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2002
BRAZ FERNANDES, Francisco M., Rui Martins, Teresa M. NOGUEIRA, Rui JC Silva, Patricia Nunes, Daniel Costa, Isabel Ferreira, and Rodrigo Martins. "Structural characterisation of NiTi thin film shape memory alloys." Sensors and actuators. A, Physical. 99.1-2 (2002): 55-58. Abstract
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Nunes, P., Braz Fernandes Silva Fortunato Martins F. M. R. J. "Structural characterisation of zinc oxide thin films produced by spray pyrolysis." Key Engineering Materials. 230-232 (2002): 599-602. AbstractWebsite

In this work, we present a study of the effect of temperature, type and concentration of the dopant on the structural characteristics of ZnO thin films produced by spray pyrolysis; the crystallite size has been determined from profile peak shape analysis. These results are compared to the electrical characterisation performed on these materials. The effect of the dopant on the properties of ZnO thin films depends on its characteristics, mainly its ionic radius. Al, Ga and In have been studied as dopants, the best one being In, since it leads to the lowest resistivity.

Fernandas, FMB, R. Martins, MT Nogueira, RJC Suva, P. Nunes, D. Costa, I. Ferreira, and R. Martins. "Structural characterization of NiTi thin film shape memory alloys." Elsevier Science SA, Sensors and Actuators A: Physical(Switzerland).1 (2002): 55-58. Abstract
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Lanca, M. C., E. R. Neagu, and J. N. Marat-Mendes Studies of space charge in electrically aged low density polyethylene., 2002. AbstractWebsite

Space charge in electrically aged LDPE was studied using a recently developed technique combining isothermal charging and discharging with non-isothermal measurements. Samples were aged in a NaCl aqueous solution at 40degreesC for 1500h under an AC field of 6MV/m (50Hz). The samples were then isothermally DC charged and discharged (both currents recorded). Next a non-isothermal experiment with constant heating rate was performed. Finally the sample was kept at the highest temperature and the final isothermal discharge current registered. The last step has to be carried on for long time to ensure an almost complete discharge of the remnant charge so that results become reproducible and possible to analyze. Selective charging (careful choice of the field, temperature and the ratio of charging/discharging times) revealed the presence of different trapping sites. From the analysis of the isothermal and non-isothermal data the relaxation times and activation energies could be obtained.

Lanca, M. C., E. R. Neagu, and J. N. Marat-Mendes Studies of space charge in electrically aged low density polyethylene., 2002. AbstractWebsite

Space charge in electrically aged LDPE was studied using a recently developed technique combining isothermal charging and discharging with non-isothermal measurements. Samples were aged in a NaCl aqueous solution at 40degreesC for 1500h under an AC field of 6MV/m (50Hz). The samples were then isothermally DC charged and discharged (both currents recorded). Next a non-isothermal experiment with constant heating rate was performed. Finally the sample was kept at the highest temperature and the final isothermal discharge current registered. The last step has to be carried on for long time to ensure an almost complete discharge of the remnant charge so that results become reproducible and possible to analyze. Selective charging (careful choice of the field, temperature and the ratio of charging/discharging times) revealed the presence of different trapping sites. From the analysis of the isothermal and non-isothermal data the relaxation times and activation energies could be obtained.

Neagu, E. R., J. N. Marat-Mendes, C. J. Dias, R. Neagu, and T. Vieira. "The study of dipolar and space charges in semicrystalline polymers." Advanced Materials Forum I. Vol. 230-2. 2002. 575-578. Abstract
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Lopes, A., P. Nunes, P. Vilarinho, R. Monteiro, E. Fortunato, and R. Martins. "Study of the sensing mechanism of SnO2 thin-film gas sensors using hall effect measurements." Key Engineering Materials. 230-232 (2002): 357-360. AbstractWebsite

Hall effect measurements are one of the most powerful techniques for obtaining information about the conduction mechanism in polycrystalline semiconductor materials, which is the basis for understanding semiconductor gas sensors. In order to investigate the correlation between the microscopic characteristics and the macroscopic performances exhibited by undoped tin oxide gas sensors deposited by spray pyrolysis, Hall effect measurements were performed at different temperatures, from room temperature up to 500 K, and in the presence of two different atmospheres, air and methane. From these measurements, it was possible to infer the potential barrier and its dependence with the used atmosphere. The obtained results were analysed in terms of the oxygen mechanism at grain boundaries on the basis of the grain boundary-trapping model. In the presence of methane gas, the electrical resistivity decreases due to the lowering of the inter-grain boundary barrier height.

