Cadmium oxide, indium oxide and cadmium indate thin films obtained by the sol–gel technique

Thin films of the mixed CdO-In2O3 system were deposited on glass substrates by the sol–gel technique. The precursor solution was obtained starting from the mixture of two precursor solutions of CdO and In2O3 prepared separately at room temperature. The In atomic concentration percentages (X) in the precursor solution with respect to Cd (1 − X), were: 0, 16, 33, 50, 67, 84 and 100. The films were sintered at two different sintering temperatures (Ts) 450 and 550 °C, and after that, annealed in a 96:4 N2/H2 gas mixture at 350 °C. X-ray diffraction patterns showed three types of films, excluding those constituted only of CdO and In2O3 crystals: i) For X ≤ 50 at.%, the films were constituted of CdO + CdIn2O4 crystals, ii) For X = 67 at.%, the films were only formed of CdIn2O4 crystals and iii) For X = 84 at.% the films were constituted of In2O3 + CdIn2O4 crystals. In all films in the 0 < X < 100 range, the formation CdIn2O4 crystals of this material was prioritized with respect to the formation of CdO and In2O3 materials. All films showed high optical transmission and an increase of the direct band gap value from 2.4 (for CdO) to 3.6 eV (for In2O3), as the X value increases. The resistivity values obtained were in the interval of 8 × 10− 4 Ω cm to 106 Ω cm. The CdIn2O4 films had a resistivity value of 8 × 10− 3 Ω cm and a band gap value of 3.3 eV.