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 Ga-doped 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 E2high 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 1.70×1019cm−3 for x=0.005,0.01,0.02,and0.03 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.