In the Normal State

This work presents the absorptance of high-temperature superconducting YBa Cu O 2 3 7 d I 1 ( ) YBCO films, deposited on Si substrates, in the far infrared from 15 to 95 cm ( ) ( wav elength from 667 to 105 m m at temperatures of 100, 200, and 300 K i.e., in the ) normal state . Our experiments show a significant difference in the absorptance for radiation incident on the film side as compared to radiation incident on the substrate side. Interference fringes associated with the Si substrate are observ ed from the measurement and used to analyze the interaction of radiation with the film ± substrate composite at the interface. The film thickness is found to hav e a strong effect on the absorptance of the film ± substrate composite, especially for radiation incident on the substrate side.