Fluctuation‐induced broadening of exciton reflection spectra in A^II B^VI solid solutions

Abstract

The validity of different fluctuation models for an explanation of the concentration dependence of exciton reflection line broadening in AIIBvI solid solutions is discussed on the example of Zn,Cdl-,S, Zn,Cdl-,Te, and ZnS,Sel-, systems. It is shown that the concentration dependence can be explained with the help of models describing the interaction of excitons with largescale fluctuations of solid solution composition. At small concentrations of one component of solid solution the model of localization of the exciton as a whole by a fluctuation potential can be used. I n the range of comparable concentrations of components there can be applied models accounting for the interaction of only the hole, or only the electron with the fluctuation potential, depending on whether there is anion or cation substitution.Am Beispiel der Zn,Cdl -,S-, Zn,Cdl -,Tc-und ZnS,Sel -,-Systeme wird die Giiltigkeit verschiedener Fluktuationsmodelle zur Erklarung der Konzentrationsabhangigkeit der Verbreiterung der Exzitonenreflexionslinien in AIIBVI-Mischkristallen diskutiert. Es wird gezeigt, daI3 die Konzentrationsabhangigkeit mit Modcllen erklart werden kann, die die Wechselwirkung von Exzitonen mit makroskopischen Fluktuationen der Mischkristallzusammensetzung beschreiben. Bei geringen Konzentrationen der einen Komponente des Mischkristalls kann das Model1 der Gesamtlokalisierung des Exzitons durch das Fluktuationspotential benutzt werden. Im Bereich vergleichbarer Konzentrationen der Komponenten konnen Modelle benutzt werden, die die Wechselwirkung des Loches diein, oder des Elektrons allein mit dem Fluktuationspotential in Abhangigkeit davon beschrciben, ob das Anion oder Kation substituiert ist.

Recombination Dynamics of CdTe/CdS Core−Shell Nanocrystals

“…Strain might be negligible as reported in refs and and explained by an incomplete CdS shell causing a release of the strain. In concern of the band alignments, the current literature provides different data sets, both from theory and experiments. − A simple estimate for a possible radial distribution of the electron and hole wave functions in a CdTe/CdS core−shell NC (CdS shell thickness 0.6 nm, CdTe core radius 3.5 nm) is illustrated with the sketch in Figure . For the shown calculation, strain has been neglected and the band parameter of ref are used.…”

“…In concern of the band alignments, the current literature provides different data sets, both from theory and experiments. − A simple estimate for a possible radial distribution of the electron and hole wave functions in a CdTe/CdS core−shell NC (CdS shell thickness 0.6 nm, CdTe core radius 3.5 nm) is illustrated with the sketch in Figure . For the shown calculation, strain has been neglected and the band parameter of ref are used. The most important result for even this very simplified picture is that under certain conditions a CdTe/CdS core-shell NC can develop an indirect-type exciton, i.e., the hole is then predominantly confined to the CdTe core, while the electron is predominantly localized in the CdS shell.…”

Preparation of Highly Luminescent CdTe/CdS Core/Shell Quantum Dots

“…Concerning the band alignments of the bulk interface between CdTe/CdS, the current literature provides different data sets, both from theory and experiments. [42][43][44][45] In some data sets, [42,43] the CdTe/CdS interface belongs to a type-I interface (i.e. the bandgap of the core is enclosed by the bandgap of the shell material, and thus, the conduction band of the shell is of higher energy than that of the core, while the valence band of the shell is of lower energy than that of core) whereas in other data sets, [44,45] it belongs to a type-II one [i.e.…”

Direct observation of the effect of isotope-induced disorder on the exciton binding energy in LiHxD1−xmixed crystals

“…The measure of broadening was the halfwidth of the line measured in the standard way (see e.g. [33]) as the distance between the maximum and the minimum in the dispersion gap of the reflection spectrum, taken at halfheight. The concentration dependence of the half-width ( E R ) of the long-wave band in the exciton reflection spectrum at 2 K is shown in figure 5.…”