Electronic properties of transition metal oxide layers for applications in organic solar cells

Gli Ossidi di Metalli di Transizione, come quelli di Molibdeno e di Titanio, sono materiali molto promettenti per lo sviluppo di applicazioni per il trasporto di carica nella fabbricazione di celle solari. Questa tesi presenta un lavoro realizzato tra il Dipartimento di Fisica e Astronomia dell'Università di Bologna e l'Istituto delle NanoScienze di Parigi della Sorbona - Paris 6 in collaborazione con la Southern Denmark University, che mira a comprendere e modificare le proprietà di tali ossidi per il miglioramento del trasporto di elettroni e lacune in film sottili. Il progetto di ricerca è stato portato a termine ricorrendo a varie tecniche di caratterizzazione strutturale, come la Microscopia a Forza Atomica (AFM), elettrica e chimica, tra cui la Microscopia Kelvin Probe (KPFM), la Spettroscopia di Fotoemissione a Raggi X e Ultravioletti (XPS/UPS) e la Microscopia a Fotoemissione di Elettroni a Raggi X (XPEEM) realizzata presso la sorgente di sincrotrone SOLEIL di Saint-Aubin (Francia). I principali risultati di questo studio includono l'identificazione dell'evoluzione della superficie con la crescita di grani per l'ossido di molibdeno su silicio, la stabilità degli ossidi di molibdeno e titanio su Ossido di Indio e Stagno (ITO) dedotta dal minor numero di aggregati visibili nelle mappe AFM, l'aumento della funzione lavoro quando i materiali sono sottoposti a cicli di riscaldamento (annealing) fino a 450°C e l'interessante comparsa di domini di policristalliti sulla superficie dell'ossido di titanio ad alta temperatura. Differenti analisi con esposizione a radiazioni hanno permesso di investigare gli effetti di luce ultravioletta e raggi X sugli ossidi e di identificare la tecnica di deposizione e le caratteristiche dei materiali più adatte per ridurre la degradazione delle proprietà elettriche causate dalla luce

Analysis of the influence of the anisotropy induced by cold rolling on duplex and super-austenitic stainless steels

This report contains the results obtained from the mechanical characterization tests carried out on two different stainless steel (duplex 6%Ni, 22%Cr and super-austenitic 31%Ni, 28%Cr) used for the manufacturing of pipes which are employed in the oil production. The activity has been performed in order to evaluate the effects of anisotropy, induced by cold rolling, on the mechanical characteristics of the investigated steels, measured in the three main directions. Considering the small size of the component, the method and the specimens used for the tests were not the standard one. The procedure carried out provided the strain measurement of the specimen during testing by means of resistive strain gages, bonded on the specimens

IGR J11215-5952: a hard X-ray transient displaying recurrent outbursts

The hard X-ray source IGRJ11215-5952 has been discovered with INTEGRAL during a short outburst in 2005 and proposed as a new member of the class of supergiant fast X-ray transients. We analysed INTEGRAL public observations of the source field in order to search for previous outbursts from this transient, not reported in literature.Our results are based on a systematic re-analysis of INTEGRAL archival observations, using the latest analysis software and instrument calibrations. We report the discovery of two previously unnoticed outbursts, spaced by intervals of ~330 days, that occurred in July 2003 and May 2004. The 5-100keV spectrum is well described by a cut-off power law, with a photon index of 0.5, and a cut-off energy ~15-20keV, typical of High Mass X-ray Binaries hosting a neutron star. A 5-100keV luminosity of 3E36 erg/s has been derived (assuming 6.2kpc, the distance of the likely optical counterpart). The 5-100keV spectral properties, the recurrent nature of the outbursts,together with the reduced error region containing the blue supergiant star HD306414,support the hypothesis that IGRJ11215-5952 is a member of the class of the Supergiant Fast X-ray Transients.Comment: 4 pages, 4 figures, accepted for publication in Astronomy and Astrophysics Letter

