UNKNOWN GA2O3 STRUCTURAL PHASE AND RELATED CHARACTERISTICS AS ACTIVE LAYERS FOR O2 SENSORS

The structural characterization of the Ga2O3 thin films, deposited onto Al2O3 substratum by reactive radio frequency magnetron sputtering, was performed with a theta:2theta powder diffractometer in the Bragg-Brentano geometry. With reference to the pattern of the substratum alone, spectra of the films show additional broad lines indicative of very small coherent domains of diffraction. However, it is not possible to match the observed lines with any of the Ga2O3 phases known in the literature (alpha, beta, gamma, delta and epsilon). Furthermore, there is a texture of this unindexed phase which develops as a function of the deposition temperature. The electrical characteristics, performed at ambient pressure in a flux of an 02/N2 mixture for various operating temperatures, show that film conductivity depends on the 02 partial pressure in the range 1%-21% according to an empirical power law sigma almost-equal-to kp(O2)n with n almost-equal-to 1/4.