Antonio Parretta
University of Ferrara, Physics and Earth Science, Faculty Member
- Finite Volume Methods, Micromachining, Finite-Difference Methods, Conservation Laws, Silicon, Psychology, and 108 moreEngineering, Education, Archaeology, Philosophy, History, Anthropology, Medicine, Climate Change, Physics, Biology, Chemistry, Geography, Languages and Linguistics, Renewable Energy, Electrical Engineering, Philosophy of Science, Ecology, Civil Engineering, Public Health, Cultural Studies, Art History, Architecture, Literature, Artificial Intelligence, Environmental Sustainability, Photovoltaic Solar Cells, Solar Energy, Solar Cell, Thin film solar cells, Photovoltaics Research, Renewable Energy Systems, Materials Science, Photovoltaics, Computer Science, Music, Technology, Information Systems, Social Psychology, Educational Technology, Design, English Literature, English, Medical Education, Health Sciences, History of Medicine, Internal Medicine (General Medicine), Epidemiology, Medical Anthropology, Theoretical Physics, Atomic, Molecular, And Optical Physics, Cosmology (Physics), Astrophysics, Quantum Physics, General Relativity, Computational Physics, Condensed Matter Physics, Cognitive Science, Cognitive Psychology, Emotion, Social Cognition, Developmental Psychology, Experimental Psychology, Social Identity, Evolutionary Psychology, Personality Psychology, Epistemology, Metaphysics, History of Philosophy, Philosophy Of Language, Philosophy of Mind, Analytic Philosophy, Kant, Aristotle, Ethics, Metaphilosophy, Mathematics, Applied Mathematics, Analysis (Mathematics), Combinatorics, Mathematics Education, Mathematical Biology, Graph Theory, Functional Analysis, Dynamical Systems, Partial Differential Equations, Chemical Engineering, Communication, Sustainable Development, Software Engineering, East African prehistory, Neanderthals, Human Evolution, Quaternary palaeontology, Palaeoenvironment, Evolutionary genetics, Palaeoclimatology, Palaeoecology, Population Genetics, Evolution, Miocene hominoids, Human evolutionary biology, Primate Postcranial Evolution, Hominin Locomotion, Hominin evolution, Paleoanthropology, Hominin Diet, Primate Functional Morphology, and Primate Behavior, Human Evolution, Paleoanthropologyedit
- Scientist with experience in the field of physical chemistry, materials science, photovoltaic and thermodynamic solar... moreScientist with experience in the field of physical chemistry, materials science, photovoltaic and thermodynamic solar energy, optics, in particular that applied to solar concentrators. Lover of mathematics, astronomy and granular matter.edit
The involvement of the “active site” zinc ions as a Lewis acid catalyst in LADH* has been suggested by many investigators, and recent spectroscopic results have been interpreted as supporting this view. Moreover, X-ray studies have shown... more
The involvement of the “active site” zinc ions as a Lewis acid catalyst
in LADH* has been suggested by many investigators, and recent spectroscopic results have been interpreted as supporting this view. Moreover, X-ray studies have shown that the inhibitors 1,10 phenanthroline and imidazole coordinate to the active sits zinc ions in the binary complexes. On this basis, a mechanism has been proposed for LADH catalysis, according to which zinc coordinates the substrate ethanol as alcoholate ion in the productive enzyme-NAD-ethanol complex. Thus far, however, no direct evidence of metal-substrate binding in ternary complexes has been presented. On the other hand, however, the ability of metal-free LADH to bind coenzymes and substrate analogs has been taken as evidence that the metal does not participate in binding. The substitution of zinc by paramagnetic cobalt(II) is potentially capable of clarifying these questions, but conflicting reports on the identification of substituted cobalt make the interpretation of previous N.M.R. and spectroscopic work on partially substituted LADH questionable. The two classes of zinc atoms are, in fact, replaceable by cobalt at different rates, and it was widely accepted that the “catalytic” pair exchanges faster than the “structural” pair, while more recent experiments indicate that the opposite is true. In the present work we use direct n.m.r. evidence both to identify the nature of the cobalt ions incorporated in partially substituted LADH, and to demonstrate that the more slowly exchangeable pair of metal ions is directly involved in binding the substrate ethanol.
in LADH* has been suggested by many investigators, and recent spectroscopic results have been interpreted as supporting this view. Moreover, X-ray studies have shown that the inhibitors 1,10 phenanthroline and imidazole coordinate to the active sits zinc ions in the binary complexes. On this basis, a mechanism has been proposed for LADH catalysis, according to which zinc coordinates the substrate ethanol as alcoholate ion in the productive enzyme-NAD-ethanol complex. Thus far, however, no direct evidence of metal-substrate binding in ternary complexes has been presented. On the other hand, however, the ability of metal-free LADH to bind coenzymes and substrate analogs has been taken as evidence that the metal does not participate in binding. The substitution of zinc by paramagnetic cobalt(II) is potentially capable of clarifying these questions, but conflicting reports on the identification of substituted cobalt make the interpretation of previous N.M.R. and spectroscopic work on partially substituted LADH questionable. The two classes of zinc atoms are, in fact, replaceable by cobalt at different rates, and it was widely accepted that the “catalytic” pair exchanges faster than the “structural” pair, while more recent experiments indicate that the opposite is true. In the present work we use direct n.m.r. evidence both to identify the nature of the cobalt ions incorporated in partially substituted LADH, and to demonstrate that the more slowly exchangeable pair of metal ions is directly involved in binding the substrate ethanol.
Research Interests:
The III-V compounds deposited as thin films on various substrates are a new perspective in the terrestrial photovoltaic solar energy conversion. The single crystal solar cells based on such compounds show, indeed, a conversion efficiency... more
The III-V compounds deposited as thin films on various substrates are a new perspective in the terrestrial photovoltaic solar energy conversion. The single crystal solar cells based on such compounds show, indeed, a conversion efficiency higher than silicon solar cells. Unfortunately these compounds are too expensive to be used as bulk materials in the flat solar modules. Taking advantage of their high absorption coefficients, many
approaches have been recently attempted for growing polycrystalline thin films of InP, GaAsP and especially GaAs on low cost substrates such as graphite, alumina and refractory materials. It was also demonstrated that a structure GaAs/Ge/Si may have the necessary features in terms of both efficiency and cost to compare these devices with single crystal silicon cells. The potential economical and technical advantages of the III-V thin film solar cells are illustrated together with the relative technology. Present activities in many laboratories are also described.
approaches have been recently attempted for growing polycrystalline thin films of InP, GaAsP and especially GaAs on low cost substrates such as graphite, alumina and refractory materials. It was also demonstrated that a structure GaAs/Ge/Si may have the necessary features in terms of both efficiency and cost to compare these devices with single crystal silicon cells. The potential economical and technical advantages of the III-V thin film solar cells are illustrated together with the relative technology. Present activities in many laboratories are also described.
