Tellurite And Fluorotellurite Glasses For Active And Passive

7. Surface properties; MDO 251
of 10 eV and 50 eV for the high-resolution peak scans and survey scans respectively. The
vacuum in the analysis chamber was typically better than 4×10 -9 mbar (4×10 -7 Pa). The
electron take-off angle used was 90 degrees and the area analysed approximately 1 × 1
cm. The XPS was calibrated monthly with a silver standard.
Glass samples were analysed using a Kratos AXIS ULTRA XPS (under the direction
of Prof. D. Briggs), with a mono-chromated AlKα source (1486.6 eV) operating at 10 mA
emission current, and 10 kV anode potential. This XPS was used in fixed analyser
transmission (FAT) mode, with pass energy of 160 eV for wide scans, and 10 eV for high
resolution scans. The magnetic immersion lens system used a slot aperture of 300 × 700
µm for wide and high resolution scans. The take-off angle the photoelectron analyser was
90°, and acceptance angle 30° (in magnetic lens mode). The analysis chamber pressure
was typically better than 1.3×10 -9 mbar (1.3×10 -7 Pa). Bulk glass samples were analysed
on polished and cleaved surfaces (see chapter 6.1.1.1 for description of polishing
process). Surfaces were cleaved in the laboratory atmosphere with a SiC glass cleaver,
immediately prior to analysis, as contamination on the sample surface such as hydrolysis,
fingerprints, residue from organic solvents (e.g. acetone), silicone release agents from
sample bags, and artefacts from polishing (mounting wax and polishing oil), can mask the
signal from the sample. As XPS is a surface technique, cleaving the sample should result
in spectra which give a better representation of bulk glass composition; however some
degree of hydrolysis will be inevitable when cleaved in the laboratory atmosphere.
Therefore, any quantitative analysis relating to hydroxide groups in the glass had to be
treated carefully.