Micro-photoluminescence from CdSe quantum dots

We have investigated CdSe quantum dots (QDs) by micro photoluminescence (PL ). To reduce the number of QDs to be observed, Al masks with sub-micron siz e apertures are deposited on the sample surfaces, which make it possible to repeatedly trace the same excitation position in taking temperature depend ent micro-PL spectra. Resolved sharp lines having linewidth similar to 500 mu eV are observed. The results of temperature dependence reveal that the l inewidths of QDs broaden with increasing temperature, which is considered t o come from lifetime broadening of ground state by absorption of phonons. T he linewidth broadening depends on the peak energy position of the QDs. The linewidths of lower-energy lines corresponding to larger size QDs, are mor e temperature-dependent than those of higher-energy lines corresponding to smaller ones. The different linewidth broadening can be qualitatively expla ined by taking into consideration of different energy level spacing between discrete states of the QDs. (C) 2000 Elsevier Science B.V. All rights rese rved.