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Staggered bottom gate transparent thin film transistors (TTFTs) have been produced by rf magnetron sputtering at room temperature, using amorphous indium-zinc-oxide (IZO) semiconductor, for the channel as well as for the drain and source regions. The obtained TTFTs operate in the enhancement mode with threshold voltages of 2.4 V, saturation mobility of 22.7 cm2/Vs, gate voltage swing of 0.44 V/dec and an ON/OFF current ratio of 7×10 7. The high performances presented by these TTFTs produced at room temperature, make these TFTs a promising candidate for flexible, wearable, disposable portable electronics as well as battery-powered applications.

In this paper we demonstrate the use of amorphous binary In2O3-ZnO oxides simultaneously as active channel layer and as source/drain regions in transparent thin film transistor (TTFT), processed at room temperature by rf sputtering. The TTFTs operate in the enhancement mode and their performances are thickness dependent. The best TTFTs exhibit saturation mobilities higher than 102 cm2/Vs, threshold voltages lower than 6 V, gate voltage swing of 0.8 V/dec and an on/off current ratio of 107. This mobility is at least two orders of magnitude higher than that of conventional amorphous silicon TFTs and comparable to or even better than other polycrystal-line semiconductors. © 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Amorphous/nanocrystalline silicon p i′ i i′ n devices fabricated on micromachined glass substrates are integrated with oligonucleotide-derivatized gold nanoparticles for a colorimetric detection method. The method enables the specific detection and quantification of unamplified nucleic acid sequences (DNA and RNA) without the need to functionalize the glass surface, allowing for resolution of single nucleotide differences between DNA and RNA sequences-single nucleotide polymorphism and mutation detection. The detector's substrate is glass and the sample is directly applied on the back side of the biosensor, ensuring a direct optical coupling of the assays with a concomitant maximum photon capture and the possibility to reuse the sensor. © 2007 American Institute of Physics.

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In this work Spectroscopic Ellipsometry (SE) was used to study metal induced crystallization (MIC) on amorphous silicon films in order to analyze the influence of different annealing conditions on their structural properties. The variation of the metal thickness has shown to be determinant on the time needed to full crystallize silicon films. Films of 100 nm thickness crystallize after 2h at 500°C using 1 nm of Ni deposited on it. When reducing the average metal thickness down to 0.05 nm the same silicon film will need almost 10 hours to be totally crystallized. Using a new approach on the modelling procedure of the SE data we show to be possible to determine the Ni remaining inside the crystallized films. The method consists in using Ni as reference on the Bruggeman Effective Medium Approximation (BEMA) layer that will simulated the optical response of the crystallized silicon. Silicon samples and metal layers with different thicknesses were analyzed and this new method has shown to be sensible to changes on the initial metal/silicon ratio. The nickel distribution inside the silicon layers was independently measured by Rutherford Backscattering Spectroscopy (RBS) to check the data obtained from the proposed approach. © 2006 Materials Research Society.

Various S = 3/2 EPR signals elicited from wild-type and variant Azotobacter vinelandii nitrogenase MoFe proteins appear to reflect different conformations assumed by the FeMo-cofactor with different protonation states. To determine whether these presumed changes in protonation and conformation reflect catalytic capacity, the responses (particularly to changes in electron flux) of the alpha H195Q, alpha H195N, and alpha Q191 K variant MoFe proteins (where His at position 195 in the alpha subunit is replaced by Gln/Asn or Gln at position alpha-191 by Lys), which have strikingly different substrate-reduction properties, were studied by stopped-flow or rapid-freeze techniques. Rapid-freeze EPR at low electron flux (at 3-fold molar excess of wild-type Fe protein) elicited two transient FeMo-cofactor-based EPR signals within 1 s of initiating turnover under N-2 with the alpha H195Q and alpha H195N variants, but not with the alpha Q191K variant. No EPR signals attributable to P cluster oxidation were observed for any of the variants under these conditions. Furthermore, during turnover at low electron flux with the wild-type, alpha H195Q or alpha H195N MoFe protein, the longer-time 430-nm absorbance increase, which likely reflects P cluster oxidation, was also not observed (by stopped-flow spectrophotometry); it did, however, occur for all three MoFe proteins under higher electron flux. No 430-nm absorbance increase occurred with the alpha Q191K variant, not even at higher electron flux. This putative lack of involvement of the P cluster in electron transfer at low electron flux was confirmed by rapid-freeze Fe-57 Mossbauer spectroscopy, which clearly showed FeMo-factor reduction without P cluster oxidation. Because the wild-type, alpha H195Q and alpha H195N MoFe proteins can bind N-2, but alpha Q195K cannot, these results suggest that P cluster oxidation occurs only under high electron flux as required for N-2 reduction. (C) 2007 Elsevier Inc. All rights reserved.

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The simultaneous separation and quantification of two casein peptides (IPP, VPP) presenting potent inhibitory activity of angiotensin-converting-enzyme (ACE) and casein in fermented milks was developed. Gradient elution was carried out at a flow-rate of 1 mL/min, using a mixture of two solvents. Solvent A was 0.1% TFA in water and solvent B was acetonitrile-water-trifluoracetic acid 95:5:0.1. The effluent was monitored by UV detector at 214 nm. Calibration curves were constructed in the interval of 0.01-1.0 mg/mL for VPP, 0.005-1.0 mg/mL for IPP, and 0.05-3.0 mg/mL for casein. R 2 invariably exceeded 0.999. The detection limits were 0.004 for VPP, 0.002 mg/mL for IPP, and 0.02 mg/mL for casein. Repeatability of the method was evaluated by six consecutive injections of two standard solutions containing VPP, IPP, and casein. The RSD values for concentration were all below 5.08%. Recovery studies were carried out to determine the accuracy of the method. Recoveries ranged between 88 and 98.2%. The methodology was applied, not only, for the monitorization of VPP, IPP, and casein in commercial fermented milks labeled as presenting anti hypertensive properties, but also, in milk with different degrees of fermentation by L Helveticus, and in other commercial functional fermented milks, such as, those presenting cholesterol lowering properties.

