Elastic Stiffness of Co Thin Films at High Temperatures Monitored by Picosecond Ultrasound

Elastic Stiffness of Co Thin Films at High Temperatures Monitored by Picosecond Ultrasound

A picosecond ultrasound system for measuring the elastic stiffness of thin films at high temperatures is developed, and the elastic stiffness of Co films is measured up to 771 K during heating and cooling processes. The elastic stiffness of an as-deposited film is smaller than that of bulk Co. Howev...

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Bibliographic Details
Published in:Japanese Journal of Applied Physics Vol. 52; no. 7; pp. 07HB05 - 07HB05-3
Main Authors: Nakamura, Nobutomo, Nakamichi, Yohei, Ogi, Hirotsugu, Hirao, Masahiko, Nishiyama, Masayoshi
Format: Journal Article
Language:English
Published: The Japan Society of Applied Physics 01-07-2013
Subjects:
Cooling systems
Elastic constants
Heating
Stiffening
Stiffness
Temperature dependence
Thin films
Ultrasound
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Summary:A picosecond ultrasound system for measuring the elastic stiffness of thin films at high temperatures is developed, and the elastic stiffness of Co films is measured up to 771 K during heating and cooling processes. The elastic stiffness of an as-deposited film is smaller than that of bulk Co. However, during heating, stiffening due to crystallization is observed, and in the cooling process, the elastic stiffness follows the temperature dependence of bulk Co. These results indicate that the as-deposited film is softer than the bulk and that once stiffening has occurred upon annealing, the Co thin film shows a similar elastic property to the bulk. The temperature dependence of acoustic attenuation is also discussed.
Bibliography:Cross-sectional schematic of vacuum chamber used for high-temperature measurement. A water-cooling pipe surrounds the chamber. Time-resolved changes in reflectivity of 62.1 nm Co film at several temperatures. The arrow indicates the direction of the heating and cooling processes. Elastic stiffness of Co films at high temperatures. Dots denote measured stiffnesses, and the dashed line shows the temperature dependence of bulk Co measured by Fisher and Dever. X-ray diffraction spectra of Co film of 62.1 nm thickness measured before (bottom) and after (top) high-temperature measurement.
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ISSN:0021-4922
1347-4065
DOI:10.7567/JJAP.52.07HB05