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    Title: 利用同步輻射技術研究飛秒雷射製成硫過量摻雜於矽之次能帶吸收
    Other Titles: Understanding of sub-band gap absorption of femtosecond-laser sulfur hyperdoped silicon using synchrotron-based techniques
    Authors: 李詔永;Lee, Chao-Yung
    Contributors: 淡江大學物理學系碩士班
    彭維鋒;Pong, Way-Faung
    Keywords: X光吸收近邊緣結構;延伸X光吸收精細結構;X光光電子能譜;black silicon;XANES;EXAFS;XPS;VB-PES
    Date: 2015
    Issue Date: 2016-01-22 14:51:31 (UTC+8)
    Abstract: 本論文主要以同步輻射相關實驗研究硫過量摻雜於p-type矽晶產生次能隙吸收與化學態、電子結構、原子結構的相關性。實驗包含光電子能譜(XPS)、X光吸收近邊緣結構(XANES)、X光延伸吸收精細結構(EXAFS)、價電帶放射能譜(VB-PES)以及第一原理理論計算。在S 2p XPS測量,隨著S2-的濃度提高,樣品之次能隙吸收也隨著提高。樣品經過退火處理後,次能隙吸收和S2-濃度同時的減少,而(Sn2-, n> 2)則有所增加,推測次能隙吸收與 S2-濃度有關。在Si的K-edge XANES量測中我們觀察到樣品中矽導帶底端附近之已佔據(未佔據)的電子態密度增加(降低)。而VB-PES測量清楚發現,硫摻雜在能隙中產生雜質態,因此提高次能隙吸收之強度。在第一原理計算態密度泛涵理論(DFT),預測當硫之濃度大於臨界濃度~0.46%時,造成樣品的Mott 絕緣-金屬相轉變,並且揭示出硫雜質態在價帶最大值與導帶最小值附近增加。
    The correlation between sub-band gap absorption and the chemical states and electronic and atomic structures of S-hyperdoped Si have been extensively studied, using synchrotron-based x-ray photoelectron spectroscopy (XPS), x-ray absorption near-edge spectroscopy (XANES), extended x-ray absorption fine structure (EXAFS), valence-band photoemission spectroscopy (VB-PES) and first-principles calculations. S 2p XPS spectra reveal that the S-hyperdoped Si with the greatest (~87%) sub-band gap absorption contains the highest concentration of S2- (monosulfide) species. Annealing S-hyperdoped Si reduces the sub-band gap absorptance and the concentration of S2- species, but significantly increases the concentration of larger S clusters [polysulfides (Sn2-, n> 2)]. The Si K-edge XANES spectra show that S hyperdoping in Si increases (decreased) the occupied (unoccupied) electronic density of states at/above the conduction-band-minimum. VB-PES spectra evidently reveal that the S-dopants not only form an impurity band deep within the band gap, giving rise to the sub-band gap absorption, but also cause the insulator-to-metal transition in samples. In the calculations by Density Function Theory further predicted the IMT of S-doped Si at a dopant concentration of about 0.46% (~2.3x1020 cm-3) and clearly indicate that the enhancement of the Density of stats at the ECBM and EVBM.
    Appears in Collections:[物理學系暨研究所] 學位論文

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