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Chapter: 4 Atomic and nuclear physics
    Section: 4.1 Electrons in atoms
        SubSection: 4.1.3 Auger spectroscopy

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4.1.3    Auger spectroscopy

Impact of electrons with a solid causes ionization of atomic energy levels of atoms in the solid. An ionized atom can relax by the ejection either of an X-ray photon or of an Auger electron; the latter process is far more probable at low primary energies, e.g. less than 10 keV. In the Auger process the ionized level, of binding energy EA, is filled by an electron from an outer level, of binding energy EB, and the excess energy (EAEB) is given to another electron either in the same level EB or in a still more shallow one of binding energy Ec. The energy EABC of the Auger transition ABC, i.e. the kinetic energy of the ejected electron, is then

 

   EABC = EAEBEC

(1)

where EC is primed to show that the binding energy of the electron in C has changed due to the fact that the electron is being ejected from an already ionized atom. To a good approximation for most purposes, the Auger energy EABC may be estimated from the Chung and Jenkins’ (1970) expression, for an atom of atomic number Z,

 

   EABC = EA(Z) − {EB(Z) + EB(Z + 1)} − {EC(Z) + EC(Z + 1)}

(2)

where EB(Z + 1), EC(Z + 1) are the binding energies of electrons in the same levels in the next element up the Periodic Table. Since equation (2) can be used in conjunction with tables of atomic energy levels to calculate the expected energies of Auger transitions, analysis of the observed Auger spectrum from a solid enables its atomic composition to be established.

In electron-excited Auger spectroscopy, the range of energies normally used is 1000–10 000 eV, and the energies of the resultant Auger electrons are typically 20–1000 eV. At these low energies, the inelastic mean free paths of electrons in solids (see section 4.5.2) are very short, and therefore the Auger electrons must originate at, or very close to, the true surface if they are to escape and be observed externally. Auger spectroscopy is thus very surface-specific.

Auger electrons may also be produced by initial excitation with X-rays, ions, and other particles.

The table sets out the experimentally observed energies of the most intense Auger transitions of the more common elements in solid elemental or compound form. Allocation of the transitions has been made on the basis of equation (2), using the tables of binding energies published by Bearden and Burr (1967).

For more comprehensive reading about Auger spectroscopy see the books by Briggs and Seah (1990) and by Rivière (1990).

References

J. A. Bearden and A. F. Burr (1967) Rev. Mod. Phys., 39, 125–142.
D. Briggs and M. P. Seah (1990) Practical Surface Analysis Vol 1: Auger and X-ray Photoelectron
    Spectroscopy
, Wiley, Chichester.
M. F. Chung and J. H. Jenkins (1970) Surface Science, 22, 479–485.
J. C. Rivière (1990) Surface Analytical Techniques, University Press, Oxford.


Energies of the major Auger lines for the more common elements

Element

Z

E/eV

Transition

Element

 Z

 E/eV

Transition


C     .    .    .    .    .


  6


270

 
  KVV

 

 


844

  
L3M2, 3V

N     .    .    .    .    .

  7

380

  KVV

 

 

917

  L3VV

O     .    .   .    .    .

  8

510

  KVV

   Zn    .    .   .    .

 30

  58

  M3VV

F      .    .   .    .    .

  9

650

  KVV

 

 

830

  L3M2, 3M2, 3

Na   .    .    .    .    .

11

  30

  L2, 3VV

 

 

910

  L3M2, 3V

 

 

990

  KL2, 3L2, 3

 

 

990

  L3VV

Mg   .    .    .    .    .

12

  47

  L2, 3VV

   Ge    .    .    .    .

 32

  24

  M4, 5VV

 

 

1180   

  KL2, 3L2, 3

 

 

  44

  M3M4, 5M4, 5

Al    .    .    .    .    .

13

  66

  L2, 3VV

 

 

  48

  M2M4, 5M4, 5

 

 

1380   

  KL2, 3L2, 3

 

 

  84

  M2, 3M4, 5V

Si    .    .    .    .    .

14

  91

  L2, 3VV

 

 

1140   

  L3M4, 5M4, 5

 

 

1610   

  KL2, 3M2, 3

 

 

1173   

  L2M4, 5M4, 5

P     .    .    .    .    .

15

116

  L2, 3VV

   As    .    .    .    .

 33

  36

  M4, 5VV

S     .    .    .    .    .

16

150

  L2, 3VV

 

 

  42

  M3M4, 5M4, 5

Cl   .    .    .    .    .

