Tellurite And Fluorotellurite Glasses For Active And Passive

7. Surface properties; MDO 250
7.1. Experimental
7.1.1. X-ray photoelectron spectroscopy (XPS)
X-ray photoelectron spectroscopy (XPS) is a technique which can be used to probe the
surface structure of materials, as the signal obtained is typically from a few nm of the
surface of the material. The radiation which is incident on the sample is of high enough
energy to result in the ejection of inner shell electrons, with a binding energy
characteristic of the atom the electron originated from. The bonding state of species
present in a material can result in a shift in the binding energies compared with those
expected from the pure element. These peaks can consist of an underlying structure if an
atom (such as oxygen) is bonded to more than one type of cation in the material.
7.1.1.1. Method and instrumentation
XPS was performed in this study using two spectrometers due to the availability of
equipment.
Powdered ZnF2 samples were analysed in their as-received and fluorinated states (i.e.
powder was not separated by mesh size), using a VG Scientific Escalab Mark II X-ray
photoelectron spectrometer, with unmonochromated AlKα X-rays operating at an anode
potential of 10kV, and a filament emission current of 20 mA. Samples were attached to a
metal substrate with carbon tape. The electron spectrometer comprised a hemispherical
analyser and was operated in the constant energy mode (CAE) at electron pass energies