Persistent hole-burning spectroscopy in semiconductor quantum dots

Nanometer-size crystals abbreviated to semiconductor nanocrystals are known as zero-dimensional dots. 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 are sharply different from other low-dimensional quantum structures, such as quantum wells and quantum wires, because they are made of as small as 103~106 atoms. Considerable fraction of atoms face the surface or the interface of quantum dots in the surrounding materials, so that the energy of quantum dots is expected to be easily modified by the surroundings.