%0 Journal Article
%T Preludes to the Lattice Compatibility Theory LCT: Urbach Tailing Controversial Behavior in Some Nanocompounds
%A K. Boubaker
%J ISRN Nanomaterials
%D 2012
%R 10.5402/2012/173198
%X We try to give an explanation to the unexpected Urbach tailing associated to some phenomena which occur in some nano-compounds lattices. The provided discussion and notes are detailed here as a prelude to the lattice compatibility theory (LCT), a guide to a plausible understanding of this unsolved intrigue. 1. Introduction Urbach tailing alterations inside nanostructured lattices (Figure 1) have been always attributed to atomic-scale topological disorder, unexpected hybrid excitonic transitions, or topological filament occurrence [1¨C4]. In the beginning of the last decade, Urbach tailing has been attributed to the hydrogen content, and precisely the different E04 and sp2 contents inside nanofilms [5]. Another more realistic explanation has been provided earlier by Dow and Redfield [6]. This explanation claims that Urbach tailing is due to the broadening of the exciton absorption band which occurs when charged impurities in the lattice induce phonon-induced microelectric fields. This phenomenon has been also described, in II¨CVI compound semiconductors, as a reduction of holes-electrons Coulombic interactions which results in more free excitons, as long as exciton radii are larger than those of alkali halides. Many other causes have been proposed in the relevant literature [7¨C10]. Figure 1: Urbach tails occurrence scheme. In this paper, a prelude to the micro-chemistry-related Lattice Compatibility Theory (LCT) is provided as an attempt to explain Urbach tailing alterations in nano-structured lattices. The study is organized as follows. In Section 2, the experimental details and motivations are presented along with the studied nanomaterials patterns. In Section 3, the fundaments of the proposed Lattice Compatibility Theory LCT are discussed. Last section is a conclusion which summarizes the aim methods and perspectives of the work. 2. Experimental Details and Motivations In this study, targeted nano-materials are some bismuth oxides BSO, BGO, and BTO. These nano-materials are technologically interesting material, because they can function as a Pockels readout optical modulation (PROM) device and photorefractive sensors [11¨C18]. Crystals of these oxides were grown from highly purified Bi2O3, SiO2 and presintered BGO, and BTO powders using the Czochralski technique [19]. Elaboration was carried out in room atmosphere and the growing temperature was about 1110¡ãC. Doped nano-crystals were prepared with doping content of 0.02£¿mol.% in the starting melt and the samples were reexcited each optically by UV radiations for photochromic effect studies. In order to
%U http://www.hindawi.com/journals/isrn.nanomaterials/2012/173198/