UV-VUV laser induced phenomena in SiO2 glass
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紫外二氧化硅1. 简介紫外二氧化硅(UV-SiO2)是一种具有特殊光学性质的材料,广泛应用于光学、电子、光电子等领域。
它是由二氧化硅(SiO2)基质中掺入少量的特殊杂质形成的。
紫外二氧化硅具有较高的折射率、低的散射损耗和优异的透明性,使其成为一种理想的光学材料。
2. 特性2.1 折射率紫外二氧化硅具有较高的折射率,这使得它在光学器件中具有重要的应用。
通过控制杂质的浓度和分布,可以调节紫外二氧化硅的折射率,以满足不同光学器件的需求。
2.2 透明性紫外二氧化硅具有优异的透明性,在紫外光谱范围内具有较高的透射率。
这使得它在紫外光学器件中能够有效地传递紫外光,实现各种光学功能。
2.3 低散射损耗紫外二氧化硅具有较低的散射损耗,这意味着它能够有效地传输光信号而不会引起能量损失。
这使得紫外二氧化硅成为一种理想的光学波导材料。
2.4 热稳定性紫外二氧化硅具有良好的热稳定性,能够在较高温度下保持其光学性能。
这使得它在高温环境下的应用得以实现,例如高功率激光器、高温光学器件等。
3. 制备方法紫外二氧化硅的制备方法主要包括溶胶-凝胶法、物理气相沉积法等。
其中,溶胶-凝胶法是一种常用的制备方法,其主要步骤包括溶胶制备、凝胶形成和热处理等。
3.1 溶胶制备溶胶制备是指将硅源溶解在适当的溶剂中,形成含有硅的溶液。
通常使用的硅源包括硅酸乙酯、硅酸正丁酯等。
在溶胶制备过程中,可以通过控制硅源的浓度和溶剂的性质,调节溶胶的粘度和稳定性。
3.2 凝胶形成凝胶形成是指在溶胶中加入适当的凝胶剂,使溶胶逐渐转变为凝胶。
常用的凝胶剂包括硝酸铵、硝酸钠等。
在凝胶形成过程中,可以通过控制凝胶剂的浓度和凝胶化条件,控制凝胶的形成速度和结构。
3.3 热处理热处理是指将凝胶在适当的温度下进行热处理,使其形成二氧化硅基质。
热处理过程中,溶胶中的溶剂会逐渐挥发,凝胶中的硅源会发生水解缩聚反应,形成二氧化硅基质。
4. 应用领域4.1 光学器件紫外二氧化硅在光学器件中具有广泛的应用,例如紫外光学透镜、紫外光学棱镜、紫外光学窗口等。
[Article]物理化学学报(Wuli Huaxue Xuebao )Acta Phys.鄄Chim.Sin .,2007,23(8):1219-1223August Received:January 9,2007;Revised:April 6,2007;Published on Web:June 13,2007.∗Corresponding author.Email:qhli@;Tel:+8621⁃50217337.国家自然科学基金青年基金(50503011),上海“浦江人才”计划(05PG14051),上海市教委重点项目(06zz95)及上海市重点学科项目(P1701)资助ⒸEditorial office of Acta Physico ⁃Chimica Sinica紫外光解法在制备低介电常数氧化硅分子筛薄膜中的应用袁昊1李庆华1,∗沙菲2解丽丽1田震1王利军1(1上海第二工业大学环境工程系,上海201209;2上海纳米材料检测中心,上海200237)摘要:以正硅酸乙酯为硅源,四丙基氢氧化铵(TPAOH)为模板剂和碱源,采取水热晶化技术,通过原位法在硅晶片表面制备出纯二氧化硅透明分子筛薄膜;采用紫外光解法代替传统高温焙烧法脱除分子筛薄膜孔道内的模板剂,制备出具有低介电常数的氧化硅分子筛薄膜.使用FTIR 、XRD 和SEM 对样品进行了结构表征,并采用阻抗分析仪测量了薄膜的介电常数,纳米硬度计测量薄膜的杨氏模量和硬度.与传统的高温焙烧方法相比,紫外光解法处理条件温和,同时省时、省能、操作简易.关键词:紫外光解法;高温焙烧法;氧化硅分子筛薄膜;低介电常数中图分类号:O649Application of Ultraviolet Treatment in the Synthesis of Pure 鄄silicaZeolite Thin Films with Low Dielectric ConstantYUAN Hao 1LI Qing ⁃Hua 1,∗SHA Fei 2XIE Li ⁃Li 1TIAN Zhen 1WANG Li ⁃Jun 1(1Department of Environmental Engineering,Shanghai Second Polytechnic University,Shanghai 201209,P.R.China ;2Shanghai Testing Center of Nanometer Materials,Shanghai 200237,P.R.China )Abstract :Transparent pure ⁃silica zeolite (PSZ)films were synthesized on silicon wafers through hydrothermal reaction ,in which tetraethyl orthosilicate (TEOS)was used as silica source ,tetrapropyl ammonium hydroxide (TPAOH)as template and alkaline source.An ultraviolet treatment was subsequently applied to remove the organic templates within the pores/channels of zeolite films.The thin films were characterized by using FTIR,XRD,and SEM techniques before and after the ultraviolet treatment.FTIR results showed that the organic templates were effectively removed via ultraviolet treatment,which was the same as the results from the calcinations treatment.In comparison with the calcined films,XRD and SEM results indicated that the crystallinity and the surface as well as the thickness of the films had no significant changes after ultraviolet treatment.Dielectric constant (ε)values of the thin films were measured by means of impedance analyzer.Elastic modulus and hardness of the thin films were measured by the nano ⁃indentation technique.All results showed that the films after ultraviolet treatment had a lower εvalue and higher mechanical strength.Therefore,it could be concluded that ultraviolet treatment was a faster,more energy ⁃conservative method to remove template from zeolite films,in comparison with conventional calcination.Key Words :Ultraviolet treatment;Calcination;Silica zeolite thin film;Low dielectric constant随着超大规模集成电路(ULSI)技术的发展,电子器件特征尺寸不断缩小,而电路的互连延迟逐渐增大[1,2],成为制约集成电路速度进一步提高的瓶颈.采用低介电常数(low ε)介质薄膜作金属线间和层间介质以代替传统SiO 2介质(ε≈4)是降低互连延迟、串扰和能耗的有效方法[2,3].通常采取以下两类方法降低材料的介电常数:第一类是利用有机化合物本身的低介电常数特性,但由于其机械性能差又不耐高温等缺陷限制了它们的应用;第二类是降低材料的有效介电常数,即在材1219Acta Phys.鄄Chim.Sin.,2007Vol.23料中增加孔隙,制备成多孔薄膜的方法.由于孔隙的增多致使平均介电常数降低.目前有可能在集成电路中应用的低介电常数介质主要有多孔氧化硅、含氟氧化硅、含氟碳膜、聚酰亚胺等[4-7].其中多孔SiO2不仅有较低的介电常数,且能与已有的单晶SiO2工艺很好地兼容,在热稳定性、对无机物的粘附性等方面明显优于有机介质,是传统SiO2理想的替代物.纳米多孔SiO2材料的制备目前多采用溶胶⁃凝胶(sol⁃gel)工艺[7,8],采用这种方法可获得较大孔隙度,但孔的结构不易控制,孔径尺寸随机分布,不适于用在集成电路中作为互连介质.另一类是与溶胶⁃凝胶技术相结合的模板法,以表面活性剂为模板,结合溶胶⁃凝胶或旋涂技术,可以得到孔径分布均匀的纳米介孔SiO2材料[9,10].与单纯的溶胶⁃凝胶方法相比,这种模板合成法可合理地控制孔隙度、孔尺寸以及膜的结构和厚度,但该类介孔薄膜材料易吸附空气中的水,从而导致薄膜的介电常数增大;同时,其薄膜材料较大的孔道和疏松的无机孔壁结构导致膜的机械性能下降,限制了介孔SiO2材料的进一步应用.近年来,一种新型基于微孔二氧化硅晶体———纯二氧化硅分子筛薄膜材料开始引起人们的关注.同具有低介电常数的有机硅酸盐、氟化硅玻璃或介孔二氧化硅薄膜相比,氧化硅分子筛薄膜具有均一的孔道结构,高热稳定性,高机械强度和高疏水性等特性[11,12],并且具有较低的理论介电常数[13].美国加州大学Yan课题组最先合成的MFI分子筛薄膜的ε值可达到2.7[14].通过选用较低骨架密度的MFI型分子筛或添加造孔剂等方法,将ε值进一步降低到2.2以下[15,16].最引人注目的是这种新型材料的机械强度(杨氏模量E)远大于其它材料[17],因此氧化硅分子筛薄膜有望代替传统二氧化硅薄膜而应用在未来超低ε材料领域.然而,尽管纯硅沸石分子筛(PSZ)薄膜材料显示出比纳米多孔SiO2材料更优异的机械强度和疏水性能,但在制备后期需要采用高温焙烧(>500℃)的方法脱除阻塞孔道的模板剂,并且加热处理过程比较缓慢.我们知道,低介电常数薄膜在实际制备中使用的温度一般不高于400℃.因此,如何解决在低温下快速有效地脱除有机模板剂成为氧化硅分子筛薄膜可以在低ε材料领域得到实际应用的关键问题.目前报道的脱除有机模板剂常用的方法除传统的高温焙烧外,还有酸萃取法和微波消解法等.但温和的酸萃取剂不能彻底脱除模板剂,而微波消解法在结合以廉价氧化性无机酸等为溶剂,利用体系中自身的压力脱除模板剂的同时对薄膜的骨架会有一定的副作用.Li等[18,19]将紫外光解技术应用在微孔分子筛领域,制备出一系列性能良好的分子筛纳米颗粒和薄膜.区别于传统的高温焙烧法,紫外光解技术是在近室温条件下将有机模板剂进行光化学分解,不仅避免高温对低介电常数材料制备影响的限制,同时也避免高温导致的薄膜材料和薄膜基底热膨胀系数不同产生的薄膜开裂.本研究是在原有工作基础上,继续探索紫外光解技术在制备低介电常数氧化硅分子筛薄膜方面的优越性.通过水热晶化方法,以四丙基氢氧化铵(TPAOH)为模板剂,在硅晶片上原位制备高质量的氧化硅分子筛薄膜.比较了传统高温焙烧法和紫外光解法对薄膜结构、组成和介电常数等的影响.1实验过程1.1原位晶化制备氧化硅分子筛薄膜将2cm×2cm双面抛光的硅晶片严格按标准的硅芯片清洗步骤清洗后,固定在自制的特富龙支架上,置于TPAOH/TEOS/H2O/EtOH的摩尔比为0.12/1/85/4的澄清溶液中,于100℃油浴中静置,2天后取出硅晶片,用0.1mol·L-1的氨水溶液洗涤后,室温下真空干燥.形成薄膜后,将其中一个薄膜基片放置在184-257nm、10-20mW·cm-2下的中压汞灯下照射3-8 h(在184-257nm波长范围内的紫外光),基片中心离紫外灯下端距离为2cm,控制实验温度<50℃.作为参比,采用传统的高温焙烧脱除模板剂的处理方法,将相同样品在氮气保护下以1℃·min-1的线性升温速率升到550℃,在550℃下焙烧6h,再以1℃·min-1降温速率降到室温,得到参比样品.整个高温焙烧的处理时间长达48h.1.2性能表征采用德国布鲁克AXS公司的D8ADVANCE X⁃ray Diffractometer确定微孔薄膜的晶态结构,使用Cu Kα为射线源,管电压40kV,管电流40mA,扫描区间5°-40°;采用德国布鲁克V70傅立叶变换红外分光光谱仪测定薄膜的红外光谱;用日本日立S⁃4800型冷场扫描电子显微镜观察薄膜的表面形貌和薄膜的厚度;介电常数的测量采用平行电容法,电容由HP4284阻抗分析仪测定;杨氏模量和硬度采用美国MTS公司的纳米压痕仪Nano⁃indenter1220No.8袁昊等:紫外光解法在制备低介电常数氧化硅分子筛薄膜中的应用DCM组件测定.2结果与讨论2.1FTIR图谱分析图1为原位晶化得到的氧化硅分子筛薄膜及其紫外光照处理/高温焙烧后产物的红外光谱图.对处理前的薄膜,图1的插图可直接表明有机分子的存在.