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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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

Si(111) substrates were functionalized with a covalent 4-ClCH2C6H4SiCl3 monolayer that binds to the surface using the −SiCl3 group and leaves an unreacted −CH2Cl group. The remaining benzyl chloride functionality at the top of the Si(111) substrate allowed additional functionalization by an atom transfer radical polymerization process, mediated by copper complexes. Ordered, surface-confined polystyrene assemblies, covalently bound to the silicon, have been obtained. Atomic force microscopy measurements show a long-range order of these nanostructures. X-ray photoelectron spectroscopy provided quantitative results on the surface atomic composition as well as on the nanostructure thickness. The polystyrene structures on the silicon surface were also investigated by attenuated total reflectance infrared spectroscopy.

An array of nanocavities in silicon offers an inner surface defined by nearly flat, highly ordered, planes which can be passivated by hydrogen injection from aqueous solution of HF. The infrared spectrum shows that the inner surface is mainly constituted by monohydrides in different morphologies. The corresponding signals are very narrow (full width at half maximum at room temperature below 5 cm-1, depending on the line), this being evidence for high local order. Such an inner surface can be used as a benchmark for the assignment of infrared signals observed on outer surfaces, where the sources of errors-and the consequent uncertainty in the spectral attribution-may be large. The comparison between the spectra from a well-characterized external Si(1 0 0) surface and from an internal one (in both cases hydrogen-terminated) has allowed a better qualification of the external surface. Copyright © 2010 John Wiley & Sons, Ltd.

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.

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.

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.

A method is described for the preparation of device-quality, nearly flat, terraced, hydrogen-terminated, (100) silicon. The method requires heating at high temperature (say, 1100 °C) in H2, cooling to moderate temperature (670–700 °C) in the same ambient, and quenching to room temperature in N2. Evidence that the process really results in the said surface is based on atomic force microscopy, infrared absorption spectroscopy in the attenuated total reflection mode, thermal programmed desorption, reflection high energy electron diffraction, and angle-resolved X-ray photoelectron spectroscopy.

Nitridation of hydrogen-terminated silicon in a diluted N2 : N2O atmosphere was studied by X-ray photoemission spectroscopy and high-resolution electron microscopy. Our analysis showed that the broad N(1s) peak of width 1.5 eV at 398-399 eV, usually reported in the literature, is preceded by the formation of a narrow peak of width around 1.0 eV at 397.5 eV, attributed to the moiety Si3N in which silicon is only marginally oxidized, and two other peaks at 400.0 eV and 401.5 eV, attributed to the moieties Si2NOSi and SiNO, respectively.

The early oxidation stages of hydrogen-terminated single-crystalline (100) silicon exposed to a diluted N2 : N2O atmosphere at 850°C for different durations have been studied by x-ray photoemission spectroscopy, 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 the oxidation states from 0 to +4, does not account for the observed Si 2p signal. An explanation for silicon in unusual oxidation states is proposed.

Nitridation of hydrogen-terminated silicon with N2:N2O has been studied by x-ray photoemission spectroscopy. Our analysis has given evidence that the broad N(1s) peak at 398–399 eV, usually reported in the literature, is preceded by the formation of a narrow peak at 397.5 eV, attributed to the moiety Si3N in which silicon is only marginally oxidized, and two other peaks at 400.0 eV and 401.5 eV, attributed to the moieties Si2NOSi and SiNO, respectively.

Time-of-flight SIMS profiles have been obtained on an SiO 2 /Si system. A dual ion beam experimental set-up has been used in order to decouple the erosion process due to an Ar + beam from the analysis done by a Ga + beam. The Ga + yield shows a characteristic double-peaked structure at the SiO 2 /Si interface. It is shown that the peak at shallower depth can be accounted for by a change in sputtering rate, whereas that located at the interface can be interpreted in terms of gallium segregation.

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.

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.