Synthesis and Characterization of ColloidalCdTe Nano crystals

摘要

We synthesized CdTe nano crystals (NCs) in uniform sizes and in good quality as characterized byphotoluminescence (PL), AFM, and X-ray diffraction. In this growth procedure, CdTe nano-crystalband gap is strongly dependent on the growth time and not on the injection temperature or organicligand concentration. This is very attractive because of nano-crystal size can be easily controlled by thegrowth time only and is very attractive for large scale synthesis. The color of the solution changes fromgreenish yellow to light orange then to deep orange and finally grayish black to black over a period ofone hour. This is a clear indication of the gradual growth of different size (and different band gap) ofCdTe nano-crystals as a function of the growth time. In other words, the size of the nano-crystal and itsband gap can be controlled by adjusting the growth time after injection of the tellurium. The preparedCdTe NCs were characterized by absorption spectra, photoluminescence (PL), AFM and X-raydiffraction. Measured absorption maxima are at 521, 560, 600 and 603 nm corresponding to band gapsof 2.38, 2.21,2,07 and 2.04 eV respectively for growth times of 15, 30, 45 and 60 minutes. From theabsorption data nano-crystal growth size saturates out after 45 minutes. AFM scanning of thesematerials indicate that the size of these particles is between 4 - 10 nm in diameter for growth time of 45minutes. XD-ray diffraction indicates that these nano crystals are of cubic zinc blende phase. Thispaper will present growth and characterization data on CdTe nano crystals for various growth times.