Oxide-based transparent conductors constitute a novel class of materials, which finds applications in many technological fields such as photovoltaics and organic light emitting devices. They can be employed in the new generation solar cells as transparent charge collectors. The transparent and conductive oxide mostly used nowadays is indium tin oxide (ITO), however due to the high cost and scarcity of indium, other materials are under research and development as potential substitutes. Many candidates are currently under study, mainly doped-ZnO, doped-CdO, doped-SnO2, doped-TiO2. The work undertaken in this thesis is a study of the doping processes of thin films of TiO2 and ZnO, two cheap, chemically stable and non-toxic materials. Two main objectives were pursued in this work: (i) the optimization of the film deposition and doping conditions for a potential replacement of ITO and (ii) the understanding of the factors dominating the doping process as well as its limitations. The approach was to explore three doping methods of the films: intrinsic doping, extrinsic doping and, with the aim to combine the benefits of both, intrinsic-extrinsic co-doping. Since the structural defects (such as oxygen vacancies) are at the basis of the intrinsic doping, a control of their formation was searched through the variation of the growth process conditions of the ZnO and TiO2 films. Niobium was selected for the extrinsic doping of the TiO2 films. The films were grown by RF plasma sputtering in different atmospheres (Argon, Ar-O2 and Ar-H2 gas mixtures) and under different plasma power conditions and substrate temperature, onto silicon and quartz substrate. The Nb-containing films were obtained by co-sputtering of either a single composite TiO2 -Nb target or two distinct niobium and TiO2 targets. Many characterization techniques were applied to define the film structural, electronic, electrical and optical properties obtained upon doping. For chemical analysis, X-ray Photoelectron Spectroscopy (XPS) was used. The structure and morphology of the films were analyzed by X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). The chemical species present in various plasmas used in deposition process were investigated by Optical Emission Spectroscopy (OES). Further, the defect structure and properties of the obtained films were studied by Positron Annihilation Spectroscopy. Analysis by this technique shed more light on the nature of the vacancies/open volume and on the effect of the latter on the electrical and structural properties of the films. A study based on a joint use of XPS and optical measurements allowed to define the electronic properties of the films (valence band edge, Fermi level position, work function, ionization potential and electron affinity). Structural analysis results revealed the formation of both anatase and rutile nanocrystalline phases for intrinsic and extrinsic doping of TiO2, while with the co-doping method only anatase phase was obtained, a phase known to be favorable for Nb incorporation in TiO2 lattice. The intrinsic doping of TiO2 films showed high transparency in the visible range, but resulted in still high resistivity values (101-103 ï —xcm). The latter could be lowered by using Ar-H2 gas mixtures during film deposition. The same trend was observed in the case of intrinsically-doped ZnO films, an increase in the electrical conductivity was observed when the concentration of defects was increased. The lowest resistivity was achieved with niobium doping of TiO2, 5x10-3 ï —xcm, with an optical absorption coefficient in the visible range of ~1x104 cm-1, however the combination of the internal defects and Nb, in co-doping, did not improve the conductivity. Nonetheless, it was found that co-doping method strongly modified the electronic properties of the TiO2 films, allowing a control of the work function, an important parameter for transparent electrodes. Low cost transparent conductive oxides were obtained when niobium was successfully incorporated in TiO2 lattice. By optimization of the deposition process of the films (dopant concentration, RF power, atmosphere, and annealing temperature) the electronic, electrical and optical properties of doped- TiO2 films can be improved. The obtained results can contribute to the development of transparent electrodes and charge collectors by RF sputtering, a suitable technique for coating on large area substrates.

