QUANTUM SIZE EFFECT AND HRTEM OBSERVATION OF CDSE MICROCRYSTALLITES DOPED INTO SIO2-GLASS FILMS PREPARED BY RF-SPUTTERING

CdSe microcrystallite-doped SiO2 glass films were prepared by the magnetron rf-sputtering technique. High resolution transmission electron microscopy (HRTEM) observation was carried out to determine the shape and the average size of the microcrystallites. The microcrystallites had a spherical configuration and they seemed to have a wurtzite structure. The optical band gap of the films clearly exhibited the blue shift compared to bulk CdSe. The shape of optical absorption spectra also changed as the microcrystallite size decreased. A simple model of the size quantization on interband absorption in a semiconductor sphere was used to explain the change of the optical absorption spectra. Taking into account the particle size distribution, the calculated absorption spectra successfully agreed with the real absorption spectra. The observed blue shifts of optical absorption were consistent with theoretical values calculated using the mean microcrystallite radii estimated from the HRTEM observations.