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The plasma enhanced chemical vapor deposition (PECVD) of silicon dioxide (SiO2) thin films from SiH4 and N2O has been executed with and without CO2 laser illumination. The quality of the film processed under a 10.6 µm CO2 laser was close to that of a film grown when the substrate was heated to 200°C. Since the temperature of the film substrate under CO2 laser illumination was only about 55°C, this method should be helpful in processes where a low thermal budget is required. CO2-laser-assisted PECVD (termed LAPECVD) with a substrate heated to 200°C resulted in a SiO2 thin film with excellent I–V characteristics and surface morphology, as well as a higher refractive index and lower etching rate in BOE solution. Application of this thin film should be explored.

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We study the renormalisation aspects of a generalised Coulomb gas by means of a novel method of renormalisation. The model corresponds to an XY system with N-fold symmetry breaking perturbation and is cast in a field-theoretical framework.The method uses the operator product expansion and the renormalisation constants are obtained from the singular terms in this expansion as the ultraviolet cutoff is removed. This method clearly exposes the multiplicative renormalisations involved. An expansion in the departure of the Kosterlitz-Thouless temperature, fugacities, and in E = N -4 to third order is performed. We find a non-trivial self-dual fixed point at which the vortex and symmetry breaking fugacities are of order A.The method also allows the identification of a new set of 'fixed-point' theories that d o not undergo renormalisation.