Ferroelectric and high dielectric permittivity films are currently being investigated in view of their use as gate dielectrics in MIS structures. Along with the suppression of tunnelling currents at small gate thickness, they provide a memory function to MIS structures, which can be used in non-volatile memory applications. In this work we report fabrication and characterization of novel metal-ferroelectric-amorphous silicon structures. The structures consist of glass/ITO substrates coated with PZT 20/80 films (sol-gel) followed by an active layer (i-a-SiC:H, deposited by plasma enhanced chemical vapor deposition (PECVD)). A strong capacitance hysteresis is observed in C-V curves in electron accumulation region (VG > 0), accompanied with a large increase in the capacitance of ferroelectric-semiconductor structures at low frequencies. Threshold voltage for electron accumulation is about 10 V being dependent on the ferroelectric polarization switching. © 2002 Elsevier Science B.V. All rights reserved.

In this paper we report results of nanocrystalline p-doped silicon films produced by hot wire chemical vapour deposition technique with Ta filaments, using a pre-mixed gas containing silane, diborane, methane, helium and hydrogen. The data obtained show that the films produced exhibit good optoelectronic properties and show a surface morphology dependent on the filament temperature and hydrogen dilution. The increase in the filament temperature, keeping constant the hydrogen dilution (87%), promotes the preferential growth of the crystals in the {220} direction, giving rise to a pyramidal-like surface structure. This behaviour is observed by the SEM micrographs as well as by the micro-Raman and X-ray diffraction analyses. On the other hand, using a constant filament temperature, the increase in the hydrogen dilution contributes to an increase in both {111} and {220} diffraction peaks. Thus, by combining both filament temperature and hydrogen dilution the film surface can be controlled from a smooth to a pyramidal-like structure, without decreasing the crystalline fraction of the films. The structure and morphology is also reflected in the stability of the electrical dark conductivity. We observe that this property depends on the temperature range of the measurements and on the exposition time of films to the atmospheric conditions. © 2002 Elsevier Science Ltd. All rights reserved.

The aim of this paper is to present a set of electric data concerning the performances before and after ageing of Cu-Sn-Cu joins used to solder power diodes and to compare the results achieved with the ones obtained in diodes soldered using the conventional technology. The set of results achieved show that the Cu-Sn-Cu joins present even better performances than the ones exhibited by diodes soldered using the conventional technology, without requiring the use of Mo discs to be inserted between the silicon crystal and the metal contacts (stud or finger) to compensate thermal mismatches.

In this paper we present an improved version of large area (5 mm × 80 mm) flexible position sensitive detectors deposited on polyimide (Kapton® VN) substrates with 75 μm thickness, produced by plasma enhanced chemical vapor deposition (PECVD). The structures presented by the sensors are Kapton/ZnO:Al/(pin)a-Si:H/Al and the heterostructure Kapton/Cr/(in)a-Si:H/ZnO:Al. These sensors were characterized by spectral response, photocurrent dependence as a function of light intensity and position detectability measurements. The set of data obtained on one-dimensional position sensitive detectors based on the heterostructure show excellent performances with a maximum spectral response of 0.12 A/W at 500 nm and a non-linearity of ±10%. © 2002 Elsevier Science B.V. All rights reserved.

In practice one has often to deal with the problem of inconsistency between constraints, as the result, among others, of the comple\-xi\-ty of real models. To overcome these conflicts we can outline two major \mbox{actions}: removal of constraints or changes in the coefficients of the model. This last approach, that can be generically described as ``model corre\-ction" is the problem we address in this paper. The correction of the right hand side alone was one of the first approaches. The correction of both the matrix of coefficients and the right hand side introduces non linearity in the constraints. The degree of difficulty in solving the problem of the optimal correction depends on the objective function, whose purpose is to measure the closeness between the original and corrected model. Contrary to other norms, the optimization of the important Frobenius was still an open problem. We have analyzed the problem using the KKT conditions and derived necessary and sufficient conditions which enabled us to unequivocally characterize local optima, in terms of the solution of the Total Least Squares and the set of active constraints. These conditions justify a set of pruning rules, which proved, in preliminary experimental results, quite successful in a tree search procedure for determining the global minimizer.