Noise, bolometric performance and aging of thin high Tc superconducting films on silicon membranes

Abstract An experimental study regarding the noise properties of thin superconducting films of composition GdBa 2 Cu 3 O 7− x on silicon membranes is reported. Noise measurements that include a determination of the Hooge parameter α H as a function of resistance have been carried out at temperatures 78 K T f f f is attributed primarily to flicker noise. This also holds for temperatures above and below the midpoint of the superconducting transition. At high frequency, resistance or Johnson noise is most pronounced. Microcrack formation, induced by thermal cycling, accounts for characteristic noise spikes at temperatures below the transition, primarily generated through electro-magnetic interference with environmental background perturbations. Electrical noise at T >200 K most likely is assigned to an increasing interaction and charge fluctuations between the metallic overlayer and the semiconducting silicon membrane material beneath. The magnetron sputtered epitaxial GdBa 2 Cu 3 O 7− x films consistently revealed Hooge parameters α H T c -films on silicon substrates. Based on these data, the achievable bolometric detectivity D * of superconducting transition edge microbolometers has been calculated. The model calculations fully confirm recent experimental data obtained for various degrees of thermal isolation.