Artificial Intelligence Algorithm Enabled Industrial-Scale Graphene Characterization

No characterization method is available to quickly perform quality inspection of 2D materials produced on an industrial scale. This hinders the adoption of 2D materials for product manufacturing in many industries. Here, we report an artificial-intelligence-assisted Raman analysis to quickly probe the quality of centimeter-large graphene samples in a non-destructive manner. Chemical vapor deposition of graphene is devised in this work such that two types of samples were obtained: layer-plus-islands and layer-by-layer graphene films, at centimeter scales. Using these samples, we implemented and integrated an unsupervised learning algorithm with an automated Raman spectroscopy to precisely cluster 20,250 and 18,000 Raman spectra collected from layer-plus-islands and layer-by-layer graphene films, respectively, into five and two clusters. Each cluster represents graphene patches with different layer numbers and stacking orders. For instance, the two clusters detected in layer-by-layer graphene films represent monolayer and bilayer graphene based on their Raman fingerprints. Our intelligent Raman analysis is fully automated, with no human operation involved, is highly reliable (99.95% accuracy), and can be generalized to other 2D materials, paving the way towards industrialization of 2D materials for various applications in the future

Microrivelatori di neutroni in diamante monocristallino CVD

Lo sviluppo della tecnologia nei più diversi settori applicativi ha portato all’introduzione dei microsistemi in nuovi campi d’impiego, caratterizzati da condizioni di funzionamento ostili, nei quali le tecnologie tradizionali basate sul silicio si mostrano decisamente inadeguate. In particolare, per le applicazioni di diagnostica neutronica “in core” e “out of core” nei moderni reattori a fissione e a fusione nucleare sono necessarie qualità di resistenza alla radiazione, stabilità e riproducibilità della risposta difficilmente ottenibili con i sensori convenzionali disponibili attualmente in commercio ed è per questo che la ricerca, a livello mondiale, si è indirizzata verso il diamante, il materiale più adatto, grazie alle sue eccellenti proprietà chimico-fisiche ed elettroniche, alla realizzazione di rivelatori operanti con alte prestazioni anche in condizioni operative critiche (in presenza di alti flussi di radiazione particellare e fotonica, alte temperature, stress meccanici e termici, agenti corrosivi, etc.). Questo lavoro di tesi è dedicato alla realizzazione e allo studio di microrivelatori di neutroni termici e veloci in diamante monocristallino CVD a partire dalla sintesi del materiale e dalla caratterizzazione di base dei dispositivi prodotti, presso i laboratori del Dipartimento di Ingegneria Meccanica dell’Università degli studi di Roma “Tor Vergata” e il generatore di neutroni FNG, fino all’installazione e al test dei detectors in grandi facilities sperimentali, quali i reattori a fissione e fusione nucleare TRIGE e JET, rispettivamente. Le proprietà fisiche dei film sintetizzati di diamante a singolo cristallo (SCD), sia intrinseci che drogati con boro, sono state approfonditamente indagate attraverso tecniche di caratterizzazione diffrattometriche, spettroscopiche, morfologiche ed elettriche. I difetti presenti nel diamante intrinseco e, in particolare, le trappole poco profonde (“shallow traps”) sono stati studiati analizzando i fenomeni di trapping-detrapping dei portatori di carica sotto irraggiamento UV, nel quadro di un modello teorico sviluppato per l’interpretazione dei dati sperimentali, individuandone così l’energia di attivazione. La combinazione di film di diamante monocristallino drogati con boro (SCD-p) e intrinseci (SCD-i), unitamente alla possibilità di realizzare giunzioni Schottky sul diamante intrinseco con banali contatti circolari di Al, ha consentito, ricorrendo a semplici strutture multilayer M/SCD-i/SCD-p, di ottenere con altissimi livelli di riproducibilità dispositivi di eccellente qualità utilizzabili efficacemente sia in ambito puramente elettrico (come diodi Schottky rettificanti) che rivelatoristico, come detectors di fotoni (UV, VUV, raggi X, gamma), particelle cariche e neutroni. La caratterizzazione di tali dispositivi, accanto alla loro realizzazione seriale, ha costituito parte integrante di questo lavoro di tesi ed è stata condotta approfonditamente al fine di indagare le proprietà sia elettriche che spettroscopiche dei rivelatori prodotti. La caratterizzazione