Fujian Wang

Photoluminescence of Ge nanoparticles embedded in SiO2 glasses fabricated by a sol–gel method

Ge nanoparticles with different sizes in silica glasses were prepared by a sol–gel method using Cl3–Ge–C2H4–COOH as a Ge source. The size of the Ge nanoparticles decreases with a reduction in the content of Ge in the starting materials, and thus the optical absorption edge shifts to a higher energy. Silica gel glasses doped with Ge nanoparticles showed a strong room-temperature photoluminescence with peaks at 568, 607, 672, 722, and 775 nm. The peak position of photoluminescence spectrum scarcely depends on the Ge/Si ratio. However, the photoluminescence intensity increases sharply as the Ge/Si ratio is reduced. The photoluminescence arises from the Ge clusters of diameter of <1–2 nm with a molecular character instead of nanocrystalline Ge with the diamond structure.

Observation of intershell and hybridized energy states in InAs/GaAs quantum dots

We have investigated the evolution of exciton state filling as a function of excitation power density in InAs∕GaAs quantum dots (QDs). In addition to the emission bands of exciton recombination corresponding to the atom-like S, P, and D, etc. shells of quantum dots, it was observed that some extra states, P′ (between the S and P shells) and D′ (between the P and D shells), appear in the spectra with increasing number of excitons occupying the QDs. The emergence of these intershell excitonic levels is an experimental demonstration of strong exciton–exciton exchange interaction and coupling as well as state mixing and hybridization of a multiexciton system in quantum dots.