17

180

  L2, 3VV

 

 

  47

  M2M4, 5M4, 5

K    .    .    .    .    .

19

250

  L2, 3VV

 

 

  91

  M2, 3M4, 5V

Ca   .    .    .    .    .

20

290

  L2, 3M2, 3M2, 3

   Zr    .    .    .    .

 40

  20

  N2, 3VV

Cr   .    .    .    .    .

24

  35

  M2, 3VV

 

 

  90

  M4, 5N1N2, 3

 

 

486

  L3M2, 3M2, 3

 

 

115

  M4, 5N2, 3N2, 3

 

 

527

  L3M2, 3V

 

 

145

  M4, 5N2, 3V

Mn  .    .    .    .    .

25

  40

  M2, 3VV

   Nb    .    .    .    .

 41

  22

  N2, 3VV

 

 

540

  L3 M2, 3M2, 3

 

 

102

  M4, 5N1N2, 3

 

 

588

  L3M2, 3V

 

 

164

  M4, 5N2, 3N2, 3

 

 

637

  L3VV

 

 

194

  M4, 5N2, 3V

Fe   .    .    .    .    .

26

  44

  M2, 3VV

   Mo    .    .    .    .

 42

  27

  N2, 3VV

 

 

594

  L3M2, 3M2, 3

 

 

120

  M4, 5N1N2, 3

 

 

647

  L3M2, 3V

 

 

185

  M4, 5N2, 3N2, 3

 

 

700

  L3VV

 

 

220

  M4, 5N2, 3V

Co   .    .    .    .    .

27

  52

  M2, 3VV

   Ag    .    .    .    .

 47

  48

  N3VV

 

 

651

  L3 M2, 3M2, 3

 

 

  56

  N2VV

 

 

711

  L3 M2, 3V

 

 

270

  M4, 5N1V

 

 

771

  L3VV

 

 

308

  M4, 5N2, 3V

Ni   .    .    .    .    .

28

  60

  M2, 3VV

 

 

362

  M4, 5VV

 

 

716

  L3M2, 3M2, 3

   Sn    .    .    .    .

 50

  22

  N4, 5VV

 

 

781

  L3M2, 3V

 

 

  64

  N2, 3N4, 5V

 

 

847

  L3VV

 

 

310

  M5N1N4, 5

Cu   .    .    .    .    .

29

  60

  M3VV

 

 

360

  M5N2, 3N4, 5

 

 

772

  L3M2, 3M2, 3

 

 

423

  M5N4, 5N4, 5

Ta    .    .    .    .    . 

73

  26

  N6, 7VV

   

 

254

  N4N6, 7V

  

 

163

  N5 N6, 7N6, 7  

   Au    .    .    .    . 

79

  42

  O3VV

 

 

173

  N4N6, 7N6, 7  

   

 

  71

  N7VV

 

 

199

  N5N6, 7V

   

 

151

  N5N6, 7N6, 7 

 

 

209

  N4N6, 7V

   

 

165

  N4N6, 7N6, 7 

 

 

341

  N3N6, 7N6, 7  

   

 

244

  N5N6, 7V

W    .    .    .    .    . 

74

  20

  N6, 7VV

   

 

261

  N4N6, 7V

 

 

164

  N5N6, 7N6, 7  

   Pb    .    .    .    .

82

  46

  O3O4, 5O4, 5 

 

 

176

  N4N6, 7N6, 7  

   

 

  57

  O2O4, 5O4, 5 

 

 

205

  N5N6, 7V

   

 

  92

  N7O4, 5O4, 5 

 

 

216

  N4N6, 7V

   

 

116

  N7O4, 5V

 

 

347

  N3N6, 7N6, 7  

   

 

246

  N5N7O4, 5 

Pt    .    .    .    .    . 

78

  13

  N7O3V

   

 

265

  N4N7O4, 5 

 

 

  45

  O3VV

   Bi    .    .    .    .

83 

  60

  O2O4, 5O4, 5 

 

 

  68

  N7VV

    

 

102

  N7O4, 5O4, 5 

 

 

160

  N5N6, 7N6, 7  

    

 

128

  N7O4, 5V

 

 

171

  N4N6, 7N6, 7  

    

 

250

  N5N7O4, 5 

 

 

238

  M5N6, 7V

    

 

270

  N4N7O4, 5

               

The symbols K, L, M, N, and O are in the usual X-ray notation for atomic energy levels; the symbol V refers to the valence band of  the solid.


J.C. Rivière/M.P. Seah

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