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In the last decade, new device concepts based on novel fabrication methods have emerged as a powerful and general class of supersensitive sensors for the direct detection of biological and chemical targets. Pushed by the opportunity to activate the physical-chemical phenomena at the nanoscale, novel patterning paradigms have gained nanofabrication accuracy accompanied by the fast development of bottom-up strategies. In this frenetic framework, the combination of some heterogeneous techniques-basically nano-imprint lithography, grafting of functional molecules, and synthesis of new ligands and probes to capture specific biological targets-have gained strong attention as enabling emerging technological mixture to fabricate ultra dense array of specialized sensors. Within the scope of this technological convergence, the paper is basically devoted to describe the processes involved in the production of stamps for nanoimprint lithography, the fabrication of printed array of silicon sensors on the micrometer and sub-micrometer resolution, the subsequent covalent biofunctionalization with single strand DNA and some preliminary electrical detection of the hybridization events via water modulating ac resistance. Among the possible choices, focus was given to planar functionalized capacitors for their intrinsic simple configuration and also because they appeared to be the most promising candidates for mass production in printed device architecture. The paper is based on original results but contains also data and achievements taken from the literature to make the discussion self-contained. © 2011 American Scientific Publishers.

Organic Optoelectronic Devices like OLED (Organic Light Emitting Diode) and OPV (Organic Photovoltaic Device) with a two-dimensional photonic crystal structure have been fabricated by several groups, but not all the opportunities are still exploited and many further steps can be done in this field of optics application. In particular the Photonic Quasi Crystal (PQC) structures are rarely employed and utilized without verify their effective potential. Through PQC structure is possible to enhance more than one optics wavelenght and so they could be very important for large spectra emission sources, i.e. white organic light emission diode (WOLED). In this work we realized many different PQC, octagonal, 12-fould and Thue-Morse, structures using a high-resolution electron beam lithography (EBL) technique. The EBL employed consisted of a Raith 150 system. The samples were obtained by exposing a layer of ZEP (electronic resist) deposited on a highly conductive PEDOT:PSS layer, spin coated onto a Corning glass substrate. A 200-nm-thick layer of colloidal doped ZEP was spin coated on top of the cleaned substrate. The resulting two-dimensional photonic crystal is made of air rods embedded into the organic matrix of ZEP. The ZEP crystal was subsequently used as a lithographic mask during the anisotropic plasma etching process of the underlying highly conductive PEDOT:PSS, which was obtained by doping the PEDOT:PSS with dimethylsulfoxide (DMSO). The plasma etching partially removes the PEDOT:PSS layer, yielding a polymeric photonic quasi crystal onto a polymeric electrode. An optical setup was adopted to evaluate the PQC properties and estimate the WOLED spectral properties. Light propagating in the glass substrate and extracted by diffraction was measured at room temperature. This apparatus has been used to analyze the optical properties of our photonic crystals in order to evaluate the resonances of the structures and the operational optical ranges. In figure is possible to observe the chromaticity diagram (CIE diagram) related to the extracted PQC spectra. It will be also showed the result obtained using the nanostructured electrode within a OLED device and will be examined its effect on the electro-optical properties.

MgB 2 thin films were grown in-situ at INFM- University of Naples by a magnetron sputtering technique in a UHV system (10-7 Pa) equipped with 3 focused 2′′ magnetron sources (a stoichiometric MgB 2 and metallic Mg and B targets by Superconducting Components Inc.). The substrates (sapphire or MgO) were placed "on axis" at 7 cm from the target surface on the surface of a molybdenum heater that could be operated up to 1000°C under vacuum. Best results were obtained codepositing MgB 2 and Mg at equal sputtering power (500W) for 10 min on cold substrates, resulting in a Mg rich Mg-B precursor film. The films were then annealed inhyphen;situ at 830°C for 10 min in a In sealed Nb box in presence of saturated Mg vapor. The process is highly reproducible and can be easily scaled to produce large area films. The resulting films were about 1μm thick, with 100nm surface roughness as measured by AFM Resistive transition showed a maximum T c of 35 K and a transition width lower than 0.5 K. The residual resistivity ratio was 1.6 for the best sample. Resistivity measurements in external magnetic field up to 8 T have been performed both in parallel and perpendicular configuration. The upper critical magnetic field vs. temperature behavior has been determined from the experimental data and the superconducting anisotropy has been calculated for samples with different T c .