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X-ray studies on crystals of sodium and rubidium deoxycholates (NaDC and RbDC, respectively) and on a macromolecular fiber of NaDC provide a reasonable helical model for describing the structure of the NaDC micellar aggregates in aqueous... more
X-ray studies on crystals of sodium and rubidium deoxycholates (NaDC and RbDC, respectively) and on a macromolecular fiber of NaDC provide a reasonable helical model for describing the structure of the NaDC micellar aggregates in aqueous solutions, at least within a certain concentration range and at natural pH. 1H and 13C NMR measurements have been performed to check the validty both of this model and of a previous model, currently accepted in the literature. The results satisfactorily agree with the helical model which is characterized by an interior part formed by Na+ ions and water molecules, arranged as in a liquidlike structure, and by an outer surface covered by nonpolar groups. A very complicated network of hydrogen bonds among water molecules and hydroxyl and carboxyl groups of deoxycholate anions stabilizes the helix together with Na+/H2O ion-dipole and Na+/COO-ion-ion interactions. Therefore, hydrophobic interactions can occur among helices, but are negligible in the formation of the micelle. The investigation of the solubilization of some hydrocarbons by NaDC aqueous solutions indicates that the solubilization sites are mainly located at the boundary between the micelles and the bulk aqueous phase, near the C19 methyl group.
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Computer simulation shows that high photocurrent densities can be achieved on p+ - n shallow GaAs solar cells by using high quality thin epitaxial films. The simple addition of a back surface field also improves open circuit voltages and... more
Computer simulation shows that high photocurrent densities can be achieved on p+ - n shallow GaAs solar cells by using high quality thin epitaxial films. The simple addition of a back surface field also improves open circuit voltages and conversion efficiencies. Unintentionally n-doped GaAs epitaxial films (~2 micron thick) were grown by metal organic chemical vapor deposition. A simple 0.5 micron thick SiO 2 layer was used as a cap in the open-tube Zn solid-state diffusion technique. Diffusion processes were carried out on both commercial bulk material and epitaxial films at low temperature (< 600°C) by using the ZnO/SiO2 mixture as a doping source. The p+ layers were well controlled in thickness in the range 250-14000 A, heavily doped (~10^20 cm-3) and very homogeneous. No damage was observed on the GaAs surface after the diffusion process. A best fit of the experimental photoresponse spectra yielded reliable values of the diffused layers thicknesses and of the minority carrier diffusion lengths. These were in the range 0.2-1.3 micron for commercial material and 3.5-5.5 micron for epitaxial films. Good agreement was found between the experimental photocurrent values and the calculated ones in both bulk and thin film devices. The thin film photocurrent density reached values as high as 24.2 mA/cm^2. A conversion efficiency of 14.1% at AM1 was obtained on a thin film device with an area of 1 cm^2 and with a p+ layer thickness of 700 A.
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Very shallow p+-n GaPs homojunction solar cells are prepared on both bulk and deposited thin film materials by utilizing a solid state diffusion process, and investigated by optical and electron beam induced current techniques (OBIC and... more
Very shallow p+-n GaPs homojunction solar cells are prepared on both bulk and deposited thin film materials by utilizing a solid state diffusion process, and investigated by optical and electron beam induced current techniques (OBIC and EBIC respectively). Some specimens are also analyzed by the scanning transmission technique (STEBIC). A spatially resolved spectral scanning apparatus is used in the OBtC experiments. Local (50-80/xm) spectral responses are worked out in order to achieve a quantitative estimate of the relevant cell parameters, such as junction depth and minority carrier diffusion length. Data are reported for two shallow homojunctions quite homogeneous in depth. A large spreading of the minority carrier diffusion length values (Lp-0.02-0.8/tin) results from the analysis of bulk devices; higher and more homogeneous values are obtained on thin films (Lp=1.2-2.3 /~m). Very small regions (<1 /tm) of electrical recombination are detected by EBIC and STEM-STFB!C and compared with their morphologies. The electrically active defects observed in epitaxial films are not generally correlated to dislocations or stacking faults; they seem rather due to local off-stoichiometry or not-resolved impurity clusters. Moreover, the density of these defects in epitaxial fdms is lower than in bulk specimens. This fact can explain the superior quality of the shallow junctions in epitaxially grown layers in comparison with the commercial single crystal ones. Homogeneity and high doping level of diffused layers prove that this sofid state diffusion process is suitable for realizing high efficiency solar ceils.
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Results of a thermodinamical analysis of the Chemical Vapour Deposition (CVD) of Si3N4 from the SiCl4-NH3-H2 system are presented.
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Electron channeling in SEM is used to detect grain structures in SiC coatings without any chemical etching. Theoretical calculations and experimental results show that grain sizes in the range 0.5-10 microns are only detectable by using... more
Electron channeling in SEM is used to detect grain structures in SiC coatings without any chemical etching. Theoretical calculations and experimental results show that grain sizes in the range 0.5-10 microns are only detectable by using particular operating conditions, specifically a high brightness electron source and low accelerating voltages.
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The microstructure and mechanical properties (adhesion, hardness) of beta-SiC coatings, prepared in a cold-wall reactor, were studied by examining different substrates and deposition process conditions. Hard (3500 HK), fine grained... more
The microstructure and mechanical properties (adhesion, hardness) of beta-SiC coatings, prepared in a cold-wall reactor, were studied by examining different substrates and deposition process conditions. Hard (3500 HK), fine grained beta-SiC coatings were deposited onto graphite at relatively high deposition temperatures (1473-1673 K) using SiCl4, C3H8, H2 gas mixtures. The thermal decomposition of methyltrichlorosilane (MTS) in hydrogen and argon allowed the production of beta-SiC coatings onto a variety of substrate materials in the temperature range 1173-1373 K. The growth mechanisms of SiC deposited from MTS/H2/Ar system onto graphite and polycrystalline alfa-SiC substrates were studied. At low (40 kPa) and atmospheric pressure, the growth kinetics is limited by surface reactions. Also, a strong dependence of the microstructure and crystallographic orientation on the deposition parameters was observed. Hard metals (WC/Co) were successfully coated with beta-SiC using the MTS/H2/Ar system. Problems of chemical compatibility between the substrate and the beta-SiC coating were minimized by the deposition of an intermediate TiN layer.
