CdTe/CdS clusters with “core-shell” structure in colloids and films:

2019-11-09 01:42:20

thermal films spectra CdS CdTe

责任者: Schreder, B.;Schmidt, T.;Ptatschek, V.;Winkler, U.;Materny, A.;Umbach, E.;Lerch, M.;Muller, G.;Kiefer, W.;Spanhel, L. 单位: Inst. fur Phys. Chem., Wurzburg Univ., Germany 来源出处: Journal of Physical Chemistry B(J. Phys. Chem. B (USA)),2000/03/02,104(8):1677-85 摘要: A new organometallic “cold-slow” route to strongly fluorescing CdTe/CdS (core-shell) colloids and transparent films is presented. Based on the optical absorption, fluorescence, FTIR, micro-Raman, XPS, and XRD data collected on these nanostructures before and after thermal annealing, a mechanistic path of the core-shell formation and thermal break up is proposed and discussed. The processing of the CdTe/CdS nanostructures starts with 0.5 M tributylphosphine (TBP) stabilized CdS colloid in dichloromethane as a solvent. 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 chalcogen atom exchange occurs within a few seconds which produces a new CdTe “core”. The expelled sulfide reacts slowly 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 of a “core-shell”-like CdTe/CdS structure. Thermal sintering of the subsequently prepared CdTe/CdS films between 100 and 200°C completely suppresses the fluorescence and initiates CdTe cluster growth, reflecting a 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 ternary nanocrystalline CdTexS1-x phases, start forming. Above 400°C, the CdTe part of the nanostructures sublimates, yielding (111)-oriented CdTe films 关键词: cadmium compounds;colloids;fluorescence;Fourier transform spectra;II-VI semiconductors;infrared spectra;light absorption;molecular clusters;Raman spectra;semiconductor thin films;visible spectra;X-ray diffraction;X-ray photoelectron spectra;CdTe/CdS clusters;core-shell structure;II-VI semiconductor;semiconductor cluster films;cluster formation;cluster thermal breakup;organometallic cold-slow route;strongly fluorescing CdTe/CdS colloids;transparent films;optical absorption;fluorescence;FT IR spectra;micro-Raman spectra;X-ray photoelectron spectra;X-ray diffraction;nanostructures;thermal annealing;mechanistic path;core-shell formation;thermal break up;tributylphosphine;dichloromethane;yellow colloidal oil;liquid bis(trimethylsilyl)telluride;excess insoluble CdCl2 salt;chalcogen atom exchange;CdCl2 salt;CdS-formation-driven CdCl2 salt dissolution;strong green-yellow fluorescence;thermal sintering;thermal sensitivity;sintering temperature;ternary nanocrystalline CdTexS1-x phases;(111)-oriented CdTe films;sublimation;CdTe-CdS