POLITECNICO DI MILANO
Dipartimento di Elettronica e Informazione
1. NEW CONCEPTS AND DEVELOPMENTS ON SILICON DETECTORS
A. Castoldi, C. Guazzoni
Collaborations: Brookhaven National Laboratory (NY, USA), Max Planck Institut (Munich), PNSensor GmbH (Munich), Sincrotrone Trieste, University College London (UK), Universita degli Studi (Milano), IfG - Institut for Scientific Instruments GmbH (Berlin, Germany), INFN - Laboratori Nazionali del Sud (Catania, Italy), INFN - Laboratorio di Tecniche Nucleari per i Beni Culturali (LABEC) (Firenze, Italy), ELETTRA Sincrotrone Trieste (Trieste, Italy), GSI - Helmoltzzentrum für Schwerionenforschung (Darmstadt, Germany), XFEL GmbH (Hamburg, Germany).
2. APPLICATIONS OF SILICON DRIFT DETECTORS IN X-RAY AND GAMMA-RAY DETECTION
C. Fiorini, A. Longoni, A. Geraci, G. Padovini
Collaborations: MPI (Munich, Germany), PNSensor GmbH (Munich, Germany), INAF-IASF (Milano), UCL (London, UK), Ospedali Riuniti Bergamo
3. LOW-NOISE VLSI CIRCUITS FOR DETECTORS READOUT
Collaborations: MPI Munich (Germany), INAF-IASF (Milano)
4. ELECTRONIC AND OPTOELECTRONIC DEVICES BASED ON ORGANIC MATERIALS
M. Sampietro, D. Natali
Collaborations: Università degli studi Milano BICOCCA, CNST-IIT
5. INSTRUMENTATION FOR HIGH-SENSITIVITY MEASUREMENTS ON BIO AND NANO STRUCTURES
M. Sampietro, G. Ferrari
Collaborations: DTU (Denmark), Institut National de la Recherche Scientifique - INRA (France), Universität Potsdam (Germany), MDM-CNR (Agrate, Italia), Institute for Bioengineering of Catalonia IBEC (Spagna), Waseda University (Japan)
6. COMPOUND SEMICONDUCTOR RADIATION DETECTORS AND RELATED ASIC'S
Collaborations: University of Catania, University of Pavia, Istituto Nazionale di Astrofisica-IASF Bologna - IASF Roma, LPE S.p.A, ETC, Selex Integrated Systems (I), Thales Alenia Space, European Space Agency}
7. LOW-NOISE, lARGE-DYNAMIC-RANGE ANALOG AND DIGITAL ELECTRONICS for IONISING-RADIATION SENSORS AND PHOTODETECTORS
Collaborations: INFN, Telecontrolli, Novatel, ASCOM, AMETEK, CAEN
8. INSTRUMENTATION FOR NUCLEAR MEASUREMENTS AND MEDICAL IMAGING
Collaborations: Instr. Div. Brookhaven Nat. Lab. (NY,USA), CRMP Univ. Wollongong (Australia), RP CERN, INFN LNL e LNS, Dip. Fisica Unimib.
9. NANOELECTRONIC NON-VOLATILE MEMORIES
A.L. Lacaita, A.S. Spinelli, D. Ielmini, C. Monzio Compagnoni
Collaborations: Micron (Agrate Brianza), Intel (Santa Clara), Lawrence Berkeley National Labs, Università Autonoma Barcellona, MDM-CNR (Agrate).
10. CMOS INTEGRATED CIRCUIT DESIGN
A. Bonfanti, A. Lacaita, S. Levantino, C. Samori
11. Digital processing of sampled pulses
G. Ripamonti, A. Geraci
12. DESIGN AND CHARACTERIZATION OF INGAAS/INP SINGLE-PHOTON AVALANCHE DIODES AND INSTRUMENTATION MODULES FOR NEAR-INFRARED DETECTION
F. Zappa, A. Tosi
Collaborations: National Research Council of Canada (Ottawa, Canada), National Institute for Standard and Technology (Gaithersburg, USA), University of California in San Diego (San Diego, USA), Queen’s University (Kingston, Canada), Istituto Nazionale per la Ricerca Metrologica (Torino, Italy)
13. 2D SINGLE-PHOTON IMAGING AND 3D RANGING WITH CMOS SPAD ARRAYS
F. Zappa, A. Tosi
Collaborations: Fraunhofer IMS (Duisburg, Germany), Heriot-Watt University (Edinburgh, UK), Centro Ricerche FIAT (Torino, Italy), Institute for Quantum Computing (Waterloo, Canada)
14. TIME-RESOLVED FAST-GATED DETECTION FOR FUNCTIONAL BRAIN IMAGING AND SPECTROSCOPY
F. Zappa, A. Tosi
Collaborations: Dipartimento di Fisica del Politecnico di Milano (Italy), Physikalisch-Technische Bundesanstalt (Berlin, Germany)
15. Large-area, high quantum efficiency avalanche diodes for picosecond time-correlated photon counting
A. Gulinatti, I. Rech, M. Ghioni, S. Cova
Collaborations: CNR – IMM, Bologna; Heriot-Watt University, Edinburgh
16. Parallel Photon Counting and Picosecond Timing with Silicon-SPAD based Compact Detector Modules
I. Rech, A. Gulinatti, M. Ghioni, S. Cova
Collaborations: University of California at Los Angeles (UCLA); CNR – IMM, Bologna; Heriot-Watt University, Edinburgh
17. MICROELECTROMECHANICAL SYSTEMS AND FRONT-END ELECTRONICS
A. Longoni, G. Langfelder
Collaborations: ST Microelectronics, Italy; Berkeley Sensors and Actuators Center (BSAC), California, USA; CEA-Leti, Grenoble, France; VTT Technologies, Finland.
NEW CONCEPTS AND DEVELOPMENTS ON SILICON DETECTORS
A. Castoldi, C. Guazzoni
The research activities of the group are devoted to the study, the design and the characterization of semiconductor detectors (for X and gamma rays or charged particles) featuring state-of-the-art performances in terms of position, energy and time sensitivity.
The research activity in 2011 was focused on the optimization of the Controlled-Drift Detector (CDD), a photon counting X-ray imager featuring excellent energy and time resolution whose basic feature is the transport of the charge packets stored in each pixel to the output electrode by means of a uniform drift field. Operated in integrate-readout mode the CDD is inherently faster than the Charge-Coupled Device as the frame frequency in the CDD is ultimately limited by the electron drift time which can be as short as 2-3 µs for 1 cm-long device. The research pursued the optimization of a novel generation of CDDs suitable for high-rate spectroscopy and imaging in the X-ray spectrum.
We pursued the application of specifically designed CDDs and Silicon Drift Detectors (SDDs) to X-ray Diffraction (XRD) Imaging, a technique able to highlight the differences in the molecular composition of the sample under analysis owing to the difference in their scattering properties and to X-ray Fluorescence Imaging. We developed and qualified a novel imaging system that delivers well-resolved images in space and energy. The key features of the proposed system are the following: i) collimation system based on micrometer-size polycapillary X-ray optics instead of the conventional mechanical collimators and ii) energy-dispersive imaging detection system based on the Controlled-Drift Detector/Silicon Drift Detector instead of conventional charge-integrating devices. The fusion of images obtained from XRD/XRF and other techniques appear the most advanced tools for deepening the investigations on biological tissues and explosive detection.
Moreover we continued the development of innovative multi-column silicon drift detector, named Multi-Linear Silicon Drift Detectors (MLSDD), specifically designed for fast 2D position sensing. A MLSDD design was developed to reach very high readout speed (i.e. a frame rate of the order of 1MHz on a 1 cm long detector) for application to X-ray imaging experiments at X-ray synchrotrons and Free Electron Laser sources.
In collaboration with other researchers of the Istituto Nazionale di Fisica Nucleare (INFN), we carried out detailed modeling and characterization of planar and segmented silicon detectors devoted to the identification in charge and mass of the fragments produced in multi-fragmentation experiments at intermediate nuclear energies as well as the optimization of the low noise frontend and of the digital acquisition system for pulse shape analysis.
The most recent research line concerns the development of novel detectors for the upcoming Free-Electron Laser (FEL) based X-ray sources that push the limits of brilliance farther than any light source today. The required dynamic range in fact can range from single photon counting to 104 times 12 keV photons per pixel per pulse and the time structure of the pulsed beam has repetition time as short as 220 ns. pulse.
