Stark Effects on Band Gap and Surface Phonons of Semiconductor Quantum Dots in Dielectric Hosts
AbstractWe have investigated quantum-confined Stark effect (QCSE) on GaAs and CdSe nanocrystals and the electric field effect on surface phonons of GaAs nanocrystals isolated in sapphire substrates. For a strongly quantum-confined system, GaAs quantum dots illustrated no exciton energy shift. When the excitons are weakly confined in CdSe, a ∼ 2 meV red-shift was observed. On the other hand, the results of the electric field effect on surface phonon are dramatic both phonon oscilator strength and freqnency. As the strength of the electric field increases, the total intensity of the surface phonon decreases. At the same time, an additional peak was also observed at 277 cm-1, which is about 3 cm-1 above the center frequency of the surface phonon mode of GaAs nanocrystals embedded in a sapphire host.
