1,762 research outputs found
Mechanism of fluorine redistribution and incorporation during solid phase epitaxial regrowth of pre-amorphized silicon
No full textThe redistribution of impurities during phase transitions is a widely studied phenomenon that has a great relevance in many fields and especially in microelectronics for the realization of Ultra Shallow Junctions (USJs) with abrupt profiles and high electrical activation. The redistribution of fluorine during solid phase epitaxial regrowth (SPER) of pre-amorphized Si has been experimentally investigated, explained and simulated, for different F concentrations and temperatures. We demonstrate, by a detailed analysis and modelling of F secondary ion mass spectrometry chemical concentration profiles, that F segregates in amorphous Si during SPER by splitting in three possible states: i) a diffusive one that migrates in amorphous Si; ii) an interface segregated state evidenced by the presence of a F accumulation peak at the amorphous-crystal interface; iii) a clustered F state. The interplay among these states and their roles in the F incorporation into crystalline Si are fully described in this thesis. It is shown that diffusive F moves by a trap limited diffusion and interacts with the advancing interface by a sticking-release dynamics that regulates the amount of F segregated at the interface. We demonstrate that this last quantity regulates the regrowth rate by an exponential law. On the other hand we show that nor the diffusive F nor the one segregated at the interface can directly incorporate into the crystal but clustering has to occur in order to have incorporation. This is in agreement with the element specific structural information on the F incorporated in crystalline Si given by a specific X-ray absorption spectroscopy analysis performed in this thesis, and also with recent experimental observations, reported in literature. The trends of the model parameters as a function of the temperature are shown and discussed obtaining a clear energetic scheme of the F redistribution in pre-amorphized Si. The above physical understanding and the model could have a strong impact on the use of F as a tool for optimising the doping profiles in the fabrication of ultra-shallow junctions.La redistribuzione di impurezze durante le transizioni di fase è un fenomeno ampiamente studiato che ha una grande rilevanza in molti campi di ricerca e specialmente nella microelettronica per la realizzazione di giunzioni ultra sottili (USJs) caratterizzate da profili di drogante ben confinati e da un’alta attivazione elettrica.
La redistribuzione del fluoro durante la ricrescita epitassiale in fase solida (SPER) del silicio pre-amorfizzato è stata studiata sperimentalmente, descritta e simulata in un ampio range di concentrazioni di F impiantato e temperature di ricrescita. Mediante una dettagliata analisi modellizzazione matematica dei profili in concentrazione di F misurati tramite la spettrometria di massa di ioni secondari, dimostriamo che il F segrega in silicio amorfo durante la SPER suddividendosi in tre possibili stati: i) uno stato diffusivo che migra in silicio amorfo; ii) uno stato segregato all’interfaccia evidenziato dalla presenza di un picco di accumulazione di F all’interfaccia amorfo-cristallo; iii) uno stato di F clusterizzato.
Questo lavoro ha descritto nel dettaglio quali scambi avvengono tra questi stati e che ruolo hanno nell’incorporazione del F nel silicio cristallino. È stato osservato che il F diffusivo è soggetto ad una diffusione limitata dalle trappole presenti nel substrato amorfo. Il F che diffonde in amorfo interagisce con l’interfaccia che avanza tramite una dinamica di tipo “attacca-stacca”, che regola l’ammontare del F segregato all’interfaccia. Dimostriamo che questa ultima quantità regola la velocità di ricrescita tramite una legge esponenziale. Dall’altra parte noi mostriamo che né il F diffusivo né quello segregato all’interfaccia possono incorporarsi direttamente nel cristallo ma del clustering deve accadere per avere l’incorporazione del F. Questa osservazione è in accordo con le informazioni strutturali del F incorporato in Silicio cristallino ottenute da una specifica analisi tramite spettroscopia di assorbimento a raggi X svolta in questa tesi e anche con le recenti osservazioni sperimentali riportate in letteratura. Gli andamenti dei parametri del modello in funzione della temperatura sono mostrati e discussi ottenendo un chiaro schema energetico della redistribuzione del F in silicio pre-amorfizzato. La suddetta comprensione fisica dei meccanismi coinvolti e il relativo modello predittivo da noi sviluppato potrebbero avere una forte impatto sull’uso del F come strumento per ottimizzare i profili dei droganti nella fabbricazione di giunzioni ultra-sottili
The nature and meaning of cryptocurrencies. Review of Massimo Amato and Luca Fantacci, Per un pugno di bitcoin. Rischi e opportunità delle monete virtuali. EGEA, 2018
No full textThe topic of cryptocurrencies is increasingly addressed in articles featured in specialized and non-specialized media, as well as in central banks’ documents and by financial intermediaries themselves. However, it rarely receives a thorough theoretical analysis. This is the attempt by Amato and Fantacci, two of the foremost Italian experts on monetary economics who recently published an updated version of a work that analyses the Bitcoin system from a technical point of view but also to make a closer examination of its macroeconomic and policy implication
Development of an experimental apparatus and a data analysis protocol for the test of hydrogen volume and flow meters in controlled environmental conditions
No full textThe decarbonization of the residential sector is fundamental for energy transition. In this context, it is promising the introduction of hydrogen in natural gas networks in specific hydrogen districts. Accordingly, hydrogen meters are needed for accounting the fuel consumptions. The topic of this work is the development and construction of an experimental apparatus for testing safely hydrogen volume and flow meters up to 24 m3/h (referred to standard conditions) in controlled environmental conditions, between -25 and +55 °C (and beyond). The apparatus realized can test up to four volume and flow meters in a climatic chamber while processing air or pure hydrogen or methane. Methane-hydrogen mixtures can be tested connecting simply bottles with synthetic blends. The aim is to verify the measurement accuracy of the meters under test. A dedicated data analysis protocol featuring statistical process control is developed to monitor the stability of the system during the test. It exploits statistical indicators representing the autocorrelation, the normality of residuals of the mean value and the lag plot. The apparatus is realized, and it complies with the leakage limits set by indications in literature. A new ultrasonic domestic meter is tested in the apparatus. It has been developed by Pietro Fiorentini S.p.A. in the framework of the Hy4Heat project. Its error trends measured at all temperatures comply with the limit of 3.5% between 0.12 and 2 m3/h and 2% between 2 and 20 m3/h, as imposed by legislations
Recuerdos de Massimo.
