420 research outputs found
Materials, instrumentation and techniques for the detection of Special Nuclear Material and Radioactive Sources: EU project MODES SNM
No full textMODES SNM project is part of the European Union effort to promote research and innovation in strategic topics; it includes seven participants from five different countries. The project aimed to carry out technical research in order to develop a prototype for a mobile, modular detection system for radioactive sources and Special Nuclear Materials (SNM). The project’s main goal was to deliver a tested prototype of a modular mobile system capable of passively detecting weak or shielded radioactive sources with accuracy higher than that of currently available systems.
The R&D involved in the project aimed at designing, constructing and testing robust, safe, and lightweight high pressure cells with an advanced read-out system, to be used as
basic components of the modular mobile system. These innovative cells use 4He and Xe as scintillation materials, exploiting the potential of noble gases in the field of radiation detection. Furthermore, a patented technology enabled the simultaneous detection of fast and thermal neutrons in the same detector, providing additional information on the possible presence of shielding around neutron sources. The final detector configuration for MODES SNM prototype includes 8 4He fast neutron tubes, 2 4He thermal neutron tubes, 1 xenon gamma ray tube and 1 NaI(Tl) gamma ray crystal.
A suitable Information System has been developed at Università degli Studi di Padova to manage the detectors, integrate and analyze the data, and provide to the user simple informations about the results of the inspections. The prototype was commissioned under laboratory conditions at NCBJ, a renowned European research establishment, then the detectors and the front-end electronics were mounted inside a van. Finally, a series of demonstrations took place in an on-field campaign driven by the end-user group established in the project.
Project MODES SNM concluded with full success on June 30th, 2014. Not only all the project milestones were achieved, but the prototype was completed on time and showed good performances. The technical requirements defined at the beginning of the project have been fulfilled, and during the demonstration tour the end users showed great appreciation to the final result of the work, to the satisfaction of all the Consortium partners. The project has been positively evaluated by EU officials, from the point of view of both the organization and the results. The prototype is now being developed at an industrial level by one of the project participants; an agreement has been signed with Universit`a di Padova for licensing the software written within the project.Il progetto MODES SNM è parte dello sforzo da parte dell’Unione Europea per promuovere la ricerca e l’innovazione in settori considerati strategici; include sette partecipanti da cinque diversi paesi. Il progetto punta a sviluppare una attivit`a di ricerca per lo sviluppo di un sistema mobile e modulare per la rivelazione di sorgenti radioattive e materiale speciale nucleare (SNM). L’obiettivo principale è la realizzazione di un prototipo funzionante capace di rivelare in modo passivo sorgenti deboli o schermate con precisione maggiore dei sistemi attualmente disponibili.
La ricerca e sviluppo svolta all’interno del progetto mirava alla costruzione di celle ad alta pressione robuste e leggere con un sistema di read-out avanzato, da usarsi come componenti di base del sistema mobile modulare. Queste celle innovative usano 4He e Xe come scintillatori, sfruttando il potenziale dei gas nobili nel campo della rivelazione di radiazione. Inoltre una tecnologia brevettata consente la rivelazione simultanea dei neutroni veloci e termici, fornendo così informazioni aggiuntive sulla possibile presenza di schermi intorno alle sorgenti. La configurazione finale dei rivelatori del prototipo di MODES SNM include 8 tubi ad 4He per neutroni veloci, 2 tubi ad 4He per neutroni termici, 1 tubo a xenon ed 1 cristallo NaI(Tl) per radiazione gamma.
Un apposito Sistema Informatico (IS) è stato sviluppato presso l’Università degli Studi di Padova per la gestione dei rivelatori, l’aggregazione e l’analisi dei dati, e per fornire all’operatore semplici informazioni riguardo i risultati delle ispezioni. Il prototipo è stato collaudato persso il centro NCBJ, una installazione di ricerca conosciuta in tutta Europa, quindi i rivelatori e l’elettronica sono stati installati dentro un van. Infine, una serie di dimostrazioni ha avuto luogo durante una campagna "sul campo" gestita dal gruppo di utilizzatori finali costituito all’interno del progetto.
