Sol−Gel Preparation and Photoluminescence of Size Controlled Germanium Nanoparticles Embedded in a SiO2 Matrix

Abstract

Germanium nanoparticles of different sizes in silica glasses were prepared via a sol−gel method, using Cl3−Ge−C2H4−COOH and Si(OC2H5)4 as the starting materials. The size of the germanium nanoparticles decreases as the heat-treatment time in a H2 gas atmosphere increases, and, thus, the optical absorption edge shifts to higher energies. Silica gel glasses doped with germanium nanoparticles showed a strong room-temperature photoluminescence, with peaks at 570, 605, 676, and 730 nm. The peak position of the photoluminescence spectrum scarcely depends on the heat-treatment time. However, the photoluminescence intensity increases sharply as the heat-treatment time is reduced. The photoluminescence arises from germanium clusters <1−2 nm in diameter with a molecular character, instead of from nanocrystalline germanium with the diamond structure.