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In this work reactive pulsed laser deposition of molybdenum- and tungsten-nitride thin films is investigated. Metallic targets were ablated in low-pressure (1, 10 and 100 Pa) nitrogen atmosphere by KrF excimer laser pulses (fluence ∼6.5 J/cm2). Films were deposited on silicon wafers heated to ∼25, 250 and 500 °C. The characteristics of the films strongly depend on the N2 pressure. By increasing N2 pressure, the nitrogen content increases in the films, which leads to a monotonous increase of the electrical resistivity. Deposition rate decreases at 100 Pa as indicated by Rutherford backscattering spectrometry. At this pressure, hardness of the films significantly decreases also, as shown by microhardness measurements. X-ray diffractometry shows that films crystallinity is improved by increasing the substrate temperature. In addition, atomic force microscopy (AFM) and scanning electron microscopy (SEM) were applied for visualising the film surface.

In the present work we focus our attention on the structural modifications induced by repeated absorption/desorption cycles on Mg–Nb layers. Samples consisting of a 30 μm thick pure Mg or Mg–5 at.% Nb doped films, coated with a 20 nm thick Pd layer were submitted to repeated H 2 sorption cycles in a volumetric apparatus. Isothermal desorption analysis at 350 °C was performed to evaluate the amount of absorbed hydrogen. X-ray diffraction (XRD), energy dispersive spectroscopy (EDS) and electron microscopy techniques (SEM and TEM) were used for the structural characterisation of the samples. Analyses show a deep modification of the material upon cycling. The presence of Nb enhances the structural modifications and induces an initial lattice contraction of the Mg matrix that tends to decrease on cycling via the formation of Nb nanoparticles (with average size of ∼10 nm). SEM and TEM observations performed in cross section evidenced the formation of a porous structure.

We systematically measured the photo-elastic parameter f σ of PbWO 4 (PWO) for crystals of different thicknesses. We observed a linear behaviour of f σ as a function of the thickness for low level applied stresses. This result was corroborated by numerical simulations. f σ allows the evaluation of the residual internal stress, useful for crystal quality control. In this work, we also propose a new polariscope based on laser light, which allows a fast measurement and mapping of the internal stress of crystals with high resolution owing to the reduced laser-beam dimension.

Direct metal laser sintering (DMLS) is a technique to manufacture complex functional mechanical parts from a computer-aided design (CAD) model. Usually, the mechanical components produced by this procedure show higher residual porosity and poorer mechanical properties than those obtained by conventional manufacturing techniques. In this work, a Co–Cr–Mo alloy produced by DMLS with a composition suitable for biomedical applications was submitted to hardness measurements and structural characterization. The alloy showed a hardness value remarkably higher than those commonly obtained for the same cast or wrought alloys. In order to clarify the origin of this unexpected result, the sample microstructure was investigated by X-ray diffraction (XRD), electron microscopy (SEM and TEM) and energy dispersive microanalysis (EDX). For the first time, a homogeneous microstructure comprised of an intricate network of thin e (hcp)-lamellae distributed inside a γ (fcc) phase was observed. The e-lamellae grown on the {111} γ planes limit the dislocation slip inside the γ (fcc) phase, causing the measured hardness increase. The results suggest possible innovative applications of the DMLS technique to the production of mechanical parts in the medical and dental fields.

Large scintillating crystals are affected by internal stresses induced by the crystal growth temperature gradient remanence. Cutting boules (ingots) into finished crystal shapes allows for a partial tension relaxation but residual stresses remain the main cause of breaking. Quality control of residual stresses is essential in the application of Scintillating Crystals to high-energy physics calorimeters (e.g. CMS ECAL at CERN LHC). In this context the industrial process optimisation towards stress reduction is mandatory. We propose a fast technique for testing samples during the production process in order to evaluate the residual stress distribution after the first phases of mechanical processing. We mapped the stress distribution in PbWO 4 slabs cut from the same production boule. The analysis technique is based on the stress intensity determination using the photo-elastic properties of the samples. The stress distribution is mapped in each sample. The analysis shows that there are regions of high residual tension close to the seed position and at the boule periphery. These results should allow for adapting the industrial process to producing crystals with lower residual stresses.