Conceptual models of first-order controls governing river channel dynamics in mountain streams have been rarely tested in the field. In this Ph.D. thesis we examine the effects of hydro-meteorological forcing and sediment supply on the bedload transport dynamics of mountain streams. To this purpose we select three step-pool mountain streams that share identical granitic lithology, but exhibit contrasting sediment supply and hydro-climatic conditions. The three study sites, which are located in Trentino, Eastern Italian Alps, include the Ussaia Creek (2.3 km2) in Val di Sole, and the Grigno and Tolvà Creeks (7 km2) in Valsugana. The former is characterized by high, sand-rich sediment supply delivered by some 20 m-thick glacigenic deposits. The latter two, which flow through glacially carved bedrock terrain, are disconnected from colluvial sediment inputs so that sediment sources are limited to channel banks and bars during high flows. Mean annual precipitation is respectively 844 mm in Ussaia Creek and 1511 mm in Grigno and Tolvà Creeks. All study streams experience, to variable extents, snowmelt and rainfall-induced bedload transporting flows. To estimate quantitatively the effects and the interactions associated with sediment supply and hydro-meteorological forcing, we monitor precipitation and atmospheric temperature. Hydrological levels at instrumented sections are recorded via pressure transducers. Bedload transport is monitored by tagging and tracking 632 stones (b-axis: 30 to 131 mm; weight 88-4004 g). The tracking of these PIT-tagged tracers was conducted from December 2013 to December 2015 by means of an RFID portable pole antenna. Cumulatively, a total of 16, 11 and 19 bedload events were monitored respectively at Grigno, Tolvà and Ussaia Creek. We measured displacement lengths occurred during inter-survey periods, induced by peak flows associated to snowmelt, rainfall or a combination of the two (mixed-type). Active channel depth was evaluated via direct digging tests at the three study sites finding a median burial depth of 0.1 m at Grigno and Tolvà Creeks, and 0.25 m at Ussaia Creek; recent findings (Schneider et al., 2014), show that ordinary bedload events of boulder-bed streams in the Alps, active layer thickness is comprised within 0.01 and 0.22 m; Houbrechts et al. (2012) demonstrated that in mountain streams the active layer thickness is lower than D50. The active layer width was evaluated via orthophoto maps obtained through Structure-from-Motion. To characterize the streambed roughness and the channel slope we conducted topographic and morphologic surveys. To evaluate event-based bedload sediment volumes we applied the virtual velocity approach (Haschenburger and Church, 1998). In particular, to assess the minimum discharge able to entrain clasts, determining the virtual transport duration of each tracer weight class, we used the competence flow method. In order to evaluate the uncertainty associated with methodology that has been customarily applied in the literature, we performed a sensitivity analysis of the evaluation of bedload transfer proposing three scenarios varying the assumptions that (i) virtual velocities are normally distributed and therefore justifying the adoption of median virtual velocities instead of the average virtual velocity, (ii) that active channel width is constant in time, hence replacing bankfull width with site-specific active widths, evaluated on the base of PIT-tagged particles displacements. The monitoring year 2014 was characterized by a total annual precipitation two times larger than the historical mean, associated to a prolonged snowmelt and to heavy storm front events. By contrast, in 2015 we observed no snowmelt and no precipitation occurred in November and December. At Grigno and Tolvà Creeks, the majority of sediment is transported during autumn storm fronts (median travel distance: 30 m) and secondarily by summer convective storms (median travel distance: 4.5 m). At Ussaia Creek, snowmelt-related events induced 17% of the observed displacement lengths (median travel distance: 2 m), but the primary source of sediment transport is associated chiefly with prolonged storm fronts (median travel distance: 200 m). The mass of tracers does not affect virtual velocities, that are instead affected by seasonal distribution of hydro-meteorological events. In fact, at Grigno and Tolvà Creeks we observe a stratification of velocities according to hydro-meteorological forcing, with the largest values observed during rainfall season, commonly associated to highest values of peak discharge. Variability of virtual velocities at Ussaia Creek does not depend on seasonal hydro-climatic forcing and peak discharge values, with distributions of virtual velocities partly overlapping among snowmelt- and rainfall-related events. The seasonal pattern is translated to bedload transport volumes, with Ussaia Creek transporting by the end of the snowmelt period in 2014, three times more sediment than Grigno Creek. This is testified by a prolonged autumn rainfall that hit simultaneously the study sites, caused a debris-flow that transported 1084 m3 at Ussaia Creek, a much larger quantity compared to the 32.2 m3 evaluated at Grigno and the 62.5 m3 at Tolvà Creek. The definition of rainfall intensity-duration thresholds of precipitation events triggering bedload at our sites shows that transport-limited systems (i.e., Ussaia Creek) result sensitive to precipitation inputs characterized by low rainfall intensity (below 5 mm hr-1) and large duration. Conversely, supply-limited systems (i.e., Grigno and Tolvà Creeks) exhibit armoured beds and interlocked, resilient structures that limit entrainment processes, mobilizing bedload only in response to short-duration/high-intensity rainfall (10 mm hr-1). These channels preserve their morphological structure even under high flow events, triggering sediment transport processes limitedly to peaked storm hydrographs. In the present study we show that the variability in bedload transport among different study reaches is linked to sediment supply conditions and to peculiar hydro-climatic settings. An additional study site characterized by dry conditions, Strimm Creek (Alto Adige, Italy), allows us to obtain a latitudinal transect from dry to wet conditions across the Eastern Italian Alps. By monitoring tracer displacements from 2011 to 2015 at this formerly-glaciated, high-elevation mountain basin, we observe that limited sediment-supply conditions exert a strong control on bedload, chiefly triggered by snowmelt events that account for 73% of the overall travel distances. At Grigno and Tolvà Creeks, also characterized by limited sediment supply, transport is dominated by rainfall events, responsible of driving 95% of the overall travel distances. Sediment availability at Ussaia Creek is responsible for triggering the largest observed bedload events, associated to prolonged autumn precipitation and secondarily to snowmelt events.

