| Abstract
| - A new organometallic “cold−slow” route to strongly fluorescing CdTe/CdS (core−shell) colloids andtransparent films is presented. Based on the optical absorption, fluorescence, FTIR, micro-Raman, XPS, andXRD data collected on these nanostructures before and after thermal annealing, a mechanistic path of thecore−shell formation and thermal break up is proposed and discussed. The processing of the CdTe/CdSnanostructures starts with 0.5 M tributylphosphine (TBP) stabilized CdS colloid in dichloromethane as asolvent. This yellow colloidal oil composed of 3−4 nm CdS clusters is reacted with liquid Bis(trimethylsilyl)-telluride (TMS2Te) in the presence of excess insoluble CdCl2 salt. During this reaction, a rapid chalcogenatom exchange occurs within a few seconds which produces a new CdTe “core”. The expelled sulfide reactsslowly with the CdCl2 salt to form new CdS clusters after several hours. Furthermore, this “CdS-formation-driven CdCl2 salt dissolution” activates a strong green-yellow fluorescence indicating a possible evolution ofa “core−shell”-like CdTe/CdS structure. Thermal sintering of the subsequently prepared CdTe/CdS filmsbetween 100 and 200 °C completely suppresses the fluorescence and initiates CdTe cluster growth, reflectinga high thermal sensitivity of the “core−shell” interfaces. By further raising the sintering temperature to 300−400 °C, the TBP ligands are released and, consequently, bare CdS- and CdTe nanocrystals, as well as ternarynanocrystalline CdTexS1-x phases, start forming. Above 400 °C, the CdTe part of the nanostructures sublimates,yielding (111)-oriented CdTe films.
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