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Controlled layering of functional material can produced a versatile film with specific chemical and physical proprieties for desirable applications. This article presented inkjet multilayer structures of ZnO nanoparticles of specific layer morphology and thickness for the development of devices where a high surface-to-volume ratio is required (e.g. micro gas sensors). Stacked multilayers were stratified through a multi-run printing process suitable to produce large-square pattern on flat silicon support. The formation of a multilayer structure was demonstrate through an extended structural characterization of the resulting film. Printed layer morphology was investigated with optical and scanning electron microscopies; atomic force microscopy profiling characterizations were conducted over the entire printed area to evaluate the pattern reproducibility. Finally, a preliminary study as gas sensing film was performed, using the alcohol/ZnO interaction experiments. more...

Artificial muscle fibers and compliant actuators are generating increasing interest from several advanced robotics applications. In this paper, we propose an integrated linear actuator design based on the synchronous linear motor concept and provide simulation data to assess its potential performance. The actuator is designed to be modular, scalable, flexible, devoid of permanent magnets, and physically structured to mimic natural muscle fibers. We use a straightforward actuation protocol to compare the force, stroke and other performance characteristics of the actuator with biological muscles. The thermal behavior is also simulated, including the effects of an integrated microfluidics cooling system that allow the force to mass ratio of a structure to increase. Results indicate such approach as a possible promising route to develop muscle like actuators in the framework of microelectronics technology. more...

In this paper, we propose a UV-A sensor based on a 6H-SiC Schottky photodiode with a thin Ni2Si front electrode and an integrated hydrogenated silicon nitride (SiN:H) dielectric filter. 6H-SiC prototypes were fabricated by using a manufacturing process to a large extent already implemented on 4H-SiC poly-type for the realization of a high signal-to-noise ratio ultraviolet (UV) sensor already commercialized. The results obtained on 6H-SiC prototypes show optimal electrical performance with dark current density lower than 0.2 nA/cm2 at room temperature and 10 V reverse bias. The use of 6H polytype allows shifting of the UV sensor response from 290 nm peak responsivity wavelength measured on standard 4H-SiC photodiodes to 360 nm wavelength in 6H-SiC prototypes with an integrated SiN:H filter exactly in the middle of the UV-A band (320-400 nm) with a simultaneous consistent reduction of the optical response in UV-C and UV-B regions below 320 nm wavelength. more...

The development of integrated sensors is a challenge currently facing biodiagnostics where multiplexing and high sensitivity detection are frequently required. This work follows an approach based on silicon photomultiplier detection, phosphorescent nanobeads and compact front-face light-source configuration. The advantages of this approach also derive from the sensitivity, compactness, robustness and low operating voltage of SiPM devices. An experiment was performed to demonstrate performance in terms of sensitivity, with the results allowing the estimation of a detection limit for proteins of 1–10 pg/mL. more...

Crosstalk and afterpulsing in silicon photomultipliers can strongly limit the photon-counting resolution and dynamic range of the sensors. In this work we present a method and a measurement (as a demonstration) to separate the afterpulse and delayed crosstalk components of the delayed correlated pulses in STMicroelectronics silicon photomultiplier signals. The contribution of delayed crosstalk can be significant since even if one suppresses afterpulses by applying a longer recharge time, the delayed crosstalk component remains unaffected. This was the case for our measurement: 207 ns recharge was long enough to suppress afterpulses (3.3%), while the delayed crosstalk remained large (12.8%). more...

