Site-selective laser spectroscopy and defect configurations of the Nd3+-Li+ centres in ZnO powders

Near-infrared emission in the 885–915 nm region was observed for two distinct Nd3+ centres that co-exist in hexagonal wurtzite ZnO:1 mol%Nd3+:10 mol%Li+ powders. The powder samples were prepared by sintering in air at 950 °C and the emission, attributed to the 4F3/2 → 4I9/2 transitions of Nd3+ ions, was measured in the 10–75 K temperature range. The sharp and well-resolved Nd3+ emission transitions are present in Nd3+-Li+ co-doped samples only, and the intensity increases with Li+ concentration. X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy were used for structural, morphology and compositional assessments of the samples. Atomistic modelling using GULP shows two favourable Nd3+-Li+ substitutional positions, in consistence with the experimental findings. •Structure and surface morphology of sintered ZnO:Nd3+:Li+ powders were determined.•Spectroscopy of the two Nd3+-Li+ centres present in ZnO powders is presented.•Crystal-field levels for 2G7/2;4G5/2, 4F3/2 and 4I9/2 multiplets of Nd3+ were deduced.•Proposed centre configurations were obtained from modelling calculations.