Light induced dielectrophoresis (LIDEP) is a variant of the dielectrophoresis (DEP) mechanism that has been used for some time to manipulate particles in a microfluidic environment. Rather than relying on lithographically created contacts to generate the required electrical fields, the electrical contacts in LIDEP are created through the selective illumination of a photoconductor. The key question we address is how microscopic traps created via LIDEP compare to optical traps based on the gradient force, in terms of power required and trap stiffness achieved, as well as the size resolution of such a trap. We highlight the complex interplay between optical power and resolution with electrical parameters, such as the electrical resistance and applied AC Voltage. We show that for a spotsize of five micrometres and larger, particles can indeed be trapped with low power. We use trap stiffness per mW to compare LIDEP with an optical trap and show that our system is 470+/- 94 times stiffer per mW than a conventional optical trap, with no loss of resolution. We also discuss the difficulties of achieving trapping at smaller spot sizes, and that the submicron resolution possible with gradient force trapping is very difficult to realise with LIDEP.

Infrared transmission spectra of a series of silicon dioxide (SiO2) films grown on silicon wafers from a HCl and O2 gas mixture at 850 °C, have been studied for film thicknesses down to 28 Å. The validity of Lambert-Bouguer’s Law for such thin films has been confirmed, and the apparent absorption coefficient calculated for the absorption at 1065 cm−1 is in good agreement with previously published data for thicker, vapor-deposited, and thermally grown films. A continuous shift of the absorption near 1065 cm−1 has been found, moving from an asymptotic limit maximum of ∼1070 cm−1 for thick films towards smaller wave numbers for thinner films. Various possibilities for the origin of this shift are discussed.

The outstanding thermal properties of diamond and its low reactivity towards hydrogen may make it an attractive plasma-facing material for fusion and calls for a proper evaluation of its behaviour under exposure to fusion-relevant plasma conditions. Micro and nanocrystalline diamond layers, deposited on Mo and Si substrates by hot filament chemical vapour deposition (CVD), have been exposed both in tokamaks and in linear plasma devices to measure the erosion rate of diamond and study the modification of the surface properties induced by particle bombardment. Experiments in Pilot-PSI and PISCES-B have shown that the sputtering yield of diamond (both physical and chemical) was a factor of 2 lower than that of graphite. Exposure to detached plasma conditions in the DIII-D tokamak have evidenced a strong resistance of diamond against erosion under those conditions.

In this research work, a comparative x-ray photoelectron spectroscopy (XPS) analysis has been performed on three allotropic carbon materials i.e. amorphous carbon films, graphite crystals and chemically vapour deposited (CVD) diamond films. These studies have shown that XPS is one of the most powerful techniques used to distinguish the diamond phase of carbon from the graphite and amorphous carbon components. In these investigations, particular attention has been paid to the effects of the post-deposition surface treatment on the diamond surfaces and the corresponding spectrum changes. The experimental results confirmed that ion surface cleaning destroys the original carbon atomic bonding configuration and implants argon atoms into the sample surface. The main spectral changes for amorphous carbon, graphite and diamond materials after the ion etching process can be attributed to bonding modification and the existence of argon contamination on the sample surfaces.

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