Controlling the growth of ultrasmall CdTe quantum dots and the diffusion of cadmium vacancies: Thermal annealing

Ultrasmall CdTe quantum dots (USQDs) were successfully grown in a silicate glass matrix by fusion and after thermal annealing. Growth control of USQDs was investigated by optical absorption (OA), atomic force microscopy (AFM), transmission electron microscopy (TEM) and photoluminescence (PL). A redshift of OA band with increasing thermal annealing time provided evidence of CdTe USQD growth. This increase of average size of the CdTe USQDs was determined by OA spectra, AFM and TEM images. In addition, PL spectra showed that longer thermal annealing times decreased deep levels luminescent intensity from cadmium vacancies (VCd) in the CdTe USQDs. This phenomenon occurred because VCd diffused to the USQDs' surface with longer thermal annealing times. Therefore, we control the growth of CdTe USQDs as well as the luminescent intensity from surface defects and VCd as a function of thermal annealing time.