The gas sensor integration in smart devices, represents a huge step forward for health and environmental sensing applications. Several technical problems as well as the insufficient rationalization in the gas-recognition mechanisms still impede their development. Addressing this challenge, an ethyl alcohol/Al-doped ZnO interaction experiment is designed, exploiting a reliable chemiresistive thin film-based gas sensor. An ink-jet printing technique is chosen to deposit the nanostructured active layer on the highly integrated micro hot plate. Deposited sensing layer, is investigated with scanning electron microscopy, energy dispersive x-ray spectroscopy and atomic force microscopy. Conformal coating and profiled signals according to the covered sensor structure were achieved. The sensing results demonstrate a reproducible dynamic gas response with a rapid initial decrease in resistance, followed by a steady rise in conductivity at a different rate, until it plateaus. The well-defined signal profile, with the peculiar inflection points, has enabled an interpretation of the chemical reaction mechanism. more...

Nanostructured materials represent a breakthrough in many fields of application. Above all for sensing, the use of nanostructures with a high surface/volume ratio is strategic to raise the sensitivity towards dangerous environmental gas species. A new Dc-Reactive sputtering Deposition method has been applied to grow highly porous p-type nitrogen-doped titanium oxide layers by modifying the previously developed reactive sputtering method called gig-lox. The doping of the films was achieved at room temperature by progressive incorporation of nitrogen species during the deposition process. Two different amounts of N2 were introduced into the deposition chamber at flow rates of 2 and 5 standard cubic centimeter per minutes (sccm) for doping. It has been found that the N2 uptake reduces the deposition rate of the TiO2 film whilst the porosity and the roughness of the grown layer are not penalized. Despite the low amount of N2, using 2 sccm of gas resulted in proper doping of the TiO2 film as revealed by XPS Analyses. In this case, nitrogen atoms are mainly arranged in substitutional positions with respect to the oxygen atoms inside the lattice, and this defines the p-type character of the growing layer. Above this strategic structural modification, the multibranched spongy porosity, peculiar of the gig-lox growth, is still maintained. As proof of concept of the achievements, a sensing device was prepared by combining this modified gig-lox deposition method with state-of-the-art hot-plate technology to monitor the electrical response to ethanol gas species. The sensor exhibited a sensitivity of a factor of &asymp, 2 to 44 ppm of ethanol at &asymp, 200 &deg, C as measured by a rise in the layer resistivity according to the p-type character of the material. At the higher temperature of &asymp, 350 &deg, C, the sensor turned to n-type as without doping. This behavior was related to a loss of nitrogen content inside the film during the annealing. It was indeed proved that p-type doping of a gig-lox sponge during growth is feasible, even at room temperature, without losing the layer porosity and the capability to host and detect environmental species. Moreover, the material integration on a device is simply done as the last production step. Easy TiO2 doping procedures, combined with porosity, are of general purpose and interest for several applications even on flexible substrates. more...

A quantitative angle-resolved XPS analysis was carried out of the carbonaceous films resulting from the derivatization under mild thermal activation of nearly flat, terraced, dihydrogen-terminated, 1 × 1 (100) Si with 1-octene or 1-octyne. The analysis of the C 1s signal gave evidence for the presence of carbon in carbide configuration (SiC bonds) at the substrate–film interface, in addition to the alkanic carbon and adventitious oxidized carbon (CO bonds) produced by the oxidizing impurities flawing the reaction. Assuming the surface as uniformly covered, the analysis showed that for both reactants the films were closely packed. Copyright © 2006 John Wiley & Sons, Ltd. more...

A lot of work has been carried out to prepare chemically homogeneous (1 0 0) silicon surfaces. The hydrogen-terminated (1 0 0) silicon surfaces are the most promising ones, especially in view of their remarkable environmental stability. The simplest way to produce hydrogen-terminated surfaces (attack in water solution of HF of a sacrificial, thermally grown, oxide) results in strongly heterogeneous rough surfaces (although with prevailing dihydride terminations). These surfaces can, however, be flattened and homogenized by treating them in H 2 at high temperature ( > 850 ° C). The morphological and chemical changes undergone by the surface during the treatment are studied X-ray photoelectron spectroscopy, atomic force microscopy, scanning tunnelling microscopy, infrared absorption spectroscopy in the attenuated total reflection mode, reflection high energy electron diffraction and thermal programmed desorption, and the mechanisms responsible for them are discussed. more...