We report experimental results obtained for electrical and structural characteristics of yttria-stabilised zirconia (YSZ) thin films deposited by pulsed laser deposition (PLD) on Si substrates at room temperature. Some samples were submitted to thermal treatments in different ambient atmospheres (vacuum, N 2 and O 2 ) at a moderate temperature. The effects of thermal treatments on the film electrical properties were studied by C – V and I – V measurements. Structural characteristics were obtained by X-ray diffraction (XRD), X-ray reflectivity (XRR) and transmission electron microscopy (TEM) analyses. The as-deposited film was amorphous with an in-depth non-uniform density. The annealed films became polycrystalline with a more uniform density. The sample annealed in O 2 was uniform over all the thickness. Electrical characterisation showed large hysteresis, high leakage current and positive charges trapped in the oxide in the as-deposited film. Post-deposition annealing, especially in O 2 atmosphere, improved considerably the electrical properties of the films.

Myosin can interact with actin in the presence of ATP and Ca2+. The resulting association gives rise to an actomyosinic complex which is involved in muscle contraction. Purified myosin contains the enzyme ATPase which catalyses the breakdown of ATP (in ADP plus inorganic phosphate (Pi)). This fundamental enzymatic mechanism is involved in transducing chemical into kinetic energy through the actomyosinic complex. The myosin ATPase activity can be inactivated by chemical (3 M urea, CO2) or physical agents (thermal shocks). Partial recovery of the inhibited activity has been obtained by exposure to low power laser radiation (GaAs and He-Ne) or weak magnetic pulsed fields. The myosin ATPase reverse reaction (ATP synthesis) occurs by incubating myosin ATPase in the presence of ADP (excess). Pi and a system for H+ production (lactate dehydrogenase, lactate, NAD+). Again the enzymatic activity is increased by exposure to low power laser fields or weak magnetic pulsed fields.

γ-ray diffraction measurements have been performed to characterize the degree of perfection of several crystals of BGO and barium fluoride. In particular the mosaic structure and homogeneity of samples grown with different techniques have been determined.

Hydrogen storage in composite materials is a feasible way to overcome the main drawbacks of the metal hydride systems. In the present paper, we report on the hydrogenation properties of three polydimethylsiloxane (PDMS)–palladium composite samples with different content of metallic fraction (5, 15, 50 in wt.%). Hydrogenation tests in different conditions of temperature and pressure were performed using a Sievert's type apparatus, while the microstructure of the samples was characterised by means of scanning electron microscopy observations and X-ray diffraction measurements. Results show that the hydrogen storage capacity is inversely proportional to the metallic content in the composite samples.

In the present work a novel approach to suicide and nitride formation on the surface of silicon single crystals wafers is reported. The compound growth occurs directly in the place of interest as a result of a laser promoted chemical reaction. Results indicate that it is possible to obtain a titanium nitride layer superimposed on a titanium suicide film with a single-step laser irradiation process. The thickness of the suicide and nitride layers can be adjusted by a proper choice of the laser fluence and number of subsequent pulses.

Experimental evidence of the anisotropy in the hot-hole drift velocity v d of Si between 300 and 430°K has been theoretically proved to be strongly correlated to the warped shape of the heavy valence band. The comparison between theory and experiments permits a valuable check on the competitive role played by the strong nonparabolicity of the Si valence band and the lattice scattering mechanisms.

All the compounds predicted from the SiNi phase diagram were observed by depositing thin layers of nickel onto silicon in known quantities and ratios to each other using an unreactive substrate such as SiO2. After deposition, the samples were annealed in the temperature range 200–750°C and analysed using 2 MeV 4He+ Rutherford backscattering spectrometry and X-ray diffraction techniques. Ni2Si is the first phase formed at a low temperature (about 250°C). Under silicon-rich conditions the system develops in a reproducible manner, subsequently giving rise, when all the nickel has reacted, to the formation of NiSi and of NiSi2 by reaction at 750°C of the NiSi with silicon. The kinetic diffusion approach accounts for the formation and sequence of Ni2Si and NiSi. The phase Ni5Si2 forms between Ni2Si and nickel under nickel-rich conditions. The phases Ni3Si2 and Ni3Si were observed at 400°C and 450°C respectively.