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The morphological features of Silicon Carbide coatings, deposited on graphite from SiCl4, C3H8 and H2 mixtures, were investigated.
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Scratch test measurements were performed on CVD TiN and TiN/SiC coated substrates after structure and mechanical characterization of coatings.
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Thin CuInSe2 films were prepared by selenization of sputtered metal precursors. The surface morphology, phase composition and adhesion at the Mo/glass substrate of the ternary compound have been correlated to the structure of the precursor.
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Thin CuInSe 2 films have been prepared in a two stage process by sputtering on Mo/glass substrates alternate Cu, In layers followed by selenization by vacuum evaporation. The compostional and the structural analysis of the compounds has... more
Thin CuInSe 2 films have been prepared in a two stage process by sputtering on Mo/glass substrates alternate Cu, In layers followed by selenization by vacuum evaporation. The compostional and the structural analysis of the compounds has been carried out by EDS and XRD, respectively. Selenium incorporated in the ternary compound assumes a constant value around 48% (at/at) while the Cu/In ratio ranges between 0.8 and 1.2. As the copper content is further lowered, selenium decisively increases up to almost 51% when Cu/In is 0.6. The inversion point in the Se-Cu/In diagram has been correlated to the formation of a secondary phase identified as the chalcopyrite vacancy-variant compound CuIn3Se 5 (OVC). The results are independent on the type of metallic precursors and on their preparation conditions.
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In this work we show the viability of laser scribing as a tool for selective patterning of CuInSe2(CIS)/Molybdenum(Mo)/Soda Lime Silica (SLS) thin film structures. The dependence of scribing quality on the basic process parameters is... more
In this work we show the viability of laser scribing as a tool for selective patterning of CuInSe2(CIS)/Molybdenum(Mo)/Soda Lime Silica (SLS) thin film structures. The dependence of scribing quality on the basic process parameters is investigated by optical microscopy, talystep, SEM and microprobe analysis. Two different configurations are used for Mo-patterning: the frontal scribing whereby the laser beam interacts first with the air/Mo interface and the back scribing with the laser beam passing through the glass slide and interacting with the SLS/Mo interface. Back scribing can result in a high quality patterning, with no droplets or swelling, but only the Mo layer is removed and the SLS is left untouched. The Mo removal is due to a laser induced stress detachement. Using the frontal scribing, is also possible to obtain good quality scribing where evaporation is the main mechanism for Mo removal. To obtain good quality scribing, it is necessary to gain accurate control of the focus position and of laser beam characteristics. When a laser with a poor gaussian profile was used, high swelling and large droplets were always present. Optimum scribing parameters for both CIS/SLS and Mo proved to be roughly equivalent. Consequently, selective scribing of an individual layer was not possible using Q-switched operation. Using cw laser power output the relatively low melting and evaporation temperatures, low thermal diffusivity, optical reflection and high absorption coefficient of the CIS layer allow for local heating and consequent evaporation of the CIS whilst leaving the Mo layer unaffected. Scribing are performed on CIS/Mo/SLS layers and the resulting selective removal of the CIS layer is shown.
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Sheet resistance measurements on sputtered Cu-In layers were performed while varying the temperature in a cyclic way between room temperature and 150 "C. A hysteresis effect was observed which can be explained by a CuInz-> Culling phase... more
Sheet resistance measurements on sputtered Cu-In layers were performed while varying the temperature in a cyclic way between room temperature and 150 "C. A hysteresis effect was observed which can be explained by a CuInz-> Culling phase transformation taking place in the alloy during the thermal cycles. A model is proposed for the phase transformation which is based on a diffusional mechanism. It is suggested that simple sheet resistance measurements made in the same system in which the metallic layers are deposited could be used to follow the phase formation and transformation in the alloy.
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The morphological and structural properties of copper-indium alloys selenized in a box have been studied varying the temperature and duration of the selenization process. At temperature >=375°C a single phase CuInSe2 is obtained with an... more
The morphological and structural properties of copper-indium alloys selenized in a box have been studied varying the temperature and duration of the selenization process. At temperature >=375°C a single phase CuInSe2 is obtained with an indium-rich precursor. At lower temperatures different copper selenides are found which affect in a different way the composition of the film. A high indium loss is found in the 250-300°C range. The results on short selenization cycles are used to identify the precursor species of CuInSe2.
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Indium oxide films were deposited on glass substrates at room temperature by reactive rf sputtering. The depositions were carried out by sputtering pure indium in an Ar + 0 2 plasma. The influence of oxygen partial pressure during... more
Indium oxide films were deposited on glass substrates at room temperature by reactive rf sputtering. The depositions were carried out by sputtering pure indium in an Ar + 0 2 plasma. The influence of oxygen partial pressure during deposition on the optical, electrical, and structural properties of the films was investigated. The properties of the films were also studied after post-deposition heat treatments in air and in argon atmosphere. The study shows that conducting transparent films with resistivity 1.3 x 52 cm and transmission above 88% can be obtained by depositing the films at high oxygen partial pressures (> 0.21 Pa) and then annealing in argon atmosphere at 500 "C for one hour.
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The morphological and structural properties of copper-indium alloys selenized in a box by selenium vapours have been studied by varying the thermal cycle of the selenization process. In the first series of selenizations, equal metallic... more
The morphological and structural properties of copper-indium alloys selenized in a box by selenium vapours have been studied by varying the thermal cycle of the selenization process. In the first series of selenizations, equal metallic precursors were exposed for 30 minutes to the selenium vapours at different temperatures in the range 175-405°C. The chalcopyrite CuInSe2 phase was found at temperatures as low as 250°C and as a single phase at T>=375°C. At low temperatures different copper selenides were found, like CuSe, Cu(2-x)Se and CuSe2, which affected in a different way the composition and morphology of the film. Indium loss was detected in the 250-300°C range and was attributed to the evolution in the gas phase of the In2Se species. Short selenization cycles were also used with the purpose of identifying the chemical precursors of CuInSe2. The determination of the selenium content in the alloys at different temperatures allowed us to determine a 7 kcal/mol activation energy for the kinetics of the selenium incorporation. Long selenizations at 450°C allowed us to obtain a large-grained, compact layer of chalcopyrite CuInSe2 which could be used for the fabrication of photovoltaic devices.