spettroscopica è stata svolta attraverso irraggiamento con particelle α da 5.5 MeV prodotte da una sorgente 241Am e si è rivelata uno strumento fondamentale per analizzare la riproducibilità, la stabilità, l’efficienza e il potere risolutivo dei rivelatori anche, e soprattutto, per la rivelazione di particelle di più alta energia e, in particolare, di neutroni termici e veloci. Le applicazioni rivelatoristiche nell’ambito della diagnostica di neutroni termici e veloci hanno confermato l’eccellente qualità a livello mondiale dei dispositivi realizzati. Accanto agli ottimi risultati ottenuti in fase di caratterizzazione preliminare presso il generatore di neutroni FNG e in sede di test presso il reattore a fissione nucleare TRIGA, questo livello di eccellenza è stato dimostrato in campo internazionale dall’installazione di alcuni detectors presso il JET, con prestazioni del tutto comparabili, se non superiori, a quelle della diagnostica ufficiale.The increasing development of technology in various sectors has led to the introduction of microsystems in new fields, for use in harsh operating conditions, where traditional technologies based on silicon show definitely inadequate. In particular, the applications of “in core” and “out of core” neutron diagnostics in modern fission and fusion nuclear reactors need qualities of radiation hardness, stability and response reproducibility hardly obtainable with currently available conventional sensors. For this reason worldwide research is directed toward diamond, which is, due to its excellent physical-chemical end electric properties, the most suitable material to the realization of detectors operating with high performance even in critical operating conditions (in presence of high fluxes of particle and photon radiation, high temperature, mechanical and thermal stress, corrosion, etc.). This thesis is dedicated to the realization and study of micro-detectors of thermal and fast neutrons based on single crystal CVD diamond (SCD), from the synthesis of the material and the basic characterization of the produced detectors at the laboratories of the Department of Mechanical Engineering of the University of Rome “Tor Vergata” and the Frascati neutron Generator (FNG), to their installation and test in large experimental facilities, such as the fission and fusion reactors TRIGA and JET, respectively. The physical properties of the synthesized single crystal diamond films, both intrinsic and boron doped, have been thoroughly investigated by means of diffractometric, spectroscopic, morphological and electrical characterization techniques. Defects in the intrinsic diamond and, in particular, its shallow traps have been studied by analyzing the charge carriers trapping-detrapping phenomena under UV irradiation, in the framework of a theoretical model developed for the interpretation of the experimental data, thus identifying their activation energy. The combination of boron doped (SCD-p) and intrinsic (SCD-i) single crystal diamond films, together with the possibility to easily build Schottky junctions on intrinsic diamond by thermal evaporation of aluminium contacts, made it possible, by using simple multilayer M/SCD-i/SCD-p structures, to obtain high quality and highly reproducible devices which can be effectively used both for electronics (rectifying Schottky diodes) and for detection of photons (UV, VUV, X- and gamma- rays), charged particles, neutrons. The characterization of these devices, besides their mere realization, has been an integral part of this thesis and has been carried out thoroughly in order to investigate both electrical and spectroscopic properties of produced detectors. The spectroscopic characterization has been carried out by irradiation with 5.5 MeV alpha particles emitted by a 241Am source and has provided an essential tool to investigate detectors reproducibility, stability, charge collection efficiency and energy resolution also, and above all, for detection of particles of higher energy and of neutrons. Radiation detection applications in the diagnostic of thermal and fast neutrons have confirmed the excellent worldwide quality of the devices. Besides the excellent results obtained during preliminary characterization at the Frascati neutron Generator (FNG) and during the test at nuclear fission reactor TRIGA, this level of excellence has been demonstrated in the international field by the installation of some detectors at JET, whose performances are fully comparable, or superior, to those of the official diagnostic