The reaction between molybdenum thin films and single-crystal Si〈111〉 substrates was studied as a function of the concentrations of impurities (mainly oxygen) in the metal film. At a low oxygen concent (1–2 at.%), only the silicide phase MoSi 2 was observed, and a thickness proportional to the square root of time corresponding to an average activation energy of 3 eV in the temperature range 545–600 °C was found. During the formation of the silicide the oxygen originally present in the molybdenum films accumulates at the interface between the silicon and the MoSi 2 . In contrast, a higher oxygen content (4–5 at.%) prevents the formation of any silicide phases in the above temperature range and leads to the formation of MoSi 2 and Mo 5 Si 3 phases at temperatures near 800 °C. MoSi 2 was always observed at the inner interface with Mo 5 Si 3 on the surface. The oxygen segregates from the silicides and accumulates at the Si-MoSi 2 and MoSi 2 -Mo 5 Si 3 interfaces to form a non-uniform layer of SiO x ( x ⩽ 2).

Phase formation at temperatures well below the melting point of the phases was studied in thin silicon–near‐noble‐metal films by means of 4He+ ion‐backscattering spectrometry and x‐ray diffractometry in SiO2/Si/M film systems, where the metal‐film thickness was larger than that of the Si film. In the initial stage of compound formation where both unreacted Si and M layers are present, the M2Si phase has been found. At increasing annealing times and temperatures, more and more metal‐rich phases have been detected. The Si‐Ni thin‐film system evolution follows exactly the phase diagram reported in the literature; moreover, for Ni, Pt, and Pd‐Si thin‐film interactions the end phases are dictated by the phase equilibrium and can be predicted by the phase diagrams.

The phase formation in planar binary systems is discussed in terms of the diffusion-kinetic approach. Application to Pt and Ni silicide thin and thick films confirms this approach and permits to interpret experimental data in terms of the physical mechanisms involved. A temperature-dependent critical thicknessW c for the transition of a compound to its subsequent one is discussed and expressed in terms of the activation energies for the growth and reaction rate.

Silicon solid‐phase epitaxy utilizing Al as the transport medium was carried out using either 〈111〉 or 〈100〉 Si single‐crystal substrates. By analyzing samples made by a different method we show that the presence of a barrier on the metal plays a fundamental role. The barrier inhibits the diffusion of the metal through the evaporated semiconductor. In the case of Al, the barrier is made by deposition of a thin oxide layer grown on top of the metal, by leaving the sample in vacuum for two days, or by heating the sample in vacuum before the Si deposition.

Electron drift velocity in silicon is studied at and above room temperature (300, 370 and 430 K) as function of field strength (up to 60 kV cm ) and orientation (〈111〉 and 〈100〉). Experimental data show a small anisotropy even at the highest considered temperature, while saturation is well evidenced only at 300 K with the field oriented along the (111) axis. The data are interpreted with theoretical Monte Carlo calculations. The model includes non-parabolicity of the band, and a non-parabolicity parameter α = 0.5 eV−1 is suggested by the comparison of theoretical and experimental results.

The AuAl compound was obtained by low temperature (190–250°C) heat treatment of a thin gold and aluminium film. The compound was identified by X-ray diffraction and its thickness was measured by 4He MeV ion backscattering. The AuAl layer grows at a fixed temperature as a function of (time)12. The activation energy of the growth compound is 1.2 eV. This compound is stable up to the maximum investigated temperature (≈500°C).

Uniform epitaxial growth has been obtained by dissolution and transport of an evaporated Si film through an evaporated Al film at temperatures below 500°C. By analyzing the samples made in different ways we show that the presence of a cap on the metal layer, which inhibits the diffusion of the metal through the evaporated Si, plays a fundamental role. The cap consists of a thin oxide layer grown on top of the metal. The cap is made by leaving the sample in vacuum for two days or by heating the sample in vacuum before the Si deposition. The study of the initial growth rate on 〈100〉 and 〈111〉Si substrates reveals that the growth starts as islands which grow until they coalesce to form a continuous layer. Different growth rates have been obtained by using 〈100〉 and 〈111〉Si substrates. Typical growth rates are 50 A/min at 330°C on 〈100〉 and 100 A/min at 392°C on 〈111〉. The activation energy of the process is 1.2 eV.

A new method of dental fluorine prophylaxis based on the chemical reaction induced by UV irradiation in dental enamel has been presented. Fluorine ions from a gel topic can be retained to the dental apatite in the lamp-irradiated samples at about 70% and in the laser-irradiated samples at about 80% of the maximum deposited value. The19F(p,α)16O nuclear reaction was used to measure the fluorine concentrations in the first 3 μm of the enamel of healthy teeth before and after the gel topic applications with and without UV irradiation. This method of dental prefenction resolves the problem of the traditional fluorine prophylaxis which brings fluorine in the enamel without binding the apatite.

