Infrared Refractive Index of Thin YBa2Cu307 Superconducting Films

[+] Author and Article Information
Z. M. Zhang, B. I. Choi, T. A. Le, M. I. Flik

Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139

M. P. Siegal, J. M. Phillips

AT&T Bell Laboratories, Murray Hill, NJ 07974

J. Heat Transfer 114(3), 644-652 (Aug 01, 1992) (9 pages) doi:10.1115/1.2911329 History: Received July 01, 1991; Revised January 01, 1992; Online May 23, 2008


This work investigates whether thin-film optics with a constant refractive index can be applied to high-Tc superconducting thin films. The reflectance and transmittance of YBa2 Cu3 O7 films on LaAlO3 substrates are measured using a Fourier-transform infrared spectrometer at wavelengths from 1 to 100 μm at room temperature. The reflectance of these superconducting films at 10 K in the wavelength region from 2.5 to 25 μm is measured using a cryogenic reflectance accessory. The film thickness varies from 10 to 200 nm. By modeling the frequency-dependent complex conductivity in the normal and superconducting states and applying electromagnetic-wave theory, the complex refractive index of YBa2 Cu3 O7 films is obtained with a fitting technique. It is found that a thickness-independent refractive index can be applied even to a 25 nm film, and average values of the spectral refractive index for film thicknesses between 25 and 200 nm are recommended for engineering applications.

Copyright © 1992 by The American Society of Mechanical Engineers
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