Cd-doped ZnO nanoparticles: An experimental and first-principles DFT studies

The sol–gel method was used for Zn_1−xCd_xO nanoparticles with various concentrations (x = 0.01, 0.02, 0.03, 0.04, 0.05, 0.1, 0.2, and 0.3). This work aimed to compare the estimated stress, strain, and crystallite size of Zn_1−xCd_xO nanoparticles using the Williamson–Hall method with the help of the least-squares method for various Cd concentrations with the Debye–Scherrer formula whose level of accuracy was found to be sufficiently comprehensive for this study. The linear regression model was also analyzed statistically and it was shown that our model was very good for 5% of Cd, where the p-values were 0.0018, 0.0202, and 0.0061 for the UDM, USDM, and UDEDM, respectively. According to the density functional theory (DFT) calculations within GGA and GGA+U based on experimental structural data deducing that high band-gap tuned via CBM instead of VB states and increasing Cd amount let band-gap lowered. A redshift was observed according to absorption spectra of the visible region which is more obvious by increasing Cd amount. In addition, one can conclude that band-gap is decreased when crystalline size is reduced through increasing guest concentration. The X-ray diffraction method was used for the structural analysis of all nanoparticles. Up to x < 0.02, Cd replaced Zn and yielded ZnO single phase; while for x ≥ 0.02, two phases (ZnO and CdO) emerged. To determine surface morphology, particle size, and shapes of the nanoparticles, the SEM technique was employed and the EDS was utilized for the elemental compositions of the nanoparticles. It was observed that the ZnCdO nanoparticles had a hexagonal wurtzite structure. Moreover, the crystallite size, microstrain, and stress values became maximum for the Zn_0.95Cd_0.05O sample.