Enhanced electron spin rotation in CdS quantum dots

We studied the spin rotation of electrons in CdS quantum dots (QDs) and CdS QDs with charge acceptors by means of time-resolved Faraday rotation (TRFR) at room temperature. The electron spin rotation had an oscillatory component in the TRFR signal and the oscillation frequency proportional to the magnetic field gave a g-factor of the electrons of 1.965 ± 0.006. The non-oscillatory component came from the population of excitons and showed an additional decay in CdS QDs with hole acceptors. The electron spin rotation signal was largely enhanced and lasted for a spin coherence time of T2* = 450 ps in CdS QDs tethered to TiO2 electron acceptors, where the spin initialization was triggered by the positive trion transition. These results give clear evidence that the electron spin rotation signal in QDs can be enhanced by transient p-doping.