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Structural and Electrical Transport Properties Research of Sn: In2O3 and Nb: TiO2 Transparent Conducting Thin Films

Author: ZhengXiaoZuo
Tutor: LiZhiQing
School: Tianjin University
Course: Materials Physics and Chemistry
Keywords: transparent conducting oxide film tin indium oxide niobium doped titanium oxide electrical transport property localized magnetic moment electron-electron scattering weak localization
CLC: TB383.2
Type: Master's thesis
Year: 2010
Downloads: 52
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Abstract


Transparent conducting oxide film （TCO） is a kind of important optoelectronic materials. Its good combination of high electrical conductivity and excellent optical transparency in visible region makes TCO a broad application. Among the various TCOs, Sn: In2O3 （ITO） has the widest use and largest industrial production, and Nb: TiO2 （NTO） has recently been demonstrated a promising TCO. However, previous research of ITO and NTO films were mostly focused on the influence of fabrication technology on films’optoelectronic property, and few reports gave basic analysis of physical property in TCO films. Thus, in this thesis, we deposit series of ITO and NTO films by radio-frequency sputtering to investigate their structural and electrical transport properties. Our work is listed below:In ITO films, the chemical valences of Sn and In are +4 and +3, respectively. As substrate temperature increases, the crystalline quality improves, the preferred orientation changes from （400） to （222）, the grain size increases, and the shape of grains changes from ellipse to triangle. As for ITO’s electrical transport properties, we find in the high temperature region where the resistivity increases with increasing temperature, electron-phonon scattering mechanism dominates its conducting mechanisms, while in the low temperature region where the resistivity decreases with increasing temperature, electron-electron scattering plays an important role in its electron transport process. In addition, we also find that its negative magnetoresistance originates from weak localization, and its positive magnetoresistance is due to Lorentz force.In NTO films, the chemical valences of Ti and Nb are +4 and +5, respectively. Films deposited below 998 K are anatase structure, and the crystalline quality improves with increasing substrate temperature. Mixed phase between anatase and rutile exist in the film grown at 1073 K. For the most conducting film, compared to electron-phonon scattering mechanism, electron-phonon-impurity interference effect is dominant. Moreover, the temperature dependence of resistivity for the mixed-phase film is described by the fluctuation induced tunneling model from 80 K to 300 K, and by the hopping mechanism from 80 K down to 30 K.As for the magnetoresistance of NTO films, the negative magnetoresistance of NTO originates from the scattering of conduction electrons due to localized magnetic moments, which can be described by a theory considering s-d exchange Hamiltonians, while the positive magnetoresistance can be explained by Lorentz effect. Measurements of magnetic properties prove the existence of ferromagnetism at both low and room temperature.

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