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We demonstrate that PECVD SiOxNy with good dielectric properties can replace thermally grown SiO2 in Organic Thin-Film Transistors (OTFT) applications. It can be used on ITO-covered glass or even flexible substrates. Poly [2-methoxy-5-(3’,7’-dimethyloctyloxy)-1,4-phenylenevinylene] (MDMO-PPV) is used as the active layer, due to its wide range of applications such as bulk heterojunction solar cells, light-emitting diodes and light-emitting transistors.We show that charge carrier mobility can be at least two times higher for MDMO-PPV on silicon oxynitride than silicon dioxide, μh 1.1x10-4 cm2/Vs. MDMO-PPV spun from solvents such as chloroform and toluene provide comparable TFT performance on SiOxNy. Preliminary studies of devices with hexamethyldisilazane-treated SiO2 demonstrate that performance can be further improved by the choice of a proper surface treatment.

X-ray Computed Tomography (X-ray CT) is a sophisticated non-destructive imaging technique to investigate structures and materials of complex objects, and its application can answer many conservation and restoration questions. However, for Cultural Heritage investigations, medical CT scanners are not optimized for many case-studies: These instruments are designed for the human body, are not flexible and are difficult to use in situ. To overcome these limitations and to safely investigate works of art on site&mdash, in a restoration laboratory or in a museum&mdash, the X-ray Tomography Laboratory of the University of Bologna designed several CT systems. Here we present two of these facilities and the results of important measurement campaigns performed in situ. The first instrument, light and flexible, is designed to investigate medium-size objects with a resolution of a few tens of microns and was used for the CT analysis of several Japanese theater masks belonging to the collection of the &ldquo, L. Pigorini&rdquo, Museum (Rome). The second is designed to analyze larger objects, up to 200 cm and was used to investigate the collection of the so-called &ldquo, Statue Vestite&rdquo, (devotional dressed statues) of the Diocesan Museum of Massa.

Since 2018, a scientific research project, the “Lilybaeum Project”, is being carried out by a collaboration of physicists and archaeologists. The goal is to apply forefront analysis techniques to the investigation of archaeological artefacts, both in situ and in the laboratory. The first case study presented in this paper concerns the original investigation through X-ray computed tomography of a collection of objects from the Regional Archaeological Museum of Lilybaeum, in Marsala, Italy. In addition to a very significant collection of clay jars mostly from children's graves of the ancient Lilybaeum necropolis, an unprecedented analysis of wooden planks belonging to the only existing wreck of a Punic Ship kept in the Museum is presented.

This paper describes the analysis of two near-spherical metallic inclusions partially incorporated within two Roman raw glass slags in order to elucidate the process that induced their formation and to determine whether their presence was related to ancient glass colouring processes. The theory of metallic scraps or powder being used in Roman times for glass-making and colouring purposes is widely accepted by the archaeological scientific community, although the assumption has been mainly based on oral traditions and documented medieval practices of glass processing. The analysis of the two inclusions, carried out by X-ray computed tomography, electrochemical analyses, and scanning electron microscopy, revealed their material composition, corrosion and internal structure. Results indicate that the two metallic bodies originated when, during the melting phase of glass, metal scraps were added to colour the material: the colloidal metal–glass system reached then a supersaturation condition and the latter ultimately induced metal expulsion and agglomeration. According to the authors’ knowledge, these two inclusions represent the first documented and studied finds directly associated with the ancient practise of adding metallic agents to colour glass, and their analysis provides clear insights into the use of metallic waste in the glass colouring process.

Detectors are a key feature of the contemporary scientific approach to cultural heritage (CH), both for diagnostics and conservation. INFN-CHNet is the network of the Italian National Institute of Nuclear Physics that develops and applies new instrumentation for the study of CH. This process results in both optimized traditional state-of-the-art and highly innovative detection setups for spectrometric techniques. Examples of the former are X-rays, gamma-rays, visible-light and particles spectrometers tailored for CH applications, with optimized performances, reliability, weight, transportability, cost, absorbed power, and complementarity with other techniques. Regarding the latter, examples are ARDESIA, the array of detectors at the DAΦNE-Light facility, the MAXRS detection setup at the Riken-RAL muon beamline and the imaging facilities at the LENA Laboratory. Paths for next-generation instruments have been suggested, as in the case of the X-ray Superconductive Detectors and X-ray Microcalorimeter Spectrometers, allowing astonishing improvement in energy resolution. Many issues in CH can now be addressed thanks to scientific techniques exploiting the existing detectors, while many others are still to be addressed and require the development of new approaches and detectors.