模板剂中甲基(CH3)和亚甲基(CH2)的C—H伸缩振动峰在2700-3100cm-1区域之间,甲基(CH3)的C—H弯曲振动在1300-1600cm-1区域之间.图1高波数段(3100-2700cm-1)显示在2883、2943、2981 cm-1处有三个吸收峰,这些分别归属于亚甲基(CH2)和甲基(CH3)的C—H伸缩振动,而在低波数段(1800-500cm-1)的1460、1474cm-1处的两个吸收峰则归属于模板剂亚甲基(CH2)和甲基(CH3)的C—H 弯曲振动[20].经过高温焙烧和紫外光照处理后FTIR图谱发生了一些明显的变化.表征有机模板剂的甲基(CH3)和亚甲基(CH2)的C—H伸缩振动和弯曲振动的特征谱峰全部消失,表明两种处理方式都能有效地脱去孔道内的模板剂(低于仪器的检测下限,残留有机物低于1%的原始含量).目前对UV/ozone空气环境下降解有机物的机理学术界还存在争论,但普遍认为UV光照过程可能包括下面的反应:低于245.4nm(最佳λ=184nm)的紫外光照促进了氧气(空气中的)分裂成臭氧和氧原子;且253.7nm波长的光线可激活和/或分裂有机基体,从而产生有活性的核素(如离子、自由基和受激分子);有活性的有机核素随时受到氧原子和臭氧的协同攻击容易形成简单的易挥发的(或可除去的)产物,如一些可从样品内部逸出的CO2、H2O和N2.同时,UV光源发出的光子表现的热效应[21],促使薄膜内部的有机成分分解挥发,且在较短的时间内使得薄膜的性能达到甚至超过传统的热处理效果.需要指出的是,脱除模板剂及其分解产物所需的紫外照射时间与使用的汞灯的功率、灯管清洁程度、薄膜离灯的距离以及薄膜自身的厚度等因素有关.红外测量结果表明,4h的照射时间足够完全除去分子筛薄膜孔道内的有机物,并且能保持样品表面的温度低于50℃,而高温焙烧法不仅需要高达550℃的高温,而且加热时间需要至少48h.所以,紫外光照技术应用在薄膜领域具有低温、快速、简易的特点,在保障低温脱除模板剂前提下,又大大缩短了模板剂脱除所需的时间.2.2XRD图谱分析图2是原位晶化后的分子筛薄膜和经紫外光照或高温焙烧处理后的XRD图谱.薄膜未经处理前的XRD图谱是MFI分子筛薄膜典型的特征衍射峰[22],表明薄膜材料具有均一有序的孔洞结构.样品经过紫外光照或高温焙烧处理后,峰位保持不变,峰的相对强度发生了明显的变化.前两个峰7.96°和8.88°的峰强度变强,11.92°和12.50°两个峰强度有所下降,这主要是由于在模板剂脱除过程中无机组分进入到骨架结构的空穴中[23].我们知道,分子筛薄膜在高温焙烧脱除有机模板剂过程中常会引起薄膜结晶度的下降,这将导致孔隙率降低,介电常数ε值增大.为避免破坏薄膜结构,通常采用氧气/氮气气氛下非常缓慢的程序控制升温过程.整个实验过程耗时、耗能,同时高温可能引起薄膜因与基底热膨胀系数不同而产生裂纹,大图1MFI薄膜原样、UV光照或焙烧处理后的FTIR图谱Fig.1FTIR absorption spectra of silica MFI films ofas⁃synthesized and treated by UV and calcinationMFI:a kind of silicazeolites图2MFI薄膜原样、UV光照/高温焙烧处理后的XRD图Fig.2XRD patterns of silica MFI films of as⁃synthesized and treated by UV and calcination1221Acta Phys.⁃Chim.Sin.,2007Vol.23大影响膜的性能.而紫外光照处理后的XRD 谱图证实紫外光照技术在高效除去模板剂的同时,在保持薄膜结晶度和完整性方面具有比传统高温焙烧法更优异的性能.2.3SEM 形貌厚度分析图3是原位晶化后的微孔分子筛薄膜和经紫外光照或高温焙烧处理后的扫描电镜照片.照片显示,无论是紫外光照处理还是高温焙烧,薄膜表面同未处理前的表面形貌没有明显差异.薄膜表面致密、连续、平整.从SEM 的截面图象中观察到三种薄膜的厚度非常接近,平均为500nm.说明紫外光照处理同高温焙烧处理一样,对薄膜厚度没有影响.2.4薄膜介电常数分析FTIR 和XRD 谱图分析表明紫外光解法比传统高温焙烧法在脱除薄膜孔道内的有机物过程中不仅保证整个过程是低温、快速进行,同时在保持薄膜结晶度完整方面紫外光解法具有更大的优势.我们进一步用平行电容法测量了两种薄膜的介电常数值,研究不同处理方法对介电常数值的影响.为了测量薄膜的介电常数,在制备好的薄膜表面通过孔状隔板真空蒸发上直径为1.5mm 、厚度为1μm 的6个圆形铝点作为上层电极,在硅片的另一面先用缓冲的HF 溶液清洗后真空蒸发沉积一层铝膜,这样它连同中间层的氧化硅介质及上层的铝点构成平板电容器.微孔薄膜的相对介电常数通过公式ε=Cd /(A ε0)算出,其中A 是圆形铝电极的面积,ε0是真空介电常数,d 是薄膜厚度,电容C 由HP4284阻抗分析仪测定.为了避免水吸附的影响,待测薄膜先在120℃下干燥12h,然后保存在干燥器中.电容测量过程在N 2保护下进行.处理前薄膜的介电常数值为ε=3.6,经紫外光照处理后ε=2.4,而经高温焙烧处理后的ε=2.6.这是由于原位晶化制备的分子筛薄膜因孔道中的模板剂占据了一定的空间,导致孔隙率降低,所以介电常数ε值较高为3.6,但经紫外光照处理和高温焙烧脱除模板剂后,ε值因孔隙的增大而分别降低到2.4和2.6,大大低于目前普遍使用的SiO 2介电材料(ε≈4).紫外光照处理比高温焙烧后的ε值低的实验结果也进一步证实了XRD 图谱分析的预测,即由紫外光照处理的样品比高温处理的样品结构更加有序、结晶度更高、缺陷更少.由此,分子筛薄膜的孔隙率增大,ε值减小.2.5薄膜杨氏模量分析经高温焙烧处理后薄膜的杨氏模量和硬度分别为43.2GPa 和2.67GPa,经紫外光照处理后薄膜的杨氏模量和硬度分别为44.0GPa 和2.73GPa.经过紫外光照和高温焙烧处理脱除模板剂后的杨氏模量分别为44.0GPa 和43.2GPa,远远高于微电子工业所要求的低ε材料的杨氏模量必须大约6GPa 的要求.同时由于紫外光解法相对于高温焙烧法具有更好的结构有序度、空间缺陷少等优点,使其具备了更好的机械性能.3结论FTIR 、XRD 、SEM 表征结果和介电常数、机械性能分析表明,紫外光解法同传统的高温焙烧处理法相比,不仅在低温(<50℃)下有效地脱除分子筛薄膜模板剂,而且大大缩短脱除模板剂所需的时间(从48h 降低到4h).需要指出的是,紫外光解法比传统高温焙烧方法在保持薄膜结晶度、有序性方面具有更大的优势,同时可以避免因膜与基底间的热膨胀系数不同而导致在膜界面产生裂缝,因此,在制备高质量低介电常数的薄膜材料方面具有独特的优越性.References1Chen,S.J.;Evans,D.F.;Ninham,B.M.J.Phys.Chem.,1984,88:16312Banerjee,K.;Amerasekera,A.;Dixit,G.;Hu,C.Technical Digest of IEEE International Electron Device Meeting.San Francisco,1996:65-683Fan,H.Y.;Bentley,H.R.;Kathan,K.R.;Clem,Y.;Lu,Y.;Brink,C.J.J.Non ⁃Cryst.Solids,2001,285:79图3薄膜的SEM 照片Fig.3SEM micrographs of films(a)as ⁃synthesized film,(b)UV treated film,(c)calcined film(a)(b)(c)1222No.8袁昊等:紫外光解法在制备低介电常数氧化硅分子筛薄膜中的应用4Bhan,M.K.;Huang,J.;Cheung,D.Thin Solid Films,1997,308/ 309:5075Kazuhiko,E.;Toru,T.J.Vac.Sci.Technol.,1997,15(6):3134 6Lu,T.M.;Moore,J.A.MRS Bulletin,1997,22(10):287Homma,T.Material Science and Engineering,1998,23(6):243 8Wu,G.M.;Shen,J.;Wang,J.;Zhou,B.;Ni,X.Y.Atomic Energy Science and Technology,2002,36(4/5):374[吴广明,沈军,王珏,周斌,倪星元.原子能科学技术,2002,36(4/5):374] 9Stupp,S.I.;Lebonheur,V.;Walker,K.;Li,L.S.;Huggins,K.E.Science,1997,276:38410Wang,J.;Zhang,C.R.;Feng,J.Acta Phys.⁃Chim.Sin.,2004,20(12):1399[王娟,张长瑞,冯坚.物理化学学报,2004,20(12):1399]11Wang,Z.B.;Mitra,A.P.;Wang,H.T.;Yan,Y.Adv.Mater., 2001,13:74612Persson,A.E.;Schoeman,B.J.;Sterte,J.Zeolites,1995,15:611 13van 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激光诱导氧化硅激光诱导氧化硅(Laser-Induced Oxidation of Silicon)引言:激光诱导氧化硅是一种利用激光辐射来控制硅材料表面氧化过程的方法。
这种技术具有高精度、高效率和无接触的特点,在微电子学、光学器件制造和化学传感器等领域具有广泛的应用前景。
一、激光诱导氧化硅原理激光诱导氧化硅利用激光束在硅材料表面产生局部高温,使硅与氧气反应生成氧化硅。
激光辐射的特定波长和功率可调节硅材料的氧化速率和深度。
通过控制激光束的位置和强度,可以实现对硅表面氧化过程的精确控制。
1. 微电子学领域:激光诱导氧化硅可用于制造微电子器件中的氧化硅层。
通过调节激光参数,可以实现不同深度和形状的氧化硅结构,用于制备晶体管、集成电路和光学器件等。
2. 光学器件制造:激光诱导氧化硅可用于制备光波导、光纤和光学波分复用器等光学器件。
通过精确控制激光参数和硅材料的氧化过程,可以实现对光学器件性能的精细调控。
3. 化学传感器:激光诱导氧化硅可用于制备化学传感器中的传感层。
通过在硅表面形成氧化硅结构,可以提高传感器对特定化学物质的灵敏度和选择性。
三、激光诱导氧化硅的优势1. 高精度:激光诱导氧化硅可以实现对硅材料表面氧化过程的精确控制,可以制备出具有特定形状和尺寸的氧化硅结构。
2. 高效率:激光诱导氧化硅过程无需使用化学试剂,减少了工艺步骤和环境污染,提高了制造效率。
3. 无接触:激光诱导氧化硅过程是一种无接触的表面处理技术,可以避免对硅材料的机械损伤和污染。
四、结语激光诱导氧化硅作为一种先进的硅表面处理技术,具有广泛的应用前景。
在微电子学、光学器件制造和化学传感器等领域,激光诱导氧化硅可以实现对硅材料表面氧化过程的精确控制,为制造高性能器件提供了新的可能。
未来,随着激光技术的不断发展和改进,激光诱导氧化硅技术将在各个领域发挥更大的作用,推动科技进步和产业发展。
射频磁控溅射制备SiO2薄膜及性能表征
宋学萍;黄飞;吕建国;孙兆奇
【期刊名称】《安徽大学学报(自然科学版)》
【年(卷),期】2010(034)006
【摘要】采用射频磁控溅射技术,制备4种不同溅射时间的SiO2薄膜.用XRD、PL、FTIR、UV-Vis等对薄膜的微结构、发光、红外吸收以及透、反射进行表征.结果表明:SiO2薄膜仍呈四方晶体结构,平均晶粒尺寸在17.39~19.92 nm之间;在430 nm附近出现了发光峰,在1 049~1 022 cm-1之间出现了明显的红外吸收峰,且随着溅射时间的增加发生红移;在可见光范围内平均透射率大于85%.
【总页数】6页(P37-42)
【作者】宋学萍;黄飞;吕建国;孙兆奇
【作者单位】安徽大学,物理与材料科学学院,安徽,合肥,230039;安徽大学,实验室与设备管理处,安徽,合肥,230039;安徽大学,物理与材料科学学院,安徽,合肥,230039;合肥师范学院,物理与电子工程系,安徽,合肥,230061;安徽大学,物理与材料科学学院,安徽,合肥,230039
【正文语种】中文
【中图分类】O484
