29 research outputs found
Optical Conductivity of Two-Dimensional Silicon: Evidence of Dirac Electrodynamics
No full textThe exotic electrodynamics properties of graphene come from the linearly dispersive electronic bands that host massless Dirac electrons. A similar behavior was predicted to manifest in freestanding silicene, the silicon counterpart of graphene, thereby envisaging a new route for silicon photonics. However, the access to silicene exploitation in photonics was hindered so far by the use of optically inappropriate substrates in experimentally realized silicene. Here we report on the optical conductivity of silicon nanosheets epitaxially grown on optically transparent Al2O3(0001) from a thickness of a few tens of nanometers down to the extreme two-dimensional (2D) limit. When a 2D regime is approached, a Dirac-like electrodynamics can be deduced from the observation of a low-energy optical conductivity feature owing to a silicene-based interfacing to the substrate
Valproate, carnitine metabolism, and biochemical indicators of liver function.
No full textThe effects of valproate (VPA) on carnitine and lipid metabolism and on liver function were assessed in 213 age- and sex-matched outpatients from five centers, with the following distribution: VPA monotherapy, 54; VPA polytherapy, 55; other monotherapies, 51; and untreated, 53. Mean total and free carnitine levels were significantly lower in patients with polytherapy; acylcarnitine was significantly higher for VPA monotherapy and the ratio of acyl- to free carnitine was
significantly higher in all patients receiving VPA. Ammonia, uric acid, and bilirubin were the only tests selectively impaired with VPA. A significant correlation was found between serum ammonia and VPA dosage. Glucose, beta-lipoproteins, triglycerides, acetacetate, and beta-hydroxybutyrate were
unchanged in the four groups. Sex and age appeared to interact with total and free carnitine values. Adverse drug reactions were apparently unrelated to carnitine metabolism impairment. Only a few patients had abnormal carnitine
values. Our data support the assumption that carnitine deficiency and abnormal liver function due to VPA are mostly subclinical events
Highly sensitive detection of inorganic contamination
No full textAs the detection of inorganic contaminants is of steadily increasing importance for the improvement
of yields in microelectronic applications, the aim of one of the joint research activity within the
European Integrated Activity of Excellence and Networking for Nano- and Micro-Electronics
Analysis (ANNA, site: www.ANNA-i3.org) is the development and assessment of new methodologies
and metrologies for the detection of low concentration inorganic contaminants in silicon and in
novel materials. A main objective consist in the benchmarking of various analytical techniques
available in the laboratories of the participating ANNA partners, including the improvement of the
respective detection limits as well as the quantitation reliablity of selected analytical techniques
such as total-reflection x-ray fluorescence (TXRF) analysi
Unveiling Retention Physical Mechanism of Ge-rich GST ePCM Technology
No full textIn this work, a comprehensive study of Ge-rich Phase Change Memory set and reset state retention realized by coupling electrical and physical characterizations is presented. The presence of amorphous residuals inside the active region of PCM devices is, for the first time, demonstrated through High Resolution Scanning Transmission Electron Microscopy. The role of such formations was studied by means of electrical characterization and supported by modeling analysis. By comparing the low and high state resistive behavior the retention physics has been analytically modeled with the same framework for both states
Large Area Growth and Phase Selectivity of MoTe2 Nanosheets through Simulation-Guided CVD Tellurization
No full textsponsorship: P.P.T. and S.G. contributed equally to this work. The authors acknowledge M. Alia (CNR-IMM) for Mo e-beam deposition, S. Mirenayat (CNR-IMM) for help in the preparation, CVD growth, and Raman measurements; and D. Codegoni, P. Targa, and A. Serafini (STMicroelectronics, Physics Lab, Agrate) for HR-TEM measurements. The authors also acknowledge L. G. Nobili (Politecnico di Milano) and M. Cocuzza (Politecnico di Torino) for academic tutorship. Financial support from aStar (PRIN grant n. 2017RKWTMY, Ministero dell'Istruzione, dell'Universita e della Ricerca) and Challenges (grant no. 861857, Horizon 2020 Framework Programme, call DT-NMBP-08-2019) projects is also acknowledged. Open Access Funding provided by Consiglio Nazionale delle Ricerche within the CRUI-CARE Agreement. (aStar (PRIN grant, Ministero dell'Istruzione, dell'Universita e della Ricerca)|2017RKWTMY, Horizon 2020 Framework Programme|861857, Horizon 2020 Framework Programme|DT-NMBP-08-2019, Consiglio Nazionale delle Ricerche within the CRUI-CARE Agreement, H2020 - Industrial Leadership|861857)status: Published onlin