In this paper, we have studied an additively manufactured metallic component, intended for ultra-high vacuum application, the exit-snout of the MACHINA transportable proton accelerator beam-line. Metal additive manufacturing components can exhibit heterogeneous and anisotropic microstructures. Two non-destructive imaging techniques, X-ray computed tomography and Neutron Tomography, were employed to examine its microstructure. They unveiled the presence of porosity and channels, the size and composition of grains and intergranular precipitates, and the general behavior of the spatial distribution of the solidification lines. While X-ray computed tomography evidenced qualitative details about the surface roughness and internal defects, neutron tomography showed excellent ability in imaging the spatial density distribution within the component. The anisotropy of the density was attributed to the material building orientation during the 3D printing process. Density variations suggest the possibility of defect pathways, which could affect high vacuum performances. In addition, these results highlight the importance of considering building orientation in the design for additive manufacturing for UHV applications. Graphical Abstract

Scientific investigations of artworks are crucial in terms of preservation since they provide a measurable evaluation of the materials and the state of conservation. This is the case of Antonello da Messina’s painting “Ecce Homo”: its delicate state of conservation, with the need for constant monitoring, required a broad and in-depth diagnostic campaign to support the restorers. The project was carried out entirely in situ using non-invasive cutting-edge techniques and proposes a multimodal and data-centric approach, integrating 3D and 2D methodologies. The surface irregularities and the support were analysed with a structured-light 3D scanner and X-ray tomography. The painting materials were investigated with X-ray fluorescence scanning (MA-XRF) and reflectance hyperspectral imaging (HSI). Primarily, the data were jointly used for a scientific scope and provided new knowledge of the painting in terms of materials and painting techniques. In addition, two web-based interactive platforms were developed: one to provide restorers and experts with a new perspective of the hidden geometries of the painting, and the other targeted at the general public for dissemination purposes. The results of the Ecce Homo scientific analysis were exhibited, using a touch-screen interface, and developed for different user levels, from adults to kids.

In recent years, research and technology made considerable progress in increasing the speed and the safety of the entire digitization process of ancient collections. Despite this, imaging ancient, fragile or un-opened documents remains a formidable challenge. We employ an alternate digitization technique for handwritten documents, exploiting x-ray tomography: Virtual X-ray Reading. Thanks to the high penetration of x-rays, we can acquire 3-dimensional (3D) tomographic images of a multi-page document without opening it. The x-ray contrast necessary for the readability is produced by the chemical composition and the consequent strong x-ray absorption of the iron gall inks - largely used for European handwritten documents. We present the development of this technology, from the chemical investigations of the inks to the tomography of an unopened Venetian testament and of an 18th century, 200-page, handwritten book.

We present the results of the broad scientific investigation campaign of an important Celestial globe by Vincenzo Coronelli, part of the Marciana National Library collection (Venice). Coronelli was one of the finest globe-makers and cartographers of the 17th century and he manufactured a large number of Terrestrial and Celestial globes of different sizes, such as the two impressive and entirely manuscript 4-meter globes commissioned for Louis XIV. Using multiple techniques, we studied the materials and the construction techniques of the first printed reproduction of the French Celestial globe, donated to the Serenissima Republic in 1689 and still in Venice. We present and discuss the results of the multispectral imaging analysis, of the chemical investigations X-ray Fluorescence (XRF), Scanning electron microscopy - Energy Dispersive X-ray Spectrometry (SEM-EDS) and Fourier Transform Infrared spectroscopy (FT-IR) and of the stratigraphic analysis by polarised-light microscopy. Moreover, we explain in detail the results of the X-ray tomographic analysis performed in situ. Thanks to this comprehensive campaign, we examined the production process of this unique globe, from the pigment to the woodworking approach of the Master globe-maker Coronelli.

We present a fundamental development step of a new technique to read and digitize ancient handwritten documents. Chemical analysis by x-ray fluorescence and x-ray tomography enabled us to decipher words and drawings from inside a closed, 200-pages 18 th century handwritten book. The ink chemistry is essential: tomographic reading is feasible thanks to the iron present in ancient inks (iron gall) over one millennium – whereas carbon or organic inks do not provide sufficient x-ray contrast. The results presented are a key progress towards the ultimate goal of the technique: non-invasive reading of fragile and/or unopenable documents.

I will describe in this paper the first results of a series of X-ray tomography applications, with different system setups, running on some ancient manuscripts containing iron-gall ink. The purpose is to verify the optimum measurement conditions with a laboratory instrumentation -that is also in fact portable- in order to recognize the text from the inside of the documents, without opening them. This becomes possible by exploiting the X-rays absorption contrast of iron-based ink and the three-dimensional reconstruction potential provided by computed tomography that overcomes problems that appear in simple radiograph practice. This work is part of a larger project of EPFL (Ecole Polytechnique Fédérale de Lausanne, Switzerland), the "Venice Time Machine" project (EPEL, Digital Heritage Venice, http://dhvenice.eu/, 2015) aimed at digitizing, transcribing and sharing in an open database all the information of the State Archives of Venice, exploiting traditional digitization technologies and innovative methods of acquisition. In this first measurement campaign I investigated a manuscript of the seventeenth century made of a folded sheet; a couple of unopened ancient wills kept in the State Archives in Venice and a handwritten book of several hundred pages of notes of Physics of the nineteenth century.

‘Venice Time Machine’ is an international program whose objective is transforming the ‘Archivio di Stato’ – 80 km of archival records documenting every aspect of 1000 years of Venetian history – into an open-access digital information bank. Our study is part of this project: We are exploring new, faster, and safer ways to digitalize manuscripts, without opening them, using X-ray tomography. A fundamental issue is the chemistry of the inks used for administrative documents: Contrary to pieces of high artistic or historical value, for such items, the composition is scarcely documented. We used X-ray fluorescence to investigate the inks of four Italian ordinary handwritten documents from the 15th to the 17th century. The results were correlated to X-ray images acquired with different techniques. In most cases, iron detected in the ‘iron gall’ inks produces image absorption contrast suitable for tomography reconstruction, allowing computer extraction of handwriting information from sets of projections. When absorption is too low, differential phase contrast imaging can reveal the characters from the substrate morphology. Copyright © 2015 John Wiley & Sons, Ltd.

