1,721,052 research outputs found
Monte Carlo simulator of the charge signal induced by external radiation on semi-insulating GaAs detectors
No full text“Linee di intervento per la valorizzazione delle colture agricole locali della Valle della Cupa”
No full textAl fine di valorizzare i cultivar tipici salentini e far sviluppare in modo eco-sostenibile nuovi processi industriali è importante fornire alle imprese operanti sul territorio - sia a quelle che “potenzialmente” potrebbero svilupparsi in un prossimo futuro - un supporto logistico, tecnologico ed informativo adeguato alle esigenze ed al passo con i tempi.Pertanto, assume una fondamentale importanza conoscere la distribuzione geografica delle produzioni agricole locali, il ciclo di vita dei prodotti e delle essenze che da essi si possono ricavare, il commercio (anche e soprattutto quello internazionale), la tendenza alla globalizzazione, l’impegno della ricerca sia nel campo dell’agro-alimentare e del “non-food”; nonché, le precauzioni da adottare in termini salvaguardia ambientale e delle questioni legate alla qualità alla sicurezza e alla salute. Con questo progetto ci si propone di individuare le aree geografiche della Valle della Cupa sulle quali, monitorare non solo le coltivazioni tradizionali di maggiore rilevanza (uliveti, vigneti, ortoftutticolo), ma anche le specie arbustive che crescono spontaneamente o come cultivar minori (more, gelsi, mirto, melograni, fichi d’india) dalle quali è possibile estrarre principi attivi ad elevato valore aggiunto. Studi di telerilevamento integrati con informazioni dettagliate del territorio permetteranno non solo una conoscenza dei luoghi e dell''uso del suolo, ma anche il censimento puntuale di alcune aree con vegetazione spontanea, specie arboree, arbusti, zone incolte, etc., dalle quali poter ricavare alcuni principi attivi di crescente interesse in campo industriale
Residual and thermal strain of ZnS epitaxial layers grown on (100)-GaAs by vapour phase epitaxy
No full textIn this work, ZnS epitaxial layers grown by vapour phase epitaxy
on [100]-oriented GaAs substrates are investigated by x-ray diffraction. The residual strain status of the as-grown samples was determined by high-resolution double-crystal x-ray diffraction measurements. Eleven diffraction curves were
recorded in the vicinity of the (400), (422) and (531) Bragg reflections in different diffraction geometries and for several azimuth angles. The analysis of the experimental data was performed by using a general model, which relates the angular distances between diffraction peaks and strain tensor components in the second-order approximation. This model considers the lowest crystallographic symmetry (triclinic) for the lattice distortion of a cubic unit cell. Our results indicate that the crystallographic symmetry of the distorted ZnS unit cell is orthorhombic. In order to determine the strain contribution due to the different thermal expansion coefficients of ZnS and GaAs (thermal strain) the temperature variation of the residual strain was measured between 25°C and the growth temperature (650°C) by using a single crystal x-ray diffractometer. From our temperature-dependent measurements we determined the thermal misfit between ZnS and GaAs and the linear thermal expansion coefficient of ZnS
Surface structural and morphological characterization of ZnTe epilayers grown on {100}GaAs by MOVPE
No full textThe surface structural and. morphological characterization of ZnTe epilayers grown on (100)GaAs by atmospheric pressure MOVPE is reported. Scanning electron microscopy (SEM), reflection high energy electron diffraction (RHEED) and reflection electron microscopy (REM) have been performed on the as-grown ZnTe epilayer surfaces. RHEED pattern allowed to estimate the ZnTe crystalline quality, whereas the layer-to-substrate epitaxial relationships have been demonstrated from both RHEED and X-ray diffraction. SEM and REM observations in combination with alpha-step surface profiling measurements allowed to obtain a quantitative description of ZnTe surface irregularities, whose dimensions range from a few nm to just above 30 nm in height, being several hundred nm wide across the surface. Also, the ZnTe surface roughness depends linearly on the epilayer thickness and approaches the initial surface roughness of the GaAs substrates when the thickness tends to zero. Finally, no evident surface anisotropy has been revealed in the present samples, apart from a characteristic [011] elongation effect of some growth defect features at the epilayer surfaces
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