These extreme conditions raise the needs of novel detector design and novel qualification techniques of detector and front-end electronics. We exploited the possibility of using a pulsed monoenergetic proton beams – coming from the DEFEL beam-line of the Tandetron accelerator at LaBEC (Laboratorio di Tecniche Nucleari per i Beni Culturali) in Sesto Fiorentino, Italy – as a diagnostic tool for the characterization of the response of semiconductor detectors at high charge densities. In fact accelerated protons owing to their limited range in silicon can deliver a large and precisely calibrated amount of charge along a track well matched to the typical silicon wafer thickness and with precisely defined position and timing. The focus is on the potentiality of the experimental technique and on the first results of the experimental characterization of fast X-ray imaging detectors.
Pubblications in 2011
1) M. Sampietro, C. E. Bottani, M. Carminati, C. Casari, A. Castoldi, G. Ferrari, M. Fusi, C. Guazzoni, A. Rottigni, M. Vergani, “Biosensors and molecular imaging”, IEEE Pulse, 2011 May-Jun, 2(3), pp. 35-40, doi: 10.1109/MPUL.2011.941521
2) Ozkan, A. Castoldi, C. Guazzoni, D. Dreossi, A. Bjeoumikhov, “Experimental Characterization of a Parallel Polycapillary Collimator for X-ray Scatter Imaging”, IEEE Trans. Nucl. Sci, Vol. 58, No. 4, Aug 2011, pp. 2124-2128, doi: 10.1109/TNS.2011.2160559.
3) F. Amorini, R. Bassini, C. Boiano, G. Cardella, E. De Filippo, L. Grassi, C. Guazzoni, P. Guazzoni, M. Kiš, E. La Guidara, Y. Leifels, I. Lombardo, T. Minniti, A. Pagano, M. Papa, S. Pirrone, G. Politi, F. Porto, F. Riccio, F. Rizzo, P. Russotto, S. Santoro, W. Trautmann, A. Trifirò, G. Verde, P. Zambon, L. Zetta, “Light Charged Particle Identification by Means of Digital Pulse Shape Acquisition in the CHIMERA CsI(Tl) Detectors at GSI Energies”, IEEE Nuclear Science Symposium Conference Records, 2011 IEEE, Valencia, Spagna, Oct. 23 – 29, 2011, pp. 202-208, doi: 10.1109/NSSMIC.2011.6154480
4) F. Amorini, C. Boiano, G. Cardella, A. Castoldi, E. De Filippo, E. Geraci, L. Grassi, C. Guazzoni, P. Guazzoni, E. La Guidara, I. Lombardo, A. Pagano, S. Pirrone, G. Politi, F. Porto, F. Riccio, F. Rizzo, P. Russotto, G. Verde, P. Zambon, L. Zetta, “Determination of CsI(Tl) Scintillation Time Constants and Intensities by Direct Fitting of Digitized Waveforms in the CHIMERA 4π Multidetector”, IEEE Nuclear Science Symposium Conference Records, 2011 IEEE, Valencia, Spagna, Oct. 23 – 29, 2011, pp. 216-221, doi: 10.1109/NSSMIC.2011.6154483.
5) A. Castoldi, C. Guazzoni, P. Lechner, D. Mezza, G. Montemurro, L. Carraresi, F. Taccetti, “Mapping of the response function of DePFET-based pixel sensors at different levels of charge injection”, IEEE Nuclear Science Symposium Conference Records, 2011 IEEE, Valencia, Spagna, Oct. 23 – 29, 2011, pp. 1747 – 1753, doi: 10.1109/NSSMIC.2011.6154675.
6) A. Castoldi, C. Guazzoni, K. Pepper, A. Gibson, J. Griffiths, G. J. Royle, A. Bjeoumikhov, “2-D Energy-Resolved Imaging of Gold Nanoparticle Distribution at Concentrations Relevant for In-Vitro Studies”, IEEE Nuclear Science Symposium Conference Records, 2011 IEEE, Valencia, Spagna, Oct. 23 – 29, 2011, pp. pp. 261 - 265, doi: 10.1109/NSSMIC.2011.6154493.
7) K. Pepper, C. Ozkan, C. Christodoulou, D. Dreossi, A. Castoldi, C. Guazzoni, A. P. Gibson, G. J. Royle, “X-ray edge subtraction imaging of gold nanoparticle concentrations for biological imaging”, IEEE Nuclear Science Symposium Conference Records, 2011 IEEE, Valencia, Spagna, Oct. 23 – 29, 2011, pp. 2877 – 2879, doi: 10.1109/NSSMIC.2011.6152509.
8) A. Castoldi, C. Guazzoni, D. Mezza, G. Montemurro, R. Hartmann, L. Strüder, L. Carraresi, F. Taccetti, “Longitudinal Profile of the Charge Cloud at High Charge Levels in Multi-Linear Silicon Drift Detectors for Position-Sensing Applications”, IEEE Nuclear Science Symposium Conference Records, 2011 IEEE, Valencia, Spagna, Oct. 23 – 29, 2011, pp. 575 – 579, doi: 10.1109/NSSMIC.2011.6154115.
9) A. Castoldi, C. Guazzoni, D. Mezza, L. Carraresi, F. Taccetti, “Characterization and diagnostics of fast X-ray imaging detectors for X-ray free electron laser sources”, Advances in X-ray Free-Electron Lasers: Radiation Schemes, X-ray Optics, and Instrumentation, edited by Thomas Tschentscher, Daniele Cocco, Proc. of SPIE Vol. 8078, pp. 80780P-1 – 80780P-12, 2011 ISSN 0277-786X/11/$18, doi: 10.1117/12.888027.
10) S. Facchinetti, L. Bombelli, A. Castoldi, C. Fiorini, C. Guazzoni, D. Mezza, M. Porro, G. De Vita, F. Erdinger, “Fast, Low-Noise, Low-Power Electronics for the Analog Readout of Non-Linear DEPFET Pixels”, IEEE Nuclear Science Symposium Conference Records, 2011 IEEE, Valencia, Spagna, Oct. 23 – 29, 2011, pp. pp. 1846 – 1851, doi: 10.1109/NSSMIC.2011.6154371.
APPLICATIONS OF SILICON DRIFT DETECTORS IN X-RAY AND GAMMA-RAY DETECTION
C. Fiorini, A. Longoni, A. Geraci, G. Padovini
Gamma-ray detectors for imaging and spectroscopy based on Silicon Drift Detector (SDD) arrays coupled to CsI(Tl) scintillators are under development for different applications in nuclear medicine, like human imaging (e.g. breast, tyroid, brain) and molecular imaging on small animals. When used as photodetector for the scintillation light the SDD allows to reach better energy and position resolutions in gamma detection with respect to system based on conventional PMTs, PIN or APD diodes. Sub-millimeter position resolutions have been achieved with SDD-based Anger Cameras based on CsI(Tl) crystals (DRAGO project). A new large area Anger camera is under development for the HICAM project. A prototype of 10 × 10 cm2 camera have been already experimented on imaging of phantoms to assess the resolution performances and on cellular imaging experiments on small animals.
We are involved in the development of a large area (200 cm2) X-ray detection system for the SIDDHARTA (Silicon Drift Detector for Hadronic Atom Research by Timing Application) project. SIDDHARTA is a Hadronic physics experiment to be realized at the DAFNE collider and supported by European Community and by Italian INFN. In this framework, we have developed a low-noise CMOS readout circuit for the readout of the SDDs. The ASIC, realized in the 0.35 µm AMS technology, contains 8 identical analog channels composed by a low-noise charge preamplifier, a 6th order Gaussian shaper, a low-frequency feedback loop for the self-adjustment of the real leakage current, a baseline holder, and a peak stretcher. A digital section manages all the signals coming from the analog channels, implements the pile-up rejections, sets the upper and lower thresholds level for the event, implements a FIFO to store the events (channel address and related analog value), implements the interface with the external acquisition system. The experimental set-up including the SDDs detectors and the related electronics has been completed and the physics experiments have been started. Runs of measurements on kaonic nitrogen, kaonic hydrogen have been carried out with first results under analysis now.
Pubblications in 2011
1) Fiorini, C.; Peloso, R.; Longoni, A.; Mennini, T.; Micotti, E.; "Study of Compatibility of a Silicon Drift Detector With a MRI System", Nuclear Science, IEEE Transactions on, Volume: 58 , Issue: 2, Publication Year: 2011 , Page(s): 559 - 568
2) M. Bazzi, G. Beer, L. Bombelli, A.M. Bragadireanu, M. Cargnelli, G. Corradi, C. Curceanu (Petrascu), A. d’Uffizi, C. Fiorini, T. Frizzi, F. Ghio, B. Girolami, C. Guaraldo, R.S. Hayano, M. Iliescu, T. Ishiwatari, M. Iwasaki, P. Kienle, P. Levi Sandri, A. Longoni, V.Lucherini, J. Marton, S.Okada, D.Pietreanu, T.Ponta, A.Rizzo, A.RomeroVidal, A.Scordo, H.Shi, D.L. Sirghi, F.Sirghi, H.Tatsuno, A.Tudorache, V.Tudorache, O.VazquezDoce, E. Widmann, J.Zmeskal, "Performance of silicon-drift detectors in kaonic atom X-ray measurements", Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, Volume 628, Issue 1, 1 February 2011, Pages 264-267.