Within the neu_ART project, funded by Regione Piemonte (Italy), a team of specialists in different scientific fields coming from Istituto Nazionale di Fisica Nucleare (INFN), Physics Department of University of Torino and Centro Conservazione e Restauro (CCR) “La Venaria Reale” has developed a new digital X-ray apparatus expressly designed for painted canvas and panels up to about 3 m × 4 m. Compared to all other systems scanning time is faster, the procedure to obtain the whole radiography is easier and images are available in real time. This apparatus has been widely tested on artworks restored at CCR “La Venaria Reale”, allowing to study and optimize the operating parameters and to evaluate its performance, thanks to the feedback provided by professionals involved in the activities of conservation. Supported by the results presented in this work, restorers had the possibility to investigate the materials characteristics and to plan the operating strategy in advance: indeed, radiographs revealed areas with losses of paint, repainted areas, canvas damages, hidden pictures, writings and previous restorations. The X-Ray system for Digital Radiography is integrated in a more complex apparatus that can be used also for computed tomography of voluminous objects up to 2.5 m in height and 2 m in width, making the apparatus developed in the neu_ART project a unique and comprehensive tool at conservators' disposal.

A study of chemical and electrochemical polishing, with and without 2 step anodization, intending to evaluate the effect of the surface roughness on TiO2 nanotube arrays formation and in dye-sensitized solar cells performance is performed. Titanium foil substrates were chemically polished (CP) and electrochemically polished (EL) prior to the anodization process for nanotube growth. The effect of the polishing treatments on the nanotube arrays morphology was analyzed by Scanning Electron Microscopy (SEM) characterization. Dye sensitized solar cells (DSSCs) were fabricated, with the produced nanotube arrays, and characterized intending to evaluate the effect of the Ti foil substrate surface polishing treatment on the device conversion efficiency. Photocurrent density–voltage characteristics (J–V curves) were measured under AM1 illumination at room temperature and the devices photocurrent density (Jsc), open circuit voltage (Voc), fill factor (FF), efficiency (%) and parallel resistance (RSH) values were extracted. The best results are obtained for the chemical polishing process where nanotube arrays without bundles and without “nanograss” presence were obtained promoting higher DSSCs photocurrent density values. These results emphasize the importance of a plane and smooth titanium substrate surface for nanotubes synthesis and further device processing.

The Italian Neutron Experimental Station (INES) located at the ISIS pulsed neutron source (Didcot, United Kingdom) provides a thermal neutron beam mainly used for diffraction analysis. A neutron transmission imaging system was also developed for beam monitoring and for aligning the sample under investigation. Although the time-of-flight neutron diffraction is a consolidated technique, the neutron imaging setup is not yet completely characterized and optimized. In this paper the performance for neutron radiography and tomography at INES of two scintillator screens read out by two different commercial CCD cameras is compared in terms of linearity, signal-to-noise ratio, effective dynamic range and spatial resolution. In addition, the results of neutron radiographies and a tomography of metal alloy test structures are presented to better characterize the INES imaging capabilities of metal artifacts in the cultural heritage field. (c) 2013 Elsevier B.V. All rights reserved.

TiO2 nanotubes arrays were obtained by Ti foil and Ti thin films on glass substrate, deposited by RF magnetron sputtering, anodization in a NH4F organic solution with different anodization voltages and times. Annealing treatment to promote nanotubes crystallization in anatase phase was done. Different photolithography pattern techniques were utilized to define nanotubes lines from 10 to 90µm wide. The obtained samples were characterized by Raman spectroscopy and Scanning Electron Microscopy (SEM).

TiO2 nanotubes and nanoparticles were obtained by anodization of metallic Ti foil in a 0.5% HF, 1:7 acetic acid aqueous solution. Voltages of 23 and 35 V were applied and the anodization time was varied. Scanning Electron Microscope (SEM) and Raman scattering spectroscopy were utilized to analyze the obtained structures. It was observed that nanotubes with larger diameter are obtained for higher anodization voltages, also a morphology and crystalline phase dependency on anodization time, for a given voltage, were observed. Nanotubes with diameters in the 20nm to 90 nm range were obtained for different anodization times and voltages.

We report the first low voltage organic P3HT transistor over glass substrates and titanium oxynitride (TiOxNy) deposited by reactive r.f. magnetron sputtering. The transistor operating voltage was -3V with a maximum current of 1.11 μA. Charger carrier mobility (μ) was 0.01 cm2/Vs, threshold voltage (Vt) -0.5 V, on-off current ratio (ION/OFF) 200 and subthreshold swing (S) 0.75 V/decade. We also present a study of the dielectric constant (k) of organic insulator PMMA in several processing conditions. ITO/PMMA/Au capacitors provided a dielectric constant of ca. 3.5, which is very similar to SiO2 performance.

