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

Abstract

Thin films of the mixed CdO-In 2O 3 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 In 2O 3 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 N 2/H 2 gas mixture at 350 °C. X-ray diffraction patterns showed three types of films, excluding those constituted only of CdO and In 2O 3 crystals: i) For X ≤ 50 at.%, the films were constituted of CdO + CdIn 2O 4 crystals, ii) For X = 67 at.%, the films were only formed of CdIn 2O 4 crystals and iii) For X = 84 at.% the films were constituted of In 2O 3 + CdIn 2O 4 crystals. In all films in the 0 < X < 100 range, the formation CdIn 2O 4 crystals of this material was prioritized with respect to the formation of CdO and In 2O 3 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 In 2O 3), as the X value increases. The resistivity values obtained were in the interval of 8 × 10 − 4 Ω cm to 10 6 Ω cm. The CdIn 2O 4 films had a resistivity value of 8 × 10 − 3 Ω cm and a band gap value of 3.3 eV.