Il progetto MODES SNM si è concluso con pieno successo il 30 giugno 2014. Non solo ha raggiunto tutti gli obiettivi, ma il prototipo è stato completato per tempo ed ha mostrato delle buone prestazioni. I requisiti tecnici definiti inizialmente sono stati rispettati, e durante le dimostrazioni gli utenti finali hanno espresso grande apprezzamento per il risultato finale del nostro lavoro, con soddisfazione di tutti i partecipanti del Consorzio. Il progetto è anche stato valutato positivamente dai funzionari europei incaricati della valutazione, sia sotto il punto di vista della gestione che dei risultati. Attualmente il prototipo sta venendo sviluppato a livello industrial da uno dei partecipanti; è stato raggiunto un accordo con l’Università di Padova per la licenza del software scritto durante il progetto
RECOVERY OF SILC IN ULTRA-THIN GATE OXIDES BY LOW FIELD ELECTRON INJECTION
No full textIn this work we have shown that SILC in thin oxides can be effectively reduced at room temperature by performing low field current injection. By increasing the amount of injected charge, SILC continuously decreases and no saturation steady state level is reached. We attribute this decrease to the passivation of the oxide weak spots by electron trapping in those defects mediating SILC. This poses some questions on the true meaning of DC SILC, on the corresponding methods of measurements, and on its impact on the device lifetime
Wear-out and breakdown of ultra-thin gate oxides after irradiation
No full textThe enhancement of gate leakage current after exposure to ionising radiation is generally believed to be the major challenge for devices and circuits operating in harsh radiation environments. How ultra-thin gate oxides subjected to heavy ion irradiation react to a subsequent electrical stress performed at low voltages has been investigated. Even in devices exhibiting small (or even negligible) enhancement of the leakage current, the time-to-breakdown is substantially reduced in comparison with unirradiated samples due to the onset of a soft or hard breakdown, in contrast with previous results found on thicker oxides
Flexible and Organic Neural Interfaces: A Review
No full textNeural interfaces are a fundamental tool to interact with neurons and to study neural networks by transducing cellular signals into electronics signals and vice versa. State-of-the-art technologies allow both in vivo and in vitro recording of neural activity. However, they are mainly made of stiff inorganic materials that can limit the long-term stability of the implant due to infection and/or glial scars formation. In the last decade, organic electronics is digging its way in the field of bioelectronics and researchers started to develop neural interfaces based on organic semiconductors, creating more flexible and conformable neural interfaces that can be intrinsically biocompatible. In this manuscript, we are going to review the latest achievements in flexible and organic neural interfaces for the recording of neuronal activity
Degradation Dynamics of Ultrathin Gate Oxides Subjected to Electrical Stress
No full textThe sigmoidal behavior exhibited by the current-time characteristics of constant voltage-stressed metal-oxide-semiconductor (MOS) capacitors with ultrathin oxides is ascribed to a self-constrained increase of the leakage sites population that assist the conduction process between the electrodes. To mathematically describe this dynamical process we consider a classical model of population growth theories such as the Verhulst differential equation. The role that might play the background tunneling current in the evolutionary trajectory of the breakdown event is also discussed
Study and implementation of a digital control of dual-gated electrolyte-gated organic field-effect transistors for cell stimulation and recording
No full textopenL’elettronica organica sta diventando particolarmente attraente per le applicazioni di biosensing, grazie ai suoi vantaggi come il basso costo dei materiali e dei processi di fabbricazione, la biocompatibilità e l’alta sensibilità. I transistor organici ad effetto di campo con gate elettrolitico (EGOFETs) sono stati ampiamente studiati negli ultimi anni in questo campo, per la loro peculiare abilità di operare a tensioni molto basse, grazie all’elevata
apacità di double-layer che si ottiene all’interfaccia con l’elettrolita. Tuttavia, il contatto con l’ossigeno e l’umidità in soluzioni acquose è dannoso per le funzionalità del transistor, modificandone le caratteristiche elettriche (variazione della tensione di soglia) e degradandolo.
Questa tesi si concentra sulla stabilizzazione del punto operativo dell’EGOFET, attraverso lo sviluppo di un controllo digitale che sfrutta un gate aggiuntivo per controllare la tensione di soglia del canale di conduzione liquid-gated. Abbiamo costruito un sistema di controllo completo che permette di ottenere un segnale di uscita ben definito per misure a lungo termine. In particolare, abbiamo mirato alla registrazione e alla stimolazione di segnali extracellulari, testando diversi metodi per rilevare e preservare ipotetici segnali di potenziale d’azione. Tutte le configurazioni sono state testate da simulazioni e prove sperimentali. Il controllo digitale include strumenti di autotuning per fornire robustezza rispetto al degrado delle proprietà dei dispositivi. Diversi parametri del sistema di controllo possono essere tarati a seconda delle priorità che vogliamo prendere in considerazione. Per quanto riguarda una futura implementazione con cellule reali, sono stati provati diversi rivestimenti per la semina delle cellule, al
fine di analizzare il loro effetto sulle proprietà elettriche. I dispositivi rivestiti conservati in aria hanno mostrato un comportamento a effetto campo per circa un mese.