3) Peloso, R.; Busca, P.; Fiorini, C.; Basilavecchia, M.; Frizzi, T.; Smeets, J.; Roellinghoff, F.; Prieels, D.; Stichelbaut, F.; Benilov, A.; "Application of the HICAM camera for imaging of prompt gamma rays in measurements of proton beam range", Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC), 2011 IEEE, Publication Year: 2011 , Page(s): 2285 - 2289
LOW-NOISE VLSI CIRCUITS FOR DETECTORS READOUT
We are involved in the development of a new class of integrated readout circuits to be employed in astrophysics missions on satellite and in experiments at synchrotron facilities. The common requirements for such circuits is to allow performing X-ray imaging at fast frame rate with ultra-low noise.
The VELA circuit represent an example of this class of circuits and a significant effort is presently dedicated to its development. VELA is the faster and the higher performance circuit available to readout a DEPFET matrix when the trade-off between noise and speed is the primary concern. The novel drain current readout scheme overcomes the limitations of the conventional voltage readout with architecture insensible to the stray capacitance (CL). As a consequence, the current readout makes possible to speed-up the readout time to 2 µs/line and achieve better spectroscopic performances. Each analog channel is composed of an input cascode stage, an IBIAS memory cell, and the time-variant shaper.
The extremely low-noise readout, achievable with VELA, is possible with of a time-limited filter which implements a true trapezoidal weighting function. This filter is a very good approximation of the optimum filter whether the series noise is concerned as the major noise source. The shaper is implemented by an integrator stage followed by a subtracting stage. These two stages, with a proper operation of the switches, implement the desired trapezoidal weighting function.
A full-format version of circuit has been realized in the 0.35 µm CMOS technology and successfully tested. VELA integrates 64 analog shaping filters performing a trapezoidal weighting function, 64 sample/hold stages (S&H), one analog multiplexer, and a fast differential output buffer. Moreover, a digital section generates all the programmable control signals for the filtering stages. Every function of the circuit can be digitally controlled with SPI (Serial Peripheral Interface) commands. The analog gain can be selected; and the readout speed can be remotely adjusted as well. Moreover, several testing features and debugging operations can be remotely performed in order to verify the proper functionality of all the integrated parts. Even the biasing condition of all the analog stages and thus the total power consumption of VELA can be adjusted using internal DACs. An independent logic is designed to operate the multiplexer and the S&Hs; this logic implements additional features to the standard multiplexing operation, like the possibility to choose between full-frame or window mode.
Pubblications in 2011
1) Facchinetti, S.; Bombelli, L.; Fiorini, C.; Porro, M.; De Vita, G.; Erdinger, F.; "Characterization of the Flip Capacitor Filter for the XFEL-DSSC Project", Nuclear Science, IEEE Transactions on, Volume: 58 , Issue: 4 , Part: 2, Publication Year: 2011 , Page(s): 2032 – 2038.
2) Uslenghi, M.; Fiorini, M.; Fiorini, C.; Bombelli, L.; Facchinetti, S.; Marone, A.; Rocco, G.; Vermi, C.; Candelori, A.; Mattiazzo, S.; Silvestrin, L.; Wyss, J.; Herrmann, S.; DeVita, G.; Porro, M.; Wassatsch, A.; Incorvaia, S.; "Study of Single Event transients on the VELA ASIC, x-ray detectors FEE for new generation astronomical instruments", Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC), 2011 IEEE, Publication Year: 2011 , Page(s): 2119 - 2123
3) Facchinetti, S.; Bombelli, L.; Castoldi, A.; Fiorini, C.; Guazzoni, C.; Mezza, D.; Porro, M.; De Vita, G.; Erdinger, F.; "Fast, low-noise, low-power electronics for the analog readout of non-linear DEPFET pixels", Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC), 2011 IEEE, Publication Year: 2011 , Page(s): 1846 – 1851.
4) Bombelli, L.; Fiorini, C.; Frizzi, T.; Alberti, R.; Longoni, A.; "“CUBE”, A low-noise CMOS preamplifier as alternative to JFET front-end for high-count rate spectroscopy", Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC), 2011 IEEE, Publication Year: 2011 , Page(s): 1972 - 1975
5) Bombelli, L.; Quaglia, R.; Fiorini, C.; Tocchio, A.; Alberti, R.; Frizzi, T.; "A multichannel integrated readout circuit for high throughput X-ray spectroscopy with Silicon Drift Detectors", Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC), 2011 IEEE, Publication Year: 2011 , Page(s): 944 - 950
ELECTRONIC AND OPTOELECTRONIC DEVICES BASED ON ORGANIC MATERIALS
M. Sampietro, D. Natali
This research aims to study the physical properties of organic semiconductors and to produce innovative electronic and optoelectronic devices. The research has focused on few specific aspects of organic electronics, namely i) the realization and characterization of photodetectors to be coupled with scintillators for the indirect detection of X-rays; ii) the modeling of organic field effect transistor.i) X-rays sensing applications might benefit from the development of detectors based on organic semiconductors. Their processing from solution and at room temperature envisages large area coverage of, in principle, any substrate. Due to the presence of two mixed moieties in the active layers, mandatory to achieve large quantum efficiency, the transport and collection of photogenerated charges and, at the same time, suppression of dark injected charge are entangled issues onto which we focused our efforts. By suitably tailoring at chemical level the organic molecules, and by optimizing the metal–semiconductor interface at a device level, leakage current <1 nA/cm2, external quantum efficiency in the visible spectrum range in excess of 10%, bandwidth in excess of 1MHz, and air stability upon proper encapsulation can be achieved (collaboration with Univ. Milano Bicocca, Dip. Scienza Materiali). Photodiodes have been coupled with CsI:Tl scintillator and by using a collimated X-ray beam it was possible to measure current variations in the order of 150 pA over a dark current floor of less than 50pA when operating the X-ray tube in switching mode, thus proving the feasibility of indirect X-ray detection by means of organic semiconductors.ii) The current understanding of injection and transport phenomena in organic semiconductors is still limited, and the field would benefit from new techniques giving access to devices relevant physical quantities (eg. charge/field distribution) under operating conditions. In this framework, we introduced a tool for detecting the electric ﬁeld in the channel of a working transistor with an all-optical, non-invasive, bulk-sensitive technique exploiting Stark confocal spectroscopy, with a nominal spatial resolution better than 500 nm. With the aid of suitable numerical modeling, it was possible not only to reconstruct the space charge proﬁle in the few-nanometer thick accumulation layer, but also to extract the AC electron mobility. (in collaboration with CNST-IIT).
Pubblications in 2011
1) Binda, M.; Iacchetti, A.; Natali, D.; Beverina, L.; Sassi, M.; Sampietro, M., High detectivity squaraine-based near infrared photodetector with nA/cm(2) dark current, Applied Physics Letters, 98, 073303, 2011.
2) de Falco, A. Iacchetti, M. Binda, D. Natali, R. Sacco and M. Verri, Modeling and Simulation of Organic Solar Cells, Scientific Computing in Electrical Engineering SCEE 2010, Mathematics in Industry, 2012, Volume 16, Part 4, 329-337
INSTRUMENTATION FOR HIGH-SENSITIVITY MEASUREMENTS ON BIO AND NANO STRUCTURES
M. Sampietro, G. Ferrari
The research activity is focused on the development of instrumentation and techniques to probe the electrical properties of nanodevices and biomolecules.
To address instrument-on-chip applications, we designed a very high sensitivity system for the detection of capacitance variations with a resolution as low as few zeptoFarad (10-21 F). This is achieved by means of a CMOS ultra-low-noise and wide-bandwidth current sensing circuit coupled to a lock-in amplifier to perform capacitance and conductance measurements in a frequency range from DC to 1MHz. The adoption of an integrated implementation, based on an original circuital topology, provides miniaturization and performance improvement. The mm-sized chip can be easily integrated in extremely compact sensing setups avoiding long connection cables, thus significantly reducing the input stray capacitance that affects the noise level. The experimental characterization has demonstrated the use of this integrated read-out circuit as a versatile tool for nanosensor development.
We used a miniaturized CMOS impedance detector within a dielectrophoretic microfluidic device for label-free separation, enabling the sorting and counting of particle suspensions in a fully electrical manner. This approach makes possible a truly portable system for cell sorting and analysis. Towards this end, the design of ad hoc coplanar electrodes for impedance sensing, supported by numerical simulations, has been performed. The validation of the system with 10m polystyrene beads has been successfully done. A USB-controlled single-chip lock-in demodulator allows high-throughput counting of resistive peaks of 1% amplitude, with a signal-to-noise ratio >10 and with a time resolution of 200s.