Microrivelatori di neutroni in diamante monocristallino CVD

Lo sviluppo della tecnologia nei più diversi settori applicativi ha portato all’introduzione dei microsistemi in nuovi campi d’impiego, caratterizzati da condizioni di funzionamento ostili, nei quali le tecnologie tradizionali basate sul silicio si mostrano decisamente inadeguate. In particolare, per le applicazioni di diagnostica neutronica “in core” e “out of core” nei moderni reattori a fissione e a fusione nucleare sono necessarie qualità di resistenza alla radiazione, stabilità e riproducibilità della risposta difficilmente ottenibili con i sensori convenzionali disponibili attualmente in commercio ed è per questo che la ricerca, a livello mondiale, si è indirizzata verso il diamante, il materiale più adatto, grazie alle sue eccellenti proprietà chimico-fisiche ed elettroniche, alla realizzazione di rivelatori operanti con alte prestazioni anche in condizioni operative critiche (in presenza di alti flussi di radiazione particellare e fotonica, alte temperature, stress meccanici e termici, agenti corrosivi, etc.). Questo lavoro di tesi è dedicato alla realizzazione e allo studio di microrivelatori di neutroni termici e veloci in diamante monocristallino CVD a partire dalla sintesi del materiale e dalla caratterizzazione di base dei dispositivi prodotti, presso i laboratori del Dipartimento di Ingegneria Meccanica dell’Università degli studi di Roma “Tor Vergata” e il generatore di neutroni FNG, fino all’installazione e al test dei detectors in grandi facilities sperimentali, quali i reattori a fissione e fusione nucleare TRIGE e JET, rispettivamente. Le proprietà fisiche dei film sintetizzati di diamante a singolo cristallo (SCD), sia intrinseci che drogati con boro, sono state approfonditamente indagate attraverso tecniche di caratterizzazione diffrattometriche, spettroscopiche, morfologiche ed elettriche. I difetti presenti nel diamante intrinseco e, in particolare, le trappole poco profonde (“shallow traps”) sono stati studiati analizzando i fenomeni di trapping-detrapping dei portatori di carica sotto irraggiamento UV, nel quadro di un modello teorico sviluppato per l’interpretazione dei dati sperimentali, individuandone così l’energia di attivazione. La combinazione di film di diamante monocristallino drogati con boro (SCD-p) e intrinseci (SCD-i), unitamente alla possibilità di realizzare giunzioni Schottky sul diamante intrinseco con banali contatti circolari di Al, ha consentito, ricorrendo a semplici strutture multilayer M/SCD-i/SCD-p, di ottenere con altissimi livelli di riproducibilità dispositivi di eccellente qualità utilizzabili efficacemente sia in ambito puramente elettrico (come diodi Schottky rettificanti) che rivelatoristico, come detectors di fotoni (UV, VUV, raggi X, gamma), particelle cariche e neutroni. La caratterizzazione di tali dispositivi, accanto alla loro realizzazione seriale, ha costituito parte integrante di questo lavoro di tesi ed è stata condotta approfonditamente al fine di indagare le proprietà sia elettriche che spettroscopiche dei rivelatori prodotti. La caratterizzazione spettroscopica è stata svolta attraverso irraggiamento con particelle α da 5.5 MeV prodotte da una sorgente 241Am e si è rivelata uno strumento fondamentale per analizzare la riproducibilità, la stabilità, l’efficienza e il potere risolutivo dei rivelatori anche, e soprattutto, per la rivelazione di particelle di più alta energia e, in particolare, di neutroni termici e veloci. Le applicazioni rivelatoristiche nell’ambito della diagnostica di neutroni termici e veloci hanno confermato l’eccellente qualità a livello mondiale dei dispositivi realizzati. Accanto agli ottimi risultati ottenuti in fase di caratterizzazione preliminare presso il generatore di neutroni FNG e in sede di test presso il reattore a fissione nucleare TRIGA, questo livello di eccellenza è stato dimostrato in campo internazionale dall’installazione di alcuni detectors presso il JET, con prestazioni del tutto comparabili, se non superiori, a quelle della diagnostica ufficiale.The increasing development of technology in various sectors has led to the introduction of microsystems in new fields, for use in harsh operating conditions, where traditional technologies based on silicon show definitely inadequate. In particular, the applications of “in core” and “out of core” neutron diagnostics in modern fission and fusion nuclear reactors need qualities of radiation hardness, stability and response reproducibility hardly obtainable with currently available conventional sensors. For this reason worldwide research is directed toward diamond, which is, due to its excellent physical-chemical end electric properties, the most suitable material to the realization of detectors operating with high performance even in critical operating conditions (in presence of high fluxes of particle and photon radiation, high temperature, mechanical and thermal stress, corrosion, etc.). This thesis is dedicated to the realization and study of micro-detectors of thermal and fast neutrons based on single crystal CVD diamond (SCD), from the synthesis of the material and the basic characterization of the produced detectors at the laboratories of the Department of Mechanical Engineering of the University of Rome “Tor Vergata” and the Frascati neutron Generator (FNG), to their installation and test in large experimental facilities, such as the fission and fusion reactors TRIGA and JET, respectively. The physical properties of the synthesized single crystal diamond films, both intrinsic and boron doped, have been thoroughly investigated by means of diffractometric, spectroscopic, morphological and electrical characterization techniques. Defects in the intrinsic diamond and, in particular, its shallow traps have been studied by analyzing the charge carriers trapping-detrapping phenomena under UV irradiation, in the framework of a theoretical model developed for the interpretation of the experimental data, thus identifying their activation energy. The combination of boron doped (SCD-p) and intrinsic (SCD-i) single crystal diamond films, together with the possibility to easily build Schottky junctions on intrinsic diamond by thermal evaporation of aluminium contacts, made it possible, by using simple multilayer M/SCD-i/SCD-p structures, to obtain high quality and highly reproducible devices which can be effectively used both for electronics (rectifying Schottky diodes) and for detection of photons (UV, VUV, X- and gamma- rays), charged particles, neutrons. The characterization of these devices, besides their mere realization, has been an integral part of this thesis and has been carried out thoroughly in order to investigate both electrical and spectroscopic properties of produced detectors. The spectroscopic characterization has been carried out by irradiation with 5.5 MeV alpha particles emitted by a 241Am source and has provided an essential tool to investigate detectors reproducibility, stability, charge collection efficiency and energy resolution also, and above all, for detection of particles of higher energy and of neutrons. Radiation detection applications in the diagnostic of thermal and fast neutrons have confirmed the excellent worldwide quality of the devices. Besides the excellent results obtained during preliminary characterization at the Frascati neutron Generator (FNG) and during the test at nuclear fission reactor TRIGA, this level of excellence has been demonstrated in the international field by the installation of some detectors at JET, whose performances are fully comparable, or superior, to those of the official diagnostic