In Europe about one third of total annual energy consumption is used in both residential and commercial buildings. In many countries already a building regulation exists to ensure the reduction of energy needs for DHW and space heating. Hence, the interest in reducing summer energy demand has grown in the last few years. The summer behavior of buildings is mostly non-stationary and, therefore, the reliability of simple quasi steady state model predictions can not be taken for granted. Since detailed hourly energy simulations emulate the dynamic interaction between environment, building structure, occupants and indoor conditions, they have the potential to provide relevant information about the building summer behavior and to indicate the possible conservation measures for the reduction of energy consumptions. However, one of the limits for the application of enhanced simulation methods, that sometimes can undermine the reliability of their results, is the difficulty to gather reliable input data. Moreover, if dynamic simulation are used in order to compare different choices, decisions are often suboptimal because of the insufficient knowledge of data that has a large consequence on results. Consequently, in order to broaden the use of building simulation in the design process, it is essentially to clarify some aspects. For instance, one of the biggest objection versus the use of detailed procedure is: "to what extent these methods are meaningful if input data are not reliable?" For this reason, the emphasis of this thesis is on the uncertainties of model predictions. In particular, the research is divided in two parts: the investigation of climate issues and the uncertainty analysis of heat transfer estimation, especially for massive wall. The purpose of the research is to support AE in the choice of the characteristics to which the model predictions are more sensitive. In fact, the results of sensitivity and uncertainty analyzes allow to know the robustness of simulation models and make AE aware if the wrong specifications can lead to uncertain results.

Il mio essere un’insegnante di matematica e fisica delle scuole superiori (il mio primo anno scolastico come insegnante è stato il 1989/90) mi ha portata a questo dottorato e mi ha guidata nella mia ricerca: il bisogno di un rinnovamento, di una modifica delle strategie didattiche e dei contenuti è per me un’emergenza della scuola. Stiamo perdendo i nostri alunni alla scienza, quando loro stessi avrebbero la massima necessità del pensare scientifico nella società contemporanea, per essere cittadini a pieno titolo; per la mia generazione era sufficiente che solo una piccola frazione degli studenti si interessasse ed appassionasse alla conoscenza scientifica, ed i metodi didattici rispecchiavano questo approccio. Non possiamo più permettercelo. Mi sono quindi orientata alla creazione di strumenti innovativi che potessero essere effettivamente utilizzati dai miei colleghi, ma che potessero avere spazio anche fuori da contesti formali come la classe. Lo sviluppo della mia tesi rispecchia il percorso che ho seguito nei tre anni di dottorato, dalla comunicazione della scienza in generale agli strumenti da me progettati. Nel primo capitolo definisco sinteticamente l’evoluzione del concetto e significato di science communication, dal modello di deficit alla partecipazione informata del pubblico alle scelte di politica della scienza. La situazione attuale evidenzia molte ambivalenze: il pubblico valuta gli scienziati, non legati al mondo degli affari, come tra le persone di cui maggiormente ci si può fidare, per poi, invece, ritirare la fiducia in certi ambiti, quali la discussione sugli OGM. Per quanto la scienza sia reputata importante per la qualità della vita, le energie dedicate ad informarsi sono poche e le conoscenze risalgono spesso agli studi scolastici. Fanno eccezione i gruppi di interesse, che, motivati da una condizione particolare (la malattia propria o di un familiare, la preoccupazione per un impianto industriale, la vicinanza ad un possibile sito di discarica), acquisiscono per vie informali approfondite conoscenze in ambiti ristretti e si pongono come interlocutori degli scienziati. Per questo aspetto, l’avvento del web e la possibilità di avere informazioni gratuite praticamente su qualsiasi tema hanno modificato l’approccio alla scienza da parte di chi ne sia interessato. Anche le scelte politiche in merito alla comunicazione della scienza e le posizioni degli scienziati sono schizofreniche: per quanto venga politicamente riconosciuto che la comunicazione con il pubblico faccia parte dei doveri di uno scienziato, questa attività non viene incentivata dal punto di vista economico e non influisce nella progressione di