Low temperature amorphous growth of semiconducting Y-Ba-Cu-O oxide thin films in view of infrared bolometric detection
Abstract
YBa(2)Cu(3)O(6) + x (YBCO) compounds are well known to exhibit superconducting properties for x > 0.5 and semiconducting properties for lower oxygen content. In this work, YBCO oxidethinfilms of the semiconducting phase were deposited by direct-current (DC) hollow cathode sputtering at lowtemperature in the 100 to 400 °C range. Structural, electrical and optical properties are investigated and discussed in relation with the envisaged bolometricdetection application. Structural characterizations show that films are amorphous, with a granular structure of low roughness (3 nm rms). DC electrical measurements both reveal that films grown at 100 °C exhibit a high temperature coefficient of resistance (TCR ~ − 3% K− 1 to − 4% K− 1 at 300 K) and an optimized low resistivity value of 345 Ω*cm at 300 K. Consequently, this material is suitable for uncooled infrared bolometer application and can be deposited at 100 °C in a complementary metal-oxide-semiconductor compatible technological process for co-integration with readout circuitry. In addition, optical measurements performed in the 0.5 to 2.2 μm wavelength range on films grown at 100 °C highlight optical conductivity values in line with those expected for YBCO material, as well as the presence of two optical band gaps that are discussed with respect to the film nanostructure.