Abstract
With mechanical and electrical components approaching nanoscale dimensions, there is great interest in the properties of thin films. Some properties, such as structure and phase transitions, can be probed with measurements of elastic constants. We have been using Resonant Ultrasound Spectroscopy (RUS) to probe such properties for a variety of thin film materials including colossal magnetoresistance (CMR) materials, carbon nanotubes, and a magnetic semiconducting film on GaAs. By accurately characterizing the substrate, the elastic constants and damping of a deposited film can be determined from changes in the frequency and quality factor (Q) of the sample resonances. Issues of precision and accuracy in RUS measurements are important for application to thin films. If one is interested in relative changes in properties (e.g., resulting from temperature variations, phase transitions, etc.), the precision from sharp resonances (Q>5,000) is more than adequate. However, since a film may occupy only 1/1000 of the sample, attaining high accuracy is challenging, as uncertainty in sample dimensions and crystallographic orientation can have severe effects on results. Temperature data for the magnetic films mentioned and attenuation of carbon nanotube films will be presented. [Work supported by ONR.]
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