中国科学技术大学：《正电子物理》课程教学讲稿（正电子在材料科学中的应用）09 正电子技术在材料科学中的应用（介孔材料）

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

Interest in porous Si PDF 文件使用 "pdfFactory" 试用版本创建 Ìwww.fineprint.cn ÿÌ

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