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紫外光敏薄膜转印石墨烯英文回答:Ultraviolet (UV) sensitive films are widely used in various applications, including photolithography, optical sensors, and protective coatings. These films possess the ability to react to UV light by undergoing a physical or chemical change, which can be utilized for different purposes.One of the most promising materials for UV sensitive films is graphene. Graphene is a single layer of carbon atoms arranged in a hexagonal lattice, and it exhibits exceptional electrical, mechanical, and optical properties. When graphene is integrated into a UV sensitive film, it can enhance the film's sensitivity to UV light and improve its overall performance.The transfer printing technique is commonly used to fabricate graphene-based UV sensitive films. This techniqueinvolves the transfer of graphene from a substrate onto a target surface using a transfer medium. The transfer medium can be a polymer film or a liquid solution, depending on the specific application requirements. By carefully controlling the transfer process, it is possible to achieve a uniform and defect-free graphene layer on the target surface.The advantages of using transfer printing for graphene-based UV sensitive films are numerous. Firstly, it allows for the fabrication of large-area films with highuniformity and quality. Secondly, it enables theintegration of graphene with different substrates, such as glass, silicon, or flexible materials. This flexibility in substrate choice opens up a wide range of potential applications for graphene-based UV sensitive films.For example, let's consider the application of UV sensors. UV sensors are used for detecting and measuring UV radiation, which can be harmful to human health in excessive amounts. By incorporating graphene into a UV sensitive film using transfer printing, it is possible tocreate highly sensitive and accurate UV sensors. These sensors can be used in various industries, such as healthcare, environmental monitoring, and industrial safety.中文回答:紫外光敏薄膜广泛应用于光刻、光学传感器和保护涂层等领域。
紫外二氧化硅紫外二氧化硅(UV-SiO2)是一种在紫外光下具有特殊性能的材料。
它具有高透明度、低折射率、低热膨胀系数和优异的耐化学性能等特点,被广泛应用于光学、电子、材料科学和生物医学等领域。
紫外二氧化硅的高透明度使其成为一种理想的光学材料。
在紫外光波段(200-400纳米)内,紫外二氧化硅的透射率高达80%以上,远远高于其他常见材料。
这使得它在紫外光学器件中具有广泛的应用,如紫外光透镜、紫外光滤光片和紫外光同轴光纤等。
此外,紫外二氧化硅的低折射率也使得它在光学涂层中起到优异的抗反射效果,提高了光学器件的传输效率。
除了光学领域,紫外二氧化硅还在电子领域发挥着重要作用。
由于其优异的绝缘性能和稳定性,紫外二氧化硅被广泛应用于集成电路(IC)制造中的氧化层和隔离层。
它可以用作电子器件的绝缘层,有效地防止电流泄漏和电子器件的互相干扰。
此外,紫外二氧化硅还具有优异的热稳定性,可以在高温条件下保持其特性不变,因此被广泛用于高温电子器件的封装和保护。
在材料科学领域,紫外二氧化硅是一种重要的纳米材料。
由于其特殊的光学性质和界面效应,紫外二氧化硅纳米颗粒被广泛应用于催化、传感、生物诊断和光学制备等领域。
例如,将紫外二氧化硅纳米颗粒表面修饰功能化基团后,可以用于催化剂的制备,提高催化剂的活性和选择性。
此外,紫外二氧化硅纳米颗粒还可以通过表面修饰来实现生物分子的固定和生物传感,为生物医学研究和临床诊断提供了新的工具和方法。
紫外二氧化硅的优异性能主要来自其特殊的结构。
它是由硅原子和氧原子通过共价键连接而成的,形成了三维网络结构。
这种结构稳定性高、硬度大,使得紫外二氧化硅具有优异的耐化学性能。
它在常见的酸碱溶液中都表现出良好的稳定性,不易溶解或被腐蚀。
这使得紫外二氧化硅成为一种理想的耐酸碱材料,广泛应用于化学、生物和医学领域。
紫外二氧化硅是一种具有特殊性能的材料,在光学、电子、材料科学和生物医学等领域具有广泛的应用前景。
第25卷第11期宿州学院学报Vol .25,No .11 2010年11月Journa l of Suzhou U n iver sity Nov .2010do i :10.3969/j .issn.1673-2006.2010.11.008紫外光照射磷钨酸制备金纳米颗粒李卫东(宿州学院继续教育学院,安徽宿州 234000)摘要:以Keg gin 结构的磷钨酸H 3P W 12O 40为光催化还原剂,以异丙醇为电子牺牲剂,用紫外可见光照射磷钨酸和氯金酸的混合溶液,制备金纳米粒子。
采用透射电子显微镜(TE M )、紫外可见吸收光谱(U V -vis )和X 射线光电子能谱(XPS)等手段对制备的金纳米颗粒的形貌、粒径大小和结构进行了表征。
UV -vis 结果表明,随着反应时间的延长,Au 的特征吸收峰逐渐红移。
制备的Au 纳米颗粒有球形、柱形和不规则的多边形,并随着反应时间的延长,粒径逐渐增加,生成的纳米Au 为立方面心晶格。
关键字:Au 纳米粒子;磷钨酸;紫外光中图分类号:O614.123 文献标识码:A 文章编号:1617-2006(2010)11-0020-04收稿日期:2010-08-28基金项目:国家自然科学基金项目(No .20871089);安徽省教育厅自然科学研究重大项目(No .K J2010Z D09);安徽省教育厅自然科学研究重点项目(N K 6)资助。
作者简介李卫东(6),安徽宿州人,助理实验师,主要研究方向生物材料。
金纳米粒子由于其独特的性质,在催化、化学分析、表面增强拉曼散射技术等领域[1-3]具有广泛的应用,目前,金纳米粒子的制备方法主要有光化学法[4]、化学还原法[5-6]、模板法[7]等,由于金纳米粒子的性质与形状和尺寸密切相关,理想的形貌可控合成方法对于推动金纳米粒子的性质及应用有重要的意义,因此探索简便、单分散性好、粒径可控的金纳米粒子的制备方法是人们追求的目标。
TiO2/SiO2复合薄膜的光学性能研究作者:贾曦刘洋溢来源:《中国科技博览》2013年第18期摘要:本文采用射频磁控溅射方法制备了TiO2/SiO2复合薄膜。
采用XRD、台阶仪和UV-Vis等测试手段表征薄膜的晶体结构、膜厚和光学性能。
系统研究了溅射气氛、溅射时间以及SiO2掺杂量对TiO2/SiO2复合薄膜光学性能的影响。
结果表明,TiO2/SiO2复合薄膜对紫外波段光波吸收强度与溅射时间成正比,与氧气含量成反比。
随着氧气含量的降低,薄膜的光波吸收限g向长波方向移动,即吸收波长呈现出明显的“红移”。
随着Si、Ti摩尔比的增加,薄膜的光波吸收限g向短波方向移动,即吸收波长呈现出明显的“蓝移”。
关键词:TiO2/SiO2复合薄膜(TiO2/SiO2 composite films);射频磁控溅射(RF magnetron sputtering);光学性能(optical properties);晶体结构(crystal structure)。
中图分类号:O734二氧化钛(TiO2)具有良好的光催化性和亲水性能,并由于其化学稳定性好、反应活性高,成本低而受青睐。
光催化TiO2材料可用于降解有机物、杀菌消毒、污水处理、空气净化、防雾玻璃、自清洁玻璃等方面,已成为环保纳米材料研究开发的一个热点。
但纯TiO2表面暴露的活性位有限,在光催化降解过程中TiO2有效利用率受到限制[1]。
而采用TiO2/SiO2复合光催化剂,不仅可以降低成本,并且在不损失有效光照的情况下,可以提高TiO2的表面活性位[2]。
TiO2/SiO2复合薄膜能有效提高光催化活性、亲水性等性能,已有大量研究[3~5]表明TiO2/SiO2复合薄膜能提高光催化活性,另外这种复合薄膜也能大大改善亲水性[6]、抗腐蚀性[7]。
因此,TiO2/SiO2复合薄膜为我们在提高材料性能方面提供了一种很重要的途径。
目前,制备TiO2/SiO2复合薄膜的技术有溶胶—凝胶法[8]、化学气相沉积法[9]、射频溅射[10]等。
非手性表面活性剂合成手性介孔二氧化硅及其机理研究龚俊波;路平超;董伟兵;孙亚娟;于博;侯杰【摘要】使用非手性表面活性剂作为模板,不添加任何辅助剂,稀氨水溶液中合成了长径比从1.5~4.5的手性介孔二氧化硅材料.透射电镜以及扫描电镜检测确认了产品手性孔道以及螺旋外貌的存在.而且,在整个手性介孔二氧化硅形成过程中通过透射电镜分别对各个阶段进行了展示,经历了定向连接和逐渐扭曲的现象.这个特殊的生长过程在手性介孔二氧化硅的形成过程中至关重要.%Chiral mesoporous silica nanorods with aspect ratios from 1.5 to 4.5 were synthesized by using achiral cati-onic surfactant as template in dilute ammonia solution without additives.The chiral channels and helical morphology of the products were confirmed by using transmission electron microscopy(TEM)and scanning electron microscopy (SEM).Furthermore,the oriented attachment growth of primary particles and the gradual twist phenomenon of nanorods were observed by TEMwith samples from different stages of the whole formation process.It was supposed that this special growth process played a pivotal role in the formation of chiral mesoporous nanorods.【期刊名称】《天津大学学报》【年(卷),期】2016(049)008【总页数】5页(P785-789)【关键词】手性硅;定向连接;介孔材料;螺旋【作者】龚俊波;路平超;董伟兵;孙亚娟;于博;侯杰【作者单位】天津大学化工学院,天津 300072; 化学工程联合国家重点实验室天津大学,天津 300072; 天津化学化工协同创新中心,天津 300072;天津大学化工学院,天津 300072; 化学工程联合国家重点实验室天津大学,天津 300072; 天津化学化工协同创新中心,天津 300072;天津大学化工学院,天津 300072; 化学工程联合国家重点实验室天津大学,天津 300072; 天津化学化工协同创新中心,天津 300072;天津大学化工学院,天津 300072; 化学工程联合国家重点实验室天津大学,天津 300072; 天津化学化工协同创新中心,天津 300072;天津大学化工学院,天津 300072; 化学工程联合国家重点实验室天津大学,天津 300072; 天津化学化工协同创新中心,天津 300072;天津大学化工学院,天津 300072; 化学工程联合国家重点实验室天津大学,天津 300072; 天津化学化工协同创新中心,天津300072【正文语种】中文【中图分类】O0613.72作为手性无机材料的重要一员,手性介孔二氧化硅(chiral mesoporous silica,CMS)因其在形貌选择性和对映选择性相关领域的潜在应用价值而备受关注[1].合成手性介孔二氧化硅的方法有很多.起初,手性表面活性剂被用来合成手性介孔二氧化硅[1-2].后来发现,使用非手性模板也可以合成手性介孔二氧化硅[3-8],这意味着手性介孔二氧化硅的手性孔道并不仅仅来自于手性模板的形貌转移.大部分使用非手性表面活性剂合成手性介孔二氧化硅的合成方法都需要共模板剂或添加剂,笔者认为这些共模板剂和添加剂与螺旋形貌的形成有关.不添加添加剂的情况下,则需要使用高浓度的氨水溶液或引入晶种[7,9].此外,手性介孔二氧化硅的手性孔道和螺旋外貌的形成机理依然存在争议,特别是使用非手性表面活性剂的情况.