Fortunato, E., P. Nunes, A. Marques, D. Costa, H. Águas, I. Ferreira, M. E. V. Costa, M. H. Godinho, PL Almeida, and J. P. Borges. "Transparent, conductive ZnO: Al thin film deposited on polymer substrates by RF magnetron sputtering." Surface and Coatings Technology. 151 (2002): 247-251. Abstract
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Fortunato, E., P. Nunes, A. Marques, D. Costa, H. Águas, I. Ferreira, M. E. V. Costa, M. H. Godinho, PL Almeida, J. P. Borges, and others. "Transparent, conductive ZnO: Al thin film deposited on polymer substrates by RF magnetron sputtering." Surface and coatings technology. 151 (2002): 247-251. Abstract
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Fortunato, E., P. Nunes, A. Marques, D. Costa, H. Águas, I. Ferreira, M. E. V. Costa, M. H. Godinho, PL Almeida, and J. P. Borges. "Transparent, conductive ZnO: Al thin film deposited on polymer substrates by RF magnetron sputtering." Surface and coatings technology. 151 (2002): 247-251. Abstract
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Neagu, E. R., J. N. Marat-Mendes, C. J. Dias, R. Neagu, and T. Vieira. "Very low frequency dielectric relaxation deduced from time domain measurements." Advanced Materials Forum I. Vol. 230-2. 2002. 579-582. Abstract
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2001
Cabeças, J. M., and Isabel L. Nunes A Produção de Energia Eléctrica e os seus Riscos. Prevenção de Acidentes nas PME'S - Semana Europeia 2001 "O sucesso não acontece por acidente". Instituto Politécnico Setúbal - Setúbal, 2001. Abstract
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Montilla, F., T. Avilés, T. Casimiro, A. A. Ricardo, and M. Nunes Da Ponte. "CpCo(CO)2-catalysed cyclotrimerisation of alkynes in supercritical carbon dioxide." Journal of Organometallic Chemistry. 632.1-2 (2001): 113-118. AbstractWebsite
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Montilla, F., E. Clara, T. Avilés, T. Casimiro, A. Aguiar Ricardo, and M. Nunes Da Ponte. "Transition-metal-mediated activation of arylisocyanates in supercritical carbon dioxide." Journal of Organometallic Chemistry. 626.1-2 (2001): 227-232. AbstractWebsite
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Águas, H., P. Nunes, E. Fortunato, R. Silva, V. Silva, J. Figueiredo, F. Soares, and R. Martins. "Hydrogenated amorphous silicon / ZnO shottky heterojunction for position sensitive detectors." Materials Research Society Symposium - Proceedings. 664 (2001). AbstractWebsite
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Fortunato, Elvira, Patrícia Nunes, António Marques, Daniel Costa, Hugo Águas, Isabel Ferreira, Maria EV Costa, and Rodrigo Martins. "Characterization of Zinc Oxide Thin Films Deposited by rf Magnetron Sputtering on Mylar Substrates." MRS Proceedings. 666.1 (2001). Abstract
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Fortunato, Elvira, Patr{\'ıcia Nunes, António Marques, Daniel Costa, Hugo Águas, Isabel Ferreira, Maria EV Costa, and Rodrigo Martins. "Characterization of Zinc Oxide Thin Films Deposited by rf Magnetron Sputtering on Mylar Substrates." MRS Proceedings. Vol. 666. Cambridge University Press, 2001. F3-21. Abstract
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Aguas, H., Y. Nunes, E. Fortunato, P. Gordo, M. Maneira, and R. Martins. "Correlation between a-Si: H surface oxidation process and the performance of MIS structures." Thin solid films. 383 (2001): 185-188. Abstract
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Nunes, P., Fortunato Vilarinho Martins E. P. R. "Effect of deposition conditions upon gas sensitivity of zinc oxide thin films deposited by spray pyrolysis." Solid State Phenomena. 80-81 (2001): 151-154. AbstractWebsite

