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Strontium Titanate, Photoluminescence And Photocatalytic And Silicon Nano-column Preparation Of Exploration

Posted on:2009-09-01Degree:MasterType:Thesis
Country:ChinaCandidate:Z H LiFull Text:PDF
GTID:2191360272960176Subject:Optics
Abstract/Summary:PDF Full Text Request
The content of this thesis consist of three main parts,the topics are focused on investigations of modulation of the photoluminescence of strontium titanate(SrTiO3, hereinafter STO for short),the photocatalysis of STO and the inducing effect of silicon nanostructures in the formation process of silicon pillar arrays.The first part of the thesis aims to modulate the photoluminescence of STO by means of fluorhydric acid etching combined with Ar+ ion bombardment.the STO crystal samples were bombarded by Ar+ ion beam with an ion flux of 1000μA·cm-2 and an ion energy of 1.5 keV to introduce oxygen vacancies,which was carried out in a vacuum chamber.Sputtering dose is adjusted by changing the sputtering time.The photoluminescence spectra of STO are measured after sputtering at room temperature. The results show that,with the increase of sputtering dose,the fluorescence intensity of STO increases at first,then reaches a saturated value and decreases gradually.In addition,when the STO crystal samples were etched by fluorhydric acid solution (HF:H2O=5%:95%),the fluorescence intensity of STO increases quickly at first,with the increasing etching time,after~100s the intensity starts to approach a saturated value,which is finally 7.2 times that before etching.The morphology of STO surface (measured by Atomic Force Microscope) after HF-etching for 30s shows porous structures from tens to several hundreds of nanometers in size.At the end,the fluorescence intensity is further enhanced by combining HF-etching and sputtering methods.The STO is firstly Ar+-sputtered for 15 minutes,and then HF-etched for 3 minutes.The PL intensity is finally 17.5 times that of the virgin one.The second part of the thesis is to study the photocatalysis of STO under UV and UV-Vis lights.The STO crystal samples were also bombarded by Ar+ ion beam with an ion flux of 1000μA·cm-2 and an ion energy of 1.5 keV,which was carried out in a vacuum chamber.The UV light and the UV-Vis lights were used in each photocatalytic process as light sources respectively.The result shows that the photocatalytic ability of STO is enhanced with the increasing of Ar+ sputtering dose at first,then decreases in the decomposition of the methylene blue(MB) under UV-light irradiation.After~7 min bombardment,its photocatalytic ability reaches a maximum. The photocatalytic ability of STO after Ar+ sputtering for 7min under UV-vis light irradiation is significantly enhanced as compared to that of the same sample irradiated only by UV-light,but no photocatalytic effect is found when irradiated only by visible light.In addition,when the STO crystal samples were etched by fluorhydric acid solution(HF:H2O=5%:95%),the photocatalytic ability of STO increases gradually to a maximum with the increasing etching time.At the end,the photocatalytic ability of STO is further enhanced by combining HF-etching and sputtering methods.The final part of the thesis is to study the guiding effect of the Si nanodot arrays on the formation of Si pillar arrays by electrochemical etching.The silicon was immersed in HF solution and applied a pulse voltage for electrochemical etching.By changing etching current,etching time and concentration of the solution,we want to find the optimum parameters to form silicon pillar arrays on silicon surface.
Keywords/Search Tags:strontium titanate, ion beam etching, fluorhydric acid etching, photoluminescence, photocatalysis, oxygen vacancy, silicon quantum dot, silicon pillar array
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