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Copper oxide thin films were prepared by reactive rf magnetron sputtering of a pure copper target in an oxygen-argon atmosphere. The phases of the deposited films strongly depend on the oxygen content in the sputtering gas. X-ray... more
Copper oxide thin films were prepared by reactive rf magnetron sputtering of a pure copper target in an oxygen-argon atmosphere. The phases of the deposited films strongly depend on the oxygen content in the sputtering gas. X-ray diffraction studies show that by controlling the oxygen partial pressure single phase CuzO and CuO can be obtained. The resistivity of the CuzO film in the present study is 43 SZ cm. The optical constants were evaluated from transmission and reflection measurements.
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Energetic losses, relative to the standard conditions of testing, in photovoltaic modules in outdoor operation, were Ž. analyzed and the role of the optical effects is discussed. The following four loss effects were estimated: a... more
Energetic losses, relative to the standard conditions of testing, in photovoltaic modules in outdoor operation, were Ž. analyzed and the role of the optical effects is discussed. The following four loss effects were estimated: a reflection of Ž. Ž. Ž. unpolarized light, b spectrum, c intensity of the light and d temperature of the module. Four independent models were used to describe these four losses. The models were validated by the experimental data of an outdoor measurement campaign performed on 08 tilted modules at 418N latitude in South Italy. Disagreement reaching 5% under clear sky conditions was found between theoretical predictions and experimental data for the instantaneous total loss. As a result of a critical analysis of the literature data on this subject, it could be explained by invoking the presence of a fifth loss mechanism: the polarization of the incident light. Final relative losses, due to the particular state of the incident sunlight, amount to about 7-8% of a total of 14-15%. Of these, 3% is due to the low irradiation level, 1-2% to the polarization of the skylight and Ž. 3% to the reflection of the incident light on the front cover of the module. The spectral effects are negligible less than 1%. The remaining 7% loss is due to temperature effects on the module. All the loss data are reported as a function of the air Ž. mass AM. The maximum operating efficiency is reached at AM f 1.5.
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The optical reflectance properties of commercial and prototype monocrystalline silicon photovoltaic PV modules were characterized in a non-destructive way by using an apparatus equipped with a 40-cm diameter integrating sphere. The... more
The optical reflectance properties of commercial and prototype monocrystalline silicon photovoltaic PV modules were characterized in a non-destructive way by using an apparatus equipped with a 40-cm diameter integrating sphere. The modules showed different reflectance properties in relation to their different fabrication technologies. The lowest reflectance values, about 4% at l s 632.8 nm and near normal incidence, were obtained from different front structures, all containing an Ž. anti-reflection coating ARC. Modules without ARC, on the contrary, showed total reflectances in the 6-9% interval. The total and diffuse reflectances were also measured as a function of the incident angle of a He-Ne laser beam at a fixed azimuth orientation of the incident plane. The modules with flat glass tops showed flat reflectance curves from 108 to 408, whereas those with textured glass tops showed flat reflectance curves from 108 to 508. In order to compare the different total reflectance curves, we introduced a 'light collection factor' for inclined light, f , with respect to the normal incidence. We IL found a certain correlation between the light collection factor and the front structure of the modules. In particular, we established that front covers with textured glass tops collect the inclined light slightly better with respect to the front covers with flat glass tops, and then are expected also to collect slightly better the diffuse light from the sky hemisphere. Finally we found that the front covers of the mono-Si modules, as far as conditions relative to normal incidence are considered, can be Ž. optically modeled as homogeneous dielectrics with refractive index higher than that of glass 1.5 and in the interval 2.5-3.0. The precise value depends on the particular structure of the module's front cover.
Research Interests:
The optical reflectance properties of commercial and prototype monocrystalline silicon photovoltaic PV modules were characterized in a non-destructive way by using an apparatus equipped with a 40-cm diameter integrating sphere. The... more
The optical reflectance properties of commercial and prototype monocrystalline silicon photovoltaic PV modules were characterized in a non-destructive way by using an apparatus equipped with a 40-cm diameter integrating sphere. The modules showed different reflectance properties in relation to their different fabrication technologies. The lowest reflectance values, about 4% at l s 632.8 nm and near normal incidence, were obtained from different front structures, all containing an Ž. anti-reflection coating ARC. Modules without ARC, on the contrary, showed total reflectances in the 6-9% interval. The total and diffuse reflectances were also measured as a function of the incident angle of a He-Ne laser beam at a fixed azimuth orientation of the incident plane. The modules with flat glass tops showed flat reflectance curves from 108 to 408, whereas those with textured glass tops showed flat reflectance curves from 108 to 508. In order to compare the different total reflectance curves, we introduced a 'light collection factor' for inclined light, f , with respect to the normal incidence. We IL found a certain correlation between the light collection factor and the front structure of the modules. In particular, we established that front covers with textured glass tops collect the inclined light slightly better with respect to the front covers with flat glass tops, and then are expected also to collect slightly better the diffuse light from the sky hemisphere. Finally we found that the front covers of the mono-Si modules, as far as conditions relative to normal incidence are considered, can be Ž. optically modeled as homogeneous dielectrics with refractive index higher than that of glass 1.5 and in the interval 2.5-3.0. The precise value depends on the particular structure of the module's front cover.
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Results of angle-dependent reflectance measurements on photovoltaic materials and solar cells are presented and discussed. The optical apparatus employs an integrating sphere of 40 cm diameter and it is suitable for working at variable... more
Results of angle-dependent reflectance measurements on photovoltaic materials and solar cells are presented and discussed. The optical apparatus employs an integrating sphere of 40 cm diameter and it is suitable for working at variable wavelengths and incidence angles of the light beam. Directional/hemispherical reflectance measurements can be performed and both the diffuse and the total components of the reflected light can be obtained. Samples of any size can be measured by this apparatus, including small prototype solar cells (< 2 cm), medium size materials and solar cells (10-12 cm), as well as glass sheets and entire photovoltaic modules. Results of reflectance on silicon materials, commercial and record efficient silicon solar cells are here presented as functions of the incidence angle and wavelength of the light beam. The measurements evidence the superior light trapping performances of the inverted pyramids (PERL) and of the new 'honeycomb' structures with respect to the traditional upright random pyramids texturization. A simple analytical model describing the effect of the grid is derived and discussed. The model was used to calculate the reflectance of the exposed semiconductor region of the cell only. It was validated by comparing the calculated reflectance of the semiconductor region with that measured on 'gridless' cells. The spectral reflectance measurements at different angles matched the light collection performances of the cells, and are very useful for their optimization in view of their outdoor application.