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Nanostructured silicon thin films were produced in a single PECVD (Plasma Enhanced Chemical Vapour Deposition) reactor using an excitation frequency of 27.12 MHz. The process parameters were selected to allow the films' production to be performed at the transition region (from amorphous to microcrystalline), aiming their use in solar cells. The real and imaginary parts of pseudo-dielectric function of these nanostructured films show a shift to higher energies and the order factor reveals an improvement on the short atomic range order of the films produced. The solar cells with a structure of ZGO/p-a-SiC:H/buffer1/buffer2/i-(nc/a-Si:H)/n-a-Si:H/Ag/Al were deposited with nanostructured intrinsic layer, showing a good performances, with current densities of about 14.48 mA/cm2, open circuit voltage of 0.94 V, and fill factor of 0.67, which lead to efficiencies of 9.12%. The solar cell degradation study performed under AM1.5 spectrum conditions up to 100 hours revealed a decrease on the solar cell efficiency of about 8.11%, mainly related to the decreasing of current density. Despite that, the open circuit voltage increases slightly after the degradation.

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This work shows the effect of the annealing temperature and atmosphere on the properties of r.f. magnetron sputtered indium-zinc oxide (IZO) thin-films of two types: one a conductive film (as-deposited, room temperature) that exhibits a resistivity of 3.5 × 10- 4 Ω cm; the other, a semiconductor film with a resistivity ∼ 102 Ω cm. The annealing temperatures were changed between 125 and 500 °C. Crystallization of the more conductive films was already noticeable at temperatures around 400 °C. Three different annealing atmospheres were used - vacuum, air and oxygen. For the conductive films, only the oxygen atmosphere was critical, leading to an increase of the electrical resistivity of more than one order of magnitude, for temperatures of 250 °C and above. Concerning the semiconductor films, both temperature and atmosphere had a strong effect on the film's properties, and the resistivity of the annealed films was always considerably smaller than the as-deposited films. Finally, some results of the application of these films to transparent TFTs are shown. © 2007 Elsevier B.V. All rights reserved.

Indium molybdenum oxide thin films were RF sputtered at room temperature on glass substrates with a reference base pressure of 7.5 × 10- 4 Pa. The electrical and optical properties of the films were studied as a function of oxygen partial pressures (OPP) ranging from 1.5 × 10- 3 Pa to 3.5 × 10- 3 Pa. The obtained data show that the bulk resistivity of the films increased by about 4 orders of magnitude (from 7.9 × 10- 3 to 7.6 × 101 Ω-cm) when the OPP increased from 1.5 × 10-3 to 3.5 × 10- 3 Pa, and the carrier concentration decreased by about 4 orders (from 1.77 × 1020 to 2.31 × 1016 cm- 3). On the other hand, the average visible transmittance of 30.54% of the films (brown colour; OPP = 1.5 × 10- 3 Pa) was increased with increasing OPP to a maximum of 80.47% (OPP = 3.5 × 10- 3 Pa). The optical band gap calculated from the absorption edge of the transmittance spectra ranges from 3.77 to 3.88 eV. Further, the optical and electrical properties of the films differ from those deposited at similar conditions but with a base pressure lower than 7.5 × 10- 4 Pa. © 2007 Elsevier B.V. All rights reserved.

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In this paper, a poly-phase disc motor innovative feeding and control strategy, based on a variable poles approach, and its application to a HTS disc motor, are presented. The stator windings may be electronically commutated to implement a 2, 4, 6 or 8 poles winding, thus changing the motor's torque?speed characteristics. The motor may be a conventional induction motor with a conductive disc rotor, or a new HTS disc motor, with conventional copper windings at its two iron semi-stators, and a HTS disc as a rotor. The conventional induction motor's operation principle is related with the induced electromotive forces in the conductive rotor. Its behaviour, characteristics (namely their torque?speed characteristics for different number of pole pairs) and modelling through Steinmetz and others theories are well known. The operation principle of the motor with HTS rotor, however, is rather different and is related with vortices' dynamics and pinning characteristics; this is a much more complex process than induction, and its modelling is quite complicated. In this paper, the operation was simulated through finite-elements commercial software, whereas superconductivity was simulated by the E-J power law. The Electromechanical performances of both motors where computed and are presented and compared. Considerations about the systems overall efficiency, including cryogenics, are also discussed.

In this paper, a poly-phase disc motor innovative feeding and control strategy, based on a variable poles approach, and its application to a HTS disc motor, are presented. The stator windings may be electronically commutated to implement a 2, 4, 6 or 8 poles winding, thus changing the motor's torque?speed characteristics. The motor may be a conventional induction motor with a conductive disc rotor, or a new HTS disc motor, with conventional copper windings at its two iron semi-stators, and a HTS disc as a rotor. The conventional induction motor's operation principle is related with the induced electromotive forces in the conductive rotor. Its behaviour, characteristics (namely their torque?speed characteristics for different number of pole pairs) and modelling through Steinmetz and others theories are well known. The operation principle of the motor with HTS rotor, however, is rather different and is related with vortices' dynamics and pinning characteristics; this is a much more complex process than induction, and its modelling is quite complicated. In this paper, the operation was simulated through finite-elements commercial software, whereas superconductivity was simulated by the E-J power law. The Electromechanical performances of both motors where computed and are presented and compared. Considerations about the systems overall efficiency, including cryogenics, are also discussed.

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