Thin films of the recently discovered magnesium diboride (MgB2) intermetalic superconducting compound have been grown using a magnetron sputtering deposition technique followed by in-situ annealing at 830 C. High quality films were obtained on both sapphire and MgO substrates. The best films showed maximum Tc = 35 K (onset), a transition width of 0.5 K, a residual resistivity ratio up to 1.6, a low temperature critical current density Jc > 1 MA/cm2 and anisotropic critical field with gamma = 2.5 close to the values obtained for single crystals. The preparation technique can be easily scaled to produce large area in-situ films., 7 pages, 4 figures

We have measured the temperature and magnetic field dependencies of the critical current density J c (H,T) in MgB 2 thin films, in situ deposited by sputtering. Three-dimensional point like normal core pinning was evidenced by measurements of the magnetic dependence of the pinning forces independently from the superconducting and structural quality of the investigated films. The analysis of the experimental data in terms of the collective pinning model has pointed out the presence of a crossover magnetic field from a single vortex to a small vortex bundle pinning regime. A ΔT c pinning mechanism, i.e., a pinning associated with spatial fluctuations of the transition temperature, has been evidenced by the temperature dependence of this crossover field, in agreement with previous observations performed on MgB 2 bulk materials.

Electrical transport properties of PVK (poly N-vinyl carbazole), a polymer exhibiting an intrinsic electroluminescence (EL) in blue region, have been investigated. In particular, resistivity and charge carrier mobility have been assessed by means of I–V measurements and by Field Effect (FET) doping, respectively. Dielectric constant has been also evaluated by means of C–V measurements performed on an ITO/PVK/Al single layer electroluminescent (EL) device. All electrical characterizations, carried out in different environmental conditions to deeply investigate PVK intrinsic conduction mechanisms, allowed to assess the good quality of spin coated PVK thin films. Electroluminescent measurements performed on ITO/PVK/Al and on ITO/PVK/Alq3/Al have been also performed. Finally, charge injection mechanisms from the electrodes to PVK have been investigated also as a function of the temperature. Experimental results have been compared with some well known theoretical models.

We report on fabrication of Y/sub 1/Nd/sub x/Ba/sub 2-x/Cu/sub 3/O/sub 7-/spl delta// and Nd/sub 1+x/Ba/sub 2-x/Cu/sub 3/O/sub 7-/spl delta// thin films deposited by high oxygen pressure dc sputtering. The structural properties are investigated by X-ray diffraction while Scanning Tunneling Microscopy (STM) has been used to determine the surface morphology. The critical temperature and the critical current density are obtained by transport and inductive measurements. The microwave properties have been studied at 19.8 GHz by a dielectric resonator technique. For both compounds highly epitaxial c-axis thin films are routinely obtained on SrTiO/sub 3/ and LaAlO/sub 3/ substrates. Depending on the deposition conditions, films characterized by surface resistance comparable of even better than YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// have been obtained, with a substantial improvement of the structural properties and of the surface morphology. The role played by the Nd/Ba substitution on the growth and on the superconducting properties is discussed.

We have studied the effect of Nd/Ba substitution on the superconducting properties of R 1 (Nd x Ba 2− x )Cu 3 O 7 (R=Nd, Y) thin films by using microwave penetration depth and surface resistance measurements. Data on samples characterised by a Nd-excess of 4–5% have been collected by using a microstrip resonator at frequencies of 1.44 and 9.7 GHz and a symmetric dielectric resonator technique in TE 0 1 1 mode at 19.8 GHz. A quadratic bT 2 low temperature dependence of the penetration depth is observed for the Nd-rich samples, with the coefficient b decreasing with the frequency. The data can be reasonably explained in a d-wave framework supposing that Nd at Ba site behaves, both in Nd 1+ x Ba 2− x Cu 3 O 7 and Y 1 (Nd x Ba 2− x )Cu 3 O 7 , as a resonant impurity, as confirmed by scanning tunnelling spectroscopy. The changes of the temperature dependence of the penetration depth with the frequency can be explained with a two fluid approach taking into account the frequency dependence of the complex conductivity.

We present a study on the power dependence of the microwave surface impedance in thin films of the novel superconductor MgB2. 500 nm thick samples exhibiting critical temperatures ranging between 26 and 38 K are synthesized by an ex-situ post-anneal of e-beam evaporated boron in the presence of an Mg vapor at 900 C. Preliminary results on films grown in situ by a high rate magnetron sputtering technique from stoichiometric MgB2 and Mg targets are also reported. Microwave measurements have been carried out employing a dielectrically loaded niobium superconducting cavity operating at 19.8 GHz and 4 K. The study shows that the electrodynamic response of MgB2 films is presently dominated by extrinsic sources of dissipation, appearing already at low microwave power, likely to be ascribed to the presence of grain boundaries and normal inclusions in the samples., 10 pages, 3 figures, proceedings of the conference EUCAS 2001, submitted to Physica C