Denoting with 'nanodevice' any device with size in one dimension at least in the nanometre length scale (NLS), the basic constituent of integrated circuits (ICs), the metal-oxide-semiconductor (MOS) field-effect transistor (FET), is by several years a nanodevice. In fact, the thickness of the SiO"2 gate dielectric is around 3nm for logics or 5nm for nonvolatile memories. However, since the factors limiting the IC integration are horizontal sizes, in electronics one speaks of nanodevice when its size in one horizontal dimension at least is in the NLS. The definition of features in the NLS is impossible via optical lithography, but can be done using electron- or ion-beam lithography. These techniques, however, are very expensive and still in their fancy, at least for what concerns their exploitation in the industry practice. Geometries in the NLS can however be produced with relative ease by the spacer patterning technique, i.e., transforming vertical features (like film thickness) in the vicinity of a step of a sacrificial layer into horizontal features. The ultimate length producible in this way is controlled by: the steepness of the step defining the sacrificial layer; the uniformity of the deposited or grown films; and the anisotropy of its etching. While useful for the preparation of a few devices with special needs, the above trick does not allow by itself the development of a nanotechnology, where each layer useful for defining the FET should be in the NLS and aligned on the underlying geometries with tolerances in the NLS. Setting up such a nanotechnology is a major problem which will involve the IC industry in the post-Roadmap era. Irrespective of the detailed structure of the basic constituents of nanoICs (molecules, supramolecular structures, clusters, etc.), any nanoIC can hardly be prepared without the ability to produce arrays of conductive strips with pitch in the NLS. This work is devoted to describe a scheme (essentially based on the existing microelectronic technology) for their production without the use of electron- or ion-beam lithography and used as host of molecular devices. more...

An experimental study via X-ray photoelectron spectroscopy at different takeoff angles of the derivatization of atomically flat, hydrogen terminated, 1 × 1 (1 0 0) Si surfaces with 1-octyne is reported. The major conclusion of the experimental analysis (that a large fraction of the grafted moieties contain unreacted π bonds) is then compared with the results of high-level ab initio modelling with model molecules of the derivatization act. more...

The structure and growth kinetics of the oxide resulting from exposure of hydrogen-terminated single-crystalline (100) silicon to diluted N2 : N2O atmospheres at moderate temperatures (in the interval 750–850 °C) have been studied byX-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (TEM), and secondary-ion mass spectrometry (SIMS). Under these conditions, the data suggest that the substoichiometric interface region is extremely narrow, and they point to O2 (resulting from N2O decomposition) as the major oxidizing species after monolayer completion. more...

An experimental study of the derivatization of Si(100) surfaces with 1-octyne has been carried out via x-ray photoelectron spectroscopy at different take-off angles, and infrared absorption spectroscopy in attenuated total reflection mode and atomic force microscopy have been used to characterize the pristine surface. Our study has shown that it is possible to prepare nearly flat, terraced, homogeneously hydrogen-terminated Si(100) surfaces via exposure to H2 at high temperature (1100 °C) and that these surfaces may be functionalized with hydrocarbon moieties by simple immersion in the unsaturated hydrocarbon at ∼200 °C. Copyright © 2004 John Wiley & Sons, Ltd. more...

Heating (100) silicon at high temperature (say, higher than 850 °C) in H2, cooling to 670–700 °C in the same ambient, and quenching to room temperature in N2 results in environmentally robust, terraced 1 × 1 (100) SiH2. Evidence for this conclusion is based on angle-resolved x-ray photoelectron spectroscopy, atomic force microscopy, infrared absorption spectroscopy in the attenuated total reflection mode, thermal programmed desorption, and reflection high-energy electron diffraction. Copyright © 2005 John Wiley & Sons, Ltd. more...

