title: Time resolved and temperature dependence of the radiative properties of thiol-capped CdS nanoparticles films.
abstract: In this work, we present the temperature-dependence and time-resolved photoluminescence (PL) of CdS nanoparticles capped independently with three different ligands thiophenol, thioglycerol, and l-cysteine over a broad temperature range from 10 to 300 K. The respective nanoparticles sizes in the three systems studied in this work are 1.5, 4, and 2 nm as determined from X-ray diffraction (XRD). From the analysis of AFM images, it was found that the lateral particle sizes of capped CdS nanoparticles are greater than those deduced from XRD or optical absorption measurements. The aim of this study is the investigation of the impact of the organic ligands on the radiative recombination dynamics in organically capped CdS nanoparticles. From the PL study and based on the temperature-dependence and time-resolved emission spectroscopy, we conclude that the emission of CdS QDs film originates from recombination of the delocalized carriers in the internal core states with a small contribution of the localized carriers at the interface. The PL decay reveals a biexponential behavior for the entire three samples at all temperatures. One of the two exponential components decays rapidly with a timeτ1in the range 0.5-0.8 ns, whereas the other decays much more slowly, with a timeτ2in the range 1-3 ns. The weak activation energy (32-37 meV) deduced from the temperature dependence of the PL intensity suggests the involvement of shallow traps. The analysis of the experimental results reveals a relatively narrow size distribution, an efficient surface passivation, and a satisfactory thermal stability of CdS nanocrystals.
authors.affiliation: Laboratoire des Interfaces et des Matériaux avancés (LIMA), Faculté des Sciences de Monastir, Université Monastir, Avenue de l'environnement, 5019 Monastir, Tunisia.
authors.forename: N
authors.initials: N
authors.lastname: Bel Haj Mohamed
authors.affiliation: Laboratoire des Interfaces et des Matériaux avancés (LIMA), Faculté des Sciences de Monastir, Université Monastir, Avenue de l'environnement, 5019 Monastir, Tunisia.
authors.forename: M
authors.initials: M
authors.lastname: Haouari
authors.affiliation: Laboratoire de Micro-Optoélectronique et Nanostructures (LMON), Faculté des Sciences de Monastir, Université Monastir, Avenue de l'environnement, 5019 Monastir, Tunisia.
authors.forename: Z
authors.initials: Z
authors.lastname: Zaaboub
authors.affiliation: Laboratoire de Micro-Optoélectronique et Nanostructures (LMON), Faculté des Sciences de Monastir, Université Monastir, Avenue de l'environnement, 5019 Monastir, Tunisia.
authors.forename: M
authors.initials: M
authors.lastname: Nafoutti
authors.affiliation: Laboratoire de Micro-Optoélectronique et Nanostructures (LMON), Faculté des Sciences de Monastir, Université Monastir, Avenue de l'environnement, 5019 Monastir, Tunisia.
authors.forename: F
authors.initials: F
authors.lastname: Hassen
authors.affiliation: Laboratoire de Micro-Optoélectronique et Nanostructures (LMON), Faculté des Sciences de Monastir, Université Monastir, Avenue de l'environnement, 5019 Monastir, Tunisia.
authors.forename: H
authors.initials: H
authors.lastname: Maaref
authors.affiliation: Laboratoire des Interfaces et des Matériaux avancés (LIMA), Faculté des Sciences de Monastir, Université Monastir, Avenue de l'environnement, 5019 Monastir, Tunisia.
authors.forename: H
authors.initials: H
authors.lastname: Ben Ouada
keywords: CdS nanoparticles; Nanostructure; Optics; Organic ligands; Radiative recombination; Surface states; Temperature; Time-correlated single photon counting