Persistent Spectral Hole Burning in Semiconductor Quantum Dots

Abstract

Nanometer-size semiconductor crystals or semiconductor nanocrystals are known as zero-dimensional quantum dots [1–6]. Their optical properties have been characterized by the quantum confinement effect, and the lowest excited states show blue shifts depending on their size. Quantum dots act independently, when they are independently embedded in host materials for the isolation of each dot. Otherwise, the quantum confinement effect is weakened or modified. Quantum dots are sharply different from other low-dimensional quantum structures such as quantum wells and quantum wires because quantum dots are made of as few as 103–106 atoms. A considerable fraction of atoms face the surface or the interface of quantum dots in the surrounding materials. Therefore, it is quite natural to consider that the electronic states of quantum dots should not be treated by themselves, but should be treated together with the real surfaces or interfaces and the surrounding materials. This consideration is correct, in general. However, it is not clearly noted that the electronic states of quantum dots are seriously affected by the surrounding host.