Low frequency 1/f noise measurements in YBa2Cu 3O7 thin films and the implications for HTS IR detectors

The low-frequency noise voltage fluctuations were measured on c-axis textured films of YBa₂Cu₃O₇ on (100) SrTiO₃ and on mixed a- and c-axis textured thin films of YBa₂Cu₃O₇ on (100) LaAlO₃. In all cases, the power spectral density S_v(f)~V²/f^α , where V is the average DC voltage across the film. Measurements on structures of different surface areas indicates S_v (f) is inversely proportional to the film surface area. From room temperature to above the superconducting transition temperature, S_v(f)/V²~T ², while near the transition S_v(f)/V ² levels off before increasing sharply as the resistance goes to zero. The linear dependence of S_v^1/2(f ) on the bias current suggests that the noise arises from resistance fluctuations. The resistance fluctuations are interpreted as arising from two different mechanisms; a weakly temperature-dependent contribution which is dominant above the superconducting transition, and a strongly temperature-dependent contribution which dominates at the transition. The implications of these measurements on the potential utility of high-temperature superconductor IR detectors is discussed