Continuous coating of ceramic fibres by industrial-scale laser driven CVD: fibre modification and structure of interfaces

A laser induced chemical vapour deposition process (L-CVD) has been developed to treat and coat ceramic fibre bundles. This method is characterised by several advantages, among them high deposition rates and very short residence times of the fibres in the deposition chamber. Laser irradiation of SiC based fibres has been found to result in strong structural changes due to recrystallisation accompanied by evolving gaseous SiO and CO. The deposition of thin py-C layers shifts this thermal SiC fibre degradation process to significantly higher power densities, which results in coated fibres without degradation. With CH4 as precursor, layers of highly ordered pyrolytic graphite have been deposited on Nicalon fibres

Ion layer gas reaction ILGAR conversion, thermodynamic considerations and related FTIR analyses

Recently ion layer gas reaction (ILGAR) has been introduced, a novel deposition technology for thin sulfide and oxide layers. Since there is typically incomplete conversion of the educt, thermodynamic calculations were carried out to elucidate the stability ranges of the desired products. It is only deeper in layers, where by-products are less easily removed and the situation resembles more a closed system, that the equilibrium can shift towards the educts. Interestingly, the rmodynamic calculations predict e.g. zinc oxide as the stable product for the IL GAR oxide process even at room temperature. Nevertheless, FTIR and XRD clearly identified the formation of zinc hydroxide at 25°C which dehydrates completely al ready at 155°C. ILGAR therefore opens the possibility of preparing mixtures of hydroxide and oxides of well defined ratios by adjusting process temperature and duration. Several possibilities were successfully tested for elimination of by-products or educt residuals from the layer

High efficiency chalcopyrite solar cells with ILGAR ZnO WEL device characteristics subject to the WEL composition

The composition of the ZnO/Zn(OH)2 material system deposited by ILGAR (Ion Layer Gas Reaction) has been investigated by means of FTIR spectroscopy. Thereby, the O/OH-ratio was of special interest. It has been shown, that from almost impurity-free ZnO to hydroxide-rich Zn(O,OH) any desired mixture can be prepared by ILGAR just by varying the process temperature. In order to attain general information about the requirements on a buffer material in chalcopyrite solar cells, such Zn(O,OH) mixtures were introduced as intermediate layer implemented by the WEL concept (Window Extension Layer). Superior solar cell performances compared to chemical bath deposited CdS buffered references were already reported earlier for ILGAR-ZnO WEL devices based on Cu(ln,Ga)(S,Se)2 ("CIGSSe"). The influence of varying material properties of the Zn(O,OH) WELs on the characteristics of corresponding CIGSSe devices has been investigated. It has been found that below a critical process temperature the WEL constitution has no major influence on the power conversion efficiency of these cells, but a significant impact on their device stability

Großflächige Plasmavorbehandlung und PECVD bei Atmosphärendruck mittels LARGE-Plasmaquelle

Using the LARGE (Long Arc Generator) plasma source, a long arc, forming a fan-shaped afterglow plasma with a width of 80 to 350 mm is formed at atmospheric pressure. In contrast to most point-form atmospheric plasma sources, the method offers an attractive means for pre-treatment of large surface areas. The reactive working gas formed by plasmachemical excitation can be used to activate or modify the surfaces of materials ranging from metals to polymers. In this article, the operation of the LARGE plasma source, the means by which coating properties can be modified and its use to deposit SiOx adhesion-promoting layers on metals are described. Of special interest were the optical properties and the morphology of these deposits as well as their potential as adhesion-promoters in metal-plasti c composite structures. Because of its very flexible stand-off distance of up to 60 mm and its compact construction, LARGE technology is ideal for a wide range of industrial applications. These include coating of 2.5 D components, and formation of nano-structured SiOx layers for mechanical and chemical bonding of epoxy adhesives to surfaces