High frequency properties of YBCO thin films diagnosed by time-domain terahertz spectroscopy

We measure the complex conductivity sigma and the surface impedance of c-ax is oriented 100-nm-thick YBa2Cu3O7-delta (YBCO) thin films deposited on (10 0)MgO substrates (0.5 mm thick) at frequencies between 0.5 and 1.5 THz, usi ng time-domain terahertz spectroscopy. The real part of sigma decreases wit h increasing frequency and its value is about 2.4 x 10(5) (S/m) at 1 THz. T he imaginary part of sigma increases with increasing frequency and then mon otonically decreases at around 750 GHz. The real part of sigma of YBCO thin films increased with decreasing temperature and decreases below 60 K. The imaginary part of sigma increased with decreasing temperature and the trend is enhanced below 60 K. The surface resistance of YBCO thin film is of the order of 10(-1) Omega and increases with increasing temperature. The surfa ce reactance of YBCO thin film is independent of the frequency in this THz region, and its value is less than 10(-3) Omega at 40 K. (C) 2001 Elsevier Science B.V. All rights reserved.