Fortunato, E., Pimentel Pereira Gonçalves Lavareda Águas Ferreira Carvalho Martins A. L. A. "
High field-effect mobility zinc oxide thin film transistors produced at room temperature."
Journal of Non-Crystalline Solids. 338-340 (2004): 806-809.
AbstractIn this paper we present the first results of thin film transistors produced completely at room temperature using ZnO as the active channel and silicon oxynitride as the gate dielectric. The ZnO-based thin film transistors (ZnO-TFT) present an average optical transmission (including the glass substrate) of 84% in the visible part of the spectrum. The ZnO-TFT operates in the enhancement mode with a threshold voltage of 1.8 V. A field effect mobility of 70 cm2/Vs, a gate voltage swing of 0.68 V/decade and an on-off ratio of 5×105 were obtained. The combination of transparency, high field-effect mobility and room temperature processing makes the ZnO-TFT very promising for the next generation of invisible and flexible electronics. © 2004 Elsevier B.V. All rights reserved.
Fortunato, E.a, Pereira Barquinha Botelho Do Rego Gongalves Vilà Morante Martins L. a P. a. "
High mobility indium free amorphous oxide based thin film transistors."
Proceedings of International Meeting on Information Display. Vol. 8. 2008. 1199-1202.
AbstractHigh mobility bottom gate thin film transistors (TFTs) with an amorphous gallium tin zinc oxide (a-GSZO) channel layer have been produced by rf magnetron cosputtering using a gallium zinc oxide (GZO) and tin (Sn) targets. The effect of the post annealing temperatures (200 °C, 250 °C and 300 °C) was evaluated and compared with two series of TFTs produced at room temperature and 150 °C during the channel deposition. From the results it was observed that the effect ofpos annealing is crucial for both series of TFTs either for stability as well as for improving the electrical characteristics. The a-GSZO TFTs operate in the enhancement mode (n-type), present a high saturation mobility of 24.6 cm2/Vs, a subthreshold gate swing voltage of 0.38 V/decade, a turn-on voltage of -0.5 V, a threshold voltage of 4.6 V and an ION/IOFF ratio of 8x107, satisfying all the requirements to be used in active-matrix backplane.
Fortunato, E., Pimentel Gonçalves Marques Martins A. A. A. "
High mobility nanocrystalline indium zinc oxide deposited at room temperature."
Materials Research Society Symposium Proceedings. Vol. 811. 2004. 437-442.
AbstractIn this paper we present results of indium doped zinc oxide deposited at room temperature by rf magnetron sputtering, with electron mobility as high as 60 cm2/Vs. The films present a resistivity as low as 5×10 -4 Ωcm with an optical transmittance of 85%. The structure of these films look-like polymorphous (mixed of different amorphous and nanocrystalline phases from different origins) as detected from XRD patterns (no clear peak exists) with a high smooth surface, as detected from SEM micrographs, highly important to ensure long life time when used in display devices.
Fortunato, E.a, Assunção Gonçalves Marques Águas Pereira Ferreira Vilarinho Martins V. a A. a. "
High quality conductive gallium-doped zinc oxide films deposited at room temperature."
Thin Solid Films. 451-452 (2004): 443-447.
AbstractTransparent and highly conducting gallium-doped zinc oxide films were successfully deposited by rf sputtering at room temperature. The lowest resistivity achieved was 2.6×10-4 Ω cm for a thickness of 1100 nm (sheet resistance ≈1.6 Ω/sq), with a Hall mobility of 18 cm2/Vs and a carrier concentration of 1.3×1021 cm-3. The films are polycrystalline with a hexagonal structure and a strongly preferred orientation along the c-axis. A linear dependence between the mobility and the crystallite size was obtained. The films present a transmittance in the visible spectra between 80 and 90% and a refractive index of approximately 2, which is very close to the value reported for bulk material. © 2003 Elsevier B.V. All rights reserved.
Fortunato, E., Malik Seco Macarico Martins A. A. A. "
High sensitivity photochemical sensors based on amorphous silicon."
Materials Research Society Symposium - Proceedings. Vol. 467. 1997. 949-954.
AbstractHydrogenated amorphous silicon photochemical sensors based on Pd-MIS structures were produced by Plasma Enhanced Chemical Vapor Deposition with two different oxidized surfaces (thermal and chemical oxidation). The behaviour of dark and illuminated current-voltage characteristics in air and in the presence of a hydrogen atmosphere is explained by the changes induced by the gases in the work function of the metal, modifying the electrical properties of the interface. The photochemical sensors produced present more than 2 orders of magnitude variation on the reverse dark current when in presence of 400 ppm hydrogen to which it corresponds a decrease of 45% on the open circuit voltage.
Fortunato, Elvira, Lavareda Guilherme Martins Rodrigo Soares Fernando Fernandes Luis. "
High-detection resolution presented by large-area thin-film position-sensitive detectors."
Proceedings of SPIE - The International Society for Optical Engineering. Vol. 2397. 1995. 259-270.
AbstractThe aim of this work is to present the main optoelectronic characteristics of large area 1D position sensitive detectors based on amorphous silicon p-i-n diodes. From that, the device resolution, response time and detectivity are derived and discussed concerning the field of applications of the 1D thin film position sensitive detectors.
Fortunato, E., Nunes Marques Costa Águas Ferreira Costa Martins P. A. D. "
Highly conductive/transparent ZnO:Al thin films deposited at room temperature by rf magnetron sputtering."
Key Engineering Materials. 230-232 (2002): 571-574.
AbstractTransparent conducting ZnO:Al thin films have been deposited on polyester (Mylar type D, 100 μm thickness) substrates at room temperature by r.f. magnetron sputtering. The structural, optical and electrical properties of the deposited films have been studied. The samples are polycrystalline with a hexagonal wurtzite structure and a strong crystallographic c-axis orientation (002) perpendicular to the substrate surface. As deposited ZnO:Al thin films have an 85% transmittance in the visible and infra-red region and a resistivity as low as 3.6×10-2 Ωcm. The obtained results are comparable to those ones obtained on glass substrates, opening a new field for low cost, light weight, small volume, flexible and unbreakable large area optoelectronic devices.