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The purpose of this study is twofold: (1) to grow undoped-GaSb epitaxial structure on a high concentration n+-GaSb substrate by molecular beam epitaxy and (2) to analyze the grown undoped-GaSb epitaxial structure through photoreflectance (PR) measurements. PR spectrum analysis of the undoped- GaSb epitaxial layer at room temperature shows three notable features. First, in the region above the fundamental band gap Eg, the Franz-Keldysh oscillation (FKO) makes the PR signals oscillate. Second, low electric field PR is observed near Eg. Third, low energetic interference oscillations (LEIOs) occur in the region below the bandgap. An electric field is formed on the surface of the undoped-GaSb layer (i.e., in the interface between the undoped-GaSb and air); by using the FKO component, the calculated magnitude is 70 kV/cm at a growth temperature of 485 °C. In addition, the analysis of the FKO and low electric field PR data indicate a fundamental band gap Eg of 0.723 eV. The thickness of the undoped- GaSb epi-layer, calculated using the LEIO PR spectrum, is 1040 nm.
This research is aimed at finding a method to improve hardness, corrosion resistance, and abrasion resistance of metal surfaces by investigating the relationship between oxide membrane formation and the corrosion of titanium. For this study, oxide membranes of titanium, zirconium, and tantalum were formed by electrochemical oxidation reaction (namely, anodizing) and the membranes were corroded with several amounts of concentration of an electrolyte solution. The extent of corrosion was measured with a potential driving method and potentiometer. A 5% concentration of several electrolyte solutions in electrolytic baths were prepared and after connecting experimental titanium on the (+) pole and a zinc plate on the (-) pole, the formation of the oxide membrane was observed according to the type of electrolyte, voltage, and time. The corrosion measurement was carried out with the potential driving method. A metal specimen of titanium measuring 1.5 cm in diameter was prepared after anodization. After dipping it in several electrolyte solutions, the specimen was connected to a circuit composed of a standard pole and a counter pole. The extent of corrosion was measured by scanning it to the potential of +16mV with the speed of 5mV per second. The extent of metal corrosion was confirmed with SEM (Model LEO 1530). From the results of metal oxidation membrane formation, the color and thickness of the membrane was differentiated from the voltage applied and the types of metal. In the analysis of corrosion of anodized metal, the extent of corrosion was dependent on the amount of electricity, types of solution, and the frequency of corrosion experiments.