Improving Ge-rich GST ePCM reliability through BEOL engineering
No full textThis paper discusses the effect of back-end of line (BEOL) process on cell performance for a Phase-Change Memory embedded in a 28nm FD-SOI platform (ePCM). The impact of BEOL is first shown by describing the microscopic evolution of the active Ge-rich GST alloy during process. Ge clustering has been proven to occur during the fabrication process, impacting the pristine resistance and the after forming cell performance. Two different BEOL processes are then benchmarked in terms of key performance. An optimized process is then identified, and an extensive electrical characterization of array performance and reliability is performed on the full 16MB chip. The optimized BEOL process results in a memory cell fully compatible with the requirements for demanding automotive applications
BEOL Process Effects on ePCM Reliability
No full textThe effect of back-end of line (BEOL) process on cell performance and reliability of Phase-Change Memory embedded in a 28nm FD-SOI platform (ePCM) is discussed. The microscopic evolution of the Ge-rich GST alloy during process is the focus of the first part of the paper. A new metric for quantification of active material modifications is introduced to better follow its evolution with process sequence. Ge clustering has been shown to occur during the fabrication, impacting the pristine resistance and the after forming cell performance. Two different BEOL processes are then benchmarked in terms of key performance. An optimized process is identified, and an extensive electrical characterization of array performance and reliability is done on the full 16MB chip. The optimized BEOL process results in a memory cell fully compatible with the requirements for demanding automotive applications
Error estimation of the Nickel concentration for calibration using an ATOMIKA 8030W TXRF wafer surface analyzer
No full textTotalreflexions-Röntgenfluoreszenzanalyse (TXRF) hat sich zur Untersuchung von Kontaminationen auf Waferöberflächen in der Halbleitertechnik etabliert. Mittlerweile bieten eine Reihe von Anbietern verschiedene Geräte in diesem Bereich an. Eines dieser Geräte, eine ATOMIKA 8030W, steht im Atominstitut der Technischen Universität Wien. Um Aussagen über die Verlässlichkeit zu ihrer Quantifizierung machen zu können, ist die Kenntnis der Unsicherheit der Messergebnisse unerlässlich. Dadurch ist auch die Vergleichbarkeit von Ergebnissen verschiedener Labors untereinander einfacher. Zu diesem Zweck gibt es mittlerweile einige Anleitungen zur Angabe von Unsicherheiten, anhand derer für das Kalibrierungselement Ni eine Fehlerabschätzung gemacht und die wichtigsten Beiträge zur Unsicherheit aufgeschlüsselt wurde. Um eine direkte Verbindung mit dem SI-System herstellen zu können, wurden neue Standardreferenzmaterialien erworben, einerseits als Probe und andererseits als Kalibrierstandard. Die Probenvorbereitung wurde eingehend untersucht. Mit mechanischen Pipetten werden Probenlösungen durch Verdünnung mit dreifach destilliertem Wasser hergestellt und die Mengen durch Wägen mit einer Laborwaage verifiziert. Mit Kenntnis der Unsicherheit der Waage wurde die Präzision der Pipetten bei verschiedenen Ausgabevolumina berechnet. Die Genauigkeit der Waage wurde als kritischer Faktor bei der Probenherstellung identifiziert. Bei der Messung von Mehrelementstandards wurde eine systematische Abweichung der Messergebnisse entdeckt. Auch bei der Messung von reinen Ni-Proben trat dies auf. Mit den Ergebnissen dieser Messungen wurde ein Korrekturfaktor und dessen Unsicherheit berechnet. Durch wiederholte Messungen des Kalibrierungsstandards wurde bestimmt, wie die Messergebnisse der ATOMIKA 8030W unter Wiederholungsbedingungen schwanken. Daraus wurde eine Unsicherheit bestimmt, die über einen Faktor in die Quantifizierungsformel einfließt. Im Rahmen der Teilnahme an einem Projekt der European Integrated Activity of Excellence and Networking for Nanö and MicröElectronics Analysis (ANNA) wurden eigens hergestellte Proben von mehreren Labors, die TXRF betreiben, vermessen und die Ergebnisse untereinander verglichen. Dabei wurden die Ergebnisse mit anderen etablierten Methoden verifiziert. Die Ergebnisse zeigten deutliche Schwankungen, was die Bestimmung der Reproduzierbarkeit der Messmethode zu diesem Zeitpunkt unmöglich gemacht hat. Es zeigten sich jedoch deutlich der Einfluss der unterschiedlichen Messgeometrien, der Probenmorphologie und der Einfluss der Kalibrierung. Die TXRF arbeitet mit der Annahme, dass die Kalibrierfunktion linear ist. Es wurde eine Eichgerade gemessen und ein Bereich festgelegt in dem Linearität gegeben ist. Auch hier wurde der Einfluss der Probenform deutlich, die für höhere Konzentrationen offenbar nicht reproduzierbar ist. Abschließend wurde die angepasste Quantifizierungsformel bei der Auswertung zweier Multielementstandards getestet und die Größe des Einflusses der unterschiedlichen Fehlerbeiträge am Beispiel für Ni wurde bestimmt. Die Ergebnisse dieser Arbeit wurden veröffentlicht in: B. Beckhoff, A. Nutsch, R. Altmann, G. Borionetti, C. Pello, M. L. Polignano, D. Codegoni, S. Grasso, E. Cazzini, M. Bersani, P. Lazzeri, S. Gennaro, M. Kolbe, M. Müller, P. Kregsamer und F. Posch, "Highly sensitive detection of inorganic contamination", UCPSS 2008 Proceedings book: Solid state Phenomena 145-146 (2009), S. 101-104 C. Streli, P. Kregsamer, F. Posch und M. Fugger, äccreditation for wafer surface analysis with TXRF-, IAEA Report on Technical meeting on Quality assurance for Nuclear spectrometry techniques, G4-TM-36923, Vienna, 12.