Advancing contact angles formed by water and aqueous ethanol solutions were measured on both bare surfaces and film-covered surfaces of acrylic, glass, hydrophilic and hydrophobic silicon, polycarbonate, polyester, and stainless steel. Each bare surface was initially characterized with respect to its hydrophilic - hydrophobic balance. Both protein films and milk films were prepared on each surface; the adsorbed mass comprising each film was measured with ellipsometry. Contact angle methods proved useful in detecting the presence of a protein film on sufficiently hydrophilic or sufficiently hydrophobic surfaces. Contact angle methods were also found to be useful for detecting the presence of a milk film on sufficiently hydrophilic solid surfaces. The results also indicated that the type of diagnostic liquid chosen for the analysis becomes an important factor for films of increasing complexity. In any event, contact angle analysis is inappropriate to quantify the actual mass of soil remaining on a solid surface. / Graduation date: 1991

Rutherford backscattering spectrometry (RBS) is shown to be an elegant, powerful tool for the chemical characterization of optical coatings. RBS studies of several thin film materials are presented to illustrate the technique's unique abilities, and to show how RBS is best exploited in investigations of thin film stoichiometry and diffusion. The text begins with an introduction to optical coatings and the practical problems encountered in their implementation. The basic principles of RBS are discussed, and the technique is compared to other popular surface analysis tools. The introductory material concludes with a chapter devoted to specific techniques for RBS data and error analysis, including the derivation of a simple formula for determining the optimum thickness of multi-element samples. The accurate stoichiometric measurements provided by RBS give new insights into the chemical structure of ion-bombarded MgF₂ coatings. The analysis shows that lightly-bombarded coatings contain a small oxygen fraction (< 6%), and the absence of this oxygen in opaque, heavily-bombarded samples implies the oxygen compensates for fluorine deficiencies and is therefore an essential ingredient for transparent films. This beneficial oxygen appears to diffuse into the coatings along columnar voids, and the implied compromise between packing density and transparency is discussed. The final chapter takes advantage of the nondestructive depth-profiles provided by RBS. We present the first direct experimental verification of the interfacial oxide layer responsible for the superior adhesion of aluminum to glass, and show that contrary to popular belief, the layer is not an artifact of oxygen adsorbed during the aluminum's evaporation. We then discuss the diffusion of copper through silver films, and show that the migration is enhanced by exposure to the RBS probe beam. Finally, we consider the diffusion of carbon, from graphite substrates, into the voids of porous coatings during the RBS measurements. This effect, like the enhanced copper diffusion, is consistent with a low temperature, measurement-induced anneal; however, we show that the migrant carbon does not alter the chemical structure of the coatings, but instead serves as a convenient, non-intrusive indicator of film porosity.

No description available.

No description available.

Diamond is of interest as an advanced functional material, since the extreme physical properties of diamond, suggests it is ideally suited to a range of new demanding applications. In this context, the thesis explores basic surface chemical properties of diamond thin films, along with electrochemical, electronic and electron emission processes involving this material. New experiments are reported concerning the nature of surface conductivity on diamond. Measurements clearly show that the conductivity only arises if a hydrogenated diamond surface is exposed to water vapour, in the presence of chemical species capable of acting as electron acceptors. The conduction properties of surface conductive diamond in aqueous solution are also studied, and the first detailed electrochemical investigations of this material are described. Comparative electrochemical studies of nanocrystalline and boron-doped diamond have been performed. Investigations of electrode stability, and the accessible "potential window" are described, as well as the behaviour of a range of 'redox' systems, including transition metal complexes, metal deposition/stripping, and bio-related organic species. Significant differences between the behaviour of nanodiamond and microcrystalline boron-doped material are observed. A range of surface chemical and threshold photoemission studies of diamond thin films are reported. The results indicate that quantum photoyields (QPYs) are insensitive to the diamond "quality", although the wavelength selectivity is dependent on it. The adsorption of oxygen strongly reduces the QPY, although this only occurs slowly in the presence of O₂ because of a low reactive sticking probability. Much more rapid uptake of oxygen and consequent reduction of photoyield is observed in the presence of atomic O or electronically excited dioxygen O₂*. The presence of alkali metals on the diamond surface increases the QPY, and reduces the sensitivity of the QPY to surface oxygen. Significant differences between the surface chemical properties of Li, and other adsorbed akali metals (K and Cs) are observed.

No description available.

No description available.

No description available.