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Increasing interest towards the observation of the highest energy cosmic rays has motivated the development of new detection techniques. The properties of the Cherenkov photon pulse emitted in the atmosphere by these very rare particles... more
Increasing interest towards the observation of the highest energy cosmic rays has motivated the development of new detection techniques. The properties of the Cherenkov photon pulse emitted in the atmosphere by these very rare particles indicate low-cost semiconductor detectors as good candidates for their optical read-out. The aim of this paper is to evaluate the viability of solar panels for this purpose. The experimental framework resulting from measurements performed with suitably-designed solar cells ~nd large conventional photovoltaic areas is presented. A discussion on the obtained and achievable sensitivities follows.
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A novel method, and the relative apparatus, are described which permit to measure the directional/hemispherical re¯ectance of a surface at incidence angles h in the interval 0±90°. The method, suitable for the characterization of... more
A novel method, and the relative apparatus, are described which permit to measure the directional/hemispherical re¯ectance of a surface at incidence angles h in the interval 0±90°. The method, suitable for the characterization of optically homogeneous as well as heterogeneous samples, is named``dierencing re¯ection method'' as the re¯ectance of the sample, R dh hY k, is derived from dierences among the re¯ectance signal measured for the sample and those measured for two diuse re¯ectance standards. In order to be applied, the method requires the knowledge of the directional/hemispherical re¯ectance of the standards for the wavelength range of interest and for incidence angle interval 0±90°. The method has been applied to measurements of R dh hY k of solar cells.
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Methods for evaluating the light intensity distribution on receivers of concentrated solar radiation systems are described. They are based on the use of Lambertian diffusers in place of the illuminated receiver and on the acquisition of... more
Methods for evaluating the light intensity distribution on receivers of concentrated solar radiation systems are described. They are based on the use of Lambertian diffusers in place of the illuminated receiver and on the acquisition of the scattered light, in reflection or transmission mode, by a CCD camera. The spatial distribution of intensity radiation is then numerically derived from the recorded images via a proprietary code. The details of the method are presented and a short survey of the main applications of the method in the photovoltaic and thermal solar energy conversion field is proposed. Methods for investigating the Lambertian character of commercial diffusers are also discussed.
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A radiometric method has been developed, suitable for both total power and flux density profile measurement of concentrated solar radiation. The high-flux density radiation is collected by a first optical cavity, integrated, and driven to... more
A radiometric method has been developed, suitable for both total power and flux density profile measurement of concentrated solar radiation. The high-flux density radiation is collected by a first optical cavity, integrated, and driven to a second optical cavity, where, attenuated, it is measured by a conventional radiometer operating under a stationary irradiation regime. The attenuation factor is regulated by properly selecting the aperture areas in the two cavities. The radiometer has been calibrated by a pulsed solar simulator at concentration levels of hundreds of suns. An optical model and a ray-tracing study have also been developed and validated, by which the potentialities of the radiometer have been largely explored.
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The optical characterization of solar concentrators for photovoltaic applications is increasing its importance with the recent first commercialization of so me CPV technologies. In th is paper two effective characterization methodologies... more
The optical characterization of solar concentrators for photovoltaic applications is increasing its importance with the recent first commercialization of so me CPV technologies. In th is paper two effective characterization methodologies are presented, applied to a representative optics of concentration. Two "inverse" methods are compared: the firstly presented inverse illu mination method and another approach, derived by the inverse lu minescence method, operating with electrolu minescent light. Both use ideal lambertian sources for producing the inverse light path and can be applied to any type of solar concentrator (photovoltaic or thermodynamic). The optical simu lations show their equivalence to get the angular distribution of the transmission efficiency function, but the original inverse illu mination method demonstrates a simpler configuration and permits a significantly faster simulation process.
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The importance of renewable sources in the construction of a resilient national energy portfolio and to reduce climate changing emissions, is widely recognized. Among those, PV technology is now mature, having developed since the 1970s,... more
The importance of renewable sources in the construction of a resilient national energy portfolio and to reduce climate changing emissions, is widely recognized. Among those, PV technology is now mature, having developed since the 1970s, but resistance still remain to its spread on a large scale due to its relatively low conversion efficiency. Unfortunately, there are still Sun-rich countries that have invested little on this technology, despite significant system cost reductions in recent years.
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The optical collection properties of the nonimaging "Rondine" solar concentrator have been investigated by indoor measurements of the angle-resolved optical efficiency. In this paper we illustrate two different methods to draw... more
The optical collection properties of the nonimaging "Rondine" solar concentrator have been investigated by indoor measurements of the angle-resolved optical efficiency. In this paper we illustrate two different methods to draw the optical efficiency curve. The first one, called "direct method", is performed by producing a collimated beam of solar divergence (~ 0.27°) and of known flux impinging on the input aperture of the concentrator at different incidence angles, and by measuring the flux collected at the exit aperture. The second one is based on a reverse illumination procedure, from which the name of "inverse method", whereby a Lambertian diffused light source is produced at the concentrator exit aperture and the radiance of the backward beam, exiting from the input aperture, is measured at different directions in space. We obtain similar results with the two methods, though the "inverse method" be largely to be preferred for the simplicity of the experimental apparatus and the extreme quickness of execution.
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The optical properties of nonimaging solar concentrators irradiated in direct mode by diffused Lambertian beams are investigated in detail adopting original simulation methods. These methods were not limited to investigate useful... more
The optical properties of nonimaging solar concentrators irradiated in direct mode by diffused Lambertian beams are investigated in detail adopting original simulation methods. These methods were not limited to investigate useful properties for the practical application of the concentrators, but were also used to study them as optical elements with specific transmission, reflection and absorption characteristics. We have investigated, therefore, besides the flux transmitted to the receiver, also the flux back reflected from input aperture and that absorbed on the wall of the concentrator. We have simulated the transmission, reflection and absorption efficiencies, the average number of reflections of the transmitted or reflected rays, their angular divergence and the distribution of flux on the receiver and on the internal wall surface, as function of the angular divergence of the input beam and of the reflectivity of the internal wall. The presented simulation methods can be fruitfully applied to any other type of solar concentrator.
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The transmission and reflection properties of nonimaging solar concentrators irradiated in direct mode by parallel light are investigated adopting original simulation methods. These methods were not limited to investigate useful... more
The transmission and reflection properties of nonimaging solar concentrators irradiated in direct mode by parallel light are investigated adopting original simulation methods. These methods were not limited to investigate useful properties for practical application of the concentrators, but were also used to study them as optical elements with specific transmission, absorption and reflection characteristics. In this work, we investigate the flux transmitted to the receiver and that back-reflected towards the entrance opening, by measuring the average number of reflections that the transmitted or reflected rays make on the internal wall of the concentrator. Results of this study are maps of the entrance opening, in which the different regions crossed by the transmitted or reflected rays are distinguishable and characterized by a different number of internal reflections. These maps are plotted for different values of the incidence angle of the parallel beam with respect to the optical axis of the concentrator. The presented simulation methods can be fruitfully applied to any other type of solar concentrator.