carriera. Gli scienziati, poi, sono in netta maggioranza convinti dell’importanza del loro public engagement, ma lo sentono spesso come un furto di tempo ed energie al loro vero lavoro, la ricerca. Nel secondo capitolo presento una teoria dell’apprendimento, il costruttivismo, che è al momento quella che viene maggiormente applicata, con forti segnali di efficacia, nel superare le difficoltà ed i problemi posti dalla didattica tradizionale, quella delle lezioni frontali per capirci. Secondo il costruttivismo, il discente non è un recipiente vuoto che possiamo riempire con la conoscenza che proponiamo, ma possiede già una serie di rappresentazioni della realtà che ha maturato nel corso della vita ed in funzione delle sue esperienze. Possiamo quindi sperare di “insegnare” qualcosa solo se possiamo dimostrare che la nuova conoscenza che proponiamo è un modello della realtà più efficace in termini di rappresentazione e previsione di quella già formata. Inoltre, un vero cambiamento concettuale è possibile solo attraverso il diretto coinvolgimento del discente nella costruzione delle propria conoscenza, nel guidare il proprio apprendimento. La conoscenza viene quindi costruita personalmente dallo studente, se questo è convinto della significatività del nuovo apprendimento e se l’insegnante riesce a creare il giusto ambiente, dove il discente potrà costruire il proprio percorso cognitivo: il ruolo del docente cambia, si sposta dietro le quinte e, invece di fornire risposte, pone domande, le domande adatte a stimolare la curiosità ed a indicare la direzione lungo la quale proseguire la ricerca. Il terzo capitolo presenta una serie di esempi di didattica costruttivista delle scienze: dalla biologia, con l’impronta genetica, alle scienze della Terra con i terremoti, all’astrofisica con il Sistema Solare. Tutte le attività sono contraddistinte dal fatto di rendere lo studente regista del proprio apprendimento: i percorsi forniscono suggerimenti, pongono domande, ed è compito degli studenti, che lavorano in piccoli gruppi, trovare risposte che possano essere inquadrate in una cornice unitaria del fenomeno. Alcune proposte tengono conto dei vincoli che regolano l’andamento di una scuola reale: lezioni scandite ad orari fissi, risorse limitate, aule che non permettono l’interazione tra studenti e tra questi e il docente. Avvicinandomi alla scelta degli strumenti su cui avrei lavorato, ho deciso di sfruttare il fascino che l’astrofisica ha sul pubblico non esperto (ma anche esperto!): galassie, supernovae, universo, ammassi stellari, satelliti sono cool, soprattutto se supportati da una serie di bellissime immagini. Sotto questo aspetto l’astronomia è imbattibile. Una cernita dei materiali già disponibili mi ha portato a scegliere come tema per un primo strumento l’evoluzione stellare: infatti il Sistema Solare è per ora l’indiscusso protagonista del materiale didattico astronomico già disponibile ed ho ritenuto che spostare l’interesse verso le stelle ed il loro ciclo vitale potesse offrire nuovi spunti. Proporre una serie di lezioni, però, non avrebbe fatto altro che ripetere gli errori che stiamo commettendo in classe: abbiamo bisogno di rendere i nostri alunni protagonisti della costruzione della loro stessa conoscenza, coinvolgendoli il più attivamente possibile nel processo. Ed abbiamo bisogno di superare quella prima resistenza che quasi tutti, arrivati alle superiori, hanno ormai sviluppato verso le materie scientifiche. Nel quarto capitolo descrivo il primo strumento che ho progettato e che si trova, in forma stampata nella appendice n.1. Mi serviva un aggancio con la realtà quotidiana degli studenti, un qualcosa che fosse per loro familiare, ma che potesse diventare anche uno strumento per “fare scienza”, ed ho scelto la macchina fotografica digitale. Ho quindi costruito un percorso didattico, sotto forma di manuale di fotografia astronomica for dummies, che unisce attività pratiche, analisi di dati con software disponibile liberamente in rete e modelli fisici. Il punto di arrivo è la costruzione di un diagramma HR con dati raccolti dall’utente stesso, ma non è questo il tratto importante del manuale: conta soprattutto il percorso per arrivarci. Partendo dai fondamenti della fotografia, dei CCD che popolano le digitali, il manuale offre spunti su contenuti della fisica molto vari: dalle basi dell’ottica ai telescopi dell’ultima generazione dell’ESO ed ai satelliti per rilevare i fotoni altamente energetici, dal colore delle stelle alla spettroscopia delle regioni HII, passando per le stelle supermassicce e l’evoluzione stellare, chiamando in gioco sia temi che fanno parte del curricolo scolastico, che risultati delle ultime ricerche pubblicate. Il manuale, comunque, non va letto, ma piuttosto