透射电子显微学课件
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电子能量损失谱
Electron Energy Loss Spectroscopy (EELS)
张庶元
入射高能电子与样品的相互作用
Atomic-scale view of electron energy loss in TEM
Incident beam electron E0 (100 to 1000 keV)
Unfiltered image projected onto CCD detector
18
Energy-filtered TEM imaging (EFTEM - core loss)
The spectrum is shifted relative to the slit opening Best to do by increasing beam energy to preserve image focus
根据等离子激发能量的大小，即谱峰的位置，可以确定物质的 种类和他的组成。
Na：
5.70ev(一次激发)
11.4ev(二次激发)
随试样厚度的增加，电子在试样中可能产生二次，甚至多次等离子激 发，其峰位出现在第一次激发峰的两倍或多倍能量的位置。
Al:
14.95ev
29.9ev
44.35ev
59.8ev
Zero loss
1 eV
CK
0
290
Electron energy loss (eV)
电子能量损失谱信息
非弹性散射过程: 声子激发 (<0.1eV) 等离子激发 (<30eV) 内壳层电子激发 (＞13eV) 自由电子激发 (二次电子) (<50eV) (背底) 韧致辐射 (背底) ∙∙∙ ∙∙∙
29
Colorized Elemental Maps
EDS
• Red: Pd • Green: Au • Despite the presence of heavy elements involved in the analysis, EELS maps show better contrast • Some details in the maps can be observed only in the EELS elemental maps
– – – Allows processing decisions after acquisition Spectrum imaging can create quantitative images / profiles Can confidently locate artifacts & understand image contrast
Final EELS readout Spectrum offset via prism current
Mn L edge
O K edge
EELS spectrum projected onto CCD
17
EFTEM: Energy Filtered TEM: GIF only
Projection section operates in imaging mode Spectrum is projected back to an image Just like forming an image from a diffraction pattern in TEM
Excited specimen electron EB + E
Scattered beam electron E0 - E
3
What is an EELS spectrum?
Elastic scattering
L K Inelastic scattering L Carbon atom K
Electrons count
Mn L La M Ti L
2012 (1024x1024)
2008 (64x64)
10nm
Acknowledgements: Julia Mundy, Carolina Adamo, Darrell Schlom, David Muller, Cornell University 31
Gatan (Tridiem) imaging filter (GIF).
Attached to the TEM column below the viewing chamber
Energy-loss spectroscopy (EELS - low loss)
Spectrum is enlarged and optimally coupled to detector
27
Elemental maps
EDS Pd EELS Pd
Intensity line profiles extracted from the region in the blue in the Pd maps
• The EELS elemental map for the Pd looks much sharper and shows higher contrast than the same map obtained using EDS. This can be directly attributed to the strong forward scattering of the EELS signal and the nearly 100% collection efficiency of detector. • The high signal to noise ratio in the data is evident from intensity line profiles extracted from the region indicated in the box in the EDS and EELS Pd elemental maps.
Dx Dy
image at DE1 image at DE2 . . . . . . . . . image at DEi
spectrum at Dxi ,Dyi
DE
Dx, Dy spatial dimensions DE energy-loss dimension
21
Spectrum imaging - STEM EELS mode
26
Atomic Resolved EELS of GaAs in the bulk
As elemental map EELS colorized elemental map Ga: Green As: Red
Ga elemental map
• The GaAs dumbbell is clearly resolved with high contrast
Core-loss image projected onto CCD detector
Spectrum offset via high tension
image mode
19
EFTEM - a five-stage process
20
Spectrum Imaging – EFTEM mode
• Collects detailed spatial and spectroscopy information
22
Spectrum imaging - STEM EELS mode
23
Elemental Mapping Using Energy Filtered Imaging
SFra Baidu bibliotekC/Si3N4
Atomic Resolved EELS of GaAs in the bulk
HAADF survey image • Analysis was carried out using the facilities at Florida State University • System: ARM200 with cold FEG equipped with GIF Quantum heavily upgraded • Sample was provided by Glasgow University and Sample was observed along the [110] direction • Sample is 4 years old and shows some oxidation
Final EELS readout
EELS spectrum projected onto CCD
16
Energy-loss spectroscopy (EELS - core loss)
The spectrum is shifted Best to do by changing prism current preserve probe focus
内壳层电子激发
偶极跃迁：Δl = ±1
Correlation between EELS and specimen feature
11
Magnetic prism spectrometer
EELS spectrometer
Optical configuration at entrance
Dispersion and focusing section Projection section
表中列出了几种物质的等离子激发峰的理论值和实测值
Specimen thickness measurement
IT ln Io t
λ 为电子非弹性散射的平均自由程
IT
Io
为第一个等离激发峰的强度
为零损失峰的强度
Rough estimate of λ : λ ~ 0.8Eo nm so for 100-keV electrons λ is 80-120 nm various materials
EELS
State of the Art SrTiO3 Example
– LaMnO3/SrMnO3 superlattice grown on SrTiO3 – NION UltraSTEM with Enfinium ER
• 2msec/pixel @ 250pA • 8GB of data!