-16.10.2009 B. Beckhoff, A. Nutsch, R. Altmann, G. Borionetti, C. Pello, M. L. Polignano, D. Codegoni, S. Grasso, E. Cazzini, M. Bersani, S. Gennaro, M. Kolbe, M. Müller, P. Kregsamer und F. Posch, ässessing Various Analytical Techniques With Different Lateral Resolution By Investigating Spin-coated Inorganic Contamination On Si Surfaces-, ECS Trans 25(3), S. 311-323, (2009) proceedings of the ALtech conference, October, ViennaTotal reflection X-ray Fluorescence Analysis (TXRF) has established itself in the investigation of contaminations on wafer surfaces. By now a number of providers offer different systems in this area. One of these, an ATOMIKA 8030W is situated at the ATI (Institute of Atomic and Subatomic Physics). To gauge the reliability of its quantification the knowledge of the uncertainty of measuring results is vital. Additionally the comparison of results between different laboratories becomes easier. For this reason a number of manuals and guides on the expression of uncertainties have been written. With these an estimation of the uncertainty for the calibration element Ni should be made and the major contributing factors identified and analysed. In order to provide a direct connection to the SIünit system, new standard reference materials were purchased for the preparation of well-known samples and for calibration. Sample preparation was thoroughly investigated. For the mixing of sample solutions mechanical pipettes were used in the dilution process. The amounts of liquid were verified using a laboratory scale. Since the uncertainty of the scale was well-known the output volumes and their uncertainties were calculated. The accuracy of the laboratory scale was identified a major factor in the preparation of samples. During the measurement of multiple element solutions a systematic deviation of the results was discovered. Measurement of pure Ni-samples also showed this behaviour. With the results of these measurements a correction factor and its uncertainty to account for the bias was calculated. Repeated measurements of the calibration standard provided information on the repeatability of results of the ATOMIKA 8030W. To account for the uncertainty associated with the repeatability a factor was calculated to modify the quantification formula. The ATI took part in a joint project of the European Integrated Activity of Excellence and Networking for Nanö and MicröElectronics Analysis (ANNA). Well-known samples were measured by several laboratories employing TXRF methods and the results compared. The results were verified with other verified methods and showed significant deviations between the laboratories, which made it impossible at this time to determine the reproducibility of TXRF. The influence of different measurement geometries, sample morphology and calibration standards was shown. TXRF works on the assumption that the calibration function is linear. For verificä tion purposes the calibration function for Ni was measured and the linearity for a range of mass determined. In the higher mass range the influence of the shape of the sample was noticeable, which is not reproducible for solutions with higher concentrations. Finally the modified quantification formula was used to determine the uncertainty of the measurement results of two multielement standards and the influence of different uncertainty contributions was determined for Ni in these samples. The results of this work were published in: B. Beckhoff, A. Nutsch, R. Altmann, G. Borionetti, C. Pello, M. L. Polignano, D. Codegoni, S. Grasso, E. Cazzini, M. Bersani, P. Lazzeri, S. Gennaro, M. Kolbe, M. Müller, P. Kregsamer and F. Posch, "Highly sensitive detection of inorganic contamination", UCPSS 2008 Proceedings book: Solid state Phenomena 145-146 (2009), p. 101-104 C. Streli, P. Kregsamer, F. Posch and M. Fugger, äccreditation for wafer surface analysis with TXRF-, IAEA Report on Technical meeting on Quality assurance for Nuclear spectrometry techniques, G4-TM-36923, Vienna, 12.-16.10.2009 B. Beckhoff, A. Nutsch, R. Altmann, G. Borionetti, C. Pello, M. L. Polignano, D. Codegoni, S. Grasso, E. Cazzini, M. Bersani, S. Gennaro, M. Kolbe, M. Müller, P. Kregsamer and F. Posch, ässessing Various Analytical Techniques With Different Lateral Resolution By Investigating Spin-coated Inorganic Contamination On Si Surfaces-, ECS Trans 25(3), p. 311-323, (2009) proceedings of the ALtech conference, October, Vienn