Questa tesi fa parte di un progetto più ampio chiamato Project Proactive 2018 "Fully printed organic array of bidirectional reference-less sensors for neuronal interfacing", led by the Principal Investigator Prof. Andrea Cester, in collaborazione con:
• VIMM Veneto Institute of Molecular Medicine
• DiSC Dipartimento di Scienze Chimiche, UNIPD
• ICMAB Institut de Ciència de Materials de BarcelonaOrganic electronics is becoming particularly attractive for biosensing applications, thanks to its advantages such as low-cost materials and fabrication processes, biocompatibility and high sensitivity. Electrolyte-Gated Organic Field Effect Transistors (EGOFETs) have been widely investigated in recent years in this field, due to their peculiar ability to operate at very low voltages, thanks to the high double-layer capacitance given by the interfaces with the electrolyte. However, the contact with oxygen and humidity in acqueous environment is detrimental for the functionality of the transistor, changing its electrical characteristics (threshold voltage shift) and degradating it.
This dissertation is focused on the stabilization of the operating point of the EGOFET, by means of the development of a digital control that exploits an
additional gate to control the threshold voltage of the liquid-gated conduction channel. We built up a complete control system that allows to achieve a well-defined output signal for long term measurements. In particular, we targeted extracellular recording and stimulation, by testing different methods
to detect and preserve hypothetical action potential signals. All the configurations have been tested by simulations and experimental evidences. The digital control includes autotuning tools to give robustness to the degradation of the devices properties. Several parameters of the control system can be tuned depending on the priorities we want to take into account. With regard to a future implementation with real cells, different coatings for cell seeding have been tried, in order to analyze their effect on the electrical properties. The coated devices stored in air showed a field-effect behaviour for approximately one month.
This thesis is part of a broader project called Project Proactive 2018 "Fully printed organic array of bidirectional reference-less sensors for neuronal interfacing", led by the Principal Investigator Prof. Andrea Cester, in collaboration with:
• VIMM Veneto Institute of Molecular Medicine
• DiSC Dipartimento di Scienze Chimiche, UNIPD
• ICMAB Institut de Ciència de Materials de Barcelon
Ionising Radiation Effects on Ultra-Thin Gate oxide MOS
No full textINVITED PAPER
We have briefly reviewed the most important degradation mechanisms affecting ultra-thin gate oxides after exposure to ionizing irradiation. The increase of the gate leakage current seems the most crucial issue for device lifetime, especially for non-volatile memory and dynamic logic. The build-up of positive charge in the oxide and the subsequent threshold voltage shift, which was the major concern for thicker oxide, are no longer appreciable in today’s devices due to the reduced oxide thickness permitting a fast recombination of trapped holes with electrons from interfaces. Among the leakage currents affecting thin oxides we have considered here the Radiation Induced Leakage Current (RILC) and the Radiation Soft Breakdown (RSB). RILC is observed after irradiation with a low Linear Energy Transfer (LET) radiation source and comes from a trap-assisted tunneling of electrons mediated by the neutral traps produced by irradiation. RILC depends on the applied bias during irradiation and the maximum is measured when devices are biased in flat band. Contrarily to RILC, RSB is observed after irradiation with high LET ions and derives from the formation of several conductive paths across the oxide corresponding to the ion hits. RSB conduction is explained by the theory of the Quantum Point Contact as also proposed for the electrically induced Soft breakdown. Finally, we present some preliminary results, which indicate that although the direct effects of irradiation (in terms of gate leakage current increase) are small for oxide thinner than 3nm, it is possible that these devices may experience an accelerated wear-out and/or breakdown after subsequent electrical stress relative to a fresh (not irradiated) device
New Issues in Radiation Effects on Semiconductor Devices
No full textWe have briefly reviewed the most important degradation mechanisms affecting ultra-thin gate oxides after exposure to ionizing irradiation. The increase of the gate leakage current seems the most crucial issue for device lifetime, especially for non-volatile memory and dynamic logic. The build-up of positive charge in the oxide and the subsequent threshold voltage shift, which was the major concern for thicker oxide, are no longer appreciable in today’s devices due to the reduced oxide thickness permitting a fast recombination of trapped holes with electrons from interfaces. Among the leakage currents affecting thin oxides we have considered here the Radiation Induced Leakage Current (RILC) and the Radiation Soft Breakdown (RSB). RILC is observed after irradiation