电子衍射图与衍衬理论

Ernst Ruska
1/2 of the prize Federal Republic of Germany Fritz-Haber-Institut der MaxPlanck-Gesellschaft Berlin, Federal Republic of Germany b. 1906 d. 1988
9000
非晶碳 石 墨 金 石 刚
强度
6000
3000
0
270
300
330
360
390
420
能 损 (eV) 量 失
2. 电子衍射图与衍射衬度理论
(1) 电子衍射图 ：斑点衍射花样的分析－－衍射几何 倒易点阵 指数标定 应用：孪晶，长周期结构… (2) 衍射衬度理论： 衍射束强度与衍射衬度象的理论 计算 运动学理论 动力学理论：波动光学法 波动力学法 动力学理论的应用
透射电子显微镜：
Gatan Specimen Holders
Cooling Heating
High Tilt Analytical
Straining
646 double tilt analytical holder, side view
10 0 10
Specimen Rod Stand
Grounding plug Must be installed when Faraday picoammeter is not being used
Circular aperture θR: Angular resolving power
The Nobel Prize in Physics 1937
"for their experimental discovery of the diffraction of electrons by crystals"
3. 电子衍射物理教程，王蓉 著，冶金工业出版
社，（2002）
引言
1. 电子衍射与电子显微镜：
Thomas Young 双缝衍射
sin θ R = 1.22
λ
d
0.61λ = n sin α
: Resolution limit nsinα: Numerical aperture λ: Wavelength
SiC
Si Substrate
2.5 m
会聚束电子衍射
Si (111)
How EELS works
Backscattered electrons Probe electrons
(S)TEM probe electrons travel through a thin specimen Probe electrons lose energy due to their interaction with the specimen (inelastic scattering) The energy-losses are characteristic of the elements and chemistry of the specimen An EELS Spectrometer can disperse the probe electron beam according to its lost energies into a spectrum
物镜极靴
（OL Polepiece）
JEM-2010FEF为超高分辨极靴 （UHR），样品转动空间小，倾转范围 为± 15o，分辨率高；JEM-2010为高倾 转型极靴（HT），样品转动空间大，倾 转范围为± 40o（X）， ± 30o（Y）。
Electron diffraction pattern taken along the tenfold symmetry axis of the Al72Ni20Co8 decagonal quasicrystal.
HRTEM micrographs of the GP-I zones. These micrographs were taken from the same area with an estimated defocus difference of about 100 nm. The line contrasts indicated by arrows in (b) are invisible in (a), whereas other contrasts are visible in both the micrographs.
a (b × c ) a (b × c )
a×b , a (b × c )
a * a b * = G 1 b c * c
倒易点阵矢 量：
a a a b a c b a b b b c G= c a c b c c
r * = ha * + kb * +lc *
c* [001]* c dab (001) b a c*⊥a, c*⊥b; |c* |=(a, b构成的平行四边形的面积）/（晶胞体积） ＝1 /dab
a * a b * = G 1 b c * c
a * a b * = b G c * c
2. 晶带定律 r * ruvw = 0
hu + kv + lw = 0
u, v, w 晶带轴的指数 （正点阵中晶向指数） h, k, l 倒易点阵矢量指数 （正点阵中晶面指数） [uvw] ruvw⊥r*hkl(或 ghkl)
由第二种定义：
a * a 1 0 0 b * a b c = G 1 b a b c = G 1 G = 0 1 0 ] ] [ [ c * c 0 0 1
第二种定义还适用于二维点阵。更普遍的定义
互为倒易
a * a b * a * b * c * = G1 b a * b * c * = G1 [ ] [ ] c * c
600 kx
8 kx
150 kx
1.2 kx
.8 m
1 m
Ion polished commercial Al alloy
Al-Cu metallization layer thinned on Si substrate
Epoxy
TEM of a 14 m thick Silicon Carbide film on Si substrate
电子衍射图与衍衬理论
1. 电子衍射图在晶体学中的应用，郭可信，
叶恒强，吴玉琨 著，科学出版社，（1983）
2. Electron Microscopy of Thin Crystals,
by P. Hirsch, A.Howie, R.B.Nicholson, D.W.Pashley, M.J.Whelan, Roberte E.Krieger Publishing Company, (1977)
- - h1 k1 l1 h1 k1 l1 h2 k2 l2 h2 k2 l2 + + + u v w
3.计算公式
晶面间距
a * h 1 b * a * b * c * k = rhkl * rhkl * = [ h k l ] [ ] 2 dhkl c * l % -1 h = hG
ghkl//晶面(hkl)的法线 |ghkl|＝1/dhkl 倒易点阵矢量ghkl 与 正点阵平面族(hkl) 一一对应
对于一种正点阵，其倒易点阵 是唯一的，与基矢的选取无关
两种定义的比较：
由第一种定义：
a a* = b b* = c c* = 1 a b* = a c* = b a* = b c* = c a* = c b* = 0
Tip detail for specimen loading
Hexring?Tool
Hexring
Anti-twist washer
Specimen grid
The anti-twist washer is used to maintain alignment of grids when specimens are clamped between two grids. Normally, the anti-twist washer is not used when clamping single grids, folding grids and disc specimens. Make sure the specimen is securely clamped by the Hexring?(loose specimens will prevent the full microscope resolution from being obtained.)
(uvw)*
ghkl
求晶带轴指数
由
b * ×c * a= = V (b * ×c*) V*
r1*×r2*=(h1a*+k1b*+l1c*) × (h2a*+k2b*+l2c*) ＝(1/v)[(k1l2-k2l1)a+(l1h2-l2h1)b +(h1k2-h2k1)c] u:v:w= (k1l2-k2l1): (l1h2-l2h1): (h1k2-h2k1)
Auger electrons
X rays (EDXS)
Specimen Secondary electrons
Elastic scattering (Diffraction)
Inelastic scattering
(EELS)
电子能量损失谱——化学成分和精细的电子结构
σ
12000
σ π π σ
The Nobel Prize in Physics 1986
"for his fundamental work in electron optics, and for the design of the first electron microscope" "for their design of the scanning tunneling microscope"