Transverse spin relaxation times in an ensemble of electrochemically self assembled CdS quantum dots

Using electron spin resonance (ESR) experiments, we have measured the ensemble transverse relaxation time (T2^*) of spins in arrays of cadmium sulfide (CdS) quantum dots self assembled by selective electrodeposition of the compound in 10-nm diameter pores of an anodic alumina film. The T2^*time is very short - a few nanoseconds at low temperatures - and it increases with increasing temperature in the range 3.7 - 20 K. The major source of dephasing contributing to the relaxation rate is believed to be spatially varying hyperfine interactions with nuclear spins. The temperature dependence is consistent with the nuclear magnetic field being increasingly depolarized at higher temperatures leading to a progressively weaker hyperfine interaction. The effective Landé g-factor in the quantum dots was found to be ∼2.