Metal oxide nanoparticles embedded in rare-earth matrix for low temperature thermal imaging applications

We report on the synthesis and characterization of nanocomposites comprising of oxide nanoparticles (NPs) (ZnO, CaHfO 3 and SrHfO 3 ) embedded in rare-earth oxide (Eu 2 O 3 , Nd 2 O 3 ) matrices by using atomic layer deposition. The different oxide surroundings allowed highlighting the role of interface defects in the recombination processes of charge carriers in the NPs. We provide a comparative analysis of optical absorption and emission properties of the constituents: thin films, free-standing and embedded NPs, and discuss the intrinsic and extrinsic nature of the luminescent sites in different nanocomposites. The photoluminescence properties of ZnO nanocomposites are clearly distinguishable from those of free-standing NPs in terms of overall quantum efficiency as well as intensity ratios of the characteristic blue and green emission bands associated with radiative transitions involving excitons and intrinsic defects, respectively. In contrast to PL enhancement due to surface-passivating effect of the surrounding media in the case of ZnO nanocomposites, the embedment of hafnia perovskites into oxide matrices generally leads to suppressed luminescence in the visible range, thus confirming its extrinsic, surface-defect related nature.