A set of TiOxNy films was deposited by reactive RF magnetron sputtering varying the nitrogen partial pressure in a Ar/N2 gaseous mixture. Utilizing these films as gate dielectric layer MOS capacitors were fabricated and characterized. The TiOxNy films were characterized by Fourier Transform Infrared Spectroscopy (FTIR), Rutherford Backscattering (RBS), optical absorption, and High Resolution Transmission Electron Microscopy (HRTEM). Capacitance-voltage (1MHz) and current-voltage measurements were used to obtain the effective dielectric constant, the effective oxide thickness (EOT), the leakage current density, and the interface quality. MOS capacitors results show that the TiOxNy films present a dielectric constant varying from 28 to 80, good interface quality with silicon, and a leakage current density of approximately 0.25 mA/cm2 for VG = -1V, which is acceptable for high performance logic circuits and low power circuits fabrication. The leakage current density is reduced in 3 orders of magnitude with an increase in nitrogen concentration.

The simulation, fabrication and characterization of ARROW waveguides using dielectric films deposited by Plasma Enhanced Chemical Vapor Deposition (PECVD) and Sputtering techniques, are presented in this work. Amorphous titanium oxide (TiO2) films were used as first cladding layer and silicon oxynitride (SiOxNy) films, as core layer. Furthermore, homemade routines based in two computational methods were used, for numerical simulations: Transfer Matrix Method (TMM) for the determination of the optimum thickness values of the Fabry-Perot layers, and the Finite Difference Method (FDM) for 2D design and determination of the maximum width that allows single-mode operation. The utilization of thermally grown silicon oxide as second anti-resonant layer, along with improvements in the Reactive Ion Etching conditions for the definition of sidewalls of the optical waveguides were responsible for diminishing optical attenuations. Optimization of the waveguide rib height was done both through FDM simulations and experimentally. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

A set of MOS capacitors with TiOxNy films as gate dielectric layer was fabricated and characterized. The TiOxNy films were deposited by reactive r.f. magnetron sputtering varying the nitrogen and oxygen partial pressure in a Ar/N2/O2 gaseous mixture. The TiOxNy films were characterized by, Rutherford Backscattering (RBS), X-ray absorption near edge spectroscopy (XANES) in oxygen K-edge (O-K), optical absorption and High Resolution Transmission Electron Microscopy (HRTEM). Capacitance-voltage (1MHz) and current-voltage measurements were performed to obtain the effective dielectric constant, the effective oxide thickness (EOT), the leakage current density, and the interface quality. MOS capacitors results show that the TiOxNyfilms dielectric constant varies from 28 to 80, present a good interface quality with silicon, and the leakage current density values are in the order of 0.25 mA/cm2 for VG = –2V, which is acceptable for high performance logic circuits and low power circuits fabrication. The leakage current density is reduced in 2 orders of magnitude for increasing nitrogen concentration (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

ARROW waveguides with sputtered-TiOxNy anti-resonant layers obtained with different nitrogen concentration in the gaseous mixture were fabricated and characterized. A study of the influence of this parameter on the losses of the waveguides is presented in this work. TiOxNy films have very high refractive indexes, which is a very important characteristic for the first ARROW layer, since this layer behaves like a Fabry-Perot resonator in anti-resonance. Optical and compositional properties of the TiOxNy films were also studied and the results are presented. These films were characterized by Rutherford Backscattering Spectroscopy (RBS), FTIRs, optical absorption and ellipsometry. The second anti-resonant layer and the core of the waveguides were composed of thermally grown SiO2 and PECVD-SiOxNy, respectively. Optical characterization results show propagation losses as low as 1.18 dB/cm for single-mode waveguides fabricated with TiOxNy films obtained with 25% of nitrogen in the gaseous mixture. (© WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Titanium oxide (TiO"2) has been extensively applied in the medical area due to its proved biocompatibility with human cells [1]. This work presents the characterization of titanium oxide thin films as a potential dielectric to be applied in ion sensitive field-effect transistors. The films were obtained by rapid thermal oxidation and annealing (at 300, 600, 960 and 1200^oC) of thin titanium films of different thicknesses (5nm, 10nm and 20nm) deposited by e-beam evaporation on silicon wafers. These films were analyzed as-deposited and after annealing in forming gas for 25min by Ellipsometry, Fourier Transform Infrared Spectroscopy (FTIR), Raman Spectroscopy (RAMAN), Atomic Force Microscopy (AFM), Rutherford Backscattering Spectroscopy (RBS) and Ti-K edge X-ray Absorption Near Edge Structure (XANES). Thin film thickness, roughness, surface grain sizes, refractive indexes and oxygen concentration depend on the oxidation and annealing temperature. Structural characterization showed mainly presence of the crystalline rutile phase, however, other oxides such Ti"2O"3, an interfacial SiO"2 layer between the dielectric and the substrate and the anatase crystalline phase of TiO"2 films were also identified. Electrical characteristics were obtained by means of I-V and C-V measured curves of Al/Si/TiO"x/Al capacitors. These curves showed that the films had high dielectric constants between 12 and 33, interface charge density of about 10^1^0/cm^2 and leakage current density between 1 and 10^-^4A/cm^2. Field-effect transistors were fabricated in order to analyze I"DxV"D"S and logI"DxBias curves. Early voltage value of -1629V, R"O"U"T value of 215M@W and slope of 100mV/dec were determined for the 20nm TiO"x film thermally treated at 960^oC.

