectrum of an isolated biomolecule (Trp) via R2PI for the determination of IE with high accuracy as ± 3 cm-1 has been recorded.

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Chan Siu-pang. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1999. / Includes bibliographical references (leaves 45-47). / Abstract also in Chinese. / TITLE PAGE --- p.i / THESIS COMMUTE --- p.ii / ABSTRACT (English) --- p.iii / ABSTRACT (Chinese) --- p.iv / ACKNOWLEDGMENT --- p.v / TABLE OF CONTENTS --- p.vi / LIST OF FIGURES --- p.vii / LIST OF TABLES --- p.viii / Chapter CHAPTER 1. --- Introduction --- p.1 / Chapter Section 1.1. --- General Introduction --- p.1 / Chapter Section 1.2. --- Background Information --- p.2 / Chapter 1.2.1. --- Si(100) Surface --- p.2 / Chapter 1.2.2. --- Structure of Cl/Si(100) --- p.7 / Chapter Section 1.3. --- Etching of Si(100) by Chlorine --- p.9 / Chapter Section 1.4. --- Theory --- p.14 / Chapter Section 1.5. --- Computational Model --- p.17 / Chapter CHAPTER 2. --- Desorption Mechanism of SiCl4 --- p.19 / Chapter Section 2.1. --- Desorption Mechanism --- p.19 / Chapter 2.1.1. --- Trajectory1 --- p.20 / Chapter 2.1.2. --- Trajectory2 --- p.23 / Chapter 2.1.3. --- Trajectory3 --- p.26 / Chapter 2.1.4. --- Trajectory4 --- p.29 / Chapter 2.1.5. --- Trajectory5 --- p.32 / Chapter 2.1.6. --- Trajectory6 --- p.35 / Chapter Section 2.2. --- Discussion --- p.38 / Chapter Section 2.3. --- Conclusion --- p.44 / REFERENCES: --- p.45