Proprietà di conduzione elettrica in campioni di grafene poroso

Il grafene, allotropo del carbonio costituito da un reticolo bidimensionale, è uno dei nanomateriali più promettenti allo stato attuale della ricerca nei campi della Fisica e della Chimica, ma anche dell'Ingegneria e della Biologia. Isolato e caratterizzato per la prima volta nel 2004 dai ricercatori russi Andre Geim e Konstantin Novoselov presso l'Università di Manchester, ha aperto la via sia a studi teorici per comprendere con gli strumenti della Meccanica Quantistica gli effetti di confinamento in due dimensioni (2D), sia ad un vastissimo panorama di ricerca applicativa che ha l'obiettivo di sfruttare al meglio le straordinarie proprietà meccaniche, elettriche, termiche ed ottiche mostrate da questo materiale. Nella preparazione di questa tesi ho personalmente seguito presso l'Istituto per la Microelettronica e i Microsistemi (IMM) del CNR di Bologna la sintesi mediante Deposizione Chimica da Fase Vapore (CVD) di grafene "tridimensionale" (3D) o "poroso" (denominato anche "schiuma di grafene", in inglese "graphene foam"), ossia depositato su una schiuma metallica dalla struttura non planare. In particolare l'obiettivo del lavoro è stato quello di misurare le proprietà di conduttività elettrica dei campioni sintetizzati e di confrontarle con i risultati dei modelli che le descrivono teoricamente per il grafene planare. Dopo un primo capitolo in cui descriverò la struttura cristallina, i livelli energetici e la conduzione dei portatori di carica nel reticolo ideale di grafene 2D (utilizzando la teoria delle bande e l'approssimazione "tight-binding"), illustrerò le differenti tecniche di sintesi, in particolare la CVD per la produzione di grafene poroso che ho seguito in laboratorio (cap.2). Infine, nel capitolo 3, presenterò la teoria di van der Pauw su cui è basato il procedimento per eseguire misure elettriche su film sottili, riporterò i risultati di conduttività delle schiume e farò alcuni confronti con le previsioni della teoria

IBIS/PICsIT in-flight performances

PICsIT (Pixellated Imaging CaeSium Iodide Telescope) is the high energy detector of the IBIS telescope on-board the INTEGRAL satellite. PICsIT operates in the gamma-ray energy range between 175 keV and 10 MeV, with a typical energy resolution of 10% at 1 MeV, and an angular resolution of 12 arcmin within a \~100 square degree field of view, with the possibility to locate intense point sources in the MeV region at the few arcmin level. PICsIT is based upon a modular array of 4096 independent CsI(Tl) pixels, ~0.70 cm^2 in cross-section and 3 cm thick. In this work, the PICsIT on-board data handling and science operative modes are described. This work presents the in-flight performances in terms of background count spectra, sensitivity limit, and imaging capabilities.Comment: 8 pages, 4 figures. Accepted for publication on A&A, special issue on First Science with INTEGRA

Organic bilayer photovoltaics for efficient indoor light harvesting

Indoor organic photovoltaics (OPVs) are a potential niche application for organic semiconductors due to their strong and well-matched absorption with the emission of indoor lighting. However, due to extremely low photocurrent generation, the device parameters critical for efficient indoor OPVs differ from those under 1 Sun conditions. Herein, these critical device parameters—recombination loss and shunt resistance (Rsh)—are identified and it is demonstrated that bilayer OPVs are suitable for indoor PV applications. Compared to bulk-heterojunction (BHJ), the open-circuit voltage loss of bilayer devices under low light intensities is much smaller, consistent with a larger surface photovoltage response, indicating suppressed recombination losses. The bilayer devices show a higher fill factor at low light intensities, resulting from high Rsh afforded by the ideal interfacial contacts between the photoactive and the charge transport layers. The high Rsh enables bilayer devices to perform well without a light-soaking process. Finally, the charge carriers are extracted rapidly in bilayers, which are attributed to strongly suppressed trap states possibly induced by isolated domains and non-ideal interfacial contacts in BHJs. This study highlights the excellent suitability of bilayer OPVs for indoor applications and demonstrates the importance of device architecture and interfacial structures for efficient indoor OPVs

