Preparation of CdS-Doped Glasses by the Sol-Gel Method,

CdS-doped Sio2 glasses have been prepared through the sol-gel process. A methanol solution of cadmium nitrate and thiourea in a molar ratio of 12 was added to the Sio2 sol prepared from silicon tetraethoxide. The mixed solution was left for gelation at 50 deg C and thereby complexes of cadmium nitrate with thiourea were confined in the gel. The gel obtained was then heat-treated at 350 OC in air for the decomposition of the complexes to CdS, the elimination of residual organics, and the densification. The above process produced the transparent SiO2 glasses doped with CdS microcrystallites up to CdSi 0.05. The optical absorption edge of the CdS-doped glasses moved to longer wavelengths from that of non-doped SiO2 glasses with increasing CdSi ratio. The size of CdS microcrystallites in the glasses was further controllable with the additional beat-treatment at around 400 deg C in a 10 H2S90 Ar stream. For these CdS microcrystallite-doped glasses, the peak of photoluminescence was shifted to shorter wavelengths relative to the absorption edge of CdS crystal, in agreement with the blue shift of the optical absorption edge these shifts were indicative of the quantum size effects.