Short communication Piezoelectric coupling effect on exciton–phonon scattering rates in CdSe quantum dots embedded in glass matrix K. Sellami a, * , S. Jaziri a,b a Laboratoire de Physique des Mate ´riaux, Faculte ´ des Sciences de Bizerte, 7021 Jarzouna, Tunisie, Tunisia b Laboratoire de Physique de la Matie `re Condense ´e, Faculte ´ des Sciences de Tunis, Tunisie, Tunisia Available online 8 November 2005 Abstract The scattering of excitons by acoustic phonons in nanostructures such as quantum dots generally controls relaxation process to the lowest energy states, and is a basis for understanding optical properties and coherence effects in these systems. In our work we have studied theoretically the scattering of excitons via acoustic phonons in a CdSe disk-shaped semiconductor quantum dot under an applied magnetic field. The scattering rate (SR) is calculated considering the exciton–phonon scattering by the piezoelectric coupling potential mechanism. We discuss the influence of the external applied magnetic field, and the quantum dot size on the SR. Our calculations show that the exciton – acoustic phonon scattering rate depends significantly on these parameters. D 2005 Elsevier B.V. All rights reserved. Keywords: Quantum dots; Exciton – phonon interactions; Decoherence; Piezoelectric coupling 1. Introduction Recently much attention has been paid to the physics of low-dimensional semiconductor structures. This has been simulated by the rapid progress in nanometer-scale fabrication technology. Among them, quantum dots (QDs), which are also defined as nanocrystals and microcrystallites, or nanoclusters, are of particular interest, which have a prospective application in devices [1]. The effect of quantum confinement on the electrons and holes in semiconductor QDs has been studied extensively both theoretically [2–7] and experimentally [8–10]. The most striking property of semiconductor QDs is the massive change in optical properties as a function of quantum dot size. Semiconductor nanocrystals have sustained tremendous interest in the chemistry and physics communities because of dramatic size-dependent effects [11]. As the physical dimensions of nanocrystals approach molecular dimensions, quantization effects become important and many bulk properties become size dependent. Furthermore, they offer an opportunity to investigate theoretically the inherent physics in such three dimensionally confined systems. The effects of an applied magnetic field on the physical properties of quantum dots have been studied with interest from the theoretical and experimental points of view. These studies have been performed with the proposal of understanding the fascinating novel phenomena and of fabricating devices with new functions or to improve the performance of the existing devices [12]. Exciton–phonon coupling is a crucial issue in nanocrystal physics, and this has motivated much of the previous work on the vibrational modes of quantum dots [13]. Research on exciton energy relaxation in semiconductor QDs has attracted much interest due to the critical importance of carrier- relaxation processes in the performance of novel semiconduc- tor devices based on QDs like lasers, infrared photodetectors and also for realization of basic units for quantum computing. Exciton decoherence in QDs is a key limitation in their use in implementations for quantum computing. The interaction of acoustic phonons with excitons in QDs have been found to control their decoherence at low temperatures [14–16]. There is also recent evidence that the corresponding homogeneous exciton linewidths in single QDs depend on the size of mesas used to isolate the dots [17]. To date, however, there is no 0928-4931/$ - see front matter D 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.msec.2005.10.006 * Corresponding author. Tel.: +216 98 222 854; fax: +216 72 590 566. E-mail address: karimsellami@yahoo.fr (K. Sellami). Materials Science and Engineering C 26 (2006) 555 – 558 www.elsevier.com/locate/msec