Tellurite And Fluorotellurite Glasses For Active And Passive

7. Surface properties; MDO 252
For both machines (i.e. all samples), a survey scan spectrum in the 0 to 1100 eV
binding energy (BE) range was collected, in addition to high resolution scans of regions
of interest (e.g. C1s, F1s, Zn2p, Te3d, and O1s regions). A Shirley background model
was used to subtract the background; individual peaks were fitted with a Gaussian /
Lorentz ratio of 70 / 30. Background removal, peak fitting and peak area determination
were performed using CasaXPS software. Semi-quantitative data (i.e. atomic %
determination) of survey spectra were derived using modified Scofield elemental
sensitivity factors for the ZnF2 powders, and Kratos elemental sensitivity factors for glass
samples. The entire spectra were calibrated (i.e. shifted) to the C1s binding energy of 285
eV. Both X-ray photoelectron spectrometers described above produce semi-quantitative
elemental analysis of similar accuracy, however the Kratos machine produces spectra of
higher resolution.
7.1.1.2. Theory of operation
The photoelectric effect, conceived by Einstein [2], showed there was a threshold in
frequency of incident radiation on a metal’s surface, below which no electrons were
ejected, regardless of the intensity of the radiation [3]. This is a direct consequence of the
fact light is quantised, with energy given by equation (6.1). This threshold in frequency,
fc, is directly proportional to the minimum energy, eΓ, required to eject these
photoelectrons, shown by equation (7.1) [3].
e Γ = hf
(7.1)
c