Thickness-Dependent Radiative Properties of Y-Ba-Cu-O Thin Films

[+] Author and Article Information
P. E. Phelan, G. Chen, C. L. Tien

Department of Mechanical Engineering, University of California, Berkeley, CA 94720

J. Heat Transfer 114(1), 227-233 (Feb 01, 1992) (7 pages) doi:10.1115/1.2911251 History: Received November 30, 1990; Revised July 01, 1991; Online May 23, 2008


Some applications of high-temperature superconductors where their radiative behavior is important, such as bolometers, optically triggered switches and gates, and space-cooled electronics, require the superconductor to be in the form of a very thin film whose radiative properties cannot be adequately represented by a semi-infinite analysis. Two properties of particular importance are the film absorptance and the combined film/substrate absorptance, which are crucial to the operation of many devices. Here, calculations of the spectral, normal-incidence absorptance of superconducting-state Y-Ba-Cu-O films on MgO substrates suggest that a decrease in the film thickness often leads to an increase in both the film and the film/substrate absorptance. Furthermore, both can exhibit a maximum at some optimal value of film thickness. Room-temperature experiments verify the qualitative features of the spectral film/substrate absorptance, indicating the assumption that the film is a smooth, continuous slab with a refractive index equal to that of well-aligned bulk Y-Ba-Cu-O is valid, at least in the normal state and for films as thin as 35 nm.

Copyright © 1992 by The American Society of Mechanical Engineers
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