In this work we present the results of a study concerning the role of the properties of zinc oxide thin films deposited by spray pyrolysis on its sensitivity to methane or ethane. It was found that using highly resistive thin layers leads to an increase in the film sensitivity. The variation of the operating temperature of the film leads to a significant change in the sensitivity of the sensor and the ideal operating temperature dependence of the gas used. The sensitivity of the ZnO thin films changes linear with the increase of the gas concentration. However these films seem to be more appropriated for the detection of methane than for ethane since the value of sensitivity obtained are higher and its variation with the gas concentration more pronounced. After the annealing treatment performed the films sensitivity decreases.

Nunes, P.a, Fortunato Vilarinho Martins E. a P. b. "Effect of different dopants on the properties of ZnO thin films." International Journal of Inorganic Materials. 3 (2001): 1211-1213. AbstractWebsite

The influence of doping on the properties of zinc oxide thin films deposited by spray pyrolysis has been studied. The results show that the doping affects the properties of the films, mainly the electrical ones, function of its concentration and nature. The most significative improvement were observed for films doped with 1 at.% of indium exhibiting a resistivity of 1.9 × 10-1 Ω m associated to a transmittance of 86%, characteristics required for applications on the optoelectronic devices. © 2001 Elsevier Science Ltd. All rights reserved.

Nunes, P., Fortunato Martins E. R. "Influence of the annealing conditions on the properties of ZnO thin films." International Journal of Inorganic Materials. 3 (2001): 1125-1128. AbstractWebsite

The effect of annealing treatment (in the presence of different types of atmospheres) on the performances of zinc oxide thin films (intrinsic and doped with In and Al) prepared by spray pyrolysis have been studied, with the aim to determine more adequate conditions to improve the properties of the films. The results show that the annealing treatment leads to substantial changes in the structural, electrical and optical characteristics of ZnO thin films. The most significant improvements were obtained after annealing in forming gas (reduction atmosphere) at 200°C during 2 h. The ZnO:In film after heat treatment was the one that exhibited the lowest resistivity (p=5.2x10-2 ωcm) and a high transmittance (T=86%). © 2001 Elsevier Science Ltd. All rights reserved.

Nunes, P., Fortunato Lopes Martins E. A. R. "Influence of the deposition conditions on the gas sensitivity of zinc oxide thin films deposited by spray pyrolysis." International Journal of Inorganic Materials. 3 (2001): 1129-1131. AbstractWebsite

In this work we present preliminary results on the sensitivity to methane gas of zinc oxide thin films deposited by spray pyrolysis. It was found that using highly resistive (above 104 Ω cm) thin films and by performing the measurements at 200°C a sensitivity better than one order of magnitude was found to detect 2000 ppm of methane. A linear dependence on the sensitivity between 100 and 2000 ppm of methane was also obtained. © 2001 Elsevier Science Ltd. All rights reserved.

Águas, Hugo, Rodrigo Martins, Yuri Nunes, Manuel JP Maneira, and Elvira Fortunato. "Influence of the Plasma Regime on the Structural, Optical, Electrical and Morphological Properties of a-Si: H Thin Films." Materials Science Forum. Vol. 382. Trans Tech Publications, 2001. 11-20. Abstract
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Nunes, P., Fortunato Martins E. R. "Influence of the post-treatment on the properties of ZnO thin films." Thin Solid Films. 383 (2001): 277-280. AbstractWebsite

In this work a study of the influence of the annealing treatment (atmosphere and temperature) on the properties of zinc oxide thin films (intrinsic and doped with indium and aluminum) prepared by spray pyrolysis is presented. The result shows that the type of atmosphere (reduction or oxidant) has an important role in the changes observed in the structural, electrical and optical properties of the ZnO thin films. The ZnO thin film doped with indium, presents the lowest resistivity (ρ = 5.8×10-3 Ωcm) associated to a high transmittance (T = 86%), characteristics required for application on optoelectronic devices.