Abstract

Silicate glass films containing CdTe have been produced using an rf-magnetron sputtering technique in which a fused silica substrate is alternately exposed to each of two sputtering sources holding targets of Pyrex 7740 glass and high purity CdTe. This process represents a highly versatile fabrication technique for the production of semiconductor-doped glass materials. We report the successful deposition of CdTe-doped glass films containing as much as 30 vol % semiconductor with average crystallite sizes ranging from 46 to 158 Å. Planar-view transmission electron microscopy has shown the isolated crystals of CdTe to possess a circular morphology and a zincblende crystal structure. Room temperature optical absorption measurements exhibit a clear blue-shift in the fundamental absorption edge as the average semiconductor crystal size is reduced, indicative of a substantial quantum confinement effect. Analysis of the behavior shows it to be governed by an effective mass term which is intermediate between the translational and reduced masses of the bulk CdTe Wannier exciton.¹ Failure of the data to exhibit a reduced mass behavior in the absorption edge shift with crystal size suggests that a substantial Coulomb interaction between the photoexcited electron and hole still exists even at crystal sizes 0.3 times the Bohr diameter of the bulk CdTe exciton.

© 1990 Optical Society of America