Hydrogen-terminated, atomically flat, 1×1 (un)reconstructed, (100)-oriented, silicon surfaces have been functionalized with 1-octyne and then studied via X-ray photoelectron spectroscopy. The C 1s signal shows that the addition of the hydrocarbon chain occurs through the formation of environmentally stable Si-C bonds, in agreement with hydrosilation as the major grafting route. more...

An X-ray photoemission spectroscopy (XPS) study at different takeoff angles of the derivatized surface resulting after prolonged (2 h) exposure of hydrogen-terminated 1×1-reconstructed (100)-oriented silicon to liquid 1-octyne at 170 °C has been carried out. The experimental data may be interpreted assuming that: (1) the grafting occurs through the formation of Si–C bonds; (2) in the considered conditions, one π bond of the octyne has a large survival probability after the grafting; and (3) side reactions leading to Si–O–C or Si–C(O) moieties are also active. more...

The structure and thermal stability in N-2 of hydrogen-terminated (100) silicon has been studied by X-ray photoemission spectroscopy, transmission electron microscopy, atomic force microscopy, thermal programmed desorption, and reflection high energy electron diffraction. Device-quality surfaces were prepared in an open-chamber reactor by exposing single crystalline, (100) oriented silicon to H-2 at high temperature (850 degreesC or 1100 degreesC) for durations on the order of 10(2) s. The observed stability with respect to N-2 at 850 degreesC is inconsistent with the reported desorption kinetics and may be accounted for in terms of either physico-chemical properties of the system (e.g., the presence of a buried layer of H-2 or of hydrogen-decorated vacancies whose out-diffusion restores the hydrogen terminations on the surface) or the reactor (persistence of hydrogen in the atmosphere even after switching it off). The nitridation by N-2 of hydrogen-terminated silicon is less efficient (per unit exposure) than that by N2O by 4 orders of magnitude. more...

This work presents a study based on x-ray photoelectron spectroscopy of the reaction of hydrogen-terminated silicon with 1-alkynes as a route for the functionalization of the (100) surface of silicon. The study (i) demonstrates that the grafting of hydrocarbon moieties is possible by simple exposure of the silicon surface to a liquid alkyne, (ii) shows that the derivatization protects the silicon against oxidation in air, (iii) indicates that the process occurs via hydrosilation of the alkyne at the hydrogen-terminated surface and (iv) suggests that grafted moieties contain in large part an unreacted π bond. more...

An experimental study of the Si 2p XPS spectrum at different take-off angles of atomically flat, hydrogen-terminated 1 × 1 Si(100) is reported. The observed spectrum can be described accurately by considering three additional contributions to the spectrum of elemental silicon. Each contribution is attributed to a chemical state of silicon on the basis of its chemical shift with respect to elemental silicon and the depth of the region where it was originated. Copyright © 2003 John Wiley & Sons, Ltd. more...

This work presents an experimental study based on X-ray photoemission spectroscopy (XPS) of hydrosilation of 1-alkyne as a tool for the functionalization of the (100) surface of silicon. In particular, the following processes are considered: (i) hydrogen termination of silicon via HF etching and subsequent exposure to H2 at high temperature, and (ii) grafting alkene chains to the resulting hydrogen-terminated surface via hydrosilation of 1-octyne. more...

The early oxidation stages of hydrogen-terminated single-crystalline Si(100) exposed to a diluted N2/N2O atmosphere at 850° C for different durations have been studied by XPS, following the evolution of the Si 2p signal. Evidence is given that the usual analysis, in terms of five pairs of peaks attributed to silicon in oxidation states from 0 to +4, does not account for the observed Si 2p signal. The spectrum is accurately reproduced only by assuming the existence of silicon in bonding configurations different from those usually assumed to occur at the Si/SiO2 interface. Copyright © 2002 John Wiley & Sons, Ltd. more...

