Study of the persistent spectral hole burning memory made by semiconductor nanocrystals

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Size-confinement effect of acoustic phonon in CuCl quantum dots embedded in glass, NaCl crystal and KCl crystal was extensively studied by utilizing persistent spectral burning as size-selective spectroscopy. The observed size-confined acoustic phonon energies were compared with energies of acoustic phonon modes confined in elastic spheres.Photostimulated luminescence was observed for the first time in CuCl quantum dots embedded in NaCl crystal. The thermal quenching, spontaneous decay and excitation-fluence dependence of the photostimulated luminescence were almost the same as those of persistent spectral hole burning, indicating that the photoionization of quantum dots and the subsequent carrier capture at the traps near the quantum dots bring forth both the photostimulated luminescence and the persistent spectral hole burning. The traps are considered to be CuィイD1+ィエD1 in NaCl which acts as electron or hole traps.Accumulated photon echo from CuCl and CuBr quantum dots was extensively investigated at low temperatures up to 0.5 K. The experimental results gave us systematic knowledge on the temperature dependent homogeneous linewidth of excitons in quantum dots. At very low temperatures, the most dominant dephasing mechanism is the interaction of the quantum dots with the two-level system formed by quantum dots and their surrounding matrix.