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Riassunto. Gli esperimenti di dispersione della luce bianca eseguiti da Newton con i prismi rimangono tra i più belli della fisica e vengono replicati frequentemente nelle scuole e nelle università. Ma c'è un aspetto cheè poco... more
Riassunto. Gli esperimenti di dispersione della luce bianca eseguiti da Newton con i prismi rimangono tra i più belli della fisica e vengono replicati frequentemente nelle scuole e nelle università. Ma c'è un aspetto cheè poco considerato, e cioè che la luce rifratta al suo interno, oltre che essere rifratta esternamente dando luogo al ben noto fascetto disperso, è riflessa internamente un numero indefinito di volte e, in seguito ad ogni riflessione, produce un fascetto rifratto esterno che può essere bianco o disperso a seconda della parità del numero di riflessioni subite. In questo lavoro analizzo, sia teoricamente che sperimentalmente, le proprietà dei principali fascetti uscenti dalle facce di un prisma equilatero, illuminato con un fascetto laser o bianco, polarizzato "s" o "p".
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White-light dispersion experiments performed by Newton with prisms remain among the most beautiful in optics and are frequently replicated in schools and universities. But there is an aspect that is little considered, namely that the... more
White-light dispersion experiments performed by Newton with prisms remain among the most beautiful in
optics and are frequently replicated in schools and universities. But there is an aspect that is little considered, namely that the light initially refracted within the equilateral prism, in addition to being further refracted and giving out the well-known spectrally dispersed bundle, is also internally reflected an indefinite number of times and, in correspondence with each reflection, produces an external refractive bundle that can be white or dispersed depending on the parity of the number of reflections previously undergone. In this paper, I analyze, both theoretically and experimentally, the properties of the main bundles coming out of the faces of the equilateral prism, when it is illuminated by p- or s-polarized white light, or by a laser beam.
optics and are frequently replicated in schools and universities. But there is an aspect that is little considered, namely that the light initially refracted within the equilateral prism, in addition to being further refracted and giving out the well-known spectrally dispersed bundle, is also internally reflected an indefinite number of times and, in correspondence with each reflection, produces an external refractive bundle that can be white or dispersed depending on the parity of the number of reflections previously undergone. In this paper, I analyze, both theoretically and experimentally, the properties of the main bundles coming out of the faces of the equilateral prism, when it is illuminated by p- or s-polarized white light, or by a laser beam.
Research Interests:
By illuminating an equilateral prism with white light, the light internally refracted, besides being refracted externally giving rise to the well-known spectrally dispersed beam, is internally reflected an indefinite number of times also... more
By illuminating an equilateral prism with white light, the light internally refracted, besides being refracted externally giving rise to the well-known spectrally dispersed beam, is internally reflected an indefinite number of times also producing an indefinite number of externally refracted beams. An external refracted beam can be white or spectrally dispersed depending on the
parity of the number of internal reflections undergone. After a brief introduction to recall the main concepts at the basis of the use of the prism as light dispersing element, I analyze, both theoretically and experimentally, the properties of the light beams exiting the faces of the equilateral prism, when it is illuminated with a laser beam, or with a white light beam, polarized "p", "s" or
unpolarized.
parity of the number of internal reflections undergone. After a brief introduction to recall the main concepts at the basis of the use of the prism as light dispersing element, I analyze, both theoretically and experimentally, the properties of the light beams exiting the faces of the equilateral prism, when it is illuminated with a laser beam, or with a white light beam, polarized "p", "s" or
unpolarized.
Research Interests:
In this paper we present a method of optical characterization of solar concentrators based on the use of a laser beam. The method, even though constrained by lengthy measurements, gives nevertheless interesting information on local mirror... more
In this paper we present a method of optical characterization of solar concentrators based on the use of a laser beam. The method, even though constrained by lengthy measurements, gives nevertheless interesting information on local mirror surface defects or manufacturing defects, like internal wall shape inaccuracies. It was applied to 3D-CPC-like concentrators and the measurements were supported by optical simulations
Research Interests:
Research Interests:
Research Interests:
ABSTRACT Copper oxide thin films were prepared by reactive rf magnetron sputtering of a pure copper target in an oxygen-argon atmosphere. The phases of the deposited films strongly depend on the oxygen content in the sputtering gas. X-ray... more
ABSTRACT Copper oxide thin films were prepared by reactive rf magnetron sputtering of a pure copper target in an oxygen-argon atmosphere. The phases of the deposited films strongly depend on the oxygen content in the sputtering gas. X-ray diffraction studies show that by controlling the oxygen partial pressure single phase Cu2O and CuO can be obtained. The resistivity of the Cu2O film in the present study is 43 Ω cm. The optical constants were evaluated from transmission and reflection measurements.
Research Interests:
Research Interests:
The gravity-driven flow of monodisperse spherical grains of different nature and diameter d, through conical cardboard hoppers, has been studied as function of the orifice diameter D for different values of the aperture angle α (~ 3° ÷... more
The gravity-driven flow of monodisperse spherical grains of different nature and diameter d, through conical cardboard hoppers, has been studied as function of the orifice diameter D for different values of the aperture angle α (~ 3° ÷ 15°) at large grains conditions (D ≤ 10d). The mass flow rate trend function has displayed, at the lowest angles, a series of linear tracts, with increasing slope, delimited by approximately odd integers of the grains diameter. The linear tracts have been associated to different flow rate regimes, governed by the formation, at the bottom of the granular column, of short-lived arches of "quantized" size (~ 5d, ~ 7d, ~ 9d, …), acting as brakes to flow, by their detachment and ejection from the hopper. This mechanism of events should give rise to a modulation of the flow whose frequency was effectively measured, for the arches of ~ 5d size, by analyzing the signal produced by the falling grains on a microphone. The data of mass flow rate W, as function of the orifice diameter D, have shown, on average, a growth following the 5/2 power-law function, as foreseen by the well-known Beverloo law. Here we analyze the simplified expression of the mass flow rate with the dimension of the square root of the acceleration of gravity, which shows only a slight dependence on the aperture angle of the hopper. The jamming of grains at the outlet opening has been also investigated throughout the transition region at D ~ 3d ÷ 4d, which characterizes the passage from the blocked to the continuous flow for few tens thousand grains, by an optical method and by measuring the frequency of the clogging events.