To track in real-time the growth and differentiation of stem cells in a microfluidic system, we have designed and operated a fully operating electronic platform that enables electrochemical measurements (quasistatic cyclic voltammetry, impedance tracking, and impedance spectroscopy). This system is under operation within a European Project aiming at investigating cell metabolism through electronic sensing.
High sensitivity instrumentation has also been designed to measure the transport properties of silicon transistors fabricated by single-ion implantation method. By placing donors in one dimensional array, we analyzed the quantum transport characteristics at low temperature (<15K). We found two distinct regimes: single-electron tunneling through isolated states in the case of two implanted donors; Hubbard band formation due to the inter-donor coupling in the case of six donors.
Pubblications in 2011
1) M. Carminati, G. Ferrari, F. Guagliardo, M. Sampietro, “ZeptoFarad capacitance detection with a miniaturized CMOS current front-end for nanoscale sensors”, Sensors and Actuators A: Physical, Vol. 172, pp. 117-123 (2011)
2) A. Rottigni, M. Carminati, G. Ferrari, MD Vahey, J. Voldman, M. Sampietro, “Handheld 2-channel impedimetric cell counting system with embedded real-time processing”, Proccedings of SPIE conference “Bioelectronics, Biomedical, And Bioinspired Systems V And Nanotechnology V”, Vol. 8068, 80680S, Prague (2011) DOI: 10.1117/12.886709
3) A. Rottigni, M. Carminati, G. Ferrari, M. Sampietro, “Handheld Bio-Impedance Measurement System Based on an Instrument-on-Chip”, 7th Conference on Ph. D. Research in Microelectronics and Electronics (PRIME 2011), Madonna di Campiglio, p. 49-52 (2011)
4) K. Zόr, M. Vergani, A. Heiskanen, E. Landini, M. Carminati, V. Coman, I. Vedarethinam, P. Skafte, Pedersen, M. Skolimowski, A. Martinez Serrano, M. Kokaia, T. Ramos Moreno, A. Ghio, W.E. Svendsen, M. Dimaki, Z. Keresztes, M. Adamovski, U. Wollenberger, D. Sabourin, G. Ferrari, R. Raiteri, M. Sampietro, M. Dufva, J. Emnéus, “Real-Time Monitoring of Cellular Dynamics Using a Microfluidic Cell Culture System with Integrated Electrode Array and Potentiostat”, Proc. of the International Conference on Miniaturized Systems for Chemistry and Life Sciences uTAS, Seattle (USA), p. 1532-1535 (2011)
5) T.Shinada, M.Hori, F.Guagliardo, G.Ferrari, A.Komatubara, K.Kumagai, T.Tanii, T.Endo, Y.Ono and E.Prati: Quantum transport in deterministically implanted single-donors in Si FETs, IEDM Tech. Dig. (2011) 697-700
6) M. Sampietro, C.E.Bottani, M.Carminati, C.S.Casari, A.Castoldi, R. Cubeddu, C. D'Andrea, G.Ferrari, M.Fusi, C.Guazzoni, A.Rottigni, P.Taroni, G.Valentini, M.Vergani, "Biosensors and Molecular Imaging", IEEE Pulse, Vol. 2, pp. 35-40 (2011)
7) M. Carminati, M. Sampietro, G. Carminati, “Analysis of instrumentation performance for distributed real-time air quality monitoring”, 2011 IEEE Workshop on Environmental Energy and Structural Monitoring Systems (EESMS), Milano (2011) DOI: 10.1109/EESMS.2011.6067044
COMPOUND SEMICONDUCTOR RADIATION DETECTORS AND RELATED ASIC'S
The research activity has been devoted to the experimental characterization of Silicon Carbide radiation detectors for spectroscopy of ionizing radiation (X-ray, alpha, beta particles) The SiC detectors have been realized within collaboration between Politecnico, University of Catania and Modena, and the companies LPE, ETC and Selex. A large format mixed-signal ASIC (3 cm2) for radiation imaging space applications has been designed, manufactured and characterized in collaboration with University of Pavia, Thales Alenia Space and the European Space Agency.
Low-noise, large-dynamic-range analog and digital electronics for ionising-radiation sensors and photodetectors
This research activity is focused on the design and develoment of innovative analog and digital electronics and processing algorithms for semiconductor sensors of ionising radiations (X, gamma, charged particles) and optical light. Applications include bio-medical imaging, gamma-ray tracking in nuclear physics experiments, confocal microscopy, dynamic scattering measurements, X-and gamma-ray imaging, contaminant analysis, environmental safeguard. The electronics used in these systems includes typically a low-noise fast preamplifier, a digitizer and a fast processor used for optimal-filtering implementation and for the final classification of the events.
A new time-variant ASIC preamplifier has been developed and is being patented, which is able to work and perform spectroscopic measurements even in soft or deep saturation regime, yielding a substantial dynamic-range boost as well as a dramatic reduction of the system dead time. The amplitude of the large signals which cause circuit saturation is estimated from the time width of a properly generated logic signal. Amazingly the relation between the signal and such time width is linear irrespective of the non-linear working mode of the circuit. Using this patented technique a virtually unlimited range is obtained in high-resolution spectroscopy measurements.
A low-noise preamplifier has been designed and is currently in use at the INFN Laboratori Nazionali del Gran Sasso for the commissioning of the GERDA-phase1 76Ge enriched detector. This underground detector has been developed in the frame of an international collaboration on double-beta decay search. The circuit works in the wide temperature range of -196°C to 50°C. A remarkable energy resolution of 2.2 keV fwhm has been obtained on the 60Co 1.3 MeV line with the circuit and the germanium detector operated immersed in liquid nitrogen.
We have finally realized an original preamplifier for photodetectors for an innovative particle sizer able to measure 50nm thin powders. The circuit has been developed for the quality-control processes of silicon fundries and IC’s manufacturers in the framework of a funded EU project. The circuit is also suited for ultra-precise characterization of the stability of laser beams and for confocal microscopy. The typical measurement system utilizing such circuit includes a laser, an optional light splitter, and one or more photodiodes. For these applications we have developed and patented a new circuit structure with auto-zero functionality able to optimize the measurement dynamic range.
Pubblications in 2011
1) A. Pullia "Interfacing low-noise charge-sensitive preamplifiers to high-resolution flash ADCs", in IEEE Nucl. Sci. Symp. Conf. Rec., 2011 IEEE NSS/MIC, 23 oct - 29 oct 2011, Valencia, Spain, doi: 10.1109/NSSMIC.2011.6154561
2) S. Akkoyun, A. Algora, B. Alikhani, F. Ameil, G. De Angelis,..., A. Pullia,..., "AGATA - Advanced GAmma Tracking Array", Nucl Instrum Methods Phys Res Sect A, vol. 668, pp. 26-58, 2012, doi: 10.1016/j.nima.2011.11.081
3) Cattadori, M. Knapp, K. Kroeninger, X. Liu, L. Pandola, A. Pullia, C. Tomei, C. Ur, F. Zocca, "Search for the neutrinoless beta-beta decay in 76Ge with the GERDA, vol. 221, p. 382, 2011, 10.1016/j.nuclphysbps.2011.10.033
4) Gadea, E. Farnea, J.J. Valiente-Dobòn, B. Million, D. Mengoni,..., A. Pullia,..., “Conceptual design and infrastructure for the installation of the first AGATA sub-array at LNL” Nucl Instrum Methods Phys Res Sect A, vol. 654, no. 1, pp.88-96, 2011, doi: 10.1016/j.nima.2011.06.004
5) A. Pullia, D. Weisshaar, F. Zocca, D. Bazzacco, "Cross-talk limits of highly segmented semiconductor detectors", IEEE Trans Nucl Sci, vol. 58, no. 3, pp. 1201-1205, 2011
6) P.A. Soederstroem, F. Recchia, J. Nyberg, A. Al-Adili, A. Ataç, S. Aydin,..., A. Pullia,..., "Interaction position resolution simulations and in-beam measurements of the AGATA HPGe detectors", Nucl Instrum Methods Phys Res Sect A, vol. 638, no. 1, pp. 96-109, 2011, doi: 10.1016/j.nima.2011.02.089
INSTRUMENTATION FOR NUCLEAR MEASUREMENTS AND MEDICAL IMAGING
The research activity is aimed to the development of silicon detectors and front-end electronics for nuclear measurements (neutron spectrometry, personal dosimetry and microdosimetry) and medical imaging (functional molecular imaging). It consists of detector and circuit design and characterisation, prototyping and beam tests at INFN Legnaro and Catania Labs, PTB (D), ISIS RAL (UK), and ANSTO (Australia).
