Spectral diffusion of the exciton transition in a single self-organized quantum dot

We report on reversible spectral shifts in the emission spectra of self-organized CdSe single quantum dots on a time scale of seconds. Energy shifts of up to 3.5 meV have been observed and can be attributed to the Stark effect caused by fluctuating local electric fields. Most surprisingly, the energy shift turns out to be quasi-periodic with time constants between 70 and 190 s. (C) 2000 American Institute of Physics. [S0003-6951(00)00614-8].