50
3 Probing Methods: STM/S, PES, APECS, XAS, ZPS
The Auger electron spectroscopy (AES) [14, 15] uses energetic electron source
in replace of X-ray in the XPS. The AES processes include the following:
(1) The process of ionization is the same to that in the PES. The incident electron
beams ionize atoms of the skin by kicking out an electron in the deeper energy
level. The ejected electron flies away from the skin and leaves a hole behind the
lower L(2p) level, for a Cu instance.
(2) The ionization of the core electron relaxes all energy levels because of the screen
weakening of both the intra- and the inter-atomic potentials.
(3) An electron then transits from the relaxed M(3d 5/2 ) upper level to filling the hole
in the initial L level. This transition releases energy that equals the separation
between the two levels, E R = E BL − E BM .
(4) The E R kicks another electron off the further relaxed and degenerated M(3d 3/2 )
level to form the Auger electron that overcomes the E BM and then escapes from
the solid with kinetic energy E KM .
The electronic energies in the PES and the AES processes conserve,
hν = E B(L ,V B) + φ + E K (L ,V B)
(P E S)
E B L − E B M = E M45 + E B M + φ + E K M (AE S)
(1)
The E M45 is the energy separation between the spin-resolved 3d 3/2 and 3d 5/2 lines
of Cu, for instance.
3.4 APECS/XAS: Dual Energy-Level Shifts
3.4.1 AES: Auger Parameter
Differentiating Eq. (1) for the L and the M levels yields immediately,
E B L = −E K L
2E B M = E B L − E K M
α
= −(E K L + E K M ) = 2E B M
(2)
The ionization and relaxation changes the φ ∼ = 0 and the E M45 = (E 3d5/2
− E 3d3/2 ) ∼ = 0 insignificantly for the same specimen. Therefore, this expression
correlates the energy shifts of the APECS involved L and M levels, for the first time.
Figure 3.5 illustrates the mechanism of APECS as a combination of AES and
XPS. Summing the kinetic energy shifts of the XPS and the AES electrons (E KL +
E KM ), conventionally called Auger parameter α
, equals twice the shift of the M
(3d) level shift in magnitude. Therefore, the APECS resolves simultaneously both
the L and the M levels without any approximation or assumption.
3 Probing Methods: STM/S, PES, APECS, XAS, ZPS
The Auger electron spectroscopy (AES) [14, 15] uses energetic electron source
in replace of X-ray in the XPS. The AES processes include the following:
(1) The process of ionization is the same to that in the PES. The incident electron
beams ionize atoms of the skin by kicking out an electron in the deeper energy
level. The ejected electron flies away from the skin and leaves a hole behind the
lower L(2p) level, for a Cu instance.
(2) The ionization of the core electron relaxes all energy levels because of the screen
weakening of both the intra- and the inter-atomic potentials.
(3) An electron then transits from the relaxed M(3d 5/2 ) upper level to filling the hole
in the initial L level. This transition releases energy that equals the separation
between the two levels, E R = E BL − E BM .
(4) The E R kicks another electron off the further relaxed and degenerated M(3d 3/2 )
level to form the Auger electron that overcomes the E BM and then escapes from
the solid with kinetic energy E KM .
The electronic energies in the PES and the AES processes conserve,
hν = E B(L ,V B) + φ + E K (L ,V B)
(P E S)
E B L − E B M = E M45 + E B M + φ + E K M (AE S)
(1)
The E M45 is the energy separation between the spin-resolved 3d 3/2 and 3d 5/2 lines
of Cu, for instance.
3.4 APECS/XAS: Dual Energy-Level Shifts
3.4.1 AES: Auger Parameter
Differentiating Eq. (1) for the L and the M levels yields immediately,
E B L = −E K L
2E B M = E B L − E K M
α
= −(E K L + E K M ) = 2E B M
(2)
The ionization and relaxation changes the φ ∼ = 0 and the E M45 = (E 3d5/2
− E 3d3/2 ) ∼ = 0 insignificantly for the same specimen. Therefore, this expression
correlates the energy shifts of the APECS involved L and M levels, for the first time.
Figure 3.5 illustrates the mechanism of APECS as a combination of AES and
XPS. Summing the kinetic energy shifts of the XPS and the AES electrons (E KL +
E KM ), conventionally called Auger parameter α
, equals twice the shift of the M
(3d) level shift in magnitude. Therefore, the APECS resolves simultaneously both
the L and the M levels without any approximation or assumption.