We demonstrate that PECVD SiOxNy with good dielectric properties can replace SiO2 in Organic Thin-Film Transistors (OTFT) applications. It can be used on ITO-covered glass or even flexible substrates thanks to the low deposition temperatures. Poly [2-methoxy-5-(3',7'-dimethyloctyloxy)-1,4-phenylenevinylene] (MDMO-PPV) is used as the active layer, due to its wide range of applications such as solar cells, light-emitting diodes and light-emitting transistors. We show also that charge carrier mobility can be at least two times higher for silicon oxynitride on p+-Si substrate than silicon dioxide, ≈ 1.1×10-4 cm2.V-1.s-1, which could be further improved by surface treatments.

Metal oxide semiconductor (MOS) capacitors with titanium oxide (TiOx) dielectric layer, deposited with different oxygen partial pressure (30, 35 and 40%) and annealed at 550, 750 and 1000 °C, were fabricated and characterized. Capacitance–voltage and current–voltage measurements were utilized to obtain, the effective dielectric constant, effective oxide thickness, leakage current density and interface quality. The obtained TiOx films present a dielectric constant varying from 40 to 170 and a leakage current density, for a gate voltage of − 1 V, as low as 1 nA/cm2 for some of the structures, acceptable for MOS fabrication, indicating that this material is a viable high dielectric constant substitute for current ultra thin dielectric layers.

SiOxNy films deposited by the PECVD (Plasma Enhanced Chemical Vapor Deposition) technique at low temperatures from silane (SiH4) nitrous oxide (N2O) and helium (He) as precursor gases at different RF power and R = N2O/SiH4, in order to produce films with good SiOxNy/Si interface quality and low effective charge density were deposited and characterized. In order to compare the film structural properties with the interface (SiOxNy/Si) quality and interface charge density MOS capacitors were fabricated using these films as dielectric layer. The structure of the films was investigated by Fourier Transform Infrared Spectroscopy (FTIR). The MOS capacitors were characterized by low and high frequency capacitance (C-V) measurements, from where the interface state density, the effective charge density and the electrical breakdown were extracted. The better interface properties and a relatively low effective charge density were obtained for a film deposited with R=10 and RF power of 125 mW/cm2.

MOS capacitors with TiO2 and TiO2/SiO2 dielectric layer were fabricated and characterized. TiO2 films where physical characterized by Rutherford Backscattering, Fourier Transform Infrared Spectroscopy and Elipsometry measurements. Capacitance-voltage (1MHz) and current-voltage measurements were utilized to obtain, the effective dielectric constant, effective oxide thickness (EOT), leakage current density and interface quality. The results show that the obtained TiO2 films present a dielectric constant of approximately 40, a good interface quality with silicon and a leakage current density, of 70 mA/cm2 for VG = 1V, acceptable for high performance logic circuits and low power circuits fabrication, indicating that this material is a viable substitute for current dielectric layers in order to prevent tunneling currents. The results for SiO2 (6nm) /TiO2(58nm) layer show a reduction of 3 orders of magnitude in leakage current density and an effec tive dielectric constant of 20, also viable to substitute the usual dielectric material in CMOS fabrication.

MOS capacitors with TiO2 deposited with different O2 partial pressure (30,35 and 40%) and annealed at 550, 750 and 1000oC were fabricated and characterized. Rutherford Backscattering, Fourier Transform Infrared Spectroscopy and Elipsometry measurements were performed to characterize the TiO2 films. Capacitance-voltage (1MHz) and current-voltage measurements were utilized to obtain: the effective dielectric constant, the effective oxide thickness (EOT), the leakage current density (J) and the interface quality. The results show that the obtained TiO2 films present a dielectric constant varying from 40 to 170 and a leakage current density, for gate voltage (VG) of -1V, attaining values as low as 1 nA/cm2, appropriated for CMOS circuits fabrication, indicating that this material is a feasible substitute for current dielectric layers in order to prevent tunneling currents.

