Optics and Photonics Journal, 2012, 2, 145-151 http://dx.doi.org/10.4236/opj.2012.23021 Published Online September 2012 (http://www.SciRP.org/journal/opj) Local Field Effects in the Luminescence of the Cone-Like Nanohills V. Lozovski 1 , A. Medvid 1,2 , V. Piatnytsia 1 1 Institute of High Technologies, National Taras Shevchenko University of Kyiv, Kyiv, Ukraine 2 Riga Technical University, Riga, Latvia Email: pyatnyx@gmail.com Received May 30, 2012; revised June 29, 2012; accepted July 14, 2012 ABSTRACT The main purpose of the work is to clarify the physical mechanisms which leads to the specific spectrums of the struc- tures [1-3]. The work is based on the ideas of the effective susceptibility. The effective susceptibility of cone-shaped nanohills located at the semiconductor surface is obtained in the frame of local-field approach. The knowledge of the effective susceptibility allows to calculate the optical absorption profiles. Using the approach similar to Levshin rule the photoluminescence spectra were calculated. Obtained results were compared with experimental luminescence spectra obtained earlier. The significant machanisms, that define the peculiarities of the spectra, is the shape of the nanoclasters and the inhomogeneity of the nanohills array are justificated. The main issue of the work is that the cause of the lu- minescence spectrums has electodynamical nature without spatial quantisation effects. Keywords: Mesoparticle; Cone Shape; Effective Susceptibility; Imperfect Array; Luminescence 1. Introduction Nowadays the experiments of luminescence of the nano- hills fabricated by laser beam scanning along the silicon surface were reported [1-3]. The effect of luminescence by the nanohills in the works [1-3] was explained by ex- isting varyband structure of the nano-rods. The spatial quantization is the cause of luminescence effect in the nanohills. This explanation seems to us rather not well- grounded and, of course, it is only for qualitative. Indeed the electron state of the quantum dot is formed in the particle as a whole. It means one should obtain the elec- tron eigenstates inside the cone-like quantum dot and, then, calculate the transition currents, effective susceptibilities and luminescence spectra. The developing of correct mi- croscopic model for explanation of discussed results be- comes very hard problem. However, one can get round the difficulties using the mesoscopic approach using the lo- cal-field method. In the frame of so-called effective sus- ceptibility concept [4] it is possible to calculate the lumi- nescence spectra by the methods of the mesoscopic elec- trodynamics. In the frame of this approach the local-field effects can give the forthcoming result. As it is well-known, the local-field effects strongly depend on the particle shape and size [4,5]. Moreover, the effective susceptibil- ity of the nanoparticle arrays depends on the particle shapes and size distribution. Then, taking into account the cone- like shape of the particles at the surface and its shape dis- tribution one can calculate the absorption spectra and, then, using the widely applicable Levshin rule [6,7]—cal- culate the luminescence spectra. This problem was solved in this work. 2. Model and Problem Set up The scanning by the laser beam of the semiconductor sur- face can lead to fabrication of the systems of the nano- hills shaped as a cone, which was reported in [1-3]. It is well known, that the mechanical stresses appear when the nano-objects are fabricated at the surface [8-11]. The stress fields lead to distortion of the electron and optical properties of the nano-systems [12,13]. Specifically, these distortions become apparent in shifts of the absorption edge and transform the indirect band energy structure to the direct one [12,13]. This fact leads, in part, to ability of the luminescence observation in Si nano-particles [12]. This effect is similar to the nanopor- ous silicon [12]. Moreover, the complicated structure of the absorption and luminescence spectra can’t be explained by the mechanical stresses [12]. Here we attempt to de- scribe the peculiarities of the absorption and lumines- cence spectra of the nanohills systems in the frame of local-field approach. There are many works where the similar effects were explained with the local field inter- actions in the nano-particles [5,14]. It is well known, that the local-field effects are strongly defined by the shapes Copyright © 2012 SciRes. OPJ