Proposal of a novel approach to reference instrument and procedure definition to measure hydrogen volume and volumetric flow in a legal metrology framework

International standards concerning hydrogen measurement in legal frameworks are still lacking. This study proposes a novel approach to instrument and procedure definition for the legal measurement of pure hydrogen volume and volumetric flow rate according to main international standards of metrology. A wet drum meter filled with water is chosen as reference meter. The selected reference instrumentation and procedures are replicable in other laboratories. Simulations and calculations demonstrate that hydrogen diffusivity in water have no influence on error estimations, while water evaporation is considered because it affects the volumetric flow rate measurement. The expanded uncertainty of the total metrological chain is less than 0.25%. This reference procedure allows to perform tests for error of indication of new meters both using hydrogen and other flowing gases with the same measurement principle, instrumentation and procedures, helping the development and certification processes of new products useful for the upcoming energy transition

Mechanism of fluorine redistribution and incorporation during solid phase epitaxial regrowth of pre-amorphized silicon

The 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

Association between Exposure to Particulate Matter during Pregnancy and Multidimensional Development in School-Age Children: A Cross-Sectional Study in Italy

Air pollutants can potentially affect the development of children. However, data on the effect of exposure to air pollution during pregnancy and developmental outcomes in school children are rare. We investigated the link between prenatal exposure to particulate matters smaller than 10 microns (PM10) and the development of school-age children in multiple domains. Cross-sectional data were collected in Italy between 2013 and 2014. Children aged between 5 and 8 years (n = 1187) were assessed on cognitive, communication, socio-emotional, adaptive, and motor developmental domains using the Developmental Profile 3 questionnaire. The monthly average concentration of PM10 during the entire fetal period was linked to the municipality of residence of the children. The increase in the prenatal PM10 was associated with a decrease in the cognitive score during the second (+13.2 µg/m3 PM10 increase: −0.30 points; 95%CI: −0.12–−0.48) and third trimesters of pregnancy (−0.31 points; 95%CI: −0.11–−0.50). The communicative domain was also negatively influenced by PM10 increases in the second trimester. The development of cognitive and communicative abilities of children was negatively associated with the exposure to PM10 during the period of fetal development, confirming that exposure to air pollution during pregnancy can potentially hinder the development of the brain

Development of an experimental apparatus and a data analysis protocol for the test of hydrogen volume and flow meters in controlled environmental conditions

The 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

Hydrogen diffusion and segregation during solid phase epitaxial regrowth of preamorphized Si

The 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

Modeling of Hydrogen Diffusion And Segregation in Amorphous Silicon During Solid Phase Epitaxy

The 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

Fluorine redistribution and incorporation during solid phase epitaxy of preamorphized Si

The 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