A simple spectrophotometer was designed using cardboard, a DVD, a pocket digital camera, a tripod and a computer. The DVD was used as a diffraction grating and the camera as a light sensor. The spectrophotometer was calibrated using a reference light prior to use. The spectrophotometer was capable of measuring optical wavelengths with a theoretical accuracy as high as 0.2 nm. Using this spectrophotometer, wavelengths are determined via image processing.

The van der Waals epitaxy of InSe films was performed on (111)GaAs surface at the growth temperature of 350°C. A spiral trigonal structure was observed on the surface of the InSe films. To improve crystal quality of the InSe films, their orientation control was investigated. The growth rate decreased rapidly as the growth temperature increased and no InSe films were obtained at growth temperatures higher than 480°C. At growth temperatures of 450°C and higher, a double-domain structure was observed, probably due to the coexistence of In4Se3 phase in the films. Therefore, the InSe film was directly grown on c-axis inclined GaSe, and it was revealed that InSe films were more easily grown on GaSe than on (001)GaAs surface, due to the same crystal structure. Furthermore, for fabrication of the quantum well structure, heteroepitaxial growth of GaSe/InSe/GaSe films on (001)GaAs substrate was investigated.

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A closed-loop temperature control system, which is composed of a thermal plant and a controller, has been developed to support undergraduate students in learning automatic control delivered in the Special Topics in Instrumentation Physics course. The thermal plant was made from a plastic box covering a lamp and a fan, which heats and drains the air in the plastic box, respectively, as well as a temperature sensor. The controller with a proportional control action was realized by employing the PIC 16F877 microcontroller. The control signal updates pulse-width modulators (PWMs) in which driver circuits turn on or off the lamp and the fan. A mathematical model of the closed-loop control system was derived and a theoretical transient response was then obtained. It is found that the experimental transient responses were always much lower than the set point and the steady-state errors were high for the proportional sensitivity (K P ) lower than 10. For K P higher than 10, the transient responses tend to approach the set point to cause small steady-state errors. These characteristics are consistent with the theoretical transient response. Further examination revealed that the closed-loop system is a higher order system due to the action of the PWMs and the driver circuits. ß

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For the heterostructure with GaSe, the epitaxial growth of GaS x Se1-x films on misoriented (001)GaAs substrate was investigated. We grew c-axis inclined GaS x Se1-x /GaSe/GaS x Se1-x heterostructure films on misoriented (001)GaAs substrate. The scanning electron microscopic (SEM) images and the photoluminescence spectra confirmed the existence of GaSe and GaS x Se1-x layers. Furthermore, multiquantum well structure of the GaSe/GaS x Se1-x system were fabricated for the first time.