Raman spectroscopy study of Ga-doped ZnO ceramics: an estimative of the structural disorder degree

Abstract

The structural disorder degree of Ga-doped ZnO (Zn1−𝑥Ga𝑥O, with x=0.005, 0.01, 0.02, and 0.03) ceramics was investigated by means of Raman spectroscopy analyzes at room temperature. The Raman spectra for Gadoped ZnO samples exhibits both activated Raman modes for wurtzite and spinel structures. The asymmetry parameter, line-width, and Raman shift could be fitted to the Breit-Wagner-Fano (BWF) function and the structural disorder degree in the wurtzite structure were analyzed by spatial phonon confinement model (PCM). For Raman E high 2 mode, the correlation length, L and defect concentration, N were found to be 2.72, 2.62, 2.56, and 2.41 nm and 1.19 × 1019 , 1.33 × 1019 , 1.21 × 1019, and 1.70 × 1019 cm−3 for x=0.005, 0.01, 0.02, and 0.03 samples, respectively. Additional Raman modes were detected in Ga-doped ZnO (𝑥 ≥ 0.01) spectra that could be attributed to ZnGa2𝑂4 spinel structure. This is an indication that the solubility limit of Ga in ZnO ceramics is certainly less than 1 mol at% which was not possible to be detected by means of x ray diffraction (XRD) experiments.