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Mechanism of fluorine redistribution and incorporation during solid phase epitaxial regrowth of pre-amorphized silicon
Full text linkThe 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
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Fluorine redistribution and incorporation during solid phase epitaxy of preamorphized Si
No full textThe redistribution of fluorine during solid phase epitaxial regrowth (SPER) of preamorphized Si has been experimentally investigated, explained, and simulated, for different F concentrations and temperatures. We demonstrate, by a detailed analysis and modeling 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. It is shown that diffusive F migrates by a trap limited diffusion mechanism and also 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 determines the regrowth rate through an exponential law. On the other hand we show that neither the diffusive F nor the one segregated at the interface can directly incorporate into the crystal but F has to cluster in the amorphous phase before being incorporated in the crystal, in agreement with recent experimental observations. 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 and incorporation in preamorphized Si. The above physical understanding and the model could have a strong impact on the use of F as a tool for optimizing the doping profiles in the fabrication of ultrashallow junctions
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Development of an experimental apparatus and a data analysis protocol for the test of hydrogen volume and flow meters in controlled environmental conditions
Full text linkThe 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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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