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    請使用永久網址來引用或連結此文件: http://ir.lib.ncu.edu.tw/handle/987654321/72590


    題名: 以具全極化二維週期奈米結構之「金屬-介電質-金屬」吸收體實現電漿子增強之光電轉換;Polarization-insensitive two-dimensional periodic metallic absorbers in structured metal-insulator-metal con guration for plasmon-enhanced photoelectric conversion
    作者: 馬林甘;Karthickraj, Muthuramalingam
    貢獻者: 光電科學與工程學系
    關鍵詞: Plasmonics;MIM;solar energy conversion;Plasmonics;MIM;solar energy conversion
    日期: 2016-10-19
    上傳時間: 2017-01-23 16:33:42 (UTC+8)
    出版者: 國立中央大學
    摘要: 本研究針對以數種尺寸之奈米六角柱週期陣列置於金屬-介電質-金屬結構(metal-insulator-metal, MIM)所形成之新式金屬吸收體,其在可見光光譜範圍內之寬頻入射電磁波吸收及電漿子(plasmon)增強之光電轉換進行相關之探討。 於反射頻譜中觀察到,以金為材料之單一六角柱其分別置於二氧化矽(SiO2)-金與二氧化矽-銀(Ag)結構之上時,其共振波長(resonance wavelength, λres)隨正六角柱邊長增加而近乎線性紅移。金奈米結構-二氧化矽-金之吸收體於入射自由波長(free space wavelength, λ0)大於500 nm所產生之寬頻入射電磁波吸收主要源自於底層金膜之材料吸收。數值模擬結果顯示該吸收體於垂直入射下具有與入射電磁光偏振(polarization)不相依之特性,且其吸收頻譜(λ0 = [300, 1100] nm)於入射仰角(elevation angle)小於40◦之範圍內幾乎恆定。對於垂直入射之橫向磁場(transverse magnetic, TM)電磁波,金-二氧化矽-金與金-二氧化矽-銀吸收體之波長平均(λ0 = [400, 700] nm)之總吸收率(absorptance)分別為91.63%及82.31%。此外,與以金為底層金屬膜之吸收體相比,於波長範圍λ0 = [400, 550] nm內,改以銀為底層金屬膜促使上層金六角柱之吸收率增加2.5倍,其主要源自於反射波增益之局域性表面電漿子(reflected wave-enhanced localized surface plasmons)與間隙電漿子(gap plasmon)共振。
    於多層結構之鋁(Al)-二氧化鈦(TiO2)-銀之吸收體,電漿子增強之光電轉換效應主要產生於六角柱之邊緣以及側壁,同時可於六角柱間之中層鋁金屬膜內所產生。對於最佳化之結構,於可見光範圍內對TM電磁波之吸收率其大於60%之頻寬約為232 nm。於本研究中,透過電子束微影(electron beam lithography)製作最佳化之具奈米六角柱之鋁-二氧化鈦-銀之吸收體並針對其外部量子效率(external quantum efficiency, EQE)進行量測。對於本研究之兩個製作樣品其波長平均(λ0 = [400, 1000] nm)之外部量子效率之量測值分別為7.616%及 1.312%,且於入射波長λ0 = 633 nm並施以偏壓0.5 V下所得之結果為12%。
    ;In this research, modified absorbers in metal-insulator-metal (MIM) configurations for
    broadband radiation absorption and plasmon-enhanced photoelectric conversion at visible
    frequencies are explored. We first studied the resonance wavelength (λres) of a single gold
    (Au) hexagon supported by the SiO2-Au and SiO2-silver (Ag) configurations as a function
    of side length of the Au hexagon. The optical resonance properties of the MIM structures
    are obtained from the 3-D finite-difference time-domain (3-D FDTD) simulations. We
    identified that the λres of the single Au hexagon in the MIM configuration is shifting
    linearly towards the longer wavelengths side (λ0 > 700 nm) of the reflectance spectrum
    with increasing side length. We also observed the broadband absorption for λ0 < 500 nm
    in our Au-SiO2-Au absorber model is mainly due to the material absorption of Au bottom
    layer. The wavelength-averaged total absorptance of the Au-SiO2-Au and Au-SiO2-Ag
    absorbers are about 91.63% and 82.31%, respectively, for transverse magnetic (TM) wave
    at normal incidence for λ0 = 400 nm-700 nm. Moreover, the insensitivity of our absorber
    models are evaluated by the simulated absorptance spectra as a function of polarization
    and incidence angles. Besides, we discovered that simply changing the Ag bottom in our
    broadband absorber model, the absorptance within the top Au hexagons is enhanced up
    to 2.5 times at wavelengths λ0 = 400 nm-550 nm.
    Moreover, a multilayered aluminum (Al)-titanium oxide (TiO2)-Ag structure is systematically
    optimized using 3-D FDTD simulations for plasmon-enhanced photoelectric
    conversion at visible frequencies. The bandwidth of absorptance greater than 70% in the
    optimized structure is about 232 nm for TM wave at visible wavelengths. The optimum
    Al-TiO2-Ag device evaluated in terms of low reflectance for the photoelectric conversion is
    fabricated and the photon to electron conversion efficiency is measured. The wavelength
    and measurement averaged quantum efficiency (QE) of the fabricated two devices are
    7.616% and 1.312%.
    顯示於類別:[光電科學研究所] 博碩士論文

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