Two Mechanisms of Fluorescence Intermittency in Single Core/Shell Quantum Dot

The temporal evolution of fluorescence intensity of a single blinking CdSe/ZnS nanocrystal (quantum dot, QD) has been measured with continuous wave (CW) laser excitation at room temperature. Tracks exhibit ON-/OFF-fluctuations with large amplitude and intensity fluctuations with small amplitude in the ON-interval. The QD photon distribution function was obtained by statistical analysis of this fluorescence track. The experimental QD photon distribution function was compared with an analogous function calculated with the Monte Carlo technique on the basis of two mechanisms for intermittency which take into account both ionization/neutralization processes in the QD core, as well as diffusive fluctuations of atoms on the core shell interface. We show that a combined model based on these two mechanisms sufficiently describes the shape of the measured photon distribution function.