Neste trabalho foram fabricados e caracterizados capacitores MOS com camada dielétrica de oxinitreto de silício de diferentes composição química, depositada pela técnica de PECVD a baixa temperatura, com o intuito de estudar suas propriedades dielétricas e de interface visando à aplicação deste material em dispositivos MOS e de filme fino. Os capacitores foram fabricados sobre lâminas de silício do tipo p que passaram pelo processo de limpeza química inicial, seguida da deposição da camada dielétrica, fotogravação, metalização e sinterização. Os filmes de SiOxNy, utilizados como camada dielétrica, foram depositados pela técnica de PECVD à temperatura de 320ºC variando os fluxos dos gases precursores de forma a obter filmes com diferentes composições químicas. Os capacitores MOS foram caracterizados por medidas de capacitância e corrente em função da tensão, de onde foram extraídas a densidade de estados de interface, a densidade de carga efetiva, constante dielétrica e campo elétrico de ruptura dos filmes. Os resultados mostraram uma variação linear da constante dielétrica do filme em função da concentração de nitrogênio, indo do valor de 3,9, correspondente ao dióxido de silício estequiométrico (SiO2) à 7,2 correspondente ao nitreto de silício estequiométrico (Si3N4). Também observamos que o nitrogênio é uma barreira eficiente à difusão de impurezas através do dielétrico. Porém, notamos uma grande dispersão de duas ordens de grandeza nos valores da carga efetiva (Nss) e de densidade de estados de interface (Dit). Por outro lado, controlando algumas variáveis de forma a manter constante o valor de Nss ( ~1012 cm-2), observamos uma variação de Dit em função da concentração de nitrogênio no filme, esta variação porém é pequena comparada com a dispersão de duas ordens de grandeza observada, que atribuímos assim a fatores externos. O menor valor obtido de Dit foi de 4,55.1010 eV-1.cm-2, que é ótimo para um filme obtido por PECVD, sem nenhum tratamento térmico e melhor que os reportados na literatura para dielétricos obtidos por técnicas que utilizam altas temperaturas (LPCVD-800ºC e oxinitretação térmica – 1100ºC). Assim, podemos concluir que a técnica de PECVD é promissora para a obtenção de dielétricos a baixas temperaturas. In this work, MOS capacitors with different chemical composition silicon oxynitride insulating layer, deposited by PECVD technique at low temperature were fabricated and characterized, in order to study its dielectric and interface properties, seeking its aplication as insulating layer in MOS and thin films devices. The MOS capacitors were fabricated onto p-silicion wafers previously cleaned by a standard process, followed by the insulating layer deposition, photolitography, metalization and sinterization. The SiOxNy insulating layer was deposited by the PECVD technique at 320ºC changing the precursor gases flows to obtain films with different chemical compositions. The MOS capacitors were characterized by capacitance and current vs. voltage measurements, from where the interface state density (Dit), the effective charge density (Nss), the dielectric constant (k) and the film electrical breakdown field (Ebd) were extracted. The results showed a dielectric constant varying linearly as a function of the films nitrogen concentration, going from a value of 3.9, corresponding to stoichiometric silicon dioxide (SiO2) to a value of 7.2, corresponding to stoichiometric silicon nitride film (Si3N4). We also observed that nitrogen is an efficient diffusion barrier against contaminants. However, a large dispersion, about two orders of magnitude, in the effective charge and in the interface state density was observed. On the other hand, controlling some variables so as to keep the Nss value constant (~1012 cm-2) we observed a Dit variation as a function of the film nitrogen concentration, this variation is small when compared with the observed dispersion of two orders of magnitude, thus attributed to external factors. The smallest obtained Dit was 4.55.1010 eV-1.cm-2, which is unexpected for a PECVD film without any anealing process and is better than the values reported in the literature for dielectrics obtained at high temperatures techniques (as LPCVD – 800ºC and thermal oxynitridation – 1100ºC). Therefore, we can conclude that the PECVD technique is promising for obtaining low temperature dielectrics.

We present x-ray imaging results for diverse iron-based-ink antique writings - single-page manuscripts, stacks and scrolls - from the 16th century on. The objective is to elaborate new digitization techniques by x-ray tomography for the “Venice Time Machine” (VTM) project in collaboration with the “Archivio di Stato”. The technique can potentially read unopened - perhaps unopenable - documents and speed up the entire digitization process of large collections. The technique is feasible thanks to the highly absorbing chemical elements in ancient European ink recipes. The corresponding x-ray contrast allows character reading with reasonably short exposure times. The impact is quite relevant: the potential feasibility of “softer” and faster digitization of huge collections like the Archivio di Stato - 80 km of documents spanning 10 centuries.

In this work we produce and characterize SiO x N y films deposited by the plasma enhanced chemical vapor deposition (PECVD) technique at low temperatures from silane (SiH 4 ) nitrous oxide (N 2 O) and helium (He) as precursor gases at different deposition pressures in order to analyze the effect of this parameter on the films structural properties and on the SiO x N y /Si interface quality. In order to compare the film structural properties with the interface (SiO x N y /Si) quality, MOS capacitors were fabricated using these films as dielectric layer. The structure and composition of the films were investigated by, X-ray absorption near-edge spectroscopy (XANES) at the N-K and O-K edges, Rutherford backscattering spectroscopy (RBS) and Fourier transform infrared spectroscopy (FTIR). The MOS capacitors were characterized by low and high frequency capacitance ( C – V ) measurements, from where the interface state density ( D it ) and the effective charge density ( N ss ) were extracted. The film deposited at 120 mTorr presented the best interface quality ( D it ∼ 4 × 10 10 eV −1 cm −2 ) and the higher concentration of N–H bonds. This result indicates that this pressure favors N–H incorporation in oxygen vacancies at Si–O–Si bridges, saturating the Si dangling bonds and consequently minimizing Si/SiO x N y interface defects, showing that it is possible to produce high quality dielectric layer by PECVD technique.

The characteristics of hydrogenated amorphous silicon carbide films prepared by PECVD and crystallized by KrF UV excimer laser annealing (ELA), for different annealing conditions, are studied to determine particulate size, surface roughness, band gap and resistivity in order to apply them to TFTs fabrication. Raman spectra for ELA SiC films indicate the presence of 6H-SiC polytype together with Si and C crystallites. We also describe the fabrication process to obtain a-Si1xCx:H TFTs and ELA TFTs on the same wafer, comparing their output and transfer characteristics. � 2005 Elsevier Ltd. All rights reserved.