with a low Linear Energy Transfer (LET) radiation source and comes from a trap-assisted tunneling of electrons mediated by the neutral traps produced by irradiation. RILC depends on the applied bias during irradiation and the maximum is measured when devices are biased in flat band. Contrarily to RILC, RSB is observed after irradiation with high LET ions and derives from the formation of several conductive paths across the oxide corresponding to the ion hits. Finally, we present some preliminary results, which indicate that although the direct effects of irradiation (in terms of gate leakage current increase) are small for oxide thinner than 3nm, it is possible that these devices may experience an accelerated wear-out and/or breakdown after subsequent electrical stress relative to a fresh (not irradiated) device
Direct Comparison of the Effect of Processing Conditions in Electrolyte-Gated and Bottom-Gated TIPS-Pentacene Transistors
No full textfirst_pagesettings
Open AccessFeature PaperArticle
Direct Comparison of the Effect of Processing Conditions in Electrolyte-Gated and Bottom-Gated TIPS-Pentacene Transistors
by Nicolò Lago 1,*ORCID,Marco Buonomo 1,Federico Prescimone 2,Stefano Toffanin 2ORCID,Michele Muccini 2 andAndrea Cester 1
1
Department of Information Engineering, University of Padova, 35131 Padova, Italy
2
Institute of Nanostructured Materials (ISMN), National Research Council (CNR), 40129 Bologna, Italy
*
Author to whom correspondence should be addressed.
Academic Editor: Horng-Long Cheng
Electron. Mater. 2022, 3(4), 281-290; https://doi.org/10.3390/electronicmat3040024 (registering DOI)
Received: 6 September 2022 / Revised: 21 September 2022 / Accepted: 23 September 2022 / Published: 27 September 2022
(This article belongs to the Special Issue Feature Papers of Electronic Materials (Second Volume))
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Abstract
Among the plethora of soluble and easy processable organic semiconductors, 6,13-Bis(triisopropylsilylethynyl)pentacene (TIPS-P5) is one of the most promising materials for next-generation flexible electronics. However, based on the information reported in the literature, it is difficult to exploit in field-effect transistors the high-performance characteristics of this material. This article correlates the HMDS functionalization of the silicon substrate with the electrical characteristics of TIPS-P5-based bottom gate organic field-effect transistors (OFETs) and electrolyte-gated organic field-effect transistors (EGOFETs) fabricated over the same platform. TIPS-P5 transistors with a double-gate architecture were fabricated by simple drop-casting on Si/SiO2 substrates, and the substrates were either functionalized with hexamethyldisilazane (HMDS) or left untreated. The same devices were characterized both as standard bottom-gate transistors and as (top-gate) electrolyte-gated transistors, and the results with and without HMDS treatment were compared. It is shown that the functionalization of the silicon substrate negatively influences EGOFETs performance, while it is beneficial for bottom-gate OFETs. Different device architectures (e.g., bottom-gate vs. top-gate) require specific evaluation of the fabrication protocols starting from the effect of the HMDS functionalization to maximize the electrical characteristics of TIPS-P5-based devices
IONIZING RADIATION EFFECTS ON ULTRA-THIN OXIDE MOS STRUCTURES
No full textWe have briefly reviewed the most important degradation mechanisms affecting ultra-thin gate oxides after exposure to ionizing irradiation. The increase of the gate leakage current seems the most crucial issue for device lifetime, especially for non-volatile memory and dynamic logic. The build-up of positive charge in the oxide and the subsequent threshold voltage shift, which was the major concern for thicker oxide, are no longer appreciable in today's devices due to the reduced oxide thickness permitting a fast recombination of trapped holes with electrons from interfaces. Among the leakage currents affecting thin oxides we have considered here the Radiation Induced Leakage Current (RILC) and the Radiation Soft Breakdown (RSB). RILC is observed after irradiation with a low Linear Energy Transfer (LET) radiation source and comes from a trap-assisted tunneling of electrons mediated by the neutral traps produced by irradiation. RILC depends on the applied bias during irradiation and the maximum is measured when devices are biased in flat band. Contrarily to RILC, RSB is observed after irradiation with high LET ions and derives from the formation of several conductive paths across the oxide corresponding to the ion hits. RSB conduction is explained by the theory of the Quantum Point Contact as also proposed for the electrically induced Soft breakdown. Finally, we present some preliminary results, which indicate that although the direct effects of irradiation (in terms of gate leakage current increase) are small for oxide thinner than 3nm, it is possible that these devices may experience an accelerated wear-out and/or breakdown after subsequent electrical stress relative to a fresh (not irradiated) device
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