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Study on Dielectric Function and Absorbing Properties of Nanometer Metal Films

Author: XuYan
Tutor: DuAn
School: Northeastern University
Course: Theoretical Physics
Keywords: metal films classical electronic theory dielectric function effective medium theory reflectivity absorbing material
CLC: TB383.1
Type: Master's thesis
Year: 2008
Downloads: 126
Quote: 0
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Abstract


Nanometer metal films, as a new type function material, attract more and more attention, which have unique optical, electrical and magnetic characteristics and potential applications based on quantum size effect, small size effect and interface effect. First of all, effective field is introduced on the basis of classical Lorenz oscillator model; secondly, the relationship of nanometer metal film of the dielectric function and frequency is analyzed, and the connection of metal particulate volume and the thickness of film are also discussed in effective medium theory; eventually, aiming at metal film structure, the influence of the composition on the absorbing capability is analyzed theoretically, and compared with the experimental results.The paper is divided into three parts. In the introduction, the international achievements of nanometer metal films are reviewed, which includes the technology of preparing the nanometer metal films, microstructure analysis, and influence of the size, shape and volume fraction of metal particles on. the optical and electrical properties of nanometer metal films. Dielectric function is deduced on the basis of the classical Lorenz oscillator model, which takes into account the effect of retreat polarization field; three effective medium theories (Maxwell-Garnett’s, Bruggeman’s and Ping Sheng’s theories) and their corresponding microstructure system are introduced to depict the dielectric properties of the compound film, and finally the obliquely incident electromagnetic wave reflectivity formula of multilayer microwave absorption materials are presented on the basis of Maxwell equation and boundary condition in the second chapter. The third chapter is devoted to analyze the theoretical results and the experimental measurements of the reflectivity of Al and Ni films. We discuss the applicability of three effective medium theories and the influence of the nanometer metal structure on the material absorption capability. The main results are as follows:(1) Based on the classical Lorenz oscillator model, the dielectric function of metal is modified, which takes into account the effect of retreat polarization field. Thus the relation between the dielectric function and the electromagnetic frequency is obtained;(2) Different effective medium theory is adapted to depiction the dielectric properties of different structure. Considering the position, intensity and shape of the absorption peak of nanometer metal films, we find that Bruggeman theory fits better to describe the nanometer metal films than Maxwell-Garnett’s and Ping Sheng’s theories;(3) The sort of metal particle, the thickness of substrate, and the size of metal films determine the intensity, location and shape of absorbing peak, and they influence greatly on the electrical and optical properties of the Nano-metal film structure.

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CLC: > Industrial Technology > General industrial technology > Materials science and engineering > Special structural materials
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