fatto: determinante è la scelta di partire dalle osservazioni e dalle foto fatte dall’utente per “scoprire” un fenomeno e solo dopo cercarne il modello che lo spiega. Un esempio: ad occhio nudo le stelle hanno colori diversi: perché? E come quantificare questa diversità? Una serie di foto di due stelle come Arcturus e Spica con la digitale attraverso tre filtri RGB (di plastica trasparente colorata) sono analizzate con un software per valutarne la luminosità nelle tre bande: perché Spica è più luminosa nel blu e meno nel rosso di Arcturus? Si tratta di un modo alternativo per presentare la radiazione di corpo nero. Questa strategia, che vede lo studente protagonista del proprio processo di apprendimento, attivamente coinvolto nelle attività, cognitivamente sfidato a trovare un modello esplicativo per un fenomeno da lui stesso osservato e che non trova soluzione nelle conoscenze già possedute, segue i dettami della didattica costruttivista. Ho formulato due proposte di percorsi didattici a partire dal temi affrontati nel manuale. Il manuale può essere utilizzato sia in un contesto formale, dove l’insegnante guida gli studenti attraverso i molteplici contenuti e li esorta ad approfondire alcuni temi, oppure dal singolo utente, motivato dalla curiosità e dalla voglia di capire. I materiali richiesti sono per scelta poco costosi ed i software suggeriti gratuiti in rete; la scrittura è volutamente informale e cerca di alleggerire contenuti a volte corposi senza perdere la correttezza scientifica. Mentre sviluppavo il manuale, ho lavorato alla creazione di un altro strumento, un gioco da tavolo, cui è dedicato il quinto capitolo. Una breve carrellata delle possibili definizioni di gioco precede un esame dello stato dell’arte dell’utilizzo dei giochi nella didattica della scienza. Sempre nell’ottica costruttivista, ho predisposto un gioco che stimolasse la curiosità ed il desiderio di “saperne di più” nel giocatore, che può essere chiunque dai dieci/dodici anni in poi. Considerazioni di carattere economico mi hanno fatto escludere un gioco a computer; la grafica ha infatti dei costi improponibili all’interno di una ricerca di dottorato. In ogni caso, sia sotto forma di videogiochi che simulazioni che giochi da tavolo, sono stati ancora realizzati ben pochi giochi per la didattica della fisica Con la collaborazione di uno studente al corso di laurea triennale di fisica presso la facoltà di Scienze di Trento, Matteo Conci, ho quindi progettato e realizzato un gioco da tavolo che simula la progettazione e realizzazione di una missione con equipaggio su Marte. Il tabellone di gioco è composto di due parti: una prima orbita interna di caselle che offrono varie opzioni per la composizione della missione, come lo scudo di protezione per le tempeste solari, il modulo in rotazione per simulare la gravità, diverse tipologie di motore e molto altro. La scelta è vincolata dai costi e dalla massa, come anche dagli imprevisti che possono accadere nel corso dell’orbita esterna, che rappresenta il viaggio vero e proprio: una micro meteorite, un incidente ad un membro dell’equipaggio, un guasto dell’impianto di riciclo possono essere superati solo se nella preparazione della missione si sono acquistate le opzioni necessarie. Una partita dura circa un’ora e per vincere è necessario realizzare per primi due esperimenti tra quelli che si hanno disponibili; il lancio dei dadi decide quali caselle vengono raggiunte. Manuale, regolamento e tabellone del gioco sono raccolti nella seconda appendice. Oltre al puro divertimento, il gioco, all’interno di una classe, stimola il desiderio di approfondire le questioni poste: che cos’è una tempesta solare e perché serve uno scudo? Perché le condizioni di microgravità protratte sono dannose alla salute? Come funziona un motore solare-elettrico? Le domande che possono nascere sono tantissime e dettate dall’interesse del giocatore, quindi significative per lui stesso; l’insegnante può allora sfruttare questa situazione e guidare gli studenti nella ricerca delle risposte alle domande che loro stessi si pongono, secondo una didattica costruttivista. Gli studi di NASA ed ESA per una missione su Marte hanno fornito la struttura della missione e i dati utilizzati. Il gioco è stato presentato all’European Science Open Forum (ESOF2010) che si è tenuto a Torino dal 2 al 7 luglio 2010; in questo contesto è stato possibile testarlo con varie tipologie di giocatori ed raccogliere informazioni per migliorarne la fruibilità. Nel sesto capitolo raccolgo le mie conclusioni, frutto anche del mio rientro in servizio come docente di scuola secondaria superiore; sono conclusioni in parte amare, che analizzano gli ostacoli che si trovano sul percorso di un rinnovamento della scuola italiana.