Energy distribution measurements of sputtered neutral particles contribute to the general knowledge of sputtering, a common technique for surface analysis. In this work emphasis was placed on the measurement of energy distribution of sputtered neutral atoms from different depths. The liquid Ga-In eutectic alloy as a sample target for this study was ideal due to an extreme concentration ratio gradient between the top two monolayers. In pursuing this study, the method of sputter-initiated resonance ionization spectroscopy (SIRIS) was utilized. SIRIS employs a pulsed ion beam to initiate sputtering and tunable dye lasers for resonance ionization. Observation of the energy distribution was achieved with a position-sensitive detector. The principle behind the detector's energy resolution is time of flight (TOF) spectroscopy. For this specific detector, programmed time intervals between the sputtering pulse at the target and the ionizing laser pulse provided information leading to the energy distribution of the secondary neutral particles. This experiment contributes data for energy distributions of sputtered neutral particles to the experimental database, required by theoretical models and computer simulations for the sputtering phenomenon.

by Ka-wai Wong. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1995. / Includes bibliographical references (leaves 106-109). / TABLE OF CONTENTS --- p.i / ABSTRACT --- p.v / LIST OF FIGURES --- p.vi / LIST OF TABLES --- p.xi / LIST OF ABBREVIATIONS --- p.x / Chapter Chapter 1 --- Research Background --- p.1 / Chapter 1.1 --- Introduction --- p.1 / Chapter 1.2 --- The effect of solid acceptance angle --- p.2 / Chapter 1.3 --- Research goals --- p.4 / Chapter 1.3.1 --- Determination of the electron spectrometer transmission function --- p.4 / Chapter 1.3.2 --- Novel depth profiling technique by adjusting the solid acceptance angle --- p.6 / Chapter 1.3.3 --- Correction to conventional ARXPS --- p.8 / Chapter 1.4 --- Thesis Structure --- p.8 / Chapter Chapter 2 --- Fundamentals of X-ray Photoelectron Spectroscopy --- p.9 / Chapter 2.1 --- Introduction --- p.9 / Chapter 2.2 --- X-ray Photoelectron Spectroscopy (XPS) --- p.9 / Chapter 2.2.1 --- Basic principles --- p.9 / Chapter 2.2.2 --- Surface sensitivity --- p.11 / Chapter 2.2.3 --- A typical XPS spectrum --- p.13 / Chapter 2.3 --- Qualitative analysis --- p.16 / Chapter 2.3.1 --- Binding energy --- p.16 / Chapter 2.3.2 --- Chemical state information --- p.17 / Chapter 2.4 --- Quantitative analysis --- p.20 / Chapter 2.4.1 --- Factors affecting intensity --- p.20 / Chapter 2.4.2 --- Homogeneous materials --- p.22 / Chapter 2.4.3 --- Layer structure --- p.23 / Chapter Chapter 3 --- Instrumentation --- p.26 / Chapter 3.1 --- XPS spectrometer --- p.26 / Chapter 3.1.1 --- Magnetic immersion lens system --- p.26 / Chapter 3.1.2 --- Tunable iris --- p.29 / Chapter 3.1.3 --- Scan plates --- p.29 / Chapter 3.1.4 --- Input lens aperture --- p.32 / Chapter 3.2 --- Calibration of the iris --- p.32 / Chapter 3.3 --- Applications --- p.35 / Chapter 3.3.1 --- Two dimensional XPS imaging --- p.35 / Chapter 3.3.2 --- ARXPS --- p.37 / Chapter 3.4 --- Summary --- p.37 / Chapter Chapter 4 --- Determination of electron spectrometer transmission function --- p.38 / Chapter 4.1 --- Introduction --- p.38 / Chapter 4.2 --- Traditional method of determination --- p.39 / Chapter 4.3 --- Methodology of the novel approach --- p.40 / Chapter 4.4 --- Calculation Procedures and Results --- p.48 / Chapter 4.5 --- Results and Discussions --- p.50 / Chapter 4.6 --- Conclusions --- p.57 / Chapter Chapter 5 --- "Depth Profiling by Adjusting the Solid Acceptance Angle: a Starting Point to “ Three-Dimensional Imaging""" --- p.59 / Chapter 5.1 --- Introduction --- p.59 / Chapter 5.2 --- Theoretical Background --- p.60 / Chapter 5.2.1 --- Quantification of Intensity --- p.60 / Chapter 5.3 --- Experimental --- p.69 / Chapter 5.3.1 --- Operation --- p.69 / Chapter 5.3.2 --- Calibration of iris --- p.70 / Chapter 5.3.3 --- Novel depth profile by adjusting the solid acceptance angle --- p.71 / Chapter 5.4 --- Results and Discussions --- p.71 / Chapter 5.4.1 --- Depth Profiles --- p.71 / Chapter 5.4.2 --- "Concept of ""Three-Dimensional XPS Imaging""" --- p.72 / Chapter 5.5 --- Conclusions --- p.76 / Chapter Chapter 6 --- Correction to Quantitative X-ray Photoelectron Spectroscopy with Consideration of the Solid Acceptance Angle --- p.79 / Chapter 6.1 --- Introduction --- p.79 / Chapter 6.2 --- The effect of the solid acceptance angle --- p.80 / Chapter 6.3 --- Theoretical Background --- p.83 / Chapter 6.4 --- Results and Discussions --- p.87 / Chapter 6.4.1 --- Homogeneous Sample --- p.87 / Chapter 6.4.2 --- Layer structure --- p.90 / Chapter 6.4.3 --- Simulation plots and further investigation --- p.92 / Chapter 6.5 --- Conclusions --- p.101 / Chapter Chapter 7 --- Conclusion --- p.103 / Acknowledgment --- p.105 / References --- p.106