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.

Auger yield

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