Cu2ZnSnS4 (CZTS) quaternary compound has attracted much attention in the last years as new abundant, low cost and non-toxic material, with desirable properties for thin film photovoltaic (PV) applications. In this work, CZTS thin films were grown using two different processes, based on vacuum deposition of precursors, followed by a heat treatment in sulphur atmosphere. The precursors were deposited using two different approaches: (i) electron-beam evaporation of multiple stacks made of ZnS, Sn and Cu and (ii) co-sputtering deposition of the three binary sulphides CuS, SnS and ZnS. All the materials were characterized both as isolated films and as absorber layer in solar cells, produced using the typical structure Mo/CZTS/CdS/i:Zno/AZO. Both growth processes were found to give good quality kesterite films, showing CZTS as the main phase, large grains and suitable properties for PV application, but higher homogeneity and stoichiometry control were achieved using the co-sputtering route. A detailed investigation on CZTS optical properties, microstructure, intrinsic defect density and their correlation with the material composition is presented. A strong effect of the tin content on the bandgap energy, sub-gap absorption coefficient, crystalline domain and grain size is shown and a model based on the increase of the intrinsic defect density induced by a reduced tin content is proposed. These studies suggested a correlation between the increase of the bandgap energy and the improvement of the material quality, which was also confirmed by the performances of the final devices. CZTS thin films were then assembled into the solar cells and their properties as absorber layer were optimized by varying both composition and thickness. CZTS samples produced from stacked evaporated precursors allowed achieving a maximum efficiency of 3.2%, but reproducibility limits of the evaporation process made difficult to obtain further and rapid efficiency improvements. The co-sputtering route was demonstrated to be a more successful strategy, assuring a fine-control of the film composition with good process reproducibility. A fast improvement of solar cell efficiency was obtained using this approach and a maximum efficiency of 5.7% was achieved. The relationship between the absorber layer stoichiometry and the device performances was investigated: the effect of the Zn enrichment and a possible influence of the Cu/Sn ratio on the device performances are discussed. Investigation on CZTS/CdS and CZTS/MoS2 interfaces revealed that the optimization of both buffer-layer and back-contact technology is a primary need for further improvement of CZTS solar cells.

The first and foremost goal of the present work was to develop novel theoretical and computational methods and use state-of-the-art techniques in electronic structure theory to interpret a specific set of physical problems mainly related, but not limited to, materials science. Our guiding principle was to relate information obtained from scattering experiments with the numerical solution of the multichannel dynamics of many-body systems, shedding light on the origin of electronic and optical properties of a variety of systems. The general approach adopted in this thesis was not to present separate chapters for theory, rather we introduced methods along with the experiments. In particular, we focused on the modeling of both ground and excited states of materials, on vibrational, core and valence electron spectroscopy of condensed matter systems using computational methods at different level of accuracy and complexity to interpret a number of experimental data. While these methods have been devised for this scope, their applicability, notably the treatment of the continuum states through multichannel scattering formalism, is totally general and can be applied to describe several different experiments, performed with a variety of apparently distant techniques. In particular, the Fano--Fesbach discrete-continuum interaction provides a common framework suitable to this task. Within this scheme, thus, the calculation of the spectral lineshapes measured by XPS, Auger, NEXAFS, and EEL spectroscopy can be reconciled on the same theoretical grounds with the investigation of the properties of ultra-cold Fermi gases at unitarity, or of the electronic capture and decay rate in ultra-hot plasma found in stellar environments or, finally, with the study of the epitaxial growth of nanostructured materials. Crossing the borders between several computational, theoretical and experimental techniques, this thesis should be of interest to a broad community, including those interested in aspects of atomic and molecular physics, electronic structure calculations, experimental and theoretical spectroscopy, astrophysics and scattering theorists in a broad sense.

