Amorphous Y-Ba-Cu-O oxide thin films: Structural, electrical and dielectric properties correlated with uncooled infrared pyroelectric detection performances

摘要

Semiconducting amorphous YBa_2Cu_3O_(6+x) (x ＜ 0.5, a-YBCO) films of 140 nm to 880 nm thickness were deposited by direct current (DC) hollow cathode sputtering at low temperature (≈150 ℃). The film microstructure was typically granular. Dielectric measurements from 100 Hz to 2 MHz were performed in the 300-430 K range to characterize the charge transport behavior. Alternating current conductivity values were extracted and the frequency dependence revealed a relaxation mechanism, which strength increased with temperature according to an Arrhenius law. The activation energy values matched those deduced from the temperature dependence of DC conductivity. The observed relaxation was in line with the hopping charge transport mechanism. A trilayer device (metal/a-YBCO/metal on Si/SiO_2 substrate) was processed using standard lithography. DC electrical tests confirmed the Schottky nature of the metal/a-YBCO contact The optical response at 850 nm wavelength exhibited a high-pass behavior (maximum response at 100 kHz/1.6 us time constant). The device current noise spectrum - of "blue" character - was investigated and discussed, in line with the frequency behavior of a-YBCO conductivity. A large signaloise ratio was obtained, resulting in detectivity D~* ＞ 10~9 cm·Hz~(1/2)·W~(-1) in the 7 kHz to 100 kHz frequency range. These results are testifying for the very good performance of a-YBCO as room temperature pyroelectric sensing material.