Spectrum plane
13
In-column omega-filter
Inserted in the imaging lens system Energy-filter imaging and electron diffraction, CBED
Post-column imaging filter
28
Elemental maps
Au EDS
Au EELS
Mean signal Au M EELS Map Au M EDS Map 14468
Std. Dev. 856
79.9
10.1
SN R 17: 1 7.9: 1
• The signal intensity was analyzed from a uniform region of a Au particle. This 16x16 pixel region is show by the red box in the Au elemental maps • The SNR for the EELS data is ~17 while that for the EDS data is ~8 giving about a 2x improvement for the EELS data. • the EELS signal is more than twice as sensitive than the EDS data
25
Atomic Resolved EELS of GaAs in the bulk
EELS SI EELS spectrum extracted from the region in the red box in the EELS SI
Ga L2,3-edges
As L2,3-edges
• Convergence angle: 25mrad • Collection angle120mrad • EELS data was acquired in single range mode • Exposure time per pixel: 50ms • Dataset size: 26x25x2048 • Total number of pixels: 650 • Total acquisition time: 51seconds
Electron Energy Loss Spectroscopy (EELS)
张庶元
入射高能电子与样品的相互作用
Atomic-scale view of electron energy loss in TEM
Incident beam electron E0 (100 to 1000 keV)
Unfiltered image projected onto CCD detector
18
Energy-filtered TEM imaging (EFTEM - core loss)
The spectrum is shifted relative to the slit opening Best to do by increasing beam energy to preserve image focus
根据等离子激发能量的大小，即谱峰的位置，可以确定物质的 种类和他的组成。
Na：
5.70ev(一次激发)
11.4ev(二次激发)
随试样厚度的增加，电子在试样中可能产生二次，甚至多次等离子激 发，其峰位出现在第一次激发峰的两倍或多倍能量的位置。
Al:
14.95ev
29.9ev
44.35ev
59.8ev
Zero loss
1 eV
CK
0
290
Electron energy loss (eV)
电子能量损失谱信息
非弹性散射过程: 声子激发 (<0.1eV) 等离子激发 (<30eV) 内壳层电子激发 (＞13eV) 自由电子激发 (二次电子) (<50eV) (背底) 韧致辐射 (背底) ∙∙∙ ∙∙∙
29
Colorized Elemental Maps
EDS
• Red: Pd • Green: Au • Despite the presence of heavy elements involved in the analysis, EELS maps show better contrast • Some details in the maps can be observed only in the EELS elemental maps
– – – Allows processing decisions after acquisition Spectrum imaging can create quantitative images / profiles Can confidently locate artifacts & understand image contrast
Final EELS readout Spectrum offset via prism current
Mn L edge
O K edge
EELS spectrum projected onto CCD
17
EFTEM: Energy Filtered TEM: GIF only
Projection section operates in imaging mode Spectrum is projected back to an image Just like forming an image from a diffraction pattern in TEM
Excited specimen electron EB + E
Scattered beam electron E0 - E
3
What is an EELS spectrum?
