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-org anized CdSe single quantum dots on a time scale of seconds. Energy shifts o f up to 3.5 meV have been observed and can be attributed to the Stark effec t caused by fluctuating local electric fields. Most surprisingly, the energ y shift turns out to be quasi-periodic with time constants between 70 and 1 90 s. (C) 2000 American Institute of Physics. [S0003-6951(00)00614-8].