• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.7
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• pp.527-534
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• 1998

Thin film deposition of InN, which is a less-studied III-nitride compound semiconductor because of the difficulty if crystal growth, was performed by rf reactive sputtering method using In target and $N_2$reactive gas. The structrual, electrical, and optical properties of the produced films were measured and disussed according to the sputtering parameters such as deposition pressure, rf power, and substrate temperature. From the result of deposition pressure, rf power, and substrate temperature, we could obtain optimal conditions of 5m Torr, 60W, $60^{\circ}C$ for preparing InN thin film with high crystallinity, low carrier concentration, and high Hall mobility. The carrier concentration, Hall mobility, and optical bandgap of the fabricated InN thin films at optimal condition were $6.242\times10^{18}cm^{-3}, 212.526cm^2/V\cdot$ｓ, and 1.912eV, respectively.

• Journal of the Korean Society for Nondestructive Testing
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• v.22 no.1
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• pp.32-37
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• 2002

The presence of hydrogen in industrial plants is a source of damage. Hydrogen attack is one such form of degradation and often causing large tube ruptures that necessitate an immediate shutdown. Hydrogen attack may reduce the fracture toughness as well as the strength of steels. This reduction is caused partially by the presence of cavities and microcracks at the grain boundaries. In the past several techniques have been used with limited results. This paper describes the application of an ultrasonic velocity and attenuation in hydrogen damage. Ultrasonic tests showed a decrease in wave velocity and an increase in attenuation. Such results demonstrate the potential for ultrasonic nondestructive testing to quantify damage. Based on this study, reliable recommendation is suggested to detect hydrogen attack.