(Surfaces and thin films studied by picosecond ultrasonics): Annual progress report for period July 1, 1986 to November 30, 1987
Research supported by this grant (DE-FG02-86ER45267) is directed towards the exploration of a new method for studying very high frequency phonons in real time. The picosecond pump and probe technique on which the method is based makes it possible to study longitudinal phonons in a much higher frequency range than the conventional ultrasonics and can be used at any temperature. In the first period of the grant we have built a new opto-electronic system dedicated for these studies. We have studied phonons in Ge:Si multilayer structures and interpreted them in terms of normal modes; in these structures we have observed a localized surface mode which appears to be ideally suited for studying phonon attenuation in the material, as well as the properties of interfaces. We have shown that some vibrations of large molecules seen by the picosecond photomodulation technique can be interpreted as normal modes of the molecule seen in real time. We have studied the transmission of phonons between two materials and have shown that the Kapitza resistance for the heat flow is easily observable in the picosecond range. We have developed a theory of the Kapitza resistance between two different materials with fcc structures. We have done some exploratory measurements on the use of this method as a non-destructive technique for studying very thin films and coatings with possible technological applications.
- Research Organization:
- Brown Univ., Providence, RI (USA)
- DOE Contract Number:
- FG02-86ER45267
- OSTI ID:
- 6082529
- Report Number(s):
- DOE/ER/45267-1; ON: DE87013920
- Resource Relation:
- Other Information: Portions of this document are illegible in microfiche products
- Country of Publication:
- United States
- Language:
- English
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