All the compounds predicted by SiPt phase diagram have been observed by depositing thin layers of Pt on Si in known quantities and ratios to each other by using an unreactive substrate. Emphasis is given to Pt6Si5 and Pt12Si5 formation. They are two new binary compounds which we have experimentally identified for the first time in planar thin film reaction. 4 He + backscattering and X-ray diffraction techniques have been used to analyse the formation of the compounds obtained by thin film deposition and annealing in 200–750°C temperature range. The phases appearance with increasing temperature exhibits a pattern which sequence is presented taking into account the formation temperature and the heat of reaction.

The backscattering technique has been used to study the interdiffusion process of Cr and Au films deposited on silicon substrates. The results indicate that Au diffuses in Cr with an effective diffusion coefficient D = const. exp (−0.68/ k T) . The activation energy is consistent with a diffusion process which occurs preferentially through grain boundaries. The high value of the diffusion coefficient justifies the presence of Au at the CrSi interface after a low temperature short-time heat treatment. At temperatures above 370 °C (the eutectic point of the SiAu system) and after a long enough heat treatment the gold is completely mixed with silicon.

Solid phase processes were used to obtain epitaxial Ge layers 0.1-0.6 μm thick. The structures were formed by evaporating Pd and Ge onto 〈111〉Ge substrates. The samples were initially heated at 250°C to form PdGe and were subsequently heated at about 450°C to obtain Ge growth. They were analysed by MeV He + backscattering and channelling effect measurements (X-ray diffraction was used to verify the stoichiometry of PdGe). The Pd profile in the grown Ge layer was determined. Channelling measurements showed that the grown Ge layers were well ordered and epitaxial with the underlying substrate.

The growth of PdGe and Pd2Ge compounds was investigated by analyzing, after annealing, samples with about 1000–3000 A thick evaporated Pd, using either bulk (single-crystal) Ge or amorphous (evaporated) Ge as substrate. The growth rate is different in both cases. The grain sizes of each compound, as determined by X-ray diffraction line-broadening, are the same for both Ge substrates. Therefore the hypothesis of formation processes controlled by grain boundary diffusion seems invalid. A different mechanism is suggested.

The following platinum X-ray absorption edges were measured in platinum silicides: Pt2Si L2,3, PtSi L2,3 and PtSi M2,3. The results are compared with the edges measured in platinum metal. As well as the known peak at the edges of index 3, a new strong peak absent in the metal appears at the edges of index 2 of the silicides. This effect is very strong in the M2 edge in spite of the linewidth which is greater than that in L2. The results are interpreted in terms of transitions to empty d states typical of the hybridization (Si p)-(Pt d) which gives rise to states with projections onto j= 3 2 and j= 5 2 so that the peak due to p-d transitions is present in the edges of index 2 and of index 3. The different localization involved in M and L transitions is also discussed.

The growth kinetics of NiSi has been evaluated by depositing a Ni film on and Si substrates. X-ray diffraction and MeV4He+ backscattering have been used to identify the compounds formed and to measure their thicknesses. Carbon and oxygen impurities have been detected with Auger electron spectrometry with Ar sputtering. During thermal annealing Ni2Si is formed first, while NiSi appears only after the total exhaustion of the Ni film. It has been found that, on both Si substrates, the thickness of NiSi increases with the square root of time. Different growth rates have been observed for the two different Si orientations. The activation energy in the (300÷370)°C temperature range is 1.83 eV for NiSi grown on and 1.23 eV for NiSi on Si. The two competing mechanisms of Ni diffusion through NiSi by grain boundary and by substitutional processes are correlated with the different microcrystalline structure of the NiSi silicide layers grown on different Si-oriented substrates.

Lateral diffusion couples of Ni on Si layers and Si on Ni layers were used in conjunction with scanning electron microprobe measurements to investigate the growth of Ni silicides in the temperature range 400–700 °C. The phase Ni2Si grows proportional to (time)1/2 until a length of 25–30 μm (at 600 °C) where the phase sequence Ni5Si2, Ni2Si, Ni3Si2, and NiSi is observed. Both Ni and Si diffuse through Ni2Si with an effective diffusion coefficient D≃0.02 cm2/s ×exp[−(1.4±0.1) eV/kT]. The diffusion of Si was also observed by the growth of Ni2Si in Ni films at the periphery of contact openings in SiO2 layers on Si.

