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

Semiconducting amorphous YBa2Cu3O6 + 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 °C). 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 tri-layer device (metal/a-YBCO/metal on Si/SiO2 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 μs 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 signal/noise ratio was obtained, resulting in detectivity D* > 109 cm*Hz1/2*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.