In this work metal/oxide/semiconductor (MOS) capacitors with different nitrogen content SiO"xN"y gate dielectric are fabricated and characterized. The dielectric films are deposited by the plasma enhanced chemical vapor deposition technique from N"2, N"2O and SiH"4 gaseous mixtures at low temperatures. The MOS capacitors were characterized by low and high frequency capacitance (C-V) measurements, from where the interface state density (D"i"t), the effective charge density (N"e"f"f) and the dielectric constant (k) were extracted. The results show a dielectric constant varying linearly in function of the films nitrogen concentration, from a value of 3.9, corresponding to SiO"2 to 7.2, corresponding to Si"3N"4. We observed a variation of D"i"t in function of the films nitrogen concentration, the smallest obtained value corresponding to the Si"3N"4 film (~1x10^1^1 cm^-^2eV^-^1), however this film presents higher leakage current density than others. In order to optimize both parameters a double dielectric layer is proposed, a first layer of Si"3N"4 film, which presents the highest dielectric constant and best interface properties, and a second layer of SiO"xN"y with high nitrogen concentration, in order to maintain the equivalent dielectric constant high but minimizing the leakage current problems.

In this work metal/oxide/silicon (MOS) capacitors using SiOxNy and SiO2 films with different nitrogen concentrations as gate dielectrics were deposited by the plasma-enhanced chemical vapor deposition (PECVD) technique, fabricated and characterized. These films were obtained through the variation of the N2O/SiH4 flow ratio (R) at low temperatures (∼320 °C). The refractive index results show that by varying the N2O/SiH4 flow ratio it is possible to obtain a precise control of this parameter in the 1.46–1.57 range. From the low- and high-frequency C–V curves, the interface state density (Dit), the effective charge density (Nss), dielectric constant (k), among others were extracted. Optimized properties were found for the capacitor with a low nitrogen concentration (∼8%) SiOxNy gate dielectric.

Introduction: X-ray computed tomography (CT) is now used in the cultural heritage field because it is non-invasive and it can give a large amount of information on the inner structure of the object under study. Until recently mainly medical CT scanners or micro-CT setups have been used, limiting the analysis to relatively small artworks or requiring multiple acquisition and difficult image-joining for objects larger than detector dimensions. Results: To overcome the limitations of ordinary CT devices, a facility for the X-ray tomography of large size artefacts has recently been designed and installed in a protected area of the Fondazione Centro Conservazione e Restauro “La Venaria Reale”, a Centre for Preservation and Restoration. This facility, based on a X-ray source, a linear X-ray detector and a high precision mechanical system, has been and will be used to gather information on materials, manufacturing techniques and conservative conditions of artworks undergoing the restoration process. In this paper the results of the tomography of the first analyzed large artistic object are presented, giving an idea of the wealth of information obtained from the CT scan. The presented artwork is the writing cabinet called “doppio corpo”, a masterpiece of furniture more than 3 m high, inlaid for Savoy Residences by Pietro Piffetti, the most famous cabinet-maker in Piedmont in the XVIII century. The artwork is now housed in the Quirinale Palace, the official residence of the Italian President in Rome. Conclusions: The CT analysis permitted us to obtain valuable information about the conservative conditions, the presence of previous interventions, the distribution of various materials and the dimensions and arrangement of several wooden pieces, thus allowing for interesting hypotheses about the building technique of this masterpiece.

Hydrogen sensors, intending to operate at low temperatures (around 25°C), based on TiO 2 nanotube arrays were fabricated and characterized in N 2 /H 2 atmosphere with different nitrogen concentrations. The nanotube arrays were obtained through Ti anodic oxidation in a NH 4 F in ethylene glycol (0, 5 % in weight) and 2 % H 2 O bath, magnetically stirred at room temperature. The TiO 2 nanotube hydrogen sensors were characterized at room temperature with hydrogen concentration varying from 50 to 4000 ppm. A linear conductance variation between 50 and 500 ppm was observed. This result is very attractive for hydrogen sensors where low operation temperatures are needed, for example, in medical applications.

TiO 2 nanotube arrays obtained by Ti foil anodization are tested as pH electrodes, showing performance close to standard glass electrodes. The TiO 2 nanotube arrays were obtained by Ti foil anodization in a NH 4 F organic solution with 20, 40 and 60 V and different anodization times. The obtained nanotubes samples were characterized by Scanning Electron Microscopy (SEM). Electrode modified by TiO 2 nanotubes were characterized in pH buffer solution (pH of 4.0, 7.0 and 10.0) and the obtained results show that electrode modified by NTs obtained with anodization voltage of 40 V with 45 minutes presents an almost linear response close to Nernst equation (59 mV/pH).

The heavy-element content of ink in ancient administrative documents makes it possible to detect the characters with different synchrotron imaging techniques, based on attenuation or refraction. This is the first step in the direction of non-interactive virtual X-ray reading., Handwritten characters in administrative antique documents from three centuries have been detected using different synchrotron X-ray imaging techniques. Heavy elements in ancient inks, present even for everyday administrative manuscripts as shown by X-ray fluorescence spectra, produce attenuation contrast. In most cases the image quality is good enough for tomography reconstruction in view of future applications to virtual page-by-page ‘reading’. When attenuation is too low, differential phase contrast imaging can reveal the characters from refractive index effects. The results are potentially important for new information harvesting strategies, for example from the huge Archivio di Stato collection, objective of the Venice Time Machine project.

The diagnostic investigations are an important resource in the studies on Cultural Heritage to enhance the knowledge on execution techniques, materials and conservation status of a work of art. In this field, due to the great historical and artistic value of the objects, preservation is the main concern; for this reason, new technological equipment has been designed and developed in the Physics Departments of the Universities of Ferrara and Bologna to enhance the non-invasive approach to the study of pictorial artworks and other objects of cultural interest. Infrared (IR) reflectography, X-ray radiography and computed tomography (CT), applied to works of art, are joined by the same goal: to get hidden information on execution techniques and inner structure pursuing the non-invasiveness of the methods, although using different setup and physical principles. In this work transportable imaging systems to investigate large objects in museums and galleries are presented. In particular, 2D scanning devices for IR reflectography and X-ray radiography, CT systems and some applications to the Cultural Heritage are described.