Investigación de la intoxicación por monóxido de carbono en la criminalística

Tesis (Especialista en Criminalística y Actividades Periciales con mención en Ciencias Naturales)--Universidad Nacional de Córdoba, Facultad de Matemática, Astronomía, Física y Computación, 2016Especialización conjunta con la Facultad de Cs. Agropecuarias, Facultad de Cs. Químicas, Facultad de Cs. Exactas, Físicas y Naturales-UNC y la Dirección General de Policía Judicial del Ministerio Público de la Provincia de Córdoba.El monóxido de carbono es un gas sumamente tóxico tanto para las personas como para los animales, el mismo es producido como consecuencia de la combustión incompleta de hidrocarburos. Carece de propiedades organolépticas, es incoloro, inodoro, insípido, y no es irritante de mucosas. Este gas tiene una afinidad por la hemoglobina de hasta 250 veces mayor que el oxígeno, formando Carboxihemoglobina e interfiriendo en el mecanismo de transporte de oxígeno, que garantiza en el organismo una renovación continua del abastecimiento del oxígeno necesario para mantener el metabolismo celular. En algunos casos los hallazgos en la autopsia como la coloración rojo cereza de las livideces cadavéricas son indicativos del agente causal. Sin embargo recomienda la realización de análisis toxicológicos, prácticamente en todos los casos forenses, especialmente, cuando tras el examen macroscópico no aparece suficientemente aclarada la causa de la muerte.Carbon monoxide is a highly toxic gas for both people and animals, that it's produced as a result of incomplete combustion of hydrocarbons. It lacks of organoleptic properties, it's colorless, odorless, tasteless, and non-irritating to mucous membranes. This gas has an affinity for hemoglobin up to 250 times higher than the oxygen, forming carboxyhemoglobin and interfering with the mechanism of oxygen transport in the body, which ensures continuous renewal of the oxygen supply necessary to maintain the cell metabolism. In some cases the autopsy findings such as the cherry red coloration of post mortem tissue are indicative of the causative agent. However, it is recommended that a toxicological analysis is conducted in practically all forensic cases, specially when after the macroscopic analysis was conducted, the cause of death was not revealed yet

Imaging extended sources with coded mask telescopes: Application to the INTEGRAL IBIS/ISGRI instrument

Context. In coded mask techniques, reconstructed sky images are pseudo-images: they are maps of the correlation between the image recorded on a detector and an array derived from the coded mask pattern. Aims. The INTEGRAL/IBIS telescope provides images where the flux of each detected source is given by the height of the local peak in the correlation map. As such, it cannot provide an estimate of the flux of an extended source. What is needed is intensity sky images giving the flux per solide angle as typically done at other wavelengths. Methods. In this paper, we present the response of the INTEGRAL IBIS/ISGRI coded mask instrument to extended sources. We develop a general method based on analytical calculations in order to measure the intensity and the associated error of any celestial source and validated with Monte-Carlo simulations. Results. We find that the sensitivity degrades almost linearly with the source extent. Analytical formulae are given as well as an easy-to-use recipe for the INTEGRAL user. We check this method on IBIS/ISGRI data but these results are general and applicable to any coded mask telescope.Comment: 9 pages, 6 figures, Accepted for publication in A&

GRB030406 an extremely hard burst outside of the INTEGRAL field of view

Using the IBIS Compton mode, the INTEGRAL satellite is able to detect and localize bright and hard GRBs, which happen outside of the nominal INTEGRAL telescopes field of view. We have developed a method of analyzing such INTEGRAL data to obtain the burst location and spectra. We present the results for the case of GRB030406. The burst is localized with the Compton events, and the location is consistent with the previous Interplanetary Network position. A spectral analysis is possible with the detailed modeling of the detector response for such a far off-axis source with the offset of 36.9 $^\circ$. The average spectrum of the burst is extremely hard: the photon index above 400 \kev is -1.7, with no evidence of a break up to 1.1 \mev at 90% confidence level.Comment: Astronomy and Astrophysics in pres