Optimizing the optical absorption coefficient of a core/shell quantum dot near a bimetallic nanoparticle
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THE EUROPEAN PHYSICAL JOURNAL D
Regular Article
Optimizing the optical absorption coefficient of a core/shell quantum dot near a bimetallic nanoparticle Naser Zamani1 , Alireza Keshavarz2,a , and Hamid Nadgaran1 1 2
Department of Physics, College of Science, Shiraz University, Shiraz 71454, Iran Department of Physics, Shiraz University of Technology, Shiraz 313-71555, Iran Received 22 December 2019 / Received in final form 30 March 2020 Published online 16 June 2020 c EDP Sciences / Societ`
a Italiana di Fisica / Springer-Verlag GmbH Germany, part of Springer Nature, 2020 Abstract. In this paper, the optical absorption coefficient of a core/shell quantum dot near a bimetallic nanoparticle is maximized. For this purpose, the Schr¨ odinger equation is solved by numerical methods to obtain the exciton energy. Then by using the density matrix method, the absorption coefficient of the hybrid system is calculated. Afterward, by applying the particle swarm optimization (PSO) algorithm, the absorption coefficient of the system is optimized. After obtaining the optimum structure, the refractive index changes, the electric field enhancement factor for the core/shell quantum dot, and the near-field enhancement for the bimetallic nanoparticle are examined. Additionally, the optical absorption coefficient is calculated for different radii of the bimetallic nanoparticle and for different distances between the surfaces of the core/shell quantum dot and the bimetallic nanoparticle. Then it is compared with that of the optimum structure. The results show that the absorption coefficient of the optimum structure is 3.41 × 106 m−1 and its electric field enhancement increases up to 9 times.
1 Introduction Due to their optical properties and their applications in solar cells, light emitting diodes, bioimaging, and other new optoelectronic systems, semiconductors have received significant attention. This interest and the demand for using semiconductors have led to the development of low-dimensional semiconductors whose optical properties depend on the material and their geometrical structures such as the size and shape [1,2]. Because the lightmatter interaction in low dimensional semiconductors is weak, their use in optoelectronic applications is limited. In this regard, researchers have proposed a number of methods to improve the light-matter interaction which in turn increases the optical properties of low dimensional semiconductors. These methods include the synthesis of a hetero-nanostructure [3,4], metal-doped semiconductor nanostructures [5], and a semiconductor quantum dot near metal a nanoparticle for hybrid nanostructures [6–10]. Therefore, the interest in the development of nanoscale optoelectronic devices by combining various nanomaterials in a hybrid nanostructure leading to complementary and optimal optical properties has increased. A significant number of researches on nanocomposites has been devoted to the study of exciton-plasmon interactions in semiconductor-metal nanostructures [11–14]. a
e-mail: keshavarz@sutech
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