Tellurite And Fluorotellurite Glasses For Active And Passive

7. Surface properties; MDO 253
where e is the charge on an electron (1.6022×10 -19 C), Γ = work function of the material,
which is the lowest energy at which an electron can escape, and h = Planck’s constant
(6.62608×10 -34 J.s). At higher incident frequency, photoelectrons are created with a
maximum kinetic energy,
the work function [3].
max
Ekin = hf − eΓ
max
E kin , reflecting the excess energy of the incident photons over
(7.2)
max
E kin is associated with electrons from around the Fermi level, i.e. the highest lying
occupied energy levels (valence band). The energy of electrons emitted from below the
conduction band, Ekin, is given by equation (7.3) [3].
E B
kin = hf − E − eΓ
(7.3)
where EB is the binding energy of the ejected electron. If the incident radiation is of much
greater energy than the work function of the material, the resulting energy spectrum will
be directly related to the electronic structure of the sample [3]; this is the basic premise of
X-ray photoelectron spectroscopy (XPS).
A wide scan XPS spectrum (i.e. low resolution or survey scan) provides instant
chemical identification of species present in a sample, as core electron binding energies
are unique to a particular element [3]. High resolution spectra of regions identified from
the wide scan can reveal chemical shifts, multiplet peaks, and satellites. This fine detail