Photovoltaic technology in the field of renewable energy has reached a high commercial interest over the past decade. The traditional silicon photovoltaic systems that is currently the most widespread, mainly due to government subsidies, have a low energy production. The wide use of material and the low efficiency of the silicon modules required the research and development of photovoltaic systems more efficient. The most promising technology is the photovoltaic concentration that increases the efficiency of the modules by reducing the area of the PV cell. The concentration photovoltaic has had considerable technological progress related to the development of multi-junction PV cells with high efficiency. Another approach is the technology of photovoltaic concentration with the spectral separation, so using the interference filters the solar spectrum is splitted into different optical bands. In this research was designed and built a CPV prototype system with spectral separation. The interference filters such as anti-reflection and dichroic mirror are made up of silicon dioxide and titanium dioxide. These oxides have been realized by means of physical vapor deposition reactive magnetron sputtering technique. The PVD technique allows to deposit thin films with a homogeneous process reproducible and reliable. In the first part of the work, the characterization of individual layers of oxide materials have allowed to extrapolate the optical constants. This is necessary for the design of the optical multilayer. The characterization has nvolved various analyzes such as atomic force microscopy (AFM) to determine the thickness and the roughness, compositional analysis Rutherforf backscattering spectrometry (RBS), and optical analysis UV-Vis-NIR. These analyzes were necesary to calibrate the deposition system in order to subsequently to realize the multilayer optics. The as deposited optical multilayers not confirm the optical design, and it was necessary to carry out an annealing at 350°C. In the second part of the work, there were also micro structural characterizations for evaluating the phase variation of the titanium dioxide with the annealing treatment. The Fourier transform infrared (FT-IR) analysis has checked the absorption peak of the Ti-O-Ti of the crystalline phase. In addition, X-ray diffraction (XRD) analysis verified the phase variation of titanium dioxide from purely amorphous phase with a slight presence of rutile to the anatase phase. Through the optical analysis it was possible to extrapolate the new optical constants corresponding to the phase of anatase. In the third part of the work, the ray tracing design of optical splitting of the CPV prototype was carry out. The CPV system is designed by coupling a concentration Fresnel a dichroic mirror. The focus of the radiation on the PV cell, is simulated by two ideal detector. The optical optimization as function of the f-number of the lens has allowed to define the layout for the prototyping phase. A further optimization is to insert a secondary optics element (SOE) of homogenization. The secondary optics will also limits the optical losses due to a misalignment of the CPV prototype. In the last part of this thesis is devoted to the preparation and the characterization of the CPV prototype. Were performed measures of solar radiation, which combined with the characteristic I-V-P curves of the solar cells have enable to evaluate the efficiency of the prototype system. The efficiency of the spectral separation system was compared with concentration multi-junction PV cells. Daily measurement were performed to compare the spectral separation technology than to the multi-junction technology. The results show that the separation system maintains a more constant performance during the day. Finally, thermal measurements were conducted on the component of the CPV prototype separation system. The experimental results allows to guarantee that the spectral separation is also a selective filter of temperature. This allows the solar cells to maximize the photovoltaic conversion and to reduce the overheating.

In this thesis work nanoscrystalline optical properties of diamond and two recent new NCD functionalisation techniques involving UV light (one step method and photochemical oxidation) have been investigated. Firstly the oxidation of diamond surface caused by the irradiation of the surface with UV-light in oxygen atmosphere was considered. Two different experiments in situ were realized in order to understand the physic-chemistry of this method. The chemical bonds between oxygen and surface carbon atoms were investigated by firstly performing an annealing treatment in ultra hight vacuum of a oxidized UV surface and then comparing the obtained result with annealing treatments of two different oxygenated diamond surfaces using other two techniques: plasma oxidation and piranha solution oxidation. An other interesting aspect on which clarity has to be made deal with amination process of diamond surface. As a first fundamental step, the efficiency on hydrogenated diamond surface was investigate. Successively the role of oxygen in the chemistry of amination process was studied performing in situ experiments using different terminated diamond surface (hydrogenated, chemically oxidized, UV oxidized) and different gaese (pure NH3 or NH3 + O2).

In this thesis I present two different research topics investigated during the course of my PhD, regarding the analysis of spatial structures in a Bose Einstein condensate. Ultracold atomic gases offer a privileged platform for such kind of experiments, thanks to the fine control that can be achieved on the system’s parameters and to the availability of advanced imaging schemes allowing for a great measurement accuracy. The first topic is about the shape of quantized vortices in an elongated condensate, with the goal of providing a quantitative analysis of the density structure of a quantized vortex filament hosted in a bulk 3D superfluid. We analyzed the shape of the vortex and studied its dynamics during a free expansion, or time of flight (TOF), of the hosting BEC, with the goal of making a quantitative comparison between theory and experiment for the structure of the core of a quantized vortex in three-dimensional (3D) condensates. Simultaneously imaging the sample along orthogonal directions after a long TOF allowed to map the complete 3D shape of the vortex at the end of the free flight, while the full expansion dynamics has been simulated with numerical solutions of the Gross-Pitaevskii equation. The same data analysis procedure has been applied to both the