Near band edge and defect emissions in wurtzite Cd0.025Mg0.10Zn0.875O nanocrystals

Abstract

We report on near band edge and local defects emissions in Cd0·025Mg0·10Zn0·875O (CdMgZnO) nanoparticles (NPs) as a function of temperature, where a strong temperature-dependent near-infrared emission around 1.7 eV (~730 nm) has been observed. The NPs were synthesized by a modified sol-gel method and were annealed at 750 °C after growing. The crystallographic parameters have been determined by 2-dimensional synchrotron x-ray diffraction (XRD) and conventional XRD analysis, confirming their growth within the wurtzite phase with a preferred orientation along the (101) plane and an apparent crystallite size of 52.72 ± 0.18 nm. This apparent crystallite size is consistent with the nearly hexagonal particle shape (50.15 ± 0.38 nm) obtained from high resolution transmission electron microscopy. Valence Electron Energy Loss Spectroscopy (VEELS) has been conducted to gain information on the band structure and interband transitions. From the VEELS spectrum, an onset bandgap of 3.2 ± 0.3 eV was attributed to Cd/Mg co-doped ZnO. The temperature-dependent photoluminescence properties and enhancement of the optically active local defects emission have been analyzed.