  Using a combination of continuous wave and time-resolved spectroscopy, we
study the effects of interfacial conditions on the radiative lifetimes and
photoluminescence intensities of colloidal CdTe/CdS quantum dots (QDs) embedded
in a three-dimensional nanostructured silicon (NSi) matrix. The NSi matrix was
thermally oxidized under different conditions to change the interfacial oxide
thickness. QDs embedded in a NSi matrix with ~0.5 nm of interfacial oxide
exhibited reduced photoluminescence intensity and nearly five times shorter
radiative lifetimes (~16 ns) compared to QDs immobilized within completely
oxidized, nanostructured silica (NSiO2) frameworks (~78 ns). Optical absorption
by the sub-nm oxidized NSi matrix partially lowers QD emission intensities
while non-radiative carrier recombination and phonon assisted transitions
influenced by defect sites within the oxide and NSi are believed to be the
primary factors limiting the QD exciton lifetimes in the heterostructures.
