The design of cost-effective standards for the quality of nano-objects was currently a key issue toward their massive use for optoelectronic applications. The observation by photoluminescence of narrow excitonic and bi-excitonic emission lines in semiconductor nanowires was usually accepted as evidence for high structural quality. Here, time-resolved cathodoluminescence experiments were performed on isolated ZnO nanobelts grown by chemical vapour deposition. Narrow emission lines were observed at low temperature, together with a clear bi-exciton line. Marked alterations in both the cathodoluminescence intensity and lifetime were observed locally along the nano-object. These were attributed to non-radiative recombination at edge dislocations, closing basal-plane stacking faults, inhomogeneously distributed along the NB length. This led to the conclusion that the observation of narrow excitonic and bi-excitonic emission lines was far from sufficient to grade the quality of a nano-object.

Biexciton Emission and Crystalline Quality of ZnO Nano-Objects. Corfdir, P., Abid, M., Mouti, A., Stadelmann, P.A., Papa, E., Ansermet, J.P., Ganière, J.D., Deveaud-Plédran, B.: Nanotechnology, 2011, 22[28], 285710