experimental images and to the density profiles computed with the simulations to ensure a faithful comparison. We were able to detail the evolution of the vortex parameters at all times combining a simple analytic scaling-law model valid at early times, experimental data for the width and the depth of the core at long expansion times, and the numerics that were used to bridge between the two. Additionally, we could check the validity of the predictions on the scaling of vortex parameters with the size of the BEC using the experimental data to interpolate between theoretical limiting models. We concluded that quantized vortex filaments can be optically imaged with standard techniques in 3D atomic BECs, at a level of accuracy which indeed is enough to show good quantitative agreement with the predictions of the GP theory for the width, depth, and overall shape of the vortex core. The second topic is a measurement of the equation of state of a single component BEC. The goal of this project is to verify the non-monotonic behaviour of the chemical potential of a homogeneous Bose gas of weakly interacting particles as a function of temperature, where one expects to find a maximum across the critical point of transition to the superfluid phase. This effect is believed to be a general feature of the normal-to-superfluid phase transition: it has been already experimentally demonstrated in unitary Fermi gases, and although the same is predicted to happen also in a gas of weakly interacting bosons, no experimental evidence has been reported so far. The measurement relies on the local density approximation, which allows to extract information about the thermodynamics of a homogeneous system from accurate measurements of the local properties of a trapped one. My work has focused on developing a series of imaging and data analysis techniques to measure the 3D density profile of a harmonically trapped gas, even in regimes of extreme density such as inside a Bose condensate. With a new high-dynamic-range method we were able to image the 3D density distribution of a trapped sample, leading to a low-noise measurement of the density distribution. We confirmed the existence of the non-monotonic behaviour of the chemicial potential across, and set the basis for further measurements of the thermodynamics of the system across the transition.In this thesis I present two different research topics investigated during the course of my PhD, regarding the analysis of spatial structures in a Bose Einstein condensate. Ultracold atomic gases offer a privileged platform for such kind of experiments, thanks to the fine control that can be achieved on the system’s parameters and to the availability of advanced imaging schemes allowing for a great measurement accuracy. The first topic is about the shape of quantized vortices in an elongated condensate, with the goal of providing a quantitative analysis of the density structure of a quantized vortex filament hosted in a bulk 3D superfluid. We analyzed the shape of the vortex and studied its dynamics during a free expansion, or time of flight (TOF), of the hosting BEC, with the goal of making a quantitative comparison between theory and experiment for the structure of the core of a quantized vortex in three-dimensional (3D) condensates. Simultaneously imaging the sample along orthogonal directions after a long TOF allowed to map the complete 3D shape of the vortex at the end of the free flight, while the full expansion dynamics has been simulated with numerical solutions of the Gross-Pitaevskii equation. The same data analysis procedure has been applied to both the experimental images and to the density profiles computed with the simulations to ensure a faithful comparison. We were able to detail the evolution of the vortex parameters at all times combining a simple analytic scaling-law model valid at early times, experimental data for the width and the depth of the core at long expansion times, and the numerics that were used to bridge between the two. Additionally, we could check the validity of the predictions on the scaling of vortex parameters with the size of the BEC using the experimental data to interpolate between theoretical limiting models. We concluded that quantized vortex filaments can be optically imaged with standard techniques in 3D atomic BECs, at a level of accuracy which indeed is enough to show good quantitative agreement with the predictions of the GP theory for the width, depth, and overall shape of the vortex core. The second topic is a measurement of the equation of state of a single component BEC. The goal of this project is to verify the non-monotonic behaviour of the chemical potential of a homogeneous Bose gas of weakly interacting particles as a function of temperature, where one expects to find a maximum across the critical point of transition to the superfluid phase. This effect is believed to be a general feature of the normal-to-superfluid phase transition: it has been already experimentally demonstrated in unitary Fermi gases, and although the same is predicted to happen also in a gas of weakly interacting bosons, no experimental evidence has been reported so far. The measurement relies on the local density approximation, which allows to extract information about the thermodynamics of a homogeneous system from accurate measurements of the local properties of a trapped one. My work has focused on developing a series of imaging and data analysis techniques to measure the 3D density profile of a harmonically trapped gas, even in regimes of extreme density such as inside a Bose condensate. With a new high-dynamic-range method we were able to image the 3D density distribution of a trapped sample, leading to a low-noise measurement of the density distribution. We confirmed the existence of the non-monotonic behaviour of the chemicial potential across, and set the basis for further measurements of the thermodynamics of the system across the transition.

The present work is conducted in the field of few-body methods and it concerns the extension of the Non-Symmetrized Hyperspherical Harmonics method in order to treat quantum systems with different species of particles and additional degrees of freedom, like particle mixing. The aim is to introduce it as a new tool in the ab-initio study of light hypernuclei, and, more in general, of few-body quantum systems composed by a variety of different objects. To this end precise benchmark results for light hypernuclei with A=3-5 are provided and the perspectives of applications to systems with A>5 and the employment of the most recent hypernuclear interactions are discussed.