In this communication reflectance and thermoreflectance spectra of films of PtSi and Pt 2 Si grown on glass substrates are reported and discussed. Weak structures superimposed on the free-carrier response of the reflectance spectra are detected by means of thermoreflectance. Attributions of such structures mainly in terms of d-d transitions are briefly discussed.

The interaction of Ni film deposited on Si has been studied. Growth kinetics of NiSi on (111) and (100) silicon single crystals are reported. Activation energies for NiSi are found to be 1.23 eV for (100) and 1.83 eV for (111).

We investigated the rate of germanide formation and the composition of the resulting compounds when thin (1000–2500 A) palladium films, vacuum evaporated onto various germanium substrates, were annealed at temperatures from 170 to 270°C for 10 min to 27 h. Both phases, Pd2Ge and PdGe, were observed on single-crystal and amorphous (vacuum-deposited) germanium substrates. In all cases the compounds layers grow with a (time) 1 2 dependence and with an activation energy of 1.5 ± 0.1 eV. Moreover the absolute value of the growth rate depends on the crystalline nature of the germanium substrate. On (111) and (100) substrates the rates are similar and they are three times lower than those on amorphous substrates.

Silicide formation is strongly affected by the presence of oxygen contained in the metal film. A study has been performed by heating at various times and temperatures samples constituted by a thin Pt film sputter deposited on a silicon substrate. Four different oxygen concentrations were implanted in the Pt film ranging from 1 to 0.1 at.%. The presence of oxygen slows down the growth rate of Pt2Si. At 315 °C in the sample with an oxygen concentration of 1 at.%, about 1000 A of Pt2Si are formed after 20 min of annealing. During the silicide formation, the oxygen originally contained in the platinum films segregates at the Pt2Si/Pt interface. This accumulation acts as a barrier for the transport of Pt and a new phase, PtSi, can form at the Pt2Si/Si interface. The dose necessary to stop the Pt2Si reaction is about (2–4)×1015 at./cm2 at 315 °C.

4He+ ions backscattering spectrometry and x-ray diffractometry were used to study interactions between PtSi and Pt, NiSi and Ni, PdGe and Pd. Due to the dissociation of the compound the formation of a phase richer in metal was observed to grow at the original compound/metal interface in the temperature range considered, 280–325°C for Pt2Si, 325°C for Ni2Si and 180–260°C for Pd2Ge. The growth kinetics of these new phases (Pt2Si and Pd2Ge) follow a parabolic relation between thickness and annealing time. At a given temperature the growth rate of Pt2Si and Pd2Ge in compound-metal structure is a factor $$\sqrt 2$$ higher than in the usual semiconductor-metal structure.

Anisotropic effect of the hole drift velocity in silicon and germanium has been investigated with the time of flight technique by applying the electric field parallel to the

Solid phase epitaxial growth has been obtained by annealing at temperatures below 500°C the structures 〈111〉 Si/evaporated Al/evaporated Si. The transport and the growth of the Si has been studied by SEM, electron microprobe, He + backscattering and channeling effect measurements. To study the growth process the structures were heated at different temperatures and times. The initial stage of epitaxial growth is laterally non-uniform and assumes an island structure. The islands grow laterally to form a uniform epilayer in the final stage. The quantity of Si transported through the Al increases linearly with time and at 392°C the transport rate is about 100 A/min. The activation energy of the crystallization process in the 363–413°C temperature range is 1.2 ± 0.1 eV. Al inclusions, found in the epi-grown layer, are preferentially localized at the 〈111〉 Si-growth interface.

Switching effects have been studied in high resistivity undoped β-rhombohedral boron in the temperature range 77 to 400°K using electrical and electro-optical measurements. The data collected must be interpreted with different models describing the origin of the switching action, i.e. double injection at low temperatures (about 77 to 250°K) and thermal instability at higher temperatures (250 to 400°K). A description of the main physical events giving rise to switching for double injection in the investigated sample is given. Emission of infrared radiation in the postswitching regime due to hole—electron recombination is also reported.