The Influence of Matrix on Quantum Size Confinement of Semiconductor Microcrystals Doped in Glass Thin Films Prepared by RF-Sputtering

Abstract

Various types of semiconductor microcrystal-doped glass thin films were successfully prepared by RF-sputtering. The blue shift of the absorption edge in the visible light region, caused by the quantum confinement effect, was observed in all the thin films. The amount of the blue shift was found to depend significantly not only on the types of semiconductor dopants and the microcrystal radius but also on the type of matrix. The blue shift of semiconductor microcrystals with a small exciton Bohr radius compared with the microcrystal radius, such as that of CuCl, showed an exciton confinement effect which was theoretically predicted. On the other hand, the blue shift of microcrystals with a large Bohr radius compared with the microcrystal radius, such as that of CdSe, has been expected to follow the electron–hole independent confinement model, but it was found to deviate significantly from the theoretical curve. In order to explain this deviation, we introduced factors, such as the Coulomb interaction between electron and hole, size-dependent dielectric constants of the dopants and the dielectric constant of matrix. Consequently, it was found that the matrices have a significant influence on the electron–hole independent confinement.