New silicon microdosimeter has been successfully compared with classical Tissue Equivalent Proportional Counters in different radiation fields.
Pubblications in 2011
1) S. Agosteo, P. Colautti, I. Fanton, A. Fazzi, M.V. Introini, D. Moro, A. Pola, and V. Varoli, “Study of a solid state microdosemeter based on a monolithic silicon telescope: irradiations with low-energy neutrons and direct comparison with a cylindrical TEPC”, Radiat Prot Dosimetry (2011) 143(2-4): 432-435
2) A. Pietropaolo, C. Andreani, M. Rebai, L. Giacomelli, G. Gorini, E. Perelli Cippo, M. Tardocchi, A. Fazzi, G. Verona Rinati, C. Verona, M. Marinelli, E. Milani, C. D. Frost, E. M. Schooneveld, “Fission diamond detectors for fast neutron ToF spectroscopy”, Europhysics Letters, 94 N°6 (2011) pp. 62001 p1-p4, European Physical Society, June 2011
3) L. Giacomelli, C. Andreani, A. Fazzi, C.D. Frost, G. Gorini, E. Perelli Cippo, A. Pietropaolo, M. Rebai, H. Schuhmacher, M. Tardocchi, C. Verona , G. Verona Rinati and A. Zimbal, “Diamond detectors for fast neutron irradiation experiments”, Nuclear Physics B (Proc. Suppl.) 215 (2011) 242–246
4) M. Rebai, C. Andreani, A. Fazzi, C.D. Frost, L. Giacomelli, G. Gorini, E. Milani, E. Perelli Cippo, A. Pietropaolo, G. Prestopino, E. Schooneveld, M. Tardocchi, C. Verona and G. Verona Rinati, “Fission diamond detector tests at the ISIS spallation neutron source”, Nuclear Physics B (Proc.Suppl.) 215 (2011) 313-315
5) S. Agosteo, A. Fazzi, M.V. Introini, A. Pola, A.B. Rosenfeld, R. Shulte, A. Wroe, “Study of a monolithic silicon telescope for solid state microdosimetry: Response to a 100 MeV proton beam”, Radiation Measurements, vol. 46, issue 12, (2011) 1529-1533, Presented at the Solid State Dosimetry SSD-16, Sydney (Australia), Sept 2010.
6) S. Agosteo, G. A. P. Cirrone, G. D’Angelo, A. Fazzi, M. V. Introini, A. Pola, Feasibility Study Of Radiation Quality Assessment With A Monolithic Silicon Telescope: Irradiations With 62 AMeV Carbon Ions At LNS-INFN”, Radiation Measurements vol. 46, issue 12, (2011) 1534 -1538, Presented at the Solid State Dosimetry SSD-16, Sydney (Australia), Sept 2010.
7) S. Agosteo, P. Colautti, J. Esposito, A. Fazzi, M.V. Introini, A. Pola, “Characterization of the energy distribution of neutrons generated by 5 MeV protons on a thick beryllium target at different emission angles”, Applied Radiation and Isotopes 69 (2011)1664–1667
NANOELECTRONIC NON-VOLATILE MEMORIES
A. L. Lacaita, A. S. Spinelli, D. Ielmini, C. Monzio Compagnoni
The research activity is focused on the investigation of the performance and limitations of decananometer non-volatile memories, with emphasis on NOR and NAND Flash technologies as well as on emerging memories based on phase-change, resistive switching and charge-trapping. An activity on volatile memories for DRAM replacement has recently been started.
The research activity on Flash memories has been mainly focused on the impact on device reliability of parameter spread and charge detrapping, investigating the effects of distributed cycling on the threshold voltage instability and developing a compact model for the evaluation and comparison of different variability effects. Concerning charge-trap memories, instead, the activity has been devoted to the analysis of the program operation in presence of atomistic dopants and traps, investigating the resulting accuracy limitations via 3D Monte Carlo simulations. Moreover, an investigation of cylindrical charge-trap devices was carried out, resulting in a simple model for the transient program operation of these devices.
Recently, an activity related to the development of a new class of devices for DRAM replacement has been started with the analysis of the physical properties
The reliability of phase change memories has been studied to assess the threshold voltage drift, which affects the stability of the programming window in memory and select devices. New models have been developed for the bipolar switching processes in resistive switching memories based on hafnium oxide. Switching and reliability models have also been developed and validated for conductive bridge memories based on Ag migration in solid electrolytes.
Pubblications in 2011
1) S. M. Amoroso, C. Monzio Compagnoni, A. Mauri, A. Maconi, A. S. Spinelli, and A. L. Lacaita, ``Semi-analytical model for the transient operation of gate-all-around charge-trap memories'', IEEE Trans. Electron Devices 58, 3116 (2011).
2) A. Miccoli, C. Monzio Compagnoni, S. Beltrami, A. S. Spinelli, and A. Visconti, ``Threshold-voltage instability due to damage recovery in nanoscale NAND Flash memories'', IEEE Trans. Electron Devices 58, 2406 (2011).
3) A. Spessot, C. Monzio Compagnoni, F. Farina, A. Calderoni, A. S. Spinelli, and P. Fantini, ``Compact modeling of variability effects in nanoscale NAND Flash memories'', IEEE Trans. Electron Devices 58, 2302 (2011).
4) A. Maconi, S. M. Amoroso, C. Monzio Compagnoni, A. Mauri, A. S. Spinelli, and A. L. Lacaita, ``Three-dimensional simulation of charge-trap memory programming -- Part II: variability'', IEEE Trans. Electron Devices} 58, 1872 (2011).
5) S. M. Amoroso, A. Maconi, A. Mauri, C. Monzio Compagnoni, A. S. Spinelli, and A. L. Lacaita, ``Three-dimensional simulation of charge-trap memory programming -- Part I: average behavior'', IEEE Trans. Electron Devices} 58, 1864 (2011).
6) D. Ielmini, R. Bruchhaus and R. Waser, “Thermochemical resistive switching: Materials, mechanisms and scaling projections,” Phase Transition 84, 570 (2011).
7) D. Ielmini and A. L. Lacaita, “Phase change materials in non-volatile storage,” Materials Today 14, 600 (2011).
8) D. Ielmini, S. Spiga, F. Nardi, C. Cagli, A. Lamperti, E. Cianci, and M. Fanciulli, “Scaling analysis of submicrometer nickel-oxide-based resistive switching memory devices,” J. Appl. Phys. 109, 034506 (2011).
9) D. Ielmini, C. Cagli and F. Nardi, “Physical models of size-dependent nanofilament formation and rupture in NiO resistive switching memories,” Nanotechnology 22, 254022 (2011).
10) F. Nardi, C. Cagli, S. Spiga and D. Ielmini, “Reset instability in pulsed-operated unipolar resistive switching memory,” IEEE Electron Device Lett. 32, 719 (2011).
11) M. Boniardi and D. Ielmini, “Physical origin of the resistance drift exponent in amorphous phase change materials,” Appl. Phys. Lett. 98, 243506 (2011).
12) D. Ielmini, F. Nardi and C. Cagli, “Universal reset characteristics of unipolar and bipolar metal-oxide RRAM,” IEEE Trans. Electron Devices 58, 3246 (2011).
13) C. Cagli, F. Nardi, B. Harteneck, Z. Tan, Y. Zhang, and D. Ielmini, “Resistive-switching crossbar memory based on Ni-NiO core-shell nanowires,” Small 7, 2899 (2011).
14) D. Ielmini, “Modeling the universal set/reset characteristics of bipolar RRAM by field- and temperature-driven filament growth,” IEEE Trans. Electron Devices 58, 4309 (2011).
15) S. Long, C. Cagli, D. Ielmini, M. Liu and J. Suñé, “Reset Statistics of NiO-Based Resistive Switching Memories,” IEEE Electron Device Lett. 32, 1570 (2011).
16) M. Rizzi, A. Spessot, P. Fantini and D. Ielmini, “Role of mechanical stress in the resistance drift of Ge2Sb2Te5 films and phase change memories,” Appl. Phys. Lett. 99, 223513 (2011).