On the Interaction between 1D Materials and Living Cells

One-dimensional (1D) materials allow for cutting-edge applications in biology, such as single-cell bioelectronics investigations, stimulation of the cellular membrane or the cytosol, cellular capture, tissue regeneration, antibacterial action, traction force investigation, and cellular lysis among others. The extraordinary development of this research field in the last ten years has been promoted by the possibility to engineer new classes of biointerfaces that integrate 1D materials as tools to trigger reconfigurable stimuli/probes at the sub-cellular resolution, mimicking the in vivo protein fibres organization of the extracellular matrix. After a brief overview of the theoretical models relevant for a quantitative description of the 1D material/cell interface, this work offers an unprecedented review of 1D nano- and microscale materials (inorganic, organic, biomolecular) explored so far in this vibrant research field, highlighting their emerging biological applications. The correlation between each 1D material chemistry and the resulting biological response is investigated, allowing to emphasize the advantages and the issues that each class presents. Finally, current challenges and future perspectives are discussed

Printing ZnO Inks: From Principles to Devices

Solution-based printing approaches permit digital designs to be converted into physical objects by depositing materials in a layer-by-layer additive fashion from microscale to nanoscale resolution. The extraordinary adaptability of this technology to different inks and substrates has received substantial interest in the recent literature. In such a context, this review specifically focuses on the realization of inks for the deposition of ZnO, a well-known wide bandgap semiconductor inorganic material showing an impressive number of applications in electronic, optoelectronic, and piezoelectric devices. Herein, we present an updated review of the latest advancements on the ink formulations and printing techniques for ZnO-based nanocrystalline inks, as well as of the major applications which have been demonstrated. The most relevant ink-processing conditions so far explored will be correlated with the resulting film morphologies, showing the possibility to tune the ZnO ink composition to achieve facile, versatile, and scalable fabrication of devices of different natures

Self-Cleaning Bending Sensors Based on Semitransparent ZnO Nanostructured Films

The design of multifunctional nanostructured materials is the key to the development of smart wearable devices. For instance, nanostructures endowed with both piezoelectric and photocatalytic activities could well be the workhorse for solar-light-driven self-cleaning wearable sensors. In this work, a simple strategy for the assembly of a flexible, semitransparent piezophotocatalytic system is demonstrated by leveraging rational wet chemistry synthesis of ZnO-based nanosheets/nanoflowers (NSs/NFs) under basic pH conditions onto flexible ITO/PET supports. A KMnO4 pretreatment before the ZnO synthesis (seeded ZnO) allows for the control of the density, size, and orientation of the NSs/NFs systems compared to the systems produced in the absence of seeding (seedless ZnO). The electrical response of the sensors is extracted at a 1 V bias as a function of bending in the interval between 0 and 90°, being the responsivity toward bending significantly enhanced by the KMnO4 treatment effect. The photocatalytic activity of the sensors is analyzed in aqueous solution (methylene blue, 25 μM) by a solar simulator, resulting in similar values between seedless and seeded ZnO. Upon bending the sensor, the photocatalytic activity of seedless ZnO is almost unaffected, whereas that of seeded ZnO is improved by about 25%. The sensor’s reusability and repeatability are tested in up to three different cycles. These results open up the way toward the seamless integration of bending sensitivity and photocatalysis into a single device

