材料科学中电子显微镜的各种技术介绍

3.2.2 Where to find the energy loss electrons?
3.3.3 EELS Spectrometer
3.2.4 Comparison of the signal generating and collection process for EDS and EELS
(1) contamination (2) Embedded particales
3.2 EELS - Electron Energy Loss Spectroscopy 3.2.1 energy loss process in thin foil TEM specimens 3.2.2 Where to find the energy loss electrons? 3.2.3 Electron energy loss spectrometer 3.2.4 Comparison of the signal generating process for EDS and EELS 3.2.5 The energy loss spectrum 3.2.6 EELS Microanalysis and the limit of analysis 3.2.7 Conclusion remarks
3.2 EELS - Electron Energy Loss Spectroscopy 3.2.1 energy loss process in thin foil TEM specimens 3.2.2 Where to find the energy loss electrons? 3.2.3 Electron energy loss spectrometer 3.2.4 Comparison of the signal generating process for EDS and EELS 3.2.5 The energy loss spectrum 3.2.6 EELS Microanalysis and the limit of analysis 3.2.7 Conclusion remarks
How to form a probe ?
Detectors needed for an AEM
3.Relationship between TEM, SEM and AEM
3.1 TEM Image mode Diffraction mode
3.2 SEM Image mode: SE, BSE, X-Ray Mapping Microanalysis: WDS, EDS
100% when collection angle is 30 mrad
3.2.5 The energy loss spectrum
(1) The zero loss peak (2) The low loss region of the spectrum
DE< 50eV plasmon peaks (3) High energy region of the spectrum DE>= 50eV energy loss peak - ionization edges pre-edge and post-edge structure
Microanalysis using ionization peaks (edges)
3.2.5 The limitations in EELS analysis
1. Detection limits MDM: In 500Å Fe foil, 103 atoms for Li and Al 3 x 104 atoms for O (k - edge) MDF: C in 300Å steel : 3at% (100 atoms) O in 600Å steel : 6at%
5.1 Terminology
ZOLZ - Zero Order Laue Zone HOLZ - Higher Order Laue Zone FOLZ - First Order Laue Zone SOLZ - Second Order Laue Zone Kikuchi Lines HOLZ Lines Dynamical Effect K- M Pattern Kossel Pattern
3.3 Comparison between EDS and EELS
X-Ray signal generation in TEM thin foil specimens
Fluorescence yield (w): w = 0 for Z ～ 5 (Boron k shell ionization)
材料科学中电子显微镜的各种 技术介绍
1、Introduction
1.Signals generated in the interaction between the incident high energy electron beam and the thin crystalline specimen 2.How to form a probe 3.Relationship between TEM, SEM and AEM 3.1 TEM
EDS - very low !!
X-Ray generation: for carbon: 1 in every 400 k-shell ionization
for Na, 1 in 40
Collection efficiency: WDS: 10-3 - 10-4 EDS: ～10-2
Gold layer (20nm): only allow 67% be transmitted !
The Dead layer below the gold layer: 37% of the 67% be transmitted!
EELS: very high!!
75% of the energy loss electrons with a collection angle of 10 mrad
Image mode Diffraction mode 3.2 SEM Image mode: SE, BSE, X-Ray Mapping Microanalysis: WDS, EDS 3.3 AEM Imaging mode: TEM, STEM, SEM, Mapping (X-Ray + EELS) Diffraction mode: Scanning probe Stationary diffraction pattern Microanalysis: EDS, EELS, micro-diffraction, convergent beam diffraction
3.3 AEM Imaging mode: TEM, STEM, SEM, Mapping (X-Ray + EELS) Diffraction mode: Scanning probe Stationary diffraction pattern Microanalysis: EDS, EELS, micro-diffraction, convergent beam diffraction
Z ～ 27 (Cobalt L shell) Z ～ 57 (lathanlum M shell)
3.2.3 Optimization of the AEM for microanalysis 3.2.4 X-Ray microanalysis
Cliff and Lorimer :
5.1 Terminology 5.2 How to get a CBDP 5.3 ZOLZ - the Zero Order Laue Zone 5.4 Thickness Measurement by CBDP 5.5 HOLZ - Higher Order Laue Zone 5.6 HOLZ Lines - Higher Order Laue Zone Lines 5.7 ZAPS - the zone Axis Patters 5.8 Acquiring 3-D symmetry information 5.9 Phase identification 5.10 summary
3.2 SEM Image mode: SE, BSE, X-Ray Mapping Microanalysis: WDS, EDS
3.3 AEM Imaging mode: TEM, STEM, SEM, Mapping (X-Ray + EELS) Diffraction mode: Scanning probe Stationary diffraction pattern Microanalysis: EDS, EELS, Micro-diffraction, Convergent beam diffraction
3、Microanalysis in AEM
3.1 X-Ray quantitative microanalysis 3.1.1 X-Ray signal generation in TEM thin foil specimens 3.2.2 Identification and elimination of spurious signals 3.2.3 Optimization of the AEM for microanalysis 3.2.4 X-Ray microanalysis 3.2.5 Microanalysis limit
2. Specimen thickness 3. Spatial resolution
Phase identification
4、Micro Diffraction
4.1 Limit of the Selected area electron diffraction (SAD) 4.2 Micro diffraction
2、Imaging in AEM
2.1.TEM 2.2.STEM - Scanning transmission electron microscopy 2.3.STEM/SEM imaging 2.4.Signal mixing - Hybrid imaging 2.5.X-Ray and EELS mapping
4.2.1 the Ricke method 4.2.2 convergent beam micro diffraction
4.1 Limit of the Selected area electron diffraction (SAD)
DD = CS 2B )3 2BDf
5、Convergent beam diffraction
1. Signal generation
EDS - secondary event
High energy incident electrons
excitation of atoms
characteristic X-rays
or Auger electrons
EELS - primary event
2. Collection efficiency
CA CB
= kAB
IA IB
CA+CB=100%
CC CA
=
KCA
IC IA
CC CB
=
KCB
IC IB
KCA
=
KCBቤተ መጻሕፍቲ ባይዱK AB
Limit for microanalysis by EDS
1. Absolute accuracy
Error(%) = N 100 N
2 Minimum detectable mass: MDM 10-20g 3 Minimum mass fraction: MMF 0.1wt% 4 Spatial resolution: 10 ～20 nm 5 Low Z limit 6 Practical limitations :