CMOS INTEGRATED CIRCUIT DESIGN
A. Bonfanti, A. Lacaita, S. Levantino, C. Samori
Main field of research is the design of mixed-signal and RF circuit and system, with particular emphasis on solid-state implementations. Contributions have been provided in the study of new architectures for the CMOS integration of radio terminals and in the analysis and design of critical building blocks such as low-phase-noise oscillators and frequency synthesizers. Currently, the group is focusing on fourth-generation wideband communication standards, such as WiMax and LTE. Taking advantage of the digitally-intensive design enabled by ultra-scaled CMOS processes, new methodologies and design strategies have been conceived which aim at highly-efficient wireless transmitters, robust to process and environmental variability. The most recent result has been the demonstration of a wideband phase modulator based on an all-digital fractional-N frequency synthesizer in 65nm CMOS, presented at the 2012 International Solid-State Circuits Conference (ISSCC) in San Francisco. The circuit features low phase noise and spurs although the power-hungry time-to-digital converter (TDC) is substituted by a simple early-late detector. This innovative realization of fractional-N synthesizer has reached the best power-jitter trade-off and the highest modulation rate so far reported. The synthesizer performance is independent of the variability of analog parameters, thanks to the adoption of digitally-intensive calibrations operating in background.
Another research topic is the design of low-power and low-noise mixed-signal circuits for recording, processing and wireless transmission of neural signal, both in laboratory-animals and in human patients.
In 2011 a first prototype was developed in 0.35um CMOS technology and successfully tested. The system was able to acquire signal from 64 channels, compress the huge amount of digital data by means of a fully-integrated DSP. Employing a narrowband Manchester-coded FSK transmitter, the transmission range was larger than 10m with a power consumption of about 250uW per channel.
In 2012, the activity is focused in designing a similar 64-channel system in a more advanced technology (0.13um CMOS) and 0.5-V of power supply. The target is to drastically reduce the power consumption per channel (less than 20uW) and transmit the acquired data all the raw data without compression employing an UWB transmitter.
Pubblications in 2011
1) D. Tasca, M. Zanuso, G. Marzin, S. Levantino, C. Samori, A. L. Lacaita (2011). A 2.9-to-4.0GHz fractional-N digital PLL with Bang-Bang phase detector and 560fsrms integrated jitter at 4.5mw power. (pp. 88-89). In: Digest of Technical Papers of the 2011 IEEE International Solid-State Circuits Conference. ISSCC 2011. 20-24 February 2011, San Francisco, USA.
2) Samori, M. Zanuso, S. Levantino, A. Lacaita (2011). Multipath Adaptive Cancellation of Divider Non-Linearity in Fractional-N PLLs. (pp. 418-421). In: Proceedings of 2011 IEEE International Circuits And Systems Conference. ISCAS 2011. 15-18 May 2011, Rio de Janeiro, Brazil.
3) A. Bonfanti, G. Zambra, G. Baranauskas, G.N. Angotzi, E. Maggiolini, M. Semprini, A. Vato, L. Fadiga, A.S. Spinelli, A.L. Lacaita, “A wireless microsystem with digital data compression for neural spike recording,” Microelectronic Engineering, Vol. 88, no.8, August 2011, pp. 1672-1675.
4) G. Baranauskas, E. Maggiolini, A. Vato, G. N. Angotzi, A. Bonfanti, G. Zambra, A. Spinelli and L. Fadiga, “The origins of 1/f2 scaling in the power spectrum of intra-cortical local field potential", Journal of Neurophysiology, Volume: 107 Issue: 3. Pages: 984-994 , Nov. 2011
5) A. Bonfanti, T. Borghi, G. Zambra, A. L. Lacaita, “Fully-Integrated Systems for Neural Signals Recording: Technology Perspective and Low-Noise Front-end Design”, edited by Krzysztof Iniewski, CMOS Biomicrosystems: Where Electronics meet Biology, John Wiley & Sons, 2011. (BOOK CHAPTER)
6) Tasca, M. Zanuso, G. Marzin, S. Levantino, C. Samori, A. L. Lacaita. A 2.9–4.0-GHz Fractional-N Digital PLL With Bang-Bang Phase Detector and 560-fsrms Integrated Jitter at 4.5-mW Power IEEE JOURNAL OF SOLID-STATE CIRCUITS (ISSN:0018-9200), (pp. 2745-2758), 46, 2011.
7) M. Zanuso, S. Levantino, C. Samori, A. L. Lacaita (2011). A Wideband 3.6 GHz Digital Delta-Sigma Fractional-N PLL With Phase Interpolation Divider and Digital Spur Cancellation IEEE JOURNAL OF SOLID-STATE CIRCUITS (ISSN:0018-9200),(pp. 627-638), 46, 2011.
8) Tasca, M. Zanuso, S. Levantino, C. Samori, A. L. Lacaita. Low-Power Divider Retiming in a 3-4GHz Fractional-N PLL IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS. II, EXPRESS BRIEFS (ISSN:1549-7747), (pp. 200-204), 58, 2011.
Digital processing of sampled pulses
G. Ripamonti, A. Geraci
Digital processors for pulse processing have been intensively investigated and developed in many fields of application as an alternative to classic analogue systems. This interest is due to the intrinsic adaptivity, easiness of calibration and capability to obtain signal-to-noise ratios very close to the optimum one. This research deals with the design, realization and test of a general purpose digital instrumentation for signal processing of random pulses analysis with throughput up to 100 kevents/sec, whose features and performances are comparable or superior to state-of-the-art analogue designs. Implementations of processors for different application environments have been carried out. The systems have been configurated as high resolution amplitude spectrometers and/or as units capable to time the occurrence of pulses of random amplitude arriving randomly in time. The achieved energy resolutions are below those of the state-of-the-art of analogue instruments. Also timing resolution is better than a sampling interval. The set-up is based on programmable logic (Field Programmable Gate Array - FPGA) and DSP (Digital Signal Processor) technology. In order to get advantages of spatial computing in programmable devices, data-path structures of temporal computing process techniques have been revised and new processing architectures have been conceived. Among relevant improvements consequent to these optimizations are the reduction of processing speed, time-continuous processing operation and adaptive dynamic management of numeric filters length.
Pubblications in 2011
1) A. Manenti, A.Merati, A. Abba, A. Geraci, S. M. Savaresi, "A New BMS Architecture Based on Cell Redundancy", IEEE Transactions on Industrial Electronics, vol. 58, no. 9, September 2011, pp. 4314-4322.
2) A. Abba, F. Caponio, P. Baruzzi, A. Geraci, G. Ripamonti, "Statistical Data Generation System for Scientific Applications", Proc. of the ERSA 2011 – Engineering of Reconfigurable Systems and Algorithms, Las Vegas, Nevada, USA, July 18-21, 2011.
3) A, Manenti, A. Abba, A. Geraci, S. Savaresi, "A New Cell Balancing Architecture for Li-ion Battery Packs Based on Cell Redundancy", Proc. of 18th World Congress of the International Federation of Automatic Control (IFAC), Milan, August 28 - September 2, 2011.
4) G. Ripamonti, A. Abba, F. Caponio, A. Geraci, "Adaptive Spectroscopy Digital Filters for Enhanced Rate and Gaussian Peaks Preservation", Proc. of 2011 IEEE Nuclear Science Symposium, October 23-29, 2011, Valencia, Spain.
A. A. Abba, F. Caponio, A. Geraci, G. Ripamonti, "Design and test equipment of digital processors for output analysis from radiation detectors", Proc. of 2011 IEEE Nuclear Science Symposium, October 23-29, 2011, Valencia, Spain.
5) A. Abba, A. Geraci, G. Ripamonti, "Digital adaptive filtering for resolution and live-time maximization", Proc. of 2011 IEEE Nuclear Science Symposium, October 23-29, 2011, Valencia, Spain.
6) A. Abba, F. Caponio, A. Geraci, G. Ripamonti, "Experimental implementation of LMS synthesis of optimum FIR filters with arbitrary time and frequency constraints and noises", Proc. of 2011 IEEE Nuclear Science Symposium, October 23-29, 2011, Valencia, Spain.
7) R. Alberti, T. Frizzi, S. Moser, A. Abba, L. Bombelli, A. Geraci, "Re-Configurable digital pulse processor for high-rate high-resolution X-ray spectroscopy", Proc. of Denver X-Ray Conference, August 1-5, 2011, Colorado Springs, Colorado, USA.
8) F. Caponio, A. Abba, P. Baruzzi, G. Ripamonti, A. Geraci, "Modular and Bi-Directional Energy Storage System Compliant with Accumulators of Different Chemistry", Proc. of EPQU '11 – IEEE Electrical Power Quality and Utilization Conference, 17-19 October, 2011, Lisbon, Portugal.
9) R. Alberti, T. Frizzi, S. Moser, A. Abba, A. Geraci, F.Caponio, P.Baruzzi, G.Ripamonti, L.Bombelli, "A digital pulse processor for high-rate high-resolution X and Gamma ray spectroscopy", Proc. of 2011 IEEE Nuclear Science Symposium, October 23-29, 2011, Valencia, Spain.
