auger electron spectroscopy (aes)
DESCRIPTION
characterizationTRANSCRIPT
Auger electron spectroscopy
SharifUniversity ofTechnology
Kamal Asadi Pakdel
History Of The Auger spectroscopy
Lise Meitner Pierre Auger
The Auger Process
K
L
M
Vacuum Level
Eject core electron
Higher electronfalls into hole
Another higher level electron is ejected to carry away excess energy.
Measure kinetic energy of ejected electron.
IncidentElectronBeam (5 kV)
Ekinetic = E(K) - E(L) - E(L)
KE of Auger electron ~ -EA – EB
EC
Emitted energy of relaxed electron
Energy needed to overcome BE of Auger electron
NOTE: KE of Auger electron is not proportional to the primary beam energy
Different from XPS
Kinetic Energy Of The Auger Electron
KLM
Source of auger electron
Origin of relaxing electron
Initial core hole
Four main Auger series:KLL, LMM, MNN, NOO
As the atomic number increases,the number possible electron transfers are also high.
electron escape depths
In addition, the entire system must be shielded from the earth’s magnetic field
AES instrument schematic configuration
Auger Instrumentation
UHV environment Electron gun Electron energy
analyzer Read-out system
Electron Gun Properties
Stability
Brightness
Longevity
Mono-energetic
Commercial Sources
Thermionic emitter
Lanthanum hexaboride
emitter
Electron energy analyzer
Cylindrical Mirror Analyzer
(CMA)
HemisphericalSector analyzer
(HSA)
Electron energy analyzer
Electron energy analyzer
Cylindrical mirror analyzer(CMA)
(HSA) henmispherical scefor alualyser
Read-out system
• Qualitative Identification of Elements
Analytical Information
Ex:
From the differential AES spectrum Ni, Fe and Cr have been identified.
Ni
Fe
Cr
Chemical Shift
Auger spectra from elemental silicon and oxidized silicon showing the chemical shift which occurs in the oxide
Quantification
External standard (1
Sensitivity factor(2
Sensitivity factor of elements
Surface AnalysisAuger Electron Spectroscopy (AES)
Depth Profiling
E- GunAr+ Sputter Gun
•The primary electron beam is focussed on the surface and scanned (similarly to SEM).
•At each point (pixel), an Auger spectrum is recorded.
•Peaks that correspond to a specific element are indentified and their intensity measured.
•A colour is assigned to each element
•The brightness of colour at each pixel is proportional to the intensity of the corresponding Auger peak.
•Result: multicoloured images as chemical element maps.
Scanning auger microscopy(SAM):
Limits of
Experimet
Spectral peak
overlap
Elemental
Detection
Sensitivity
Sample chargin
g
Electron Beam
Artifacts
High vapor
pressure
samples
XPS vs. Auger
