An architecture for the operation of a recuperative-type glass furnace is introduced in this paper. It is based on a hierarchical scheme, with two main parts: process optimisation and process modelling. Process optimisation is carried out by an expert controller, and uses genetic algorithms to solve a multiobjective optimisation problem. Process modelling is performed by a learning system, based on a fuzzy learning-by-examples algorithm. Results of real and simulated experiments with the glass manufacturing process are presented.

In this paper, we present results concerning the thickness dependence (from 70 to 890 nm) of electrical, structural, morphological and optical properties presented by gallium-doped zinc oxide (GZO) deposited on polyethylene naphthalate (PEN) substrates by r.f. magnetron sputtering at room temperature. For thicknesses higher than 300 nm an independent correlation between the electrical, morphological, structural and optical properties are observed. The lowest resistivity obtained was 5 × 10-4 Ω cm with a sheet resistance of 15 Ω/□ and an average optical transmittance in the visible part of the spectra of 80%. It is also shown that by passivating the surface of the polymer by depositing a thin silicon dioxide layer the electrical and structural properties of the films are improved nearly by a factor of two. © 2003 Elsevier B.V. All rights reserved.

In this letter we compare the room temperature ozone sensing properties of intrinsic zinc oxide (ZnO) thin films deposited by spray pyrolysis, dc and r.f. magnetron sputtering. Their sensor response exceeds 8 orders of magnitude when the film structure is constituted by nanocrystallites. These preliminary results clearly demonstrate that the films could be potentially used for ozone detection at room temperature.

Highly conducting and transparent gallium doped zinc oxide thin films have been deposited at high growth rates by r.f. magnetron sputtering at room temperature on inexpensive soda lime glass substrates. The argon sputtering pressure was varied between 0.15 and 2.1 Pa. The lowest resistivity was 2.6 × 10-4 Ω cm (sheet resistance ≈6 Ω/sq. for a thickness ≈600 nm) and was obtained at an argon sputtering pressure of 0.15 Pa and a r.f. power of 175 W. The films present an overall transmittance in the visible spectra of approximately 90%. The increase on the resistivity for higher sputtering pressures is due to a decrease of both, mobility and carrier concentration, and is associated to a change on the surface morphology. The low resistivity, accomplished with a high growth rate (290 Å/min) and with a room temperature deposition enables these films deposition onto polymeric substrates for flexible optoelectronic devices. © 2002 Elsevier Science B.V. All rights reserved.

This work presents for the first time a study on the deposition of polymorphous silicon at an excitation frequency of 27.12 MHz in a large-area plasma enhanced chemical vapor deposition (PECVD) reactor. Moreover, the films produced at 13.56 MHz were also investigated to compare their performance with that of the films produced at 27.12 MHz. The SiH4/H2 plasma was characterized by impedance probe measurements, aiming to identify the plasma conditions that lead to produce polymorphous films, under quasi-isothermal conditions. The films were characterized by spectroscopic ellipsometry, infrared absorption, Raman spectroscopy, and hydrogen exodiffusion experiments. These techniques enable a detailed structural characterization of the polymorphous films and a study of the differences between the films deposited at 27.12 MHz and 13.56 MHz. Conductivity measurements were also performed to determine the transport properties of the films. The results show that by using a 27.12 MHz frequency, the growth rate increased by 70% and a more stable, relaxed and denser structure was obtained.

Gallium-doped zinc oxide films were prepared by r.f. magnetron sputtering at room temperature as a function of the substrate-target distance. The best results were obtained for a distance of 10 cm, where a resistivity as low as 2. 7 × 10-4 Ω cm, a Hall mobility of 18 cm2/Vs and a carrier concentration of 1.3 × 1021 cm-3 were achieved. The films are polycrystalline presenting a strong crystallographic c-axis orientation (002) perpendicular to the substrate. The films present an overall transmittance in the visible part of the spectra of approximately 85%, on average. © 2003 Elsevier B.V. All rights reserved.