Temperature dependence of photoluminescence bands inZn1−xCdxS

A. A. Klochikhin

¹

,

A. Reznitsky

²

,

B. Dal Don

³

et al.

Abstract

We have studied the temperature dependence of the photoluminescence ͑PL͒ spectra of molecular beam epitaxy grown ultrathin Zn 1Ϫx Cd x Se/ZnSe quantum wells with random and inhomogeneous Cd distributions over cation sublattice within the temperature interval 2-300 K. Depending on the Cd concentration, the PL band maximum position E max PL (T) follows either a ''normal'' or an ''anomalous'' ͑known as ''S-shaped''͒ temperature dependence. We have analyzed both dependences in detail for a model of an island ensemble which can be characterized by a single-mode distribution of the most important parameters governing the optical properties of the quantum well. We demonstrate that the anomalous behavior arises due to the strong temperature dependence of the lifetimes of a family of metastable states participating in formation of the PL band at low temperatures. The metastablility of some island states is ascribed to a complex topological structure of the islands. The mechanism of the exciton-phonon interaction responsible for the fast decrease of the lifetime of these states with the increase of temperature has the same origin as the mechanism leading to the vanishing of narrow lines in -PL. We also present results of time-resolved experiments which yield the shift of the PL band for hot excitons cooling in a cold lattice.

Temperature effects on the spectral properties of colloidal CdSe nanodots, nanorods, and tetrapods

“…5 We further conclude from our data that it does not depend significantly on the NC shape. Also ⌰ is close to the value reported for the bulk, 5,18 although the smaller value of ⌰ for NDs, which corresponds to some average phonon energy, might indicate increased coupling of the optical transition to lower energy acoustic phonons and reduced coupling to LO phonons compared to the other shapes. It could also be a consequence of the reduced volume.…”

Highly Luminescent ZnxCd1−xSe/C Core/Shell Nanocrystals: Large Scale Synthesis, Structural and Cathodoluminescence Studies

“…22 To meet technological demands for large scale synthesis, Kim et al reported subkilogram-scale one-pot synthesis of the quantum dots, which involved the use of organic surfactants and solvents. 1 In the current study, the Zn x Cd 1Ϫx Se/C nanocrystals were synthesized in sealed reactors, without the use of solvents and organic chemicals.…”

Резонансный Перенос Энергии В Плотном Массиве II-VI Квантовых Точек

“…Область (I) содержит QDs, для основного экситонного уровня, в которых нет соответствующего возбужденного уровня QDs-акцепторов и, следовательно, специфический меха-низм типа FRET 1 с быстрой релаксацией возбуждения на нижний экситонный уровень для них невозможен. Следует отметить, что граница между областью (I) и (II) спектрально приблизительно совпадает с краем подвижности (mobility edge), обсуждаемым ранее в ра-боте [9]. Квантовые точки, размеры которых попадают в область (II), могут участвовать в переносе энергии по механизму FRET 1 на возбужденные уровни (2e−1h) в QDs в области (IV).…”

“…Рассмотрение таких планар-ных массивов в модели разупорядоченных квантовых ям (QW) проблематично, поскольку при низкой темпера-туре рекомбинирующие носители должны быть хорошо локализованы. Согласование этих противоречивых мо-ментов потребовало в работе [9] включения в состав QW нано-островков различных типов -изолированных, перекрывающихся и метастабильных.…”