DESIGN AND CHARACTERIZATION OF INGAAS/INP SINGLE-PHOTON AVALANCHE DIODES AND INSTRUMENTATION MODULES FOR NEAR-INFRARED DETECTION
F. Zappa, A. Tosi
Single-photon counting and single-photon timing in the near-infrared (NIR) wavelength range (800 nm - 1700 nm) get increasingly important in a number of applications such as quantum key distribution (QKD), non-invasive testing of VLSI circuits, time-resolved photoluminescence, optical time-domain reflectometry (OTDR), and time-of-flight laser ranging and imaging. Silicon Single-Photon Avalanche Diodes (SPAD) are currently available with remarkable performance up to 1 um.
III-V APDs able to detect photons up to 1.7 um are usually devoted only to linear, telecom applications. The optimization of InGaAs/InP detectors explicitly devised to work as SPADs requires quite different design approaches. We designed, fabricated and characterized InGaAs/InP SPADs explicitly aimed to single-photon detection. We analyzed the temperature dependence of ionization coefficients, detection efficiency, dark count rate, afterpulsing, and timing jitter. We studied the variation in doping concentrations and thicknesses that leads to variations in the internal electric field profiles and therefore in SPAD performance. From the device modeling we extracted design rules in order to optimize detector performances to different aims (detection efficiency, edge breakdown, timing jitter). The main drawback of InGaAs SPADs is the strong afterpulsing due to capture and delayed release of avalanche carriers by deep levels inside the InP multiplication layer. We investigated the effectiveness of traps within InP, in order to find guidelines for reducing afterpulsing. Moreover, we designed custom electronics in order to quench the avalanche as soon as possible, thus limiting the amount of carriers flowing through the junction and further reducing afterpulsing. We also designed a new read-out electronics able to extract the best timing resolution from SPADs operated in gated-mode, attaining about 30ps (FWHM) of timing precision. Thanks to the deep InGaAs/InP SPAD characterization, we identified working conditions that optimize detector performance: dark count rate of 3 kHz, detection efficiency up to 45%, with timing jitter as low as 30 ps at 200 K. Based on such experience, we designed a new electronic detection module based on InGaAs SPADs that properly operates the SPAD so that the end users has just do connect such module and use it in the final applications.
Pubblications in 2011
1) I. Bargigia et al., “Time-domain diffuse optical spectroscopy up to 1700 nm using an InGaAs/InP single-photon avalanche diode,” Proc. of SPIE, vol. 7895, p. 78950C-78950C-4, 2011.
2) F. Acerbi, A. Tosi, A. Dalla Mora, M. Anti, and F. Zappa, “Experimental characterization of afterpulsing and timing jitter of InGaAs/InP SPAD,” in Proceedings of SPIE, 2011, vol. 7934, no. 1, p. 79340L-79340L-8.
3) M. Anti, F. Acerbi, and A. Tosi, “Integrated simulator for single photon avalanche diodes,” in Numerical Simulation of Optoelectronic Devices (NUSOD), 2011 11th International Conference on, 2011, pp. 47-48.
4) I. Bargigia et al., “Time-resolved diffuse optical spectroscopy up to 1700 nm using a time-gated InGaAs/InP single-photon avalanche diode,” in Proceedings of SPIE, 2011, vol. 8090, no. 1, p. 80900U-80900U-5.
5) M. A. Itzler et al., “Advances in InGaAsP-based avalanche diode single photon detectors,” Journal of Modern Optics, vol. 58, no. 3–4, pp. 174-200, 2011.
6) A. Bahgat Shehata, C. Scarcella, A. Tosi, and A. Della Frera, “Photon counting module based on InGaAs/InP Single-Photon Avalanche Diodes for near-infrared counting up to 1.7 µm,” in 7th Conference on Ph.D. Research in Microelectronics and Electronics, 2011, pp. 177-180.
7) A. Tosi, F. Acerbi, A. Dalla Mora, M. A. Itzler, and X. Jiang, “Active Area Uniformity of InGaAs/InP Single-Photon Avalanche Diodes,” IEEE Photonics Journal, vol. 3, no. 1, pp. 31-41, Feb. 2011.
8) M. Anti, A. Tosi, F. Acerbi, and F. Zappa, “Modeling of afterpulsing in single-photon avalanche diodes,” in Proceedings of SPIE, 2011, vol. 7933, no. 1, p. 79331R-79331R-8.
9) A. Tosi et al., “Compact detection module based on InGaAs/InP SPADs for near-infrared single-photon counting up to 1.7 μm,” in Proceedings of SPIE, 2011, vol. 7945, no. 1, p. 79452L-79452L-7.
10) A. Tosi, A. Dalla Mora, A. Della Frera, F. Acerbi, A. Bahgat Shehata, and F. Zappa, “Advanced single photon counting instrumentation for SPADs,” in Proceedings of SPIE, 2011, vol. 7945, no. 1, p. 79452O-79452O-9.
2D SINGLE-PHOTON IMAGING AND 3D RANGING WITH CMOS SPAD ARRAYS
F. Zappa, A. Tosi
Goal of this research is the fabrication of advanced 2D and 3D cameras based on a silicon monolithic array of photon-counting imagers based on SPAD (Single-Photon Avalanche Diode) arrays fabricated in standard CMOS technologies, for the visible wavelength range. Such imagers are monolithic chips with arrays of smart-pixels, each comprising the SPAD detector, an analog front-end electronics and an in-pixel digital electronics for pre-processing. Each pixel can perform either photon counting, thus providing an information on the intensity of the scene, or Time-of-Flight (ToF) measurements, thus providing an information on the distance of the object in the scene. The former is the basic building block for 2D imagers, while the latter allows the exploitation of 3D lidar ranging cameras. The surrounding on-chip global electronics manages the operation of the overall array sensor, the parameter settings (like frame-rate, integration time, detector gating), and the data read-out.
The developed CMOS SPAD arrays have both a linear (32 smart-pixels in a column) and a squared (32 rows by 32 columns of smart-pixels, for a total of 1024 photon-counting pixels) layouts. The 2D in-pixel digital pre-processing is based on individual 8 bit counters able to accumulate the number of detected photons, within the frame. The frame-time is easily adjustable between 300 ns up to milliseconds, depending on the application. The 3D smart-pixels are based on three different techniques: direct ToF by means of an in-pixel Time-to-Digital Converter; indirect ToF through sinusoidally modulated light; and indirect ToF through pulsed excitation of the scene under observation.
In the developed 2D cameras, the CMOS SPAD arrays are packaged and assembled together with an FPGA board for ease of data read-out. Each frame is composed of 1024 bytes, one for each pixel, and each pixel can be read out in 10 ns. With a system clock of 100 MHz, the 32x32 pixel imager can be read out in 10 æs. The system shows state-of-the-art performances, achieving single-photon sensitivity in the visible range, together with sufficiently low noise, very high frame rate (up to 100,000 frames/s) and parallel readout (in a global shutter mode).
The research focuses on different 2D imaging applications. For instance in astrophysical applications, such as Adaptive Optics, Fast Transient Imaging (for instance of optical counterparts of gamma-ray bursts) and Atmospheric Layer Sensing, where even high-sensitivity EM-CCDs (Electron-Multiplying CCDs) cannot be operated at the required high frame rates without severely degrading the SNR. And in Fluorescence Correlation Spectroscopy, where fast and faint bursts of photons are expected from labeled single molecules or protein.
The research also focuses on various 3D ranging applications. First of all in the automotive field, for pre-crash safety systems and in the field of security and monitoring of sensitive surveilled areas.
Pubblications in 2011
1) B. Markovic, S. Tisa, A. Tosi, and F. Zappa, “Smart-pixel for 3D ranging imagers based on single-photon avalanche diode and time-to-digital converter,” in Proceedings of SPIE, 2011, vol. 8033, pp. 80330A-1-80330A-6.
2) F. Guerrieri, S. Tisa, A. Tosi, S. Bellisai, B. Markovic, and F. Zappa, “Linear arrays of single-photon detectors for photon counting and timing,” in Proceedings of SPIE, 2011, vol. 7875, no. 1, p. 78750N-78750N-9.
3) S. Bellisai, F. Guerrieri, S. Tisa, and F. Zappa, “3D ranging with a single-photon imaging array,” in Proceedings of SPIE, 2011, vol. 7875, no. 1, p. 78750M-78750M-6.
4) S. Bellisai, F. Guerrieri, S. Tisa, F. Zappa, A. Tosi, and A. Giudice, “1024 pixels single photon imaging array for 3D ranging,” in Proceedings of SPIE, 2011, vol. 7942, no. 1, p. 79420L-79420L-8.