鉴于不管是手性还是非手性表面活性剂都可以制备出手性介孔二氧化硅,Che 等[9]提出是因为非对称的分子(不管是手性还是非手性)的螺旋排列导致了螺旋介孔结构的形成.除了这种几何学诱导模型,熵驱动模型[7,10]和界面作用机理[3]也被用来解释手性介孔二氧化硅的形成.前者主要关注系统环境对最终产品的影响,而后者则关注纳米棒本身的形貌转变.本文的目的一是开发一种既经济又简单的合成手性介孔二氧化硅的方法;二是得到手性介孔二氧化硅的合成过程机理.最近,本课题组合成一种双层聚合物纳米棒[11],使用棒状介孔二氧化硅作为硬模板时,发现手性介孔二氧化硅可以使用非手性表面活性剂,不添加任何添加剂,在极稀的氨水溶液中被合成出来.笔者报道了一种长径比可以调整的制备手性介孔二氧化硅的方法,并对合成过程进行了检测,提出了手性介孔二氧化硅的合成过程机理.1.1 试剂十六烷基三甲基溴化铵(CTAB),购自上海阿拉丁公司;正硅酸乙酯(TEOS)、氨水和乙醇,购自天津市科密欧化学试剂有限公司.全部试剂未经进一步纯化.1.2 表征方法(1)透射电子显微镜(TEM)分析采用的是日本电子光学实验室 JEOL JEM-2100F型透射电子显微镜.(2)扫描电子显微镜(SEM)分析采用的是日本电子光学实验室JEOL S-4800型扫描电子显微镜.(3) X射线衍射(XRD)分析使用的是日本理学D/MAX-2500型X射线衍射仪(铜靶,λ=0.154,nm,100,mA,40,kV).(4)氮气吸附/脱附测试使用的是 Micromeritics ASAP Tristar3000系统.1.3 手性介孔二氧化硅的合成保持氨水和水的量不变,通过调整 CTAB和TEOS的量,制备出一系列的手性介孔二氧化硅,分别命名为 S1、S2和 S3,原料 CTAB、TEOS、NH3·H2O、H2O 的摩尔比分别为1∶7∶76∶10,100、1∶7∶38∶5,050、1∶7∶19∶2,525.典型的合成过程如下.首先,将氨水溶液(4,mL,质量分数 25%~28%,)和CTAB(0.28,g)于40,℃溶于水(140,g)中.然后,在搅拌条件(400,r/min)下将1.22,mL的TEOS逐滴加入上述溶液,并反应 4,h.得到的产品经离心分离,用水和乙醇洗涤数次后,在空气中干燥.最后在600,℃下煅烧6,h以除去有机模板.如图1所示,样品的颗粒尺寸均一,易于调节.随着CTAB和TEOS用量的增加,样品的颗粒尺寸随之增加,样品长径比分别为 1.5(直径 75,nm,长度 112,nm,见图1(a)、(b))、3.0(直径 100,nm,长度300,nm,见图1(c)、(d))和 4.5(直径 100,nm,长度450,nm,见图1(e)、(f)).可以看到,在实验条件范围内,随着CTAB和TEOS量的成倍增加,制备所得的产品的长径比也相应增加.TEM照片上的条纹证明所制备出的确为手性介孔二氧化硅[1](如图1(b)、(d)、(f)箭头所示).图2为3个样品小角度XRD谱图.在2θ=1.5°~6°之间存在3个很明显的峰值,分别为10、11、20面,说明制备出来的产品为 2D 六方介孔结构(p6m)[12].图3为 3个样品的氮气吸附/脱附等温曲线,图4为通过脱附曲线计算得到的孔径分布,具有典型的 MCM-41型材料的等温曲线特征.样品的平均孔径、BET比表面积以及总孔容如表1所示.由于手性介孔二氧化硅的形成机理现在尚存在争议,研究产品的形成机理具有重大价值.如引言所述,目前,不同的模型被提出,用来解释手性介孔二氧化硅的形成机理.但不同反应时间产品的具体形貌变化却少有关注.这里,对不同反应时间取得的样品进行了TEM分析.如图5所示,最初,当硅源滴加到溶液中不久,就形成大量不规则的类球状小颗粒,有些小颗粒已经聚集成约 100,nm的初级颗粒(见图5(a)).随着 TEOS的持续滴加,越来越多的初级粒子出现.非常有趣的是,这些初级粒子开始相互连接(见图5(b),矩形框标注了典型区域).5,min后,拥有粗糙表面的长棒状颗粒开始出现(见图5(c)),随后,棒状颗粒表面开始出现代表样品中存在螺旋孔道的条纹,且条纹之间的距离逐渐缩短,这意味着产品的螺旋程度在逐渐增加.基于以上检测结果,这里提出以下手性介孔二氧化硅的形成过程机理,主要分为 3个阶段,示意见图6.1)初级粒子的形成在这一阶段,TEOS逐滴加入含有胶束的溶液中,并迅速水解聚合形成硅的低聚体.然后这些硅的低聚体通过静电作用吸附在胶束上并自组装形成初级粒子.为了方便起见,图6(a)中把初级粒子画成六方柱状形貌,但实际上初级粒子的形貌在这一阶段并不规则.2)初级粒子定向连接及进一步生长在这一阶段,两个或者更多的初级粒子相互连接形成更长的粒子.溶液系统的条件,包括温度、搅拌速度、溶液浓度等,都会影响定向连接的结果[13-14],从而导致不同的产品长径比.值得一提的是,初级粒子中Si—O—Si键的交联程度是很低的,因此在外界的作用力以及内部结构重整的共同作用下,最终导致纳米棒的扭曲. 3)纳米棒的扭曲初始纳米棒形成以后,纳米棒开始逐渐扭曲.在这一阶段,初始纳米棒内部的Si—O—Si键不断提高交联度,在外界作用力的作用下,纳米棒逐渐扭曲,最终与胶束的扭曲力达到平衡,得到一定扭曲的纳米棒.相比前人的制备方法,本文中的制备方法没有使用手性表面活性剂,不添加任何添加剂,使用了极稀的氨水溶液,因此前人提出的几何学诱导模型(需要使用手性表面活性剂)、熵驱动模型(需要使用浓氨水)和界面作用(不能解释形成过程)等机理都不能较好地解释这种现象的产生.因此,本文提出:这种特殊的生长方式是导致手性介孔二氧化硅形貌形成的原因.比如,随着表面活性剂和硅源用量的增加,初级粒子的碰撞连接几率变大,从而形成更长的棒状产品并且具有更大的扭曲程度.此外,温度等条件的改变也会影响硅源的水解交联速度,从而影响最终产品的形貌.因此手性介孔硅的形成,是各个因素合力作用的结果,但定向连接在其中起着至关重要的作用,甚至起着决定性作用.在使用非手性表面活性剂、不使用任何添加剂的情况下,不同长径比(1.5、3.0和4.5)的手性MCM-41型介孔二氧化硅纳米棒被制备出来.产品的长径比可以通过改变CTAB和TEOS的量进行控制.反应过程中取样的 TEM分析发现,手性介孔二氧化硅的形成过程经过了定向连接和逐渐扭曲的过程,基于此可以认为手性介孔二氧化硅的形成过程可以分为以下 3个阶段:①初级粒子的形成;②初级粒子定向连接以及进一步生长;③纳米棒的扭曲.这个特殊的形成过程为解释不同形貌纳米颗粒的形成过程提供了新的线索.【相关文献】[1] Che S,Liu Z,Ohsuna T,et al. 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飞秒激光诱导硅表面微纳结构及其SERS应用关键词:飞秒激光、硅表面微纳结构、SERS增强、甲苯分子、拉曼光谱引言表面增强拉曼散射(SERS)是一种分外灵敏的分析技术,已经被广泛用于化学、生物、环境等领域的物质分析和检测。
其中,表面结构对于SERS效应的影响分外重要,因为它们控制着局部电磁场的分布和增强效率。
因此,探究如何制备具有优异SERS增强效应的表面结构,一直是SERS探究的热点和难点之一。
近年来,飞秒激光成为一种分外有前途的微纳加工技术。
它具有聚焦尺寸小、能量高、时间短等优点,可以实现直接在材料表面制备微纳结构,而且具有较好的三维控制能力,因此在SERS应用中,飞秒激光来制备表面结构已经得到了广泛的探究和应用。
试验方法1. 制备硅表面微纳结构试验接受飞秒激光加工系统进行微纳结构制备。
硅片表面先进行清洗和去氧化处理,然后以不同的激光功率和扫描速度进行加工,制备出不同类型的微纳结构。
接受扫描电子显微镜(SEM)观察微结构的形态,同时进行拉曼光谱测试和SERS数据分析。
2. SERS测试将甲苯分子溶液滴于制备好的微纳结构表面,通过拉曼光谱测试,得到了和无结构样品对比的SERS增强效应。
结果和谈论SEM观察结果表明,飞秒激光加工可制备出具有不同形态和尺寸的微纳结构,如圆形凸台、圆形坑、无序纳米结构等。
对于同一种微纳结构,其SERS增强效应与制备条件有关。
例如,对于圆形凸台微结构,随着激光功率的增大和扫描速度的减小,其SERS增强效应逐渐增强。
同时,对于不同类型微纳结构下的甲苯溶液样品,探究得到了不同的拉曼光谱图谱和SERS增强效应。
结论本文利用飞秒激光直接在硅表面制备微纳结构,结果表明,制备条件对微纳结构形态和SERS增强效应有显著影响。
通过试验可得到具有优异SERS增强效应的硅表面微纳结构,为SERS应用提供了一种新的材料选择。
本文的试验方法主要是接受飞秒激光加工系统对硅片表面进行微纳结构制备,并通过拉曼光谱测试和SERS数据分析对制备出的微纳结构进行性能评估。
准二维锡基钙钛矿材料的制备及其光电性能研究准二维锡基钙钛矿材料的制备及其光电性能研究摘要:准二维锡基钙钛矿材料是一类具有优异光电性能的新型材料,被广泛用于光电器件的制备。
本研究旨在通过制备准二维锡基钙钛矿材料,并对其光电性能进行深入研究,为其在光电器件中的应用提供理论和实验依据。
本研究采用化学沉积法制备准二维锡基钙钛矿薄膜,通过扫描电子显微镜(SEM)和X射线衍射(XRD)表征其表面形貌和晶体结构,利用紫外-可见光谱仪(UV-Vis)和电化学工作站对其光电性能进行测试。
1. 引言锡基钙钛矿材料具有优异的光电转换效率和稳定性,已广泛应用于光电器件领域。
然而,由于其三维结构的限制,锡基钙钛矿材料存在一些问题,如不稳定性和能带结构复杂等。
近年来,研究人员通过调控制备工艺,成功制备出具有准二维结构的锡基钙钛矿材料,具有更好的光电性能和稳定性。
2. 实验方法2.1 化学沉积法制备首先,制备锡基钙钛矿的前体溶液。
将无水甲醇和正丁胺加入到锡盐和钛盐的混合溶液中,搅拌混合并加入异丙醇胺作为稳定剂。
然后,在200℃的热板上旋涂前体溶液,使之均匀分布在基底上。
最后,将样品转移到高温炉中,进行热处理。
2.2 表征利用SEM观察样品的表面形貌,通过XRD分析来确定样品的晶体结构。
2.3 光电性能测试利用UV-Vis光谱仪测试样品的吸收特性,通过电化学工作站测量其光电池性能。
3. 结果和讨论通过化学沉积法制备的准二维锡基钙钛矿材料具有光滑且致密的表面形貌,XRD分析显示其为钙钛矿结构。
UV-Vis测试结果表明,样品在可见光区域具有良好的吸收性能,且吸收峰位于550 nm附近。
光电池性能测试显示,准二维锡基钙钛矿材料具有良好的光电转化效率,稳定性也较高。
4. 结论本研究成功制备了准二维锡基钙钛矿材料,并对其光电性能进行了研究。
结果显示,制备的准二维锡基钙钛矿材料具有较好的光电性能和稳定性,可作为光电器件的候选材料。
未来的研究可以进一步优化制备工艺,提高其光电转换效率和稳定性。
UV–VUV laser induced phenomena in SiO2glass Koichi Kajihara a,*,Yoshiaki Ikuta a,Masanori Oto b,Masahiro Hirano a,Linards Skuja a,c,Hideo Hosono a,da Transparent Electro-Active Materials Project,ERATO,Japan Science and Technology Agency,KSP C-1232,3-2-1Sakado Takatsu-ku,Kawasaki213-0012,Japanb Syowa Electric Wire and Cable Co.Ltd,Minami-Hashimoto,Sagamihara229-1133,Japanc Institute of Solid State Physics,University of Latvia,Riga LV1063,Latviad Materials and Structures Laboratory,Tokyo Institute of Technology,4259Nagatsuta,Midori-ku,Yokohama226-8503,JapanAbstractCreation and annihilation of point defects were studied for SiO2glass exposed to ultraviolet(UV)and vacuum UV (VUV)lights to improve transparency and radiation toughness of SiO2glass to UV–VUV laser light.Topologically disordered structure of SiO2glass featured by the distribution of Si A O A Si angle is a critical factor degrading trans-mittance near the fundamental absorption edge.Doping with terminal functional groups enhances the structural relaxation and reduces the number of strained Si A O A Si bonds by breaking up the glass network without creating the color centers.Transmittance and laser toughness of SiO2glass for F2laser is greatly improved influorine-doped SiO2 glass,often referred as‘‘modified silica glass’’.Interstitial hydrogenous species are mobile and reactive at ambient temperature,and play an important role in photochemical reactions induced by exposure to UV–VUV laser light.They terminate the dangling-bond type color centers,while enhancing the formation of the oxygen vacancies.Thesefindings are utilized to develop a deep-UV opticalfiber transmitting ArF laser photons with low radiation damage.