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It is my great pleasure to introduce the fifth volume from our popular open access Book Series ‘Advances in Optics: Reviews’ started by the IFSA Publishing in 2018. The Vol. 5 of this Book Series is also published as an Open Access Book... more
It is my great pleasure to introduce the fifth volume from our popular open access Book Series ‘Advances in Optics: Reviews’ started by the IFSA Publishing in 2018. The Vol. 5 of this Book Series is also published as an Open Access Book in order to significantly increase the reach and impact of this volume, which also published in two formats: electronic (pdf) with full-color illustrations and print (paperback). ‘Advances in Optics: Reviews’ Book Series is a comprehensive study of the field of optics, which provides readers with the most up-to-date coverage of optics, photonics and lasers with a good balance of practical and theoretical aspects. Directed towards both physicists and engineers this Book Series is also suitable for audiences focusing on applications of optics. A clear comprehensive presentation makes these books work well as both a
teaching resources and a reference books. The book is intended for researchers and scientists in physics and optics, in academia and industry, as well as postgraduate students. Like the first four volumes of this Book Series, the fifth volume also has been organized by topics of high interest to offer a fast and easy reading of each topic, every chapter in this book is independent and self-contained. All chapters have the same structure: first an introduction to specific topic under study; second particular field description including sensing or/and measuring applications. Each of chapter is ending by well selected list of references with books, journals, conference proceedings and web sites. The fifth volume is devoted to optics, lasers, optical communication and networks, and written by 53 authors from academia and industry from 12 countries: Belgium, Bulgaria, China, France, Italy, Iraq, Japan, Russia, Spain, Turkey, USA and Vietnam. But it is not a simple set of reviews. As usually, each chapter contains the extended state-of-the-art followed by new, unpublished before, obtained by the authors results. This book ensures that our readers will stay at the cutting edge of the field and get the right and effective start point and road map for the further researches and developments. By this way, they will be able to save more time for productive research activity and eliminate routine work. I shall gratefully receive any advices, comments, suggestions and notes from readers to
make the next volumes of ‘Advances in Optics: Reviews’ Book Series very interesting and useful.
Dr. Sergey Y. Yurish Editor
IFSA Publishing Barcelona, Spain
teaching resources and a reference books. The book is intended for researchers and scientists in physics and optics, in academia and industry, as well as postgraduate students. Like the first four volumes of this Book Series, the fifth volume also has been organized by topics of high interest to offer a fast and easy reading of each topic, every chapter in this book is independent and self-contained. All chapters have the same structure: first an introduction to specific topic under study; second particular field description including sensing or/and measuring applications. Each of chapter is ending by well selected list of references with books, journals, conference proceedings and web sites. The fifth volume is devoted to optics, lasers, optical communication and networks, and written by 53 authors from academia and industry from 12 countries: Belgium, Bulgaria, China, France, Italy, Iraq, Japan, Russia, Spain, Turkey, USA and Vietnam. But it is not a simple set of reviews. As usually, each chapter contains the extended state-of-the-art followed by new, unpublished before, obtained by the authors results. This book ensures that our readers will stay at the cutting edge of the field and get the right and effective start point and road map for the further researches and developments. By this way, they will be able to save more time for productive research activity and eliminate routine work. I shall gratefully receive any advices, comments, suggestions and notes from readers to
make the next volumes of ‘Advances in Optics: Reviews’ Book Series very interesting and useful.
Dr. Sergey Y. Yurish Editor
IFSA Publishing Barcelona, Spain
Research Interests:
Preface It is my great pleasure to introduce the third volume of new Book Series ‘Advances in Optics: Reviews’ started by the IFSA Publishing in 2018. Three volumes were published in this year. The ‘Advances in Optics: Reviews’ Book... more
Preface
It is my great pleasure to introduce the third volume of new Book Series ‘Advances in Optics: Reviews’ started by the IFSA Publishing in 2018. Three volumes were published in this year.
The ‘Advances in Optics: Reviews’ Book Series is published as an Open Access Books in order to significantly increase the reach and impact of these volumes, which also published in two formats: electronic (pdf) with full-color illustrations and print
(paperback).
The third of three volumes of this Book Series has organized by topics of high interest. In order to offer a fast and easy reading of each topic, every chapter in this book is independent and self-contained. All chapters have the same structure: first an introduction to specific topic under study; second particular field description including sensing or/and measuring applications. Each of chapter is ending by complete list of carefully selected references with books, journals, conference proceedings and web sites.
The Vol.3 is devoted to various topics of applied optics and contains 17 chapters written by 49 experts in the field from 14 countries: Australia, China, India, Israel, Italy, Japan, Malaysia, Mexico, The Netherlands, Poland, Taiwan, UK, USA and Vietnam.
‘Advances in Optics: Reviews’ Book Series is a comprehensive study of the field of optics, which provides readers with the most up-to-date coverage of optics, photonics and lasers with a good balance of practical and theoretical aspects. Directed towards both physicists and engineers this Book Series is also suitable for audiences focusing on applications of
optics. A clear comprehensive presentation makes these books work well as both a teaching resources and a reference books. The book is intended for researchers and scientists in physics and optics, in academia and industry, as well as postgraduate students. I shall gratefully receive any advices, comments, suggestions and notes from readers to make the next volumes of ‘Advances in Optics: Reviews’ Book Series very interesting and useful.
Dr. Sergey Y. Yurish Editor
IFSA Publishing Barcelona, Spain.
It is my great pleasure to introduce the third volume of new Book Series ‘Advances in Optics: Reviews’ started by the IFSA Publishing in 2018. Three volumes were published in this year.
The ‘Advances in Optics: Reviews’ Book Series is published as an Open Access Books in order to significantly increase the reach and impact of these volumes, which also published in two formats: electronic (pdf) with full-color illustrations and print
(paperback).
The third of three volumes of this Book Series has organized by topics of high interest. In order to offer a fast and easy reading of each topic, every chapter in this book is independent and self-contained. All chapters have the same structure: first an introduction to specific topic under study; second particular field description including sensing or/and measuring applications. Each of chapter is ending by complete list of carefully selected references with books, journals, conference proceedings and web sites.
The Vol.3 is devoted to various topics of applied optics and contains 17 chapters written by 49 experts in the field from 14 countries: Australia, China, India, Israel, Italy, Japan, Malaysia, Mexico, The Netherlands, Poland, Taiwan, UK, USA and Vietnam.