Neutron Detectors Based Upon Artificial Single Crystal Diamond

This paper reports about state-of-the-art artificial Single Crystal Diamond (SCD) neutron detectors based on a multilayered structure and grown by chemical vapour deposition (CVD) technique. Multilayered SCD detectors covered with a thin layer of 6LiF allow the simultaneous detection of both slow and fast neutrons and can operate in pulse and current mode. These detectors can also be produced with a thin layer of Boron. Application of SCD detectors to neutron detection around fusion tokamak is reported. Some problems related to the processing of the very fast electrical pulse produced by diamond are addressed and the achieved and foreseen development of the processing electronics is reported as well

Correlation analysis for energy losses, waiting times and durations of type I edge-localized modes in the Joint European Torus

Several important ELM control techniques are in large part motivated by the empirically observed inverse relationship between average ELM energy loss and ELM frequency in a plasma. However, to ensure a reliable effect on the energy released by the ELMs, it is important that this relation is verified for individual ELM events. Therefore, in this work the relation between ELM energy loss (W-ELM) and waiting time (Delta t(ELM)) is investigated for individual ELMs in a set of ITER-like wall plasmas in JET. A comparison is made with the results from a set of carbon-wall and nitrogen-seeded ITER-like wall JET plasmas. It is found that the correlation between W-ELM and Delta t(ELM) for individual ELMs varies from strongly positive to zero. Furthermore, the effect of the extended collapse phase often accompanying ELMs from unseeded JET ILW plasmas and referred to as the slow transport event (STE) is studied on the distribution of ELM durations, and on the correlation between W-ELM and Delta t(ELM). A high correlation between W-ELM and Delta t(ELM), comparable to CW plasmas is only found in nitrogen-seeded ILW plasmas. Finally, a regression analysis is performed using plasma engineering parameters as predictors for determining the region of the plasma operational space with a high correlation between W-ELM and Delta t(ELM)

Effect of the relative shift between the electron density and temperature pedestal position on the pedestal stability in JET-ILW and comparison with JET-C

The electron temperature and density pedestals tend to vary in their relative radial positions, as observed in DIII-D (Beurskens et al 2011 Phys. Plasmas 18 056120) and ASDEX Upgrade (Dunne et al 2017 Plasma Phys. Control. Fusion 59 14017). This so-called relative shift has an impact on the pedestal magnetohydrodynamic (MHD) stability and hence on the pedestal height (Osborne et al 2015 Nucl. Fusion 55 063018). The present work studies the effect of the relative shift on pedestal stability of JET ITER-like wall (JET-ILW) baseline low triangularity (\u3b4) unseeded plasmas, and similar JET-C discharges. As shown in this paper, the increase of the pedestal relative shift is correlated with the reduction of the normalized pressure gradient, therefore playing a strong role in pedestal stability. Furthermore, JET-ILW tends to have a larger relative shift compared to JET carbon wall (JET-C), suggesting a possible role of the plasma facing materials in affecting the density profile location. Experimental results are then compared with stability analysis performed in terms of the peeling-ballooning model and with pedestal predictive model EUROPED (Saarelma et al 2017 Plasma Phys. Control. Fusion). Stability analysis is consistent with the experimental findings, showing an improvement of the pedestal stability, when the relative shift is reduced. This has been ascribed mainly to the increase of the edge bootstrap current, and to minor effects related to the increase of the pedestal pressure gradient and narrowing of the pedestal pressure width. Pedestal predictive model EUROPED shows a qualitative agreement with experiment, especially for low values of the relative shift

Layered Double Hydroxides

The impact of layered double hydroxides (LDHs) within the multidisciplinary fields of materials sciences, physics, chemistry, and biology is rapidly growing, given their easiness of synthesis, flexibility in composition, tunable biocompatibility and morphology. LDHs constitute a versatile platform for the realization of new classes of functional systems, showing unique enhanced surface effects and unprecedented properties for application in very different fields, namely, surface chemistry and catalysis, storage and triggered release of functional anions, flame retardants, drug delivery and nanomedicine, remediation, energy storage and conversion. These systems can be synthesized as self-assembled hierarchical nanosheet thin films by means of low temperature solution-based approaches, which are accessible by many laboratories and have the advantages of low cost, mild conditions, and environmental friendliness. In addition, the possibility of LDHs to be exfoliated into 2D nanosheets has been demonstrated to further improve their performance in many applications, as well as to be an attractive route to achieve building blocks for fabricating a wide plethora of hybrid functional architectures. LDHs are therefore a playground for exciting new research covering all of the most intriguing features of 2D materials and more. This Special Issue on “Layered Double Hydroxides” gathers a multidisciplinary collection of original contributions and review articles from authors with diverse scientific backgrounds and who employ LDHs for very different applications, permitting the demonstration of their versatility. Along with LDH-focused papers, this Special Issue also includes some research in which materials different to LDHs resulted in a convenient choice for selected purposes