Elastic scattering
L K Inelastic scattering L Carbon atom K
Electrons count
Mn L La M Ti L
2012 (1024x1024)
2008 (64x64)
10nm
Acknowledgements: Julia Mundy, Carolina Adamo, Darrell Schlom, David Muller, Cornell University 31
Gatan (Tridiem) imaging filter (GIF).
Attached to the TEM column below the viewing chamber
Energy-loss spectroscopy (EELS - low loss)
Spectrum is enlarged and optimally coupled to detector
27
Elemental maps
EDS Pd EELS Pd
Intensity line profiles extracted from the region in the blue in the Pd maps
• The EELS elemental map for the Pd looks much sharper and shows higher contrast than the same map obtained using EDS. This can be directly attributed to the strong forward scattering of the EELS signal and the nearly 100% collection efficiency of detector. • The high signal to noise ratio in the data is evident from intensity line profiles extracted from the region indicated in the box in the EDS and EELS Pd elemental maps.
Dx Dy
image at DE1 image at DE2 . . . . . . . . . image at DEi
spectrum at Dxi ,Dyi
DE
Dx, Dy spatial dimensions DE energy-loss dimension
21
Spectrum imaging - STEM EELS mode
26
Atomic Resolved EELS of GaAs in the bulk
As elemental map EELS colorized elemental map Ga: Green As: Red
Ga elemental map
• The GaAs dumbbell is clearly resolved with high contrast
Core-loss image projected onto CCD detector
Spectrum offset via high tension
image mode
19
EFTEM - a five-stage process
20
Spectrum Imaging – EFTEM mode
• Collects detailed spatial and spectroscopy information
22
Spectrum imaging - STEM EELS mode
23
Elemental Mapping Using Energy Filtered Imaging
SFra Baidu bibliotekC/Si3N4
Atomic Resolved EELS of GaAs in the bulk
HAADF survey image • Analysis was carried out using the facilities at Florida State University • System: ARM200 with cold FEG equipped with GIF Quantum heavily upgraded • Sample was provided by Glasgow University and Sample was observed along the [110] direction • Sample is 4 years old and shows some oxidation
Final EELS readout
EELS spectrum projected onto CCD
16
Energy-loss spectroscopy (EELS - core loss)
The spectrum is shifted Best to do by changing prism current preserve probe focus
内壳层电子激发
偶极跃迁：Δl = ±1
Correlation between EELS and specimen feature
11
Magnetic prism spectrometer
EELS spectrometer
Optical configuration at entrance
Dispersion and focusing section Projection section
表中列出了几种物质的等离子激发峰的理论值和实测值
Specimen thickness measurement
IT ln Io t
λ 为电子非弹性散射的平均自由程
IT
Io
为第一个等离激发峰的强度
为零损失峰的强度
Rough estimate of λ : λ ~ 0.8Eo nm so for 100-keV electrons λ is 80-120 nm various materials
EELS
State of the Art SrTiO3 Example
– LaMnO3/SrMnO3 superlattice grown on SrTiO3 – NION UltraSTEM with Enfinium ER
• 2msec/pixel @ 250pA • 8GB of data!
Spectrum plane
13
In-column omega-filter
Inserted in the imaging lens system Energy-filter imaging and electron diffraction, CBED
Post-column imaging filter
28
Elemental maps
Au EDS
Au EELS
Mean signal Au M EELS Map Au M EDS Map 14468
Std. Dev. 856
79.9
10.1
SN R 17: 1 7.9: 1
• The signal intensity was analyzed from a uniform region of a Au particle. This 16x16 pixel region is show by the red box in the Au elemental maps • The SNR for the EELS data is ~17 while that for the EDS data is ~8 giving about a 2x improvement for the EELS data. • the EELS signal is more than twice as sensitive than the EDS data
25
Atomic Resolved EELS of GaAs in the bulk
EELS SI EELS spectrum extracted from the region in the red box in the EELS SI
Ga L2,3-edges
As L2,3-edges
• Convergence angle: 25mrad • Collection angle120mrad • EELS data was acquired in single range mode • Exposure time per pixel: 50ms • Dataset size: 26x25x2048 • Total number of pixels: 650 • Total acquisition time: 51seconds