Silicon oxide and silicon nitride surfaces have been treated with 1-octadecene at ∼200°C. The resulting film topography has been inspected by atomic force microscopy (AFM), showing a densely packed organic coating with a corrugation of some tenths of a nanometre. High-mass-resolution time-of-flight secondary ion mass spectrometry (ToF-SIMS) spectra from such surfaces display octadecene- as well as substrate-related peaks. Furthermore, peaks diagnostic of the formation of SiOC or SiC linkages are observed in the case of silicon oxide, whereas the same peaks and those due to SiNC species have been observed in the case of silicon nitride. These results suggest that 1-octadecene molecules are chemisorbed on the substrate. Contact angle measurements and AFMforce spectroscopy measurements allow comparison upon the macroscopic and nanoscopic scale, respectively, of the surface free energy modification due to the formation of the organic coating. more...

Exposure to ultraviolet (UV) radiation is a major risk factor for most skin cancers. The sun is our primary natural source of UV radiation. The strength of the sun's ultraviolet radiation is expressed as Solar UV Index (UVI). UV-A (320–400 nm) and UV-B (290–320 nm) rays mostly contribute to UVI. UV-B is typically the most destructive form of UV radiation because it has enough energy to cause photochemical damage to cellular DNA. Also overexposure to UV-A rays, although these are less energetic than UV-B photons, has been associated with toughening of the skin, suppression of the immune system, and cataract formation. The use of preventive measures to decrease sunlight UV radiation absorption is fundamental to reduce acute and irreversible health diseases to skin, eyes and immune system. In this perspective UV sensors able to monitor in a monolithic and compact chip the UV Index and relative UV-A and UV-B components of solar spectrum can play a relevant role for prevention, especially in view of the integration of these detectors in close at hand portable devices. Here we present the preliminary results obtained on our UV-A sensor technology based on the use of hydrogenated Silicon Nitride (SiN:H) thin passivating layers deposited on the surface of thin continuous metal film Ni2Si/4H-SiC Schottky detectors, already used for UV-Index monitoring. The first UV-A detector prototypes exhibit a very low leakage current density of about 0.2 pA/mm2 and a peak responsivity value of 0.027 A/W at 330 nm, both measured at 0V bias. more...

Peptides, with their well-established chemistry and fully automated synthesis, provide an invaluable tool for the screening of protein ligands, for epitope mapping, and for antibody diagnostics on the microarray format.The method described in this chapter shows that the sensitivity of a peptide-based microimmunoassay is greatly improved by using a new, specifically developed substrate made of silicon coated by an optimized layer of silicon oxide. A set of six peptides corresponding to the sequences of human and rat acetylcholine receptor subunits was immobilized on glass and silicon slides coated by a copolymer of N,N-dimethylacrylamide, N-acryloyloxysuccinimide, and 3-(trimethoxysilyl) propyl methacrylate, copoly(DMA-NAS-MAPS). The spotted probes were incubated with rabbit anti-sera and with purified antibodies raised against the corresponding peptides. The coated silicon slides, in comparison against the glass substrates, showed a five- to tenfold enhancement of the fluorescence signals, leading to the specific detection of the full set of antibodies down to a concentration of 0.5-1 ng/mL in serum. The sensitivity provided by the test allows its use for the diagnosis of antibodies in clinical samples. more...