Ó2003Elsevier B.V.All rights reserved.1.IntroductionExcimer lasers such as KrF(5.0eV or248nm), ArF(6.4eV or193nm)and F2(7.9eV or157nm) lasers are important coherent light sources in the ultraviolet(UV,<400nm)and vacuum-ultraviolet (VUV,<200nm)wavelength regions.Among the known amorphous optical materials,high-purity synthetic SiO2glass is most widely used for optical components in UV–VUV wavelength pared to crystalline optical materials,amor-phous optical materials are distinctively featured by good shape workability and optical isotropy. However,UV–VUV optical properties of SiO2 glass are often degraded by pre-existing and laser-induced point defects since they induce optical absorption bands andfluctuation of the refractive index[1].In particular,weak optical absorptions near the fundamental absorption edge of SiO2 glass prevented SiO2glass to be used for F2laser optics,which is expected to be a light source in the next-generation photolithography[2].In the present paper,we review our resent studies to develop SiO2glass for UV–VUV lasers.More general reviews on laser-induced point *Corresponding author.Tel.:+81-44-850-9759;fax:+81-44-819-2205.E-mail address:k-kajihara@net.ksp.or.jp(K.Kajihara).0168-583X/$-see front matterÓ2003Elsevier B.V.All rights reserved.doi:10.1016/j.nimb.2003.12.032Nuclear Instruments and Methods in Physics Research B218(2004)323–331/locate/nimbdefects in SiO2glass are available in[1,3].We dis-cuss the effects of topologically disordered struc-ture inherent in SiO2glass on optical absorption near the absorption edge of SiO2glass,and the reduction of the absorption byfluorine doping. We also describe the influence of mobile interstitial hydrogenous species on UV–VUV transparency of SiO2glass through photochemical reactions in-duced by UV–VUV laser irradiations.Finally, utilizing the obtainedfindings,we demonstrate a development of deep-UV(DUV,<300nm)optical fiber which is transparent and tough for ArF laser light.2.Effects of topological disorder on VUV transmit-tance of SiO2glass2.1.Topologically disordered structure of SiO2glassMost forms of the stoichiometric oxides of sil-icon,SiO2,consist of three-dimensionally extend-ing network of corner-linked regular SiO4 tetrahedra[4].Among the crystalline SiO2poly-morphs,optical properties have been most studied for a-quartz.In a-quartz,all the tetrahedra are equivalent and two adjacent tetrahedra are bridged by an equal Si A O A Si angle.On the other hand,amorphous SiO2(SiO2glass)is a polymorph of SiO2featured by disordered arrangement of the tetrahedra.Amorphous SiO2includes various structural variants since the topological arrange-ment of the tetrahedra is not unique.However,in contrast to crystalline SiO2,atomic position is not a useful parameter to describe the structure of amorphous SiO2since the translational symmetry is lost.One of the parameters commonly used to characterize SiO2glass is the Si A O A Si angle[5], which has been measured by X-ray diffraction[6], nuclear magnetic resonance[7]and infrared spec-troscopy[8].Here,degree of distribution of the Si A O A Si angle is considered to indicate the degree of disorder in SiO2glass,since there is no distri-bution in the Si A O A Si angle in crystalline SiO2. Several observations have suggested that VUV transparency of SiO2glass depends on the Si A O A Si angle.Decrease in the average Si A O A Si angle accompanied with densification[9]shifts the fundamental absorption edge to lower energy side [10].Further,bandgap energy of SiO2glass is smaller than that of a-quartz[11].Evidently,it is crucial to modify the degree of disorder of SiO2 glass in improving the transparency of SiO2glass near the fundamental absorption edge.Although it is an important subject when developing SiO2glass used with F2laser,systematic studies have not been performed.Transmittance and toughness for F2laser light were examined for SiO2glass samples with differ-ent distribution of the Si A O A Si angle,which was controlled by changing the thermal anneal tem-perature[12].High-purity synthetic SiO2glass (SiOH:2·1018cmÀ3)containing negligible amount of pre-existing defects was thermally an-nealed for120h at900°C,20h at1100°C,1h at 1200°C,or0.1h for1400°C to obtain equili-brated glass structures at anneal temperatures (referred as T f hereafter).Both the optical absorption near the fundamental edge of SiO2 glass(Fig.1)and the optical absorption induced by exposure to F2laser($2.5mJ cmÀ2,8.4·106 pulses)(Fig.1(inset))increased with an increase in T f.Color centers dominating the laser-induced absorption bands were the E0center(a silicon dangling bond,B SiÅ,5.8eV)and the non-bridging oxygen hole center(NBOHC,an oxygen dangling bond,B SiOÅ,4.8and6.8eV).Since comparable324K.Kajihara et al./Nucl.Instr.and Meth.in Phys.Res.B218(2004)323–331concentrations of the E0centers and NBOHC were formed,photolysis of the Si A O A Si bond is sug-gested to dominate the defect processesB Si A O A Si B!B SiÅþÅO A Si B:ð1ÞNext,defect formation was examined as a function of pulse energy of F2laser.At K10mJ cmÀ2,the concentration of laser-induced defects depended linearly on the pulse energy of F2laser[12,13]. This result indicates that at this pulse energy re-gion the reaction described by Eq.(1)proceeds viaone-photon excitation of the precursors which absorb F2laser photons.Above the threshold pulse energy,however,concentration of laser-in-duced defects increased proportionally with the pulse energy squared(Fig.2)[13].Such quadratic dependence of defect concentration on pulse en-ergy is commonly found for SiO2glasses exposed to KrF or ArF laser pulses.Here defects are cre-ated by the two-photon absorption processes since the one-photon absorption coefficient of SiO2glass is very small for KrF and ArF laser lights.To examine the mechanism of the quadratic depen-dence,the quantum yield of defect formation was evaluated.The quantum yield of F2-laser-induced two-photon defect formation was$3orders of magnitude larger than that expected for the simple two-photon absorption processes[13].This dis-crepancy indicates that two-step absorption via real intermediate state dominates defect creation in SiO2glass exposed to F2laser pulses of J10 mJ cmÀ2.This observation again suggests that electronic states which absorb F2laser photons play an important role in defect creation.Finally,the actual structure of defect precursors is considered.With increasing T f up to1500°C,the density of SiO2glass increases[14]and the average Si A O A Si angle decreases[15].Thus the inset of Fig.1indicates that reduction of the average Si A O A Si angle increases the concentration of de-fect precursors.On the other hand,molecular orbital calculations have suggested that the strain energy of the Si A O A Si bond increases more strongly with decreasing the Si A O A Si angle from the most relaxed angle($140–150°)than with increasing the angle[16,17].Further,Raman spectroscopy indicates that increase in T f enhances 3-and4-membered ring structures of the SiO4 tetrahedral units,which are much strained than the larger ring structures[17].A part of such strained Si A O A Si bonds are most likely to be defect precursors since they release strain energies on dissociation to enhance the stability of resultant defect pairs(Fig.3).2.2.Fluorine doping into SiO2glassObservations shown in Section2.1indicate that the reduction of the strained and unstable Si A O A Si bonds is crucial to enhance the F2laser toughness of SiO2glass.Although low-tempera-ture thermal anneal is a possible approach to de-crease T f,it is not practical since the structural change of SiO2glass is very slow at low tempera-tures.On the other hand,it is possible to accelerate the structural change by incorporating terminal functional groups such as the SiOHand SiClK.Kajihara et al./Nucl.Instr.and Meth.in Phys.Res.B218(2004)323–331325groups[18,19],which break up the glass network and reduce the viscosity.This technique allows to prepare SiO2glass with low T f within a reasonable time scale.Indeed,SiO2glass containing the SiOH groups(wet SiO2glass)exhibits good KrF and ArF laser toughness[20,21].We selected the SiF group as a terminal func-tional group to prepare SiO2glass for F2laser because of the following reasons:First,the SiF groups do not exhibit optical absorption withinthe band gap.Second,they are expected to be stable against the exposure to F2laser light since the Si A F bond is stronger than the Si A O bond. Indeed,good VUV transparency[22,23]and radiation toughness to c-rays[22]and ArF laser light[23]have been reported for F-doped SiO2 glasses.Fig.4demonstrates that F-doped SiO2glass exhibits excellent transparency and toughness for F2laser light[24,25].On the other hand,wet SiO2 glass is not transparent for F2laser light since the SiOHgroups have optical absorption at J7.4eV (Fig.4)[26].Another class of technically-impor-tant synthetic SiO2glass is dry(SiOH-free)SiO2 glass,which is widely used for opticalfibers for telecommunication.However,since oxygen vacancies(the Si A Si bonds)generated during elimination of SiOHexhibit optical absorption at 7.6eV,dry SiO2glass is also difficult to use with F2 laser(Fig.4).The transparency and laser toughness are sig-nificantly improved while doping with SiF groups in concentrations up to1mol%,whereas only a slight further improvement is achieved by an additional increase in SiF concentration[27,28]. This observation indicates that the effect of F-doping is not due to the substitutional effects between O and F where the bandgap depends al-most linearly on the SiF content.In contrast,this result suggests that the role of the F-doping is to enhance the structural relaxation where the SiF content of1mol%is sufficient.Fig.5schemati-cally shows how the F-doping reduces the strain of the glass network and enhances the laser toughness.3.Mobile hydrogenous species in SiO2glass3.1.In situ observation of mobile hydrogenous species in SiO2glassSince the corner-shared network of the SiO4 tetrahedra does not allow close packing of the tetrahedra,structure of SiO2glass is relatively sparse.Thus small molecules are frequently found in the lattice interstitial spaces of SiO2glass. Among known interstitials,hydrogenous species, such as the atomic hydrogen(H0)and hydrogen molecule(H2),have attracted attentions since they are mobile and reactive at ambient temperature, and affect various laser-induced defect processes.In situ measurements are useful to study reac-tions involving mobile hydrogenous species since the reactions are relatively rapid.In situ mea-surements of mobile hydrogenous species in SiO2326K.Kajihara et al./Nucl.Instr.and Meth.in Phys.Res.B218(2004)323–331glass have been mostly performed by radiolysing the pre-existing SiOHgroup into H0and NBOHC and measuring the following decay kinetics of these species by electron paramagnetic resonance (EPR)[29–33].However,EPR is not suitable to perform measurements in wide temperature range since EPR signals are significantly influenced by temperature and several paramagnetic centers(e.g. NBOHC)are even difficult defect at temperatures as high as ambient temperature due to the line broadening[34].In addition,excitation sources such as X-rays,c-rays and pulsed electron beams photolyze not only the SiO A Hbond but also the Si A O A Si bonds.To selectively photolyze the SiO A Hbond,we used an F2laser since F2laser light directly excites the optical absorption band of the SiOHgroup at J7.4eV to create pairs of H0and NBOHC with a quantum yield as large as$0.1to0.3(Fig.6)[35].Dissociation of the Si A O A Si bonds is negligible here(quantum yield:$10À4).On the other hand,the created NBOHC can be detected down to1014cmÀ3in situ by its1.9eV photolu-minescence(PL)at all temperatures below ambient temperature using a fourth-harmonic of Nd:YAG laser(4.7eV,266nm)as a probe source.During thermal anneal,NBOHCs are annihilated by reacting with mobile H0and H2.Thus diffusion and reactions of H0and H2are sensitively mea-sured by utilizing NBOHC PL as a probe(Fig.6).Wet SiO2samples were irradiated with an F2 laser pulse at10K,and subsequently heated to 330K while measuring the concentration change of NBOHC(Fig.7)[36].The decay of NBOHC was separated into three temperature ranges:(I) below100K,(II)100–160K and(III)above 200K.Such three temperature ranges are also seen in NBOHC decay curves taken with respect to time under a constant temperature(Fig.7(inset)).A simultaneous decay of H0and NBOHC with temperature,which was observed by an EPR measurement,indicates that ranges I and II are due to reaction of NBOHC with H0[36].On the other hand,range III is attributable to reaction of NBOHC with H2judging from the low tempera-ture shift of range III by H2impregnation.K.Kajihara et al./Nucl.Instr.and Meth.in Phys.Res.B218(2004)323–331327Further,as range III also appeared in the sample which was H2-free before the F2laser irradiation,a part of H0is considered to turn into H2.Activa-tion energy(E a)for diffusion was derived by sim-ulating the decay curves in Fig.7.It was assumed that E a has a distribution reflecting the topologi-cally disordered structure of SiO2glass.The E a value for H0peaked at$0.1and0.2eV,probably attributable to free and shallow-trapped H0, respectively[36].These values are consistent with the reported E a values[31–33,37,38].The E a value for H2peaked at$0.4eV[36].This value also agrees well with those of the precedent studies [30,39–41]which include macroscopic H2diffusion through bulk SiO2glass[39–41].Fig.8shows formation and decay of NBOHC for the samples irradiated with10F2laser pulses at ambient temperature.The‘‘spike’’-like spectrum indicates that a part of NBOHCs rapidly disap-pears as soon as they are formed.Further,decay of NBOHC was much faster in the H2-impreg-nated sample,demonstrating that H2is mobile enough at ambient temperature to rapidly termi-nate NBOHC[35].On the other hand,Fig.8 shows that the concentrations of NBOHC created by F2laser pulses are comparable between the H2-free and H2-impregnated samples.Thus it is evident that H2-impregnated glass leaves less NBOHCs not because of the low quantum yield of NBOHC formation,but because or rapid decay of NBOHC.3.2.Effects of mobile hydrogens on defect formation and annihilationAs shown in Section 3.1,the interstitial H2 effectively reduces the laser-induced dangling bonds such as NBOHC.This phenomenon is attractive to improve the long-term laser tough-ness of SiO2glasses used for UV–VUV optical components.Indeed,it has been concluded that H2-loading generally improves the radiation toughness of SiO2glasses for KrF and ArF lasers [42–44].However,influence of H2on F2laser toughness of SiO2glass has been unclear.We examined effects of the interstitial H2on the formation of color centers in SiO2glass exposed to ArF or F2laser light(Fig.9)[45].In H2-free samples,laser irradiation induced a broad UV–VUV optical absorption dominated by the E0 center(5.8eV)and NBOHC(4.8and6.8eV).In H2-impregnated samples,on the other hand, optical absorption at<6.5eV due to the E0center and NBOHC was suppressed,as expected from the results shown in Section3.1.However,impregna-tion of H2enhanced the formation of the oxygen vacancy(the Si A Si bond),and its absorption band centered at7.6eV reduced the transmittance at 7.9eV.We suggest that the Si A Si bonds are created by‘‘photochemical reduction’’of glass net-328K.Kajihara et al./Nucl.Instr.and Meth.in Phys.Res.B218(2004)323–331work by the interstitial H2,which proceeds simul-taneously with the termination of the dangling bonds.These results conclude that H2loading is not suitable for SiO2glasses used with F2lasers.4.Deep-UV opticalfiberExcellent UV–VUV transparency and shape workability of SiO2glass are suitable properties in preparing opticalfibers transmitting UV–VUV light.Such opticalfibers are attractive to deliver UV–VUV light and to be used for an optical probe in UV–VUV scanning near-field optical micro-scope(SNOM).However,transmittance and radiation toughness at<200nm have not been satisfactory for opticalfibers manufactured so far [46,47].Development of suchfiber seems to bevery difficult because of the following reasons. First,due to the long optical path of opticalfibers, the concentrations of color centers should be sev-eral orders of magnitudes lower than that of the bulk glasses.Second,a part of dangling bonds, which are inevitably created by the deformation during the drawing,often remains in the resultant fibers as the drawing-induced defects[48,49]. Third,as a result of quenching from$2000°C,the fibers generally contains high concentration of the strained Si A O A Si bonds and defect precursors which potentially turn to color centers with expo-sure to UV–VUV light.These problems have been partly overcome by doping SiOHgroups to en-hance the structural relaxation[47].However,ArF laser toughness is not good enough,possibly be-cause a small portion of the SiOHgroups is turned into color centers,which are not significant in bulk SiO2glasses.As discussed in Section2,fluorine doping is also effective in enhancing the structural relaxation. Further,the SiF groups are more stable than the SiOHgroups against exposure to VUV light.Thus we used F-doped SiO2glass for the core part of DUVfiber[50].The clad part also consisted of F-doped SiO2glass with higher SiF content to de-crease the refractive index.As shown in Fig.10,1 m transmittance of the resultantfiber was as high as$60%for ArF laser light.However,it rapidly decreased with ArF laserfluence(Fig.10(inset))because of the formation of the E0center(Fig.10). To suppress the formation of the E0center,the fiber was loaded with H2based on the observa-tions shown in Section3.Transmittance of the H2-loadedfiber degraded only little with exposure to ArF laser up to$105pulses at$50mJ cmÀ2 since the E0center was not accumulated(Fig.10). An additional benefit of thisfiber is that thefiber tip can be easily sharpened by immersion into hydrofluoric acid(Fig.11).This feature is useful for preparation of probe tips for deep-UV SNOM.Fig.11.Scanning electron microscopic photograph of the end of deep-UVfiber sharpened by etching with hydrofluoric acid.K.Kajihara et al./Nucl.Instr.and Meth.in Phys.Res.B218(2004)323–3313295.SummaryTopologically disordered structure of SiO2glass is an intrinsic origin of optical absorption near the fundamental absorption edge of SiO2glass,and its reduction byfluorine doping improves transmit-tance and laser toughness of SiO2glass for F2 laser.Doping by the SiOHgroups is also effective to reduce the structural disorder.However,the SiOHgroups absorb F2laser light and can also be precursors of color centers.The interstitial H2 terminates the dangling-bond type defects, whereas it enhances the formation of the oxygen vacancies by photochemical reduction of the SiO2 network.Since effects of the SiOHgroups and interstitial H2are not simple as described above, appropriate control of their content is important to optimize the UV–VUV optical properties of SiO2glass.These knowledge opened a way to de-velop a deep-ultraviolet opticalfiber transmitting ArF laser pulses with maintaining a loss as low as $1.7dB mÀ1.References[1]G.Pacchioni,L.Skuja,D.L.Griscom(Eds.),Defects inSiO2and Related Dielectrics:Science and Technology, NATO Science Series,Kluwer Academic Publishers, Dordrecht,Netherlands,2000.[2]V.Liberman,T.M.Bloomstein,M.Rothschild,J.H.C.Sedlacek,R.S.Uttaro,A.K.Bates,C.V.Peski,K.Orvec,J.Vac.Sci.Technol.B17(1999)3273.[3]L.Skuja,H.Hosono,M.Hirano,K.Kajihara,Proc.SPIE5112(2003)2.[4]L.W.Hobbs,X.Yuan,in:G.Pacchioni,L.Skuja,D.L.Griscom(Eds.),Defects in SiO2and Related Dielectrics: Science and Technology,NATO Science Series,Kluwer Academic Publishers,Dordrecht,Netherlands,2000,p.37.[5]A.C.Wright,in:G.Pacchioni,L.Skuja,D.L.Griscom(Eds.),Defects in SiO2and Related Dielectrics:Science and Technology,NATO Science Series,Kluwer Academic Publishers,Dordrecht,Netherlands,2000,p.1.[6]R.L.Mozzi,B.E.Warren,J.Appl.Cryst.2(1969)164.[7]R.Dupree,R.F.Pettifer,Nature308(1984)523.[8]F.L.Galeener,Phys.Rev.B19(1979)4292.[9]R.A.B.Devine,R.Dupree,I.Farnan,J.J.Capponi,Phys.Rev.B35(1987)2560.[10]N.Kitamura,K.Fukumi,K.Kadono,H.Yamashita,K.Suito,Phys.Rev.B50(1994)132.[11]I.T.Godmanis,A.N.Trukhin,K.H€u bner,Phys.StatusSolidi B116(1983)279.[12]H.Hosono,Y.Ikuta,T.Kinoshita,K.Kajihara,M.Hirano,Phys.Rev.Lett.87(2001)175501.[13]K.Kajihara,Y.Ikuta,M.Hirano,H.Hosono,Appl.Phys.Lett.81(2002)3164.[14]R.Br€u ckner,J.Non-Cryst.Solids5(1970)123.[15]A.E.Geissberger,F.L.Galeener,Phys.Rev.B28(1983)3266.[16]N.D.Newton,G.V.Gibbs,Phys.Chem.Miner.6(1980)221.[17]F.L.Galeener,J.Non-Cryst.Solids49(1982)53.[18]G.Hetherington,K.H.Jack,J.C.Kennedy,Phys.Chem.Glasses5(1964)130.[19]A.J.Ikushima,T.Fujiwara,K.Saito,J.Appl.Phys.88(2000)1201.[20]M.Shimbo,K.Sato,Jpn.J.Appl.Phys.34(1995)5640.[21]N.Kamisugi,N.Kuzuu,Y.Ihara,T.Nakamura,Jpn.J.Appl.Phys.36(1997)6785.[22]K.Awazu,H.Kawazoe,K.Muta,J.Appl.Phys.69(1991)4183.[23]M.Kyoto,Y.Ohoga,S.Ishikawa,Y.Ishiguro,J.Mater.Sci.28(1993)2738.[24]H.Hosono,M.Mizuguchi,H.Kawazoe,T.Ogawa,Appl.Phys.Lett.74(1999)2755.[25]M.Mizuguchi,L.Skuja,H.Hosono,T.Ogawa,J.Vac.Sci.Technol.B17(1999)3280.[26]Y.Morimoto,S.Nozawa,H.Hosono,Phys.Rev.B59(1999)4066.[27]H.Hosono,Y.Ikuta,Nucl.Instr.and Meth.B166–167(2000)691.[28]K.Saito,A.J.Ikushima,J.Appl.Phys.91(2002)4886.[29]A.R.Silin,L.N.Skuja,J.Mol.Struct.61(1980)145.[30]D.L.Griscom,J.Non-Cryst.Solids68(1984)301.[31]T.Miyazaki,N.Azuma,K.Fueki,J.Am.Ceram.Soc.67(1984)99.[32]T.E.Tsai,D.L.Griscom,E.J.Friebele,Phys.Rev.B40(1989)6374.[33]I.A.Shkrob,A.D.Trifunac,Phys.Rev.B54(1996)15073.[34]M.Stapelbroek,D.L.Griscom,E.J.Friebele,G.H.SigelJr.,J.Non-Cryst.Solids32(1979)313.[35]K.Kajihara,L.Skuja,M.Hirano,H.Hosono,Appl.Phys.Lett.79(2001)1757.[36]K.Kajihara,L.Skuja,M.Hirano,H.Hosono,Phys.Rev.Lett.89(2002)135507.[37]K.L.Brower,P.M.Lenahan,P.V.Dressendorfer,Appl.Phys.Lett.41(1982)251.[38]D.L.Griscom,J.Appl.Phys.58(1985)2524.[39]R.W.Lee,R.C.Frank,D.E.Swets,J.Chem.Phys.36(1962)1062.[40]R.W.Lee,J.Chem.Phys.38(1963)448.[41]J.E.Shelby,J.Appl.Phys.48(1977)3387.[42]S.Yamagata,Miner.J.15(1991)333.[43]D.R.Sempolinski,T.P.Seward,C.Smith,N.Borrelli,C.Rosplock,J.Non-Cryst.Solids203(1996)69.[44]M.Shimbo,T.Nakajima,N.Tsuji,T.Kakuno,T.Obara,Jpn.J.Appl.Phys.38(1999)L848.[45]Y.Ikuta,K.Kajihara,M.Hirano,S.Kikugawa,H.Hosono,Appl.Phys.Lett.80(2002)3916.330K.Kajihara et al./Nucl.Instr.and Meth.in Phys.Res.B218(2004)323–331[46]R.K.Brimacombe,R.S.Taylor,K.E.Leopold,J.Appl.Phys.66(1989)4035.[47]K.F.Klein,R.Arndt,G.Hillrichs,M.Ruetting,M.Veidemanis,R.Dreiskemper,J.Clarkin,G.Nelson,Proc.SPIE4253(2001)42.[48]P.Kaiser,J.Opt.Soc.Am.64(1974)475.[49]Y.Hibino,H.Hanafusa,J.Appl.Phys.60(1986)1797.[50]M.Oto,S.Kikugawa,N.Sarukura,M.Hirano,H.Hosono,IEEE Photo.Technol.Lett.13(2001)978. 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