Y-Ba-Cu-O thin films as active high power switches

Abstract

The authors have studied the active switching of nonshunted YBaCuO films. Therefore films of 10-300 nm thickness were deposited on substrates by thermal co-evaporation. Bridges, 5 mm/spl times/26 mm and 10 mm/spl times/42 mm, were structured by standard photolithography. No topcoat of gold was used to retain higher switching powers. The active switching of the DC-biased YBaCuO bridges was triggered by heat pulses or radio frequency. For the thermal trigger, a resistive thin film heater was evaporated on the back side of the substrate. The samples were biased by currents up to 20A and triggered by heat pulses (up to 500 W) at 10-70 K. A resonant circuit was used in the case of the RF-trigger. The pancake coil of this circuit was placed 2 mm above the 10 mm wide YBaCuO bridge. At 77 K the stripes were biased by currents up to 40A and triggered with RF-pulses of >1 ms duration and 3-40 W (10 MHz). Active switching was observed in both cases. In comparison to the thermal trigger, power for RF induced switching power is very low.