In this work, we report on the improvement of microarray sensitivity provided by a crystalline silicon substrate coated with thermal silicon oxide functionalized by a polymeric coating. The improvement is intended for experimental procedures and instrumentations typically involved in microarray technology, such as fluorescence labeling and a confocal laser scanning apparatus. The optimized layer of thermally grown silicon oxide (SiO(2)) of a highly reproducible thickness, low roughness, and fluorescence background provides fluorescence intensification due to the constructive interference between the incident and reflected waves of the fluorescence radiation. The oxide surface is coated by a copolymer of N,N-dimethylacrylamide, N-acryloyloxysuccinimide, and 3-(trimethoxysilyl)propyl methacrylate, copoly(DMA-NAS-MAPS), which forms, by a simple and robust procedure, a functional nanometric film. The polymeric coating with a thickness that does not appreciably alter the optical properties of the silicon oxide confers to the slides optimal binding specificity leading to a high signal-to-noise ratio. The present work aims to demonstrate the great potential that exists by combining an optimized reflective substrate with a high performance surface chemistry. Moreover, the techniques chosen for both the substrate and surface chemistry are simple, inexpensive, and amenable to mass production. The present application highlights their potential use for diagnostic applications of real clinical relevance. The coated silicon slides, tested in protein and peptide microarrays for detection of specific antibodies, lead to a 5-10-fold enhancement of the fluorescence signals in comparison to glass slides. more...

An experimental study based on x-ray photoelectron spectroscopy of room-temperature oxidation in air of nearly flat, terraced, hydrogen terminated (100) silicon has been carried out. The oxidation kinetics are characterized by two temporal domains, essentially associated with the formation of the substoichiometric oxide and for its transformation into the stoichiometric oxide: the substoichiometric oxide grows (with kinetics that may described in terms of an autocatalytic process) showing saturation at about $5\ifmmode\times\else\texttimes\fi{}{10}^{14}\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}2}$, while the stoichiometric oxide grows following a time logarithmic law. The entire process is characterized by the increase of a feature, with binding energy shifted by about $+0.3\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ with respect to that of elemental silicon, attributed to silicon atoms or clusters embedded in the growing oxide. more...

Among the processes devoted to the preparation of chemically homogeneous (100) silicon surfaces, the ones for hydrogen termination are the most promising, especially in view of the remarkable environmental stability of such surfaces. The simplest way to produce hydrogen-terminated silicon (attack of a sacrificial, thermally grown, oxide in aqueous solution of HF) results in rough, strongly heterogeneous (although with prevailing dihydride terminations) surfaces. These surfaces can, however, be flattened and homogenized by treating them in ${\mathrm{H}}_{2}$ at high temperature $(g850\phantom{\rule{0.2em}{0ex}}\ifmmode^\circ\else\textdegree\fi{}\mathrm{C})$. The morphological and chemical changes undergone by the surface during the treatment are studied ex situ (via x-ray-photoelectron spectroscopy, atomic force microscopy, scanning tunneling microscopy, infrared absorption spectroscopy in the attenuated total reflection mode, reflection high-energy electron diffraction, and thermal programmed desorption) and the mechanisms responsible for them are discussed. more...

Oxynitridation of hydrogen-terminated silicon with N2O has been studied by x-ray photoemission spectroscopy. Our analysis has given evidence that the broad N(1s) peak at 398.3 eV usually reported in the literature is preceded by the formation of a very narrow peak at 397.3 eV, attributed to the moiety Si3N in which nitrogen is only marginally oxidized, and two other peaks (previously never reported) at 400.0 eV and 401.5 eV, attributed to the moieties Si2NOSi and SiNO, respectively. more...

An experimental study on In implantation in Si was performed, considering some factors that affect its electrical activation. One of the critical issues concerning In is represented by its outdiffusion, during the post-implantation annealing, a limiting factor to get active In concentration suitable for applications in microelectronics. The use of different thermal processes was evaluated, aimed to achieve a reduction of the outdiffusion and an increase of the electrical activation of In in silicon. The influence of the substrate purity on the electrical activation was shown to be of great importance: in particular, it was shown that C., present in the silicon substrate as a contaminant or as a co-implanted species, has a key-role in the electrical activation and diffusion of In in silicon. Furthermore, for the first time at our knowledge, the behaviour of In implanted in Si1−xGex layers grown by CVD on Si wafers was investigated, for Ge concentration of 0.5% and 1%. An enhancement in the electrical activation was observed with increasing the Ge content in the alloy. more...