introduction to auger electron spectroscopy (aes) matse 305 - november 23, 1998
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Introduction to Auger Electron Spectroscopy (AES) MATSE 305 - November 23, 1998. Center for Microanalysis of Materials Frederick Seitz Materials Research Laboratory University of Illinois at Urbana-Champaign. What is Auger?. - PowerPoint PPT PresentationTRANSCRIPT
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Introduction to Introduction to Auger Electron Auger Electron
Spectroscopy (AES)Spectroscopy (AES)MATSE 305 - November 23, 1998MATSE 305 - November 23, 1998
Center for Microanalysis of MaterialsCenter for Microanalysis of Materials
Frederick Seitz Materials Research Frederick Seitz Materials Research LaboratoryLaboratory
University of Illinois at Urbana-University of Illinois at Urbana-ChampaignChampaign
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What is Auger?What is Auger?
Auger Electron Spectroscopy (AES) is a Auger Electron Spectroscopy (AES) is a widely used technique to investigate the widely used technique to investigate the chemical composition of surfaces.chemical composition of surfaces.
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The M ach ine
The M an
Auger (as in ‘Pierre’)
1923:Pierre Auger
d iscovers
the A uger process
Electron Spectroscopy
Why the Odd Name?Why the Odd Name?
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W hy is A uger so surface sensitive?
Re f: C ha rle s Eva ns & Asso c . we b p a g e tuto ria l b y Ro n Flle m ing http ://www.c e a .c o m
Surface SensitivitySurface Sensitivity
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IncidentElectron
STEP 3(alternative)an x-ray is emittedto conserve energyreleased in step 2
STEP 3KLL Auger electronemitted to conserveenergy released instep 2
STEP 2L electron fallsto fill vacancy
STEP 1Ejected electron
-or-
K
L1
L2
L3
1s
2s
2p
CONDUCTION BAND
VALENCE BAND
FREEELECTRONLEVEL
FERMILEVEL
E(Auger)=E(K)-E(L2)-E(L3)
E(X-ray)=E(K)-E(L2)
Auger Transition Named:KLL
The Auger ProcessThe Auger Process
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Auger Energy ScaleAuger Energy Scale
The AES instrument measures The AES instrument measures the kinetic energy of all collected the kinetic energy of all collected electrons.electrons.
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AES Electron vs. X-ray PhotonAES Electron vs. X-ray Photon
Relative Probabilities of RelaxationRelative Probabilities of Relaxationof a K Shell Core Holeof a K Shell Core Hole
5
B Ne P Ca M n Z n Br Z r
10 15 20 25 30 35 40 Atom ic Number
Elem en ta l Sym bol
0
0.2
0.4
0.6
0.8
1.0
Pro
ba
bili
ty
Note: The lightNote: The lightelements have aelements have alow cross sectionlow cross sectionfor X-rayfor X-rayemission.emission.
Auger ElectronAuger ElectronEmissionEmission
X-ray PhotonX-ray PhotonEmissionEmission
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Auger StatsAuger Stats
Primary Beam = 3 - 20 KeV electrons
Detection Sensitivity = ~1 atomic %
Sampling Distance (depth) = 2 to 4 nm
Analysis Diameter = 80nm to several mm
Elements Detectable = Li and above
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Auger Data FormatsAuger Data Formats
Raw Data Differentiated Data
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AES Can Identify ElementsAES Can Identify Elements
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E lem enta l varia tion in sensitiv ity factors
3kV P rim ary B eam Vo ltage
5kV P rim ary B eam Vo ltage
Re f: C ha rle s Eva ns & Asso c . we b p a g e tuto ria l b y Ro n Flle m ing http ://www.c e a .c o m
AES Sensitivity FactorsAES Sensitivity Factors
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Peak Height / QuantitationPeak Height / Quantitation
For quantitation the derivativeform of the data is used.
Sensitivity Factors are usedto adjust the peak heights ofall elements present in thesample.
The composition is normalizedto 100% to determine the amountof each element.
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Identify surface contaminants and Identify surface contaminants and composition.composition.
Study composition as a function of Study composition as a function of depth.depth.
Analyze sample features as small as Analyze sample features as small as 80nm. Using an electron gun for the 80nm. Using an electron gun for the primary beam allows small analysis primary beam allows small analysis spot sizes.spot sizes.
Additional Capabilities of AugerAdditional Capabilities of Auger
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Remove adsorbed gases from Remove adsorbed gases from the sample.the sample.
Eliminate adsorption of Eliminate adsorption of contaminants on the sample. contaminants on the sample.
Prevent arcing and high voltage Prevent arcing and high voltage breakdown.breakdown.
Increase the mean free path for Increase the mean free path for electrons, ions and photons.electrons, ions and photons.
Degree of VacuumDegree of Vacuum1010
1010
1010
1010
1010
22
-1-1
-4-4
-8-8
-11-11
Low VacuumLow Vacuum
Medium VacuumMedium Vacuum
High VacuumHigh Vacuum
Ultra-High VacuumUltra-High Vacuum
PressurePressureTorrTorr
Why UHV for Surface Analysis?Why UHV for Surface Analysis?
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AES Instrument ConfigurationAES Instrument Configuration
Elements of Typical Auger System: Electron Gun Analyzer Secondary Electron Detector Ion Gun Sample Stage Introduction System
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Significance of Primary Beam Significance of Primary Beam
The Electron Beam is functioning The Electron Beam is functioning both as the imaging beam and the both as the imaging beam and the primary beam for analysis. This meansprimary beam for analysis. This meansthat the area of interest on the samplethat the area of interest on the samplecan be directly aligned for analysis.can be directly aligned for analysis.
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MRL InstrumentationMRL Instrumentation
PHI Model 660 Scanning Auger Microprobe
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Sputtering SamplesSputtering Samples
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Al/Pd/GaN Thin Film ExampleAl/Pd/GaN Thin Film Example
(cross section)
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Al/Pd/GaN Profile DataAl/Pd/GaN Profile Data
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Al/Pd/GaN Atomic Concentration DataAl/Pd/GaN Atomic Concentration Data
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Area Specific Depth Profile ExampleArea Specific Depth Profile Example
SP UTTER T IM E (M IN .)
PE
AK
-TO
-PE
AK
Fracture surface of Carbon fibers in BN matrix - analysis area outlined in black
Depth profile on fiber to determ ine point of fracture. Variations in fracture surfaceinterface for d ifferent sam ple treatments w ill be reflected in depth profile.
From research by C . C ofer/J. Econom y, M aterials Science D ept.
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Summary of Surface TechniquesSummary of Surface Techniques