The development of high sensitive miniaturized sensors is of special importance for “Lab on a Chip” and biosensors development [1]. In this context and due to its n-type semiconductor character and its high chemical stability, TiO 2 thin films have been proposed for application as pH and H sensors [2]. Even more, taking advantage of their high specific surface, TiO 2 nanotubes have been also considered as a natural candidate for application in pH detection [3].

The neu_ART project aims at developing state of the art transmission imaging and computed tomography techniques, applied to art objects, by using neutrons as well as more conventional X-rays. In this paper a facility for digital X-ray radiography of large area paintings on canvas or wooden panels and for the X-ray tomography of large size wooden artifacts, recently installed in a protected area, is presented. The results of a K-edge radiography facility that will soon be installed in the same area are also shown.

Monochromatic X-ray sources can be used for several applications, like in medicine or in studying our cultural heritage. We are investigating imaging systems based on a tuneable energy band X-ray source, to obtain an element mapping of painting layers using the K-edge technique. The narrow energy band beams are obtained with conventional X-ray source via Bragg diffraction on a mosaic crystal; such an analysis has been performed at different diffraction angles, tuning the energy to investigate spectra of interest from the artistic point of view, like zinc and copper. In this paper the characteristics of the system in terms of fluence rate are reported, and first results of this technique on canvas samples and painting are presented.

Foram estudados filmes de oxinitreto de silício obtidos por PECVD à 320°C, a partir da mistura gasosa de N2O+SiH4+He, com diferentes valores de pressão e potência de deposição com o objetivo de produzir boa qualidade de interface deste material com o Si e de obter uma baixa densidade de carga efetiva visando a aplicação desses filmes em dispositivos semicondutores MOS. Os resultados mostraram que com uma pressão de deposição de 0,160 mbar e potências menores que 125 W/cm2 é possível obter um valor de densidade de estados de interface (Dit) de 4x1010 eV-1.cm-2, campo elétrico de ruptura (Ebd) de 13 MV/cm, valores comparáveis ao SiO2 térmico e uma densidade de carga efetiva (Nss) de 4x1011 cm-2. Segundo resultados experimentais esse valor de Nss é o mínimo possível que se pode atingir com a limpeza química utilizada em nosso laboratório. Pode-se dizer que estes são resultados bastante interessantes considerando que se trata de um material obtido por PECVD à baixa temperatura, porém viável para aplicação em dispositivos MOS. Iniciando os estudos com dielétricos de maiores valores de constante dielétrica optamos por estudar filmes de TiOx (k=40-100), obtidos por sputtering reativo, a partir da mistura gasosa de Ar+O2 e utilizando alvo de Ti. Foram fabricados capacitores MOS com estes filmes e obteve-se valores de constante dielétrica que variaram de 40-160. Porém esses materiais ainda apresentavam valores apreciáveis de corrente de fuga que foram minimizadas em ordens de grandeza quando utilizados dielétricos de dupla camada com SiO2 ou SiOxNy (otimizado neste trabalho) na interface, além de se observar uma melhora significativa da qualidade de interface. Utilizando dupla camada dielétrica com filmes de SiOxNy e SiO2, ainda espessos (³ 1nm) para camada intermediária, obteve-se uma constante dielétrica efetiva em torno de 20. Vale ressaltar que os dois filmes SiOxNy e TiOx, conseqüentemente a dupla camada, foram fabricados a baixas temperaturas. Silicon oxynitride films obtained by the PECVD technique from N2O+SiH4+He gaseous mixtures, at 320°C, with different deposition pressure and RF power were studied intending to improve the interface quality with Si, decreasing the effective charge density and the interface state density in order to utilize them in MOS semiconductor devices. The results showed that with a deposition pressure of 0.160 mbar and a RF power density lower than 125 W/cm2 it is possible to obtain interface state density (Dit) values of 4x1010 eV-1.cm-2, Electrical Breakdown (Ebd) of 13 MV/cm, comparable with the obtained for thermally grown SiO2 , and an effective charge density (Nss) of 4x1011 cm-2. According with experimental results this Nss value is the minimum attainable with our chemical cleaning process. In this way it can be said that these results are very promising, considering that these materials were obtained by PECVD at low temperatures, but still viable for MOS devices application. In order to initiate studies with high dielectrics constant material, TiOx films (k= 40-180), obtained by reactive sputtering through the Ar+O2 gaseous mixture utilizing a Ti target, were chosen. MOS capacitors with these films were fabricated and dielectric constant values varying from 40 to 160 were obtained. However, until now, these materials have presented appreciable leakage current values, which were, minimize by orders of magnitude with the addition of a thin SiO2 or SiOxNy (optimized in this work) layer at the interface were utilized. This thin layer also resulted in a significant improvement of the interface quality. Utilizing double dielectric layer with SiOxNy or SiO2, still thick (³ 1nm) as intermediate layer a dielectric constant value of 20 was obtained. Its important to mention that the SiOxNy and TiOx films, and consequently the double layer, were deposited at low temperatures.