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Information × Registration Number 0206U009063, 0105U008995 , R & D reports Title ELECTRON SPECTRA AND RADIATIVE RECOMBINATION MECHANISMS IN COLLOIDAL SYSTEMS WITH SEMICONDUCTOR NANOCRYSTALS popup.stage_title Head Valakh Mikhail Yakovlevitch, Доктор фізико-математичних наук Registration Date 21-12-2006 Organization V.Laskaryov Institute of Semiconductor Physics NAS of Ukraine popup.description2 Variations in absorption and emission spectra induced by thermal treatment are reported for aqueous solutions of thiol-stabilized CdTe nanocrystals with different Cd2+:Te2- molar ratios. Heating of colloids was shown to result in appearance of two photoluminescence lines that were assigned to two ensembles of nanocrystals with different mean diameters. Effect of heat treatment on size distribution, absorption and emission properties, and stability of nanocrystals with various Cd2+:Te2- molar ratios is discussed in the terms of different coverage of the nanocrystal surfaces with tellurium atoms (ions?) and with thioglycolic acid molecules. Room temperature PL spectra of the NCs consisted of an intensive line due to near-edge recombination and a weak low-energy tail connected with the recombination via deep traps. Depending on the synthesis parameters, the maximum position could vary during the solution storage at room temperature in dark. For some samples, freezing of the solution containing NCs resulted in a red-shift of the PL maximum. After that the energy position of the PL line followed the temperature dependence of the CdTe band gap. We suggest that such an unusual behavior is caused by changes in the passivation conditions at solution freezing. Low-temperature PL spectra measured at different excitation energies clearly showed that the main PL line consists of several components. To explain the observed features, a model which accounts for both the near-edge recombination and the recombination via the states created by the cadmium - thiol and tellurium - OH complexes at the surface is proposed.5635 Product Description popup.authors popup.nrat_date 2020-04-02 Close