5) B. Markovic, S. Tisa, A. Tosi, and F. Zappa, “Monolithic single-photon detectors and time-to-digital converters for picoseconds time-of-flight ranging,” in Proceedings of SPIE, 2011, vol. 7875, no. 1, p. 78750P-78750P-6.
6) B. Markovic, S. Tisa, A. Tosi, and F. Zappa, “Towards arrays of smart-pixels for time-correlated single photon counting and time of flight application,” in Proceedings of SPIE, 2011, vol. 7942, no. 1, p. 79420K-79420K-6.
TIME-RESOLVED FAST-GATED DETECTION FOR FUNCTIONAL BRAIN IMAGING AND SPECTROSCOPY
F. Zappa, A. Tosi
Light propagation in highly scattering media (photon migration) has been applied to a number of biomedical fields, particularly noninvasive clinical diagnostics. The most general photon migration measurement involves illuminating a diffusive medium with a point source and collecting the reemitted optical signal at a given distance from the injection point. The distribution of the scattered photons varies with the absorption and scattering properties of the medium and can be useful in locating abnormalities or functional activations in biological tissue.
Following this concept we have investigated the properties of an ideal TDR measurement for a small or zero source-detector (interfiber) distance. We obtained higher spatial resolution, more photons detected at any time, higher contrast. The most severe obstacle to TDR at small source-detector separation is the presence of early photons, which increase at a much faster pace than the late photons and saturate the detection electronics. An efficient mechanism to gate the early photons is needed and we demonstrated experimentally the feasibility of this novel approach using a single-photon avalanche diode (SPAD) operated in time-gated mode at high rate (50 MHz) and with fast rise and fall times (few hundreds of ps). The system was used for TDR both on homogeneous as well as on inhomogeneous tissue phantoms.
We performed also preliminary in vivo tests of functional brain activation with successful results. We are working also on the contactless imaging of the brain activity, through a scanning of the patient forehead.
Pubblications in 2011
1) A. Tosi et al., “Fast-gated single-photon counting technique widens dynamic range and speeds up acquisition time in time-resolved measurements,” Optics Express, vol. 19, no. 11, pp. 10735-10746, 2011.
2) R. Cubeddu et al., “Photonics for Life,” IEEE Pulse, no. June, pp. 16-23, 2011.
3) G. Boso, A. Dalla Mora, A. Tosi, A. Pifferi, and D. Contini, “Fast-gated single-photon detector module for wide dynamic range optical measurements,” in 7th Conference on Ph.D. Research in Microelectronics and Electronics, 2011, pp. 173-176.
4) M. Mazurenka et al., “Non-contact time-domain scanning brain imager: results of proof of principle tests,” in Proceedings of SPIE, 2011, vol. 8088, pp. 80880A-1-80880A-6.
Large-area, high quantum efficiency avalanche diodes for picosecond time-correlated photon counting
A. Glinatti, I. Rech, M. Ghioni, S. Cova
Silicon Single-Photon Avalanche-Diodes (SPADs) have gained wide acceptance for single photon counting (SPC) and time-correlated single photon-counting (TCSPC) over the visible spectral range up to 1 micron wavelength. In recent years detector modules employing low-voltage SPAD devices with diameter up to 50 µm have become commercially available from various manufacturers. Such devices are fabricated in planar technology compatible with CMOS circuits and join the typical advantages of microelectronic devices (small size, ruggedness, low operating voltage and low power dissipation, etc.) to photon detection efficiency (PDE) higher than Photomultiplier Tubes (PMTs) and excellent photon timing performance, with full-width at half-maximum resolution (FWHM) better than 50ps. The features and performance of these detectors are winning the favor of users and the prospect of further improvements is calling great attention to future developments in this field. Expectations are focused mainly on the development of SPAD detectors that maintain the features above outlined and offer wider sensitive area and higher PDE in the red and near infrared spectral range.
To meet these requirements we developed an improved planar silicon technology for fabricating SPAD devices with 200 µm active area diameter and fairly low dark counting rate (DCR). Peak photon detection efficiency of 48% around 530 nm and 35ps FWHM time resolution were obtained at room temperature. We showed that deep cooling of the device at 120 K by means of a compact liquid-nitrogen Dewar brings several advantages, such as extremely low dark counting rates (down to 1 counts/s), better time resolution (down to 20ps), and higher quantum efficiency in the visible range. To increase the PDE we proposed and demonstrated a resonant-cavity-enhanced (RCE) SPAD fabricated on a reflecting silicon-on-insulator (SOI) substrate. These detectors have peak photon detection efficiencies ranging from 41% at 780nm to 32% at 850nm and time resolution of 35ps FWHM.
We also investigated the optical crosstalk between adjacent detectors in a SPAD array, showing that a significant contribution to crosstalk comes from photons reflected internally at the bottom of the chip. These photons can bypass trenches making them ineffective.
Pubblications in 2011
1) M. Assanelli, A. Ingargiola, I. Rech, A. Gulinatti, and M. Ghioni, “Photon-Timing Jitter Dependence on Injection Position in Single-Photon Avalanche Diodes”, IEEE Journal of Quantum Electronics, vol. 47, iss. 2, pp. 151—159, Feb. 2011.
2) M. Assanelli, A. Gulinatti, I. Rech, and M. Ghioni, “Timing Enhanced Silicon SPAD design”, in Proc. Nusod 2011, The 11th International Conference on Numerical Simulation of Optoelectronic Devices, Rome, Sept. 5-8, 2011.
3) P. J. Clarke, R. J. Collins, A. Mccarthy, N. J. Krichel, M. J. Garcia-Martinez, M. G. Tanner, J. A. O'Connor, C. M. Natarajan, S. Miki, M. Sasaki, Z. Wang, I. Rech, M. Ghioni, A. Gulinatti, P. A. Hiskett, R. H. Hadfield, P. D. Townsend, and G. S. Buller, “An Analysis of Single–photon detectors in an environmentally robust gigahertz clock rate quantum key distribution system”, in Proc. CLEO QELS 2011, May 1-6, 2011.
4) P. J. Clarke, R. J. Collins, P. A. Hiskett, M. J. Garcia-Martinez, N. J. Krichel, A. Mccarthy, M. G. Tanner, J. A. O'Connor, C. M. Natarajan, S. Miki, M. Sasaki, S. Wang, M. Fujiwara, I. Rech, M. Ghioni, A. Gulinatti, R. H. Hadfield, P. D. Townsend, and G. S. Buller, “Analysis of detector performance in a gigahertz clock rate quantum key distribution system”, New Journal of Physics, vol. 13, iss. 7, pp. 1—23, July 2011.
5) A. Gulinatti, I. Rech, M. Assanelli, M. Ghioni, and S. Cova, “A physically based model for evaluating the photon detection efficiency and the temporal response of SPAD detectors”, Journal of Modern Optics, vol. 58, iss. 3 & 4, pp. 210—224, Jan. 2011.
6) A. Gulinatti, F. Panzeri, I. Rech, P. Maccagnani, M. Ghioni, and S. Cova, “Planar silicon SPADs with improved photon detection efficiency”, in Proc. Quantum Sensing and Nanophotonic Devices VIII, vol. 7945, 79452P, San Francisco (CA - USA), Jan. 22-27, 2011.
7) A. Gulinatti, I. Rech, P. Maccagnani, M. Ghioni, and S. Cova, “Improving the performance of silicon single photon avalanche diodes”, in Proc. SPIE Defense, Security and Sensing 2011 - Advanced Photon Counting Techniques V, Orlando (FL - USA), Apr. 25-29, 2011.
8) A. Gulinatti and I. Rech, “New Silicon SPAD technology for enhanced red-sensitivity, high-resolution timing and system integration”, in Proc. Single Photon Workshop 2011, Braunschweig, June 27-27, 2011.
9) Ingargiola, M. Assanelli, I. Rech, A. Gulinatti, and M. Ghioni, “Avalanche Current Measurements in SPADs by Means of Hot-Carrier Luminescence”, Photonics Technology Letters, vol. 23, iss. 18, pp. 1319—1321, Sept. 2011.
10) N. J. Krichel, A. Mccarthy, I. Rech, M. Ghioni, A. Gulinatti, and G. S. Buller, “Cumulative data acquisition in comparative photon-counting three-dimensional imaging”, Journal of Modern Optics, vol. 58, iss. 3 & 4, pp. 244—256, Jan. 2011.
11) F. Panzeri, A. Gulinatti, I. Rech, M. Ghioni, and S. Cova, “Silicon SPAD with near-infrared enhanced spectral response”, in Proc. SPIE Optics + Optoelectronics - Semiconducting Photon Counters, vol. 8072, p. 807206, Prague (Czech Republic), Apr. 18-21, 2011.
12) A. Tosi, A. Dalla Mora, F. Zappa, A. Gulinatti, D. Contini, A. Pