正电子概况X 正电子技术在材料科学中 的应用-一介孔材料 叶邦角 核固体物理研究室 Laboratory of Nuclear Solid State Physics,USTC PDF文件使用"pdfFactory”试用版本创建耀w.fineprint.cn
正电子技术在材料科学中 的应用---介孔材料 叶邦角 核固体物理研究室 Laboratory of Nuclear Solid State Physics, USTC 正电子概况IX
内容 一、介孔的基本概念和分析方法 二、Low-k materials 三、Summary PDF文件使用"pdfFactory”试用版本创建ww.fineprint.cn
内 容 一、介孔的基本概念和分析方法 二、Low-k materials 三、Summary
1000 100- 10 0 1950 1960 1970 1980 19902000 Year Interest in porous Si PDF文件使用"pdfFactory”试用版本创建击.fineprint.cn
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一、介孔的基本概念和分析方法 macropores 2μm Top view SEM image of Si(100)sample PDF文件使用"pdfFactory”试用版本创建ww.fineprint.cn
Top view SEM image of Si(100) sample macropores 一、介孔的基本概念和分析方法
1.Positron interactions with condensed matter Backscattered Ps Secondary (~140ns) e*reemission electrons o-Ps defect trapping o-Ps defect trapping p-Ps(0.125ns)annihilation or e*free Annihilation (0.5 ns) PDF文件使用"pdfFactory”试用版本创建敛w.fineprint.cn
1. Positron interactions with condensed matter PDF 文件使用 "pdfFactory" 试用版本创建 餀www.fineprint.cn
lifetimes 曦Reemitted positrons Positron free annihilation:500 ps Backscattered Ps:formed by positrons diffuse back to the vacuum and capture an electron on the way.Lifetime is 入 142ns. 嫩 Secondary electrons:positrons can knock off secondary electrons while entering the solid material.(the signal is used as lifetime start signal in PALS) Singlet state (p-Ps):lifetime~125 psec, Triplet state (o-Ps)in vacuum:lifetime 142 nsec, Triplet state (o-Ps)in condensed matter:prefers to stay in defects or pores.Lifetime is reduced by interaction with molecular electrons during collisions with the pore surface PDF文件使用"pdfFactory”试用版本创建ff.fineprint.cn
lifetimes Reemitted positrons Positron free annihilation: < 500 ps Backscattered Ps: formed by positrons diffuse back to the vacuum and capture an electron on the way. Lifetime is ~ 142 ns . Secondary electrons: positrons can knock off secondary electrons while entering the solid material. (the signal is used as lifetime start signal in PALS) Singlet state (p-Ps): lifetime ~ 125 psec, Triplet state (o-Ps) in vacuum: lifetime ~ 142 nsec, Triplet state (o-Ps) in condensed matter: prefers to stay in defects or pores. Lifetime is reduced by interaction with molecular electrons during collisions with the pore surface. PDF 文件使用 "pdfFactory" 试用版本创建 f www.fineprint.cn ÿf
2.介孔结构和尺寸 a b 理想化的结构 (a)cylindrical pores;(b)voids between packed spheres and schematic boundary structure showing. (c)closed (latent)pores;(d)ink bottle;(e)funnel;and (f)open pores. PDF文件使用"pdfFactory'” 试用版本创建www.fineprint..cn
2. 介孔结构和尺寸 (a) cylindrical pores; (b) voids between packed spheres and schematic boundary structure showing. (c) closed (latent) pores; (d) ink bottle; (e) funnel; and (f) open pores. 理想化的结构 PDF 文件使用 "pdfFactory" 试用版本创建 www.fineprint.cn
12 10 8 6 ㄖ 4 s8 D 2 0 D 10 20 30 40 50 60 70 80 Porosity (% FIG.6.Average pore size vs total porosity for several sol-gel based mate- rials(data points include porous SiO2,HSQ,and MSQ based dielectrics,the average pore size was determined by several techniques (see Ref.24). PDF文件使用"pdfFactory”试用版本创建w,fineprint..cn
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106 10s 6ns 109 49ns 10 140ns 判w* 10 0 200 400 600 800 1000 Channel A typical PALS spectrum with three film Ps lifetimes fitted using POSFIT.The points for each channel have been connected with a line for visual clarity.Each channel corresponds to 1.25 ns. PDF文件使用"pdfFactory”试用版本创建l.fineprint.cn
• A typical PALS spectrum with three film Ps lifetimes fitted using POSFIT. The points for each channel have been connected with a line for visual clarity. Each channel corresponds to 1.25 ns. PDF 文件使用 "pdfFactory" 试用版本创建 Ìwww.fineprint.cn ÿÌ
T-E公式 Excluded vohune +A 0.106un 1pa-on=11r-w=。∫r）产b egsy-1 R,1 2x .+三Sn pore R+△2x R+△ e 如果半径>2.3nm Ta01972. J.Chem.Phys.56.5499 T Upick-off T self Eldrup et al.1981 where in air =100 ns but in vacuum 142 ns Chem.Phys.63.51 PDF文件使用"pdfFactory”试用版本创建ww.fineprint.cn
T-E公式 Tao 1972, J.Chem.Phys. 56, 5499 Eldrup et al. 1981 Chem. Phys. 63, 51 , pick off self t t t 1 1 1 = + - 如果半径>2.3 nm where in air =100 ns but in vacuum 142 ns PDF 文件使用 "pdfFactory" 试用版本创建 ÿwww.fineprint.cn
