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Oxidation Effect in Low-dimensional Structure of Si1-xGex Alloys and Related PL Spectra

Author: WangHaiXu
Tutor: HuangWeiQi
School: Guizhou University
Course: Theoretical Physics
Keywords: Photoluminescence Silicon germanium film Laser irradiation Electrochemical etching Annealing Oxide interface states
CLC: TG139
Type: Master's thesis
Year: 2009
Downloads: 13
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Abstract


GE x of the undoped Si 1 -x alloy film ( the silicon generated by the MBE technique , wherein x = 0.25 , a film thickness of 2000nm) as a sample , intense pulsed laser ( wavelength of 1064nm, pulse instantaneous power density of approximately 10 < / sup> W / cm 2 , a repetition rate of 1000 times / sec ) irradiation method continuous laser light (wavelength of 532nm, power is 20mW) the irradiation assisted electrochemical etching method of the sample processing, and then the sample is placed in the different degrees of annealing oxidation treatment in the oxidation furnace (800 ℃) . High - resolution scanning electron microscope (SEM) to observe the morphology of the low - dimensional structure analysis of the silicon germanium alloy samples , and found that oxidation of the point, linear and sheet generated under different processing conditions , other low-dimensional structures, and annealing after structural changes ; 514nm alkylene ion laser Raman / fluorescence spectrometer measurement of photoluminescence (PL) spectra of these low-dimensional structures corresponding , found that due to the PL spectrum corresponding to the structure of the different oxidation conditions these generated either intensity or peak the bits are significant changes occurred . This article analyzes the reasons for the formation of these structures using laser interaction with the material and the silicon - germanium alloy oxidation mechanism model . Experiments, due to the laser energy , time, and the annealing conditions are different , such that the thickness of the silicon oxide layer and the size of the clusters of the nanocrystalline change , thereby causing the nanocrystalline silicon germanium energy band structure and its oxidation interface state changes , thereby impact samples of PL . According to the quantum confinement (QC) and quantum to limited light emitting center (QCLC) model , to the cashier crystalline silicon germanium oxide interface states model to explain the the sample PL emission changes . The model considers : the corresponding low dimensional nanostructures of silicon germanium quantum confinement effect of broadening the energy gap , different oxidation conditions to generate various interface states oxide ; oxide interface states energy levels below the broadening of the bottom of the conduction band level oxide, interface states can capture the bottom of conduction band electrons to form a metastable , the metastable and the top of the valence band inversion may be formed even by the excitation light , thereby generating a strong PL emission . The PL spectra of a frequency variation can be explained by the level of the oxide interface state energy level .

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CLC: > Industrial Technology > Metallurgy and Metal Craft > Metallurgy and Heat Treatment > The alloy learn with a variety of properties of alloys > Other special nature of the alloy
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