No full textEl presente ensayo recuerda la rica relación personal e intelectual entre Massimo Pavarini e Iñaki Rivera Beiras desde que el segundo conoció siendo muy joven a Pavarini. En ese sentido, el trabajo recuerda los inicios de su fecunda relación en la ciudad de Bologna cuando Iñaki Rivera acudía a presentar a Massimo Pavarini los desarrollos de lo que sería su tesis doctoral. Las contribuciones de Pavarini al proceso de aprendizaje de Rivera, en el terreno de una epistemología crítica en la penología contemporánea, son analizados como un homenaje a la memoria y a la obra del autor italiano, tras su fallecimiento en septiembre de 2015.This paper recalls the rich personal and intellectual relationship between Massimo Pavarini and Iñaki Rivera Beiras. In that sense , the work recalls the beginning of his fruitful relationship in the city of Bologna when Iñaki Rivera came to present Massimo Pavarini’ developments in what would be his PhD thesis. Pavarini contributions to the learning process of Rivera, on the ground of a critical epistemology in contemporary penology , are analyzed as a tribute to the memory and to the work of Italian author, after his death in September 2015 .El presente ensayo recuerda la rica relación personal e intelectual entre Massimo Pavarini e Iñaki Rivera Beiras desde que el segundo conoció siendo muy joven a Pavarini. En ese sentido, el trabajo recuerda los inicios de su fecunda relación en la ciudad de Bologna cuando Iñaki Rivera acudía a presentar a Massimo Pavarini los desarrollos de lo que sería su tesis doctoral. Las contribuciones de Pavarini al proceso de aprendizaje de Rivera, en el terreno de una epistemología crítica en la penología contemporánea, son analizados como un homenaje a la memoria y a la obra del autor italiano, tras su fallecimiento en septiembre de 2015
Modeling of Hydrogen Diffusion And Segregation in Amorphous Silicon During Solid Phase Epitaxy
No full textThe diffusion and segregation of hydrogen in surface amorphous
silicon layers during solid phase epitaxy (SPE) is modeled. The
SPE and H concentration profiles from J. Roth et al., Mat. Res.
Soc. Symp. Proc. 205, 45 (1992) are used to test H segregation and
diffusion models. Excellent agreement is obtained with a trap
limited diffusion model. This model has previously been found to
describe the diffusion of fluorine well. The H segregation
coefficient at the crystalline-amorphous interface is determined at a
temperature of 606oC to be 0.064. The possible temperature
dependence of the segregation coefficient and its effect on SPE are
also discussed
Feasibility and reproducibility of shear wave elastography in evaluating biceps brachii tendon in healthy dogs: preliminary results
No full textPredoni a casa nostra e il geografo solidale: Massimo Quaini tra terra e acqua
No full textIn accordance with the main goals of this collection of essays in honour of Massimo Quaini, the text focuses on a peculiar character of the Ligurian geographer’s sensibility, his attention to landscape protectionresearch activity developed in the context of the humanistic geography. Starting from a personal narrative based on his own reminiscences and neglected memories, the author tries to shed light on the relationships between civil commitment and cultural reflection which characterize environmental sensitivity, bringing together his interests with Quaini’s emotional geographies. Finally, some of Quaini’s everyday practicalities are highlighted as the easiest doorway to improve the cognitive procedures of cultural geography
Hydrogen diffusion and segregation during solid phase epitaxial regrowth of preamorphized Si
No full textThe redistribution of hydrogen during solid phase epitaxial regrowth (SPER) of preamorphized silicon has been experimentally investigated, modeled, and simulated for different H concentrations and temperatures. H was introduced by H implantation and/or infiltration from the sample surface during partial thermal anneals in air in the 520-620 degrees C temperature range. We characterized the time evolution of the H redistribution by secondary ion mass spectrometry and time resolved reflectivity. The good agreement between all experimental data and the simulations by means of full rate equation numerical calculations allows the quantitative assessment of all the phenomena involved: in-diffusion from annealing atmosphere and the H effect on the SPER rate. We describe the temperature dependence of microscopic segregation of H at the amorphous/crystal (a-c) interface. Only a fraction of H atoms pushed by the a-c interface can be incorporated into the crystal bulk. We propose an energetic scheme of H redistribution in amorphous Si. The segregation of H at the a-c interface is also considered for (110) and (111) orientated substrates. Our description can also be applied to other material systems in which redistribution of impurities during a solid-solid phase transition occurs. (C) 2016 AIP Publishing LLC
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