Electronic and atomic structures of gold nanoparticles embedded in silica nanowires and icosahedral quasi-crystals Al70Pd22.5(Re1−xMnx)7.5

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Title:	Electronic and atomic structures of gold nanoparticles embedded in silica nanowires and icosahedral quasi-crystals Al70Pd22.5(Re1−xMnx)7.5
Other Titles:	金奈米粒子崁入二氧化矽奈米線與二十面準晶體Al70Pd22.5(Re1−xMnx )7.5的電子與原子結構之研究
Authors:	包志文;Pao, Chih-wen
Contributors:	淡江大學物理學系博士班彭維鋒;Pong, Way-faung
Keywords:	輻射;吸收光譜;光電子發射能譜;螢光發射譜;XANES;EXAFS;XES;VB-PES;Au-Peapod
Date:	2009
Issue Date:	2010-01-11 02:20:32 (UTC+8)
Abstract:	利用X-光吸收光譜(XAS)、X-光價電帶光電子發射能譜(VB-XPS)以及X-光螢光發射譜(XES)研究金奈米粒子崁入二氧化矽奈米線與二十面準晶體Al70Pd22.5(Re1−xMnx )7.5的電子與原子結構。其中金奈米粒子崁入二氧化矽奈米線具有相當奇特的光電流反應。尤其在照射綠光雷射之後，電阻值降低的幅度相對於照射藍光與紅光雷射要來的大上許多。由光吸收的量測數據可推斷此一奇特的現象應與其金奈米粒子的表面電漿共振有關。由O K-edge X光吸收進邊結構(XANES)與O Kα-螢光發射譜可得知金奈米粒子崁入二氧化矽奈米線的能系為6.8eV。另外由金的L3-edge XANES與O K-edge XANES可以觀察到入射不同波段的雷射光會引起電荷轉移的現象。二十面準晶體Al70Pd22.5(Re1−xMnx )7.5是一種相當奇特的材料。可藉由其電阻值比r來判斷其電性為金屬態或絕緣態。由Al K-edge、Pd L3-edge、Re L3-edge XANES譜圖可得知其未占據態密度與Mn參雜的量無關。由Mn L3-edge XANES可得知其導電性與Mn的未占據態密度成正比。由Mn K-edge EXAFS譜圖可得知Mn園子周圍的原子結構不隨Mn參雜的含量改變。再者，由共振光電子發射能譜可得知Mn原子在靠近費米面的位置有貢獻相當強的電子態密度分布。並且藉由針對費米面的分析可得知r值無法用來判斷二十面準晶體Al70Pd22.5(Re1−xMnx )7.5的電性。 The photoresponse associated with the electronic and atomic structures of Au nanoparticles embedded in silica nanowires (Au-peapod) and icosahedral quasi-crystals (i-QCs) Al70Pd22.5(Re1−xMnx)7.5 were studied using Al K-, Au L3-, Re L3-, Pd L3-, Si L3,2- Mn L3-, and O K-edge x-ray absorption near edge structure (XANES), Au L3- and Mn-K edge extended x-ray absorption fine structure (EXAFS), valance-band photoemission (VB-PES), and x-ray emission spectroscopy (XES). The band gap of SiOx-NWs was determined to be 6.8eV by XES and XANES measurements. The XANES results showed illumination induced electron transfer from Au nanoparticles to SiOx-NWs. Photo-conductivity was found to be small for illumination with red and blue light, but greatly enhanced with green light at surface plasmon resonance, which also suggests an Au-silica interface barrier higher than 3.1 eV possibly due to interface-state pinning of the Fermi level or chemical potential. Additionally, Pd and Re L3-edge and Al K-edge XANES spectra for reveal that the unoccupied Pd 4d, Re 5d and Al 3p states are insensitive to the Mn doping. The VB-PES and resonant VB-PES spectroscopy analysis indicate a marked Mn 3d contribution within ~5 eVof the Fermi level, suggesting that the Mn doping increases the conductivity of Al70Pd22.5(Re1−xMnx)7.5 i-QCs.
Appears in Collections:	[Graduate Institute & Department of Physics] Thesis

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