‘Advances in Optics: Reviews’ Book Series is a comprehensive study of the field of optics, which provides readers with the most up-to-date coverage of optics, photonics and lasers with a good balance of practical and theoretical aspects. Directed towards both physicists and engineers this Book Series is also suitable for audiences focusing on applications of
optics. A clear comprehensive presentation makes these books work well as both a teaching resources and a reference books. The book is intended for researchers and scientists in physics and optics, in academia and industry, as well as postgraduate students. I shall gratefully receive any advices, comments, suggestions and notes from readers to make the next volumes of ‘Advances in Optics: Reviews’ Book Series very interesting and useful.
Dr. Sergey Y. Yurish Editor
IFSA Publishing Barcelona, Spain.
Research Interests:
Scientific papers
Research Interests:
We study, by SEM-EDX and XRD analysis, the Selenium incorporation in a series of near-stoichiometric CuInSe2 thin films obtained selenizing the Cu and In precursors by vacuum evaporation of Selenium.
Research Interests:
The surface morphology, phase composition and adhesion to Mo-glass substrate, of thin films of CuInSe2, prepared by selenization of sputtered metal precursors, were correlated to the structure of the precursors. Single-phase, homogeneous,... more
The surface morphology, phase composition and adhesion to Mo-glass substrate, of thin films of CuInSe2, prepared by selenization of sputtered metal precursors, were correlated to the structure of the precursors. Single-phase, homogeneous, small-grained CuInSe2 arises from precursors showing stable phases (Cu11In9 and In). Precursors with high content of CuIn2 metastable phase show poor adhesion to the substrate.
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The morphological and structural properties of Cu-In metallic alloys, prepared by sputtering at different temperatures and at different configurations (Cu over In, In over Cu, Cu/In/CU), were studied by SEM and XRD.
Research Interests:
The Scanning Transmission Electron Microscopy, when used in the Electron Beam Induced Current mode (STEM-STEBIC), can allow the correlation, at high spatial resolution, of structural and electrical properties of individual defects in... more
The Scanning Transmission Electron Microscopy, when used in the Electron Beam Induced Current mode (STEM-STEBIC), can allow the correlation, at high spatial resolution, of structural and electrical properties of individual defects in semiconductor materials. In this paper we describe the STEM-STEBIC defect analysis in gallium arsenide (bulk and epitaxial) and polycrystalline silicon with both p-n and Schottky barriers, in order to put in light some spurious effects associated to multiple scattering of the primary beam and to assess the potentiality of this technique. A proper device for a JEOL 200 kV transmission electron microscope was set up with facilities of double tilting and applying bias voltages. This apparatus allowed us to study correlations between diffraction contrast, at different orientation conditions, and conductive contrast, at different junction barrier amplitudes. The typical black recombination contrast at the electrical defects was not observed in poly-Si, unless very thick regions were examined or a direct bias voltage was applied. Recombining electrical defects were easily detected, on the contrary, in GaAs, also near the thinnest region of the specimen.
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The adhesion of CVD TiN and TiN-SiC layers on WC-Co cermets and superalloys (Ni based) substrates was evalueted by using scratch test measurements.
Research Interests:
The microstructure and mechanical properties (adhesion, hardness) of beta-SiC coatings, prepared in a cold-wall reactor, were studied by examining different substrates and deposition process conditions. Hard (3500 HK), fine grained... more
The microstructure and mechanical properties (adhesion, hardness) of beta-SiC coatings, prepared in a cold-wall reactor, were studied by examining different substrates and deposition process conditions. Hard (3500 HK), fine grained beta-SiC coatings were deposited onto graphite at relatively high deposition temperatures (1473-1673 K) using SiCl4, C3H8, H2 gas mixtures. The thermal decomposition of methyltrichlorosilane (MTS) in hydrogen and argon allowed the production of beta-SiC coatings onto a variety of substrate materials in the temperature range 1173-1373 K. The growth mechanisms of SiC deposited from MTS/H2/Ar system onto graphite and polycrystalline alfa-SiC substrates were studied. At low (40 kPa) and atmospheric pressure, the growth kinetics is limited by surface reactions. Also, a strong dependence of the microstructure and crystallographic orientation on the deposition parameters was observed. Hard metals (WC/Co) were successfully coated with beta-SiC using the MTS/H2/Ar system. Problems of chemical compatibility between the substrate and the beta-SiC coating were minimized by the deposition of an intermediate TiN layer.
Research Interests:
The morphological features of silicon carbide coatings, deposited on graphite from SiCl4, C3H8 and H2 mixtures, were investigated. Based on preliminary thermodynamic calculations, the experiments were performed at atmospheric pressure in... more
The morphological features of silicon carbide coatings, deposited on graphite from SiCl4, C3H8 and H2 mixtures, were investigated. Based on preliminary thermodynamic calculations, the experiments were performed at atmospheric pressure in a cold wall reactor by varying the deposition temperature Td in the 1473-1673 K range and the deposition time between 10 and 120 min. SEM examinators showed considerable differences in surface morphology depending on the process parameters. A transition from a modular to a faceted structure was observed by moving towards higher Td values. A double layer structure was detected on the thickest coatings due to a sharp columnar-microcrystalline transition. The coatings prepared at Td = 1673 K showed surface microhardness values as high as 4000 HK and an optimum capability to protect graphite substrates against oxidation at 1273 K.
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In this paper we present experimental results on imaging of polycrystalline structure of fine-grained SiC coatings.
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It is described the Chemical Vapor Deposition process for the growth of hard ceramic materials (SiC) to protect superalloy surfaces.
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This note reports some applications of the QUANTIMET 970 Image Analyzer to the study of EBIC data obtained on different devices.
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We report a thermodynamical analysis of the NH3-SiCl4-H2 system, suitable to achieve high deposition rates of Silicon Nitride. The calculations are performed on seven equilibrium reactions involving nine gaseous species, including those... more
We report a thermodynamical analysis of the NH3-SiCl4-H2 system, suitable to achieve high deposition rates of Silicon Nitride. The calculations are performed on seven equilibrium reactions involving nine gaseous species, including those at input.
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The EBIC technique is used to correlate the electrical activity of defects with its crystallographic structure in semiconductor junctions. The junctions examined are those of polysilicon, thin layer of GaAs and GaAs single crystal.
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A new approach to directional solidification of Silicon in crucible is presented.
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A flat-ingot heat-transfer model has been developed to project the industrial solidification of Silicon.
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The following techniques for the electrical and optical characterization of polycrystalline silicon solar cells are described: resistivity, diffusion length, spectral response.
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The design of a GaAs thin film solar cell is described.
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È descritta la problematica della deposizione di semiconduttori a film sottile.