Carrier relaxation dynamics of Zn_x Cd_1-x Se/C core/shell nanocrystals with phase separation as studied by time-resolved cathodoluminescence

The optical properties and carrier relaxation kinetics of Zn_x Cd_1-x Se/C core/shell nanocrystals with compositional phase separation occurring on a ∼1-5 nm size scale were examined with time-resolved cathodoluminescence (CL) spectroscopy and imaging. The CL spectral lineshape was found to depend on the level of excitation, temperature, and the time-window during time-delayed spectroscopy. The kinetics of carrier thermalization and transfer between Cd-rich phase-separated regions and the homogenous ZnCdSe alloy were examined. We show that the rare phenomenon of compositional phase separation in II-VI nanocrystals leads to interesting and potentially useful optical properties.