69 research outputs found
Alcuni spunti in materia di primogenitura e maggiorascato. Giampietro Attolini, un giurista di Garfagnana.
No full textPrimogenitura e maggiorascato furono oggetto di studio da parte della dottrina di diritto comune per la diffusione che ebbero a partire dal Cinquecento. Fra i giuristi, Giampietro Attolini, originario della Garfagnana, espresse una opinione che sarebbe diventata "communis opinio doctorum" quasi un secolo dopo.Primogeniture and "majoratus" were often studied by "ius Commune" (roman and canon law) doctrine due to the spread they had the Sixsteenth century. Among jurists, Giovanni Pietro Attolini from Garfagnana expressed an opinion that would become "communis opinio doctorum" almost a century later
Photo-Induced Nonlinearities in Fowler-Nordheim Plots for Field Emission of SiC Nanowires
No full textIn this contribution the field emission by tunneling of electrons of 3C-SiC nanowires on Si substrate, grown by CVD method via Ni catalyst, has been investigated. Scanning electron images have quantified the low density of the nanowires over the sample surface. In order to exclude any contribution to the Field Emission phenomenon from the Si substrate, the field emission measurements have been performed before and after removing the SiC nanowires. The Field Emission experiments have been carried out in dark conditions and by shining the sample surface. The extracted Fowler-Nordheim (F-N) plots show that the Field Emission from nanowires is highly sensitive to illumination parameters. When using lighting, a partition in three regions of the F-N plot has been observed. In the low field region, the F-N plot is linear or metallic-like, then it follows a saturation-current region and finally the high field region is characterized by a sharp increase.
Departure from the standard F-N theory, that is the influence of light and temperature on the Field Emission phenomenon, is well assessed for bulk semiconductor cathodes [1], but it has been rarely observed in single SiC nanowires [2]. To the authors’ knowledge, this contribution reports for the first time the strong deviation from F-N linear behavior for multiple SiC nanowires dispersed over planar substrate.
Field Emission data from quantum-confined structures are both useful for the study of their fundamental physics, but also because of promising technological applications, such as electron sources, high-resolution electron beam instruments, and Field Emission displays.
[1] G. N. Fursey, Field Emission in Vacuum Microelectronics (Kluwer Academic, New York, 2005)
[2] M. Choueib , A. Ayari, P. Vincent, M. Bechelany, D. Cornu, and S. T. Purcell, "Strong deviations from Fowler-Nordheim behavior for field emission from individual SiC nanowires due to restricted bulk carrier generation", Physical Review B 79, 075421 (2009
Hydrogen plasma treatment confers enhanced bioactivity to silicon carbide-based nanowires promoting osteoblast adhesion.
No full textNanomaterials play a pivotal role in modern regenerative medicine and tissue engineering, due to their peculiar physical, optical and biological properties once they are used in the nanometric size. Many evidences are showing the importance of biomaterial micro- and nano-topography on cellular adhesion, proliferation and differentiation, and hence, tissue regeneration. It is well known that nanowires (NWs) can mimic many different tissues as a result of their shape and their surface characteristics, and that surface hydrophilicity affects early protein adsorption and cellular adhesion. Therefore a material able to induce bone regeneration might be obtained by combining optimal surface topography and hydrophilicity. Based on these evidence, we designed silicon carbide (SiC) and core/shell silicon carbide/silicon dioxide (SiC/SiOx) nanowires with modified wettability in order to analyze cell behavior, using an in-vitro osteoblastic model. First, we synthetized SiC NWs and SiC/SiOx NWs through a chemical-vapour-deposition (CVD) process, and then we used hydrogen plasma to modify their hydrophilicity. Subsequently we evaluated the four types of NWs in terms of their morphology and contact angle, and we studied their behavior in the presence of MC3T3-E1 murine osteoblasts. Cell metabolic activity, viability, morphology and focal adhesions formation were considered. Morphological data showed different dimensions between SiC and SiC/SiOx NWs. SiC NWs before the hydrogen plasma treatment showed a very low contact angle, that was absent after the treatment. Osteoblastic cells appeared healthy on all of the samples. Interestingly, both hydrophilic SiC NWs and SiC/SiOx NWs generated a favorable distribution of focal adhesions around the cell body confirmed also by scanning electron microscopy images. Moreover, osteoblasts grown on hydrogen plasma treated SiC/SiOx NWs showed an increased metabolic activity testified by a significantly higher cell number. In conclusion, we are here demonstrating that hydrogen plasma treatment of SiC and SiC/SiOx NWs induce a better osteoblastic cellular adhesion by increasing NWs wettability. We are therefore suggesting that hydrogen plasma treatment of SiC/SiOx can offer a suitable method to develop scaffolds for bone tissue engineering applications
Influence of the Carrier Gas Flow in the CVD Synthesis of 2-Dimensional MoS2 Based on the Spin-Coating of Liquid Molybdenum Precursors
No full textAtomically thin molybdenum disulfide (MoS2) is a two-dimensional semiconductor with versatile applications. The recent adoption of liquid molybdenum precursors in chemical vapor deposition has contributed significantly to the reproducible wafer-scale synthesis of MoS2 monolayer and few-layer films. In this work, we study the effects of the carrier gas flow rate on the properties of two-dimensional molybdenum disulfide grown by liquid-precursor-intermediate chemical vapor deposition on SiO2/Si substrates. We characterized the samples using Optical Microscopy, Scanning Electron Microscopy, Raman spectroscopy, and Photoluminescence spectroscopy. We analyzed samples grown with different nitrogen carrier flows, ranging from 150 to 300 sccm, and discussed the effect of carrier gas flows on their properties. We found a correlation between MoS2 flake lateral size, shape, and number of layers, and we present a qualitative growth model based on changes in sulfur provision caused by different carrier flows. We show how the use of liquid precursors can allow for the synthesis of homogeneous, single-layer flakes up to 100 μm in lateral size by optimizing the gas flow rate. These results are essential for gaining a deeper understanding of the growth process of MoS2
Electrical characterisation of epitaxially grown 3C-SiC films
No full text3C-SiC have been epitaxially grown through vapour phase expitaxy under a different grow conditions. Key electrical properties of these SiC layers have been characterised by fabrication and measurement of metal-SiC-metal devices. The electrical properties of SiC grown at different conditions have been analysed based on their structural and crystalline quality
Wafer curvature analysis in 3C-SiC layers grown on (0 0 1) and (1 1 1) Si substrates
No full textTo assess deformation issues in the vapor phase epitaxy of 3C-SiC on (0 0 1) and (1 1 1) Si substrates, weinvestigated different pre-growth (carburisation) procedures, adding various amount of SiH4 to C3H8. Themechanical deformation of the samples was measured by quantitative Makyoh topography, throughwhich 3D deformation maps of the entire wafers were obtained. X-ray diffraction was used to check thecrystal quality of the layers and, in transmission geometry, to assess whether the observed deformationwas plastic or elastic. Residual stress of the deposited 3C-SiC layers was investigated across the entirewafer substrates by using Raman spectroscopy and values between 0.5 and 1 GPa were found. It wasobserved that, for a given carburisation procedure, the crystalline orientation of the Si substrates plays animportant role in the substrate curvature (convex and concave). The addition of SiH4 during carburisationramp leads to increased deformation for SiC/Si (0 0 1), while decreased deformation for SiC/Si (1 1 1)
Evaluation of curvature and stress in 3C-SiC grown on differently oriented Si substrates
No full textTo assess deformation issues in SiC/Si, different pre-growth procedures were investigated, involving the addition of SiH4 to C3H8 during the temperature ramps used for the carbonization. 3C-SiC layers were deposited on (001) and (111) Si substrates by VPE. The mechanical deformation of the wafer was measured by makyoh, obtaining 2D maps of the entire wafers. For the same pre-growth procedures, the substrate curvature depends strongly on the orientation of the substrate, (001) or (111), being generally lower for (111) substrates. The deformation results were compared with XRD and Raman spectroscopy. Plastic deformation of the substrate was evidenced by XRD, while the presence of tensile stress is suggested by Raman analysis
Effect of a halogen-based precursor on dopant incorporation in 3C-SiC film epitaxy
No full textSilicon carbide thin films were synthesised by vapour phase epitaxy technique on silicon substrates using silane and propane as precursors. Methyltrichlorosilane (MTS) was added, and nitrogen was used as dopant precursor. Samples with different doping concentrations were obtained varying the nitrogen flow during the growth. Doping level for each sample was assessed using Raman technique, and a correlation between dopant flow and doping level was confirmed. The influence of MTS on nitrogen incorporation is analysed and discussed: the introduction of MTS increases the growth rate and increases the doping level. We exclude a direct doping effect by the MTS, but we think that it promotes the incorporation of nitrogen doping species. The crystalline quality of the as-grown films was evaluated using X-ray diffraction, assessing the good crystalline quality even in samples obtained using high growth rates and high doping level.IM
Structural characterization of 3C-SiC grown using methyltrichlorosilane
No full text3C-SiC layers were grown on Si substrates using standard precursors (SiH4 and C3H8) and by
adding methyl trichloro silane (MTS) to the gas phase, with growth temperatures between 1200 and
1300 °C. Characterization of the 3C-SiC layers shows that 3C-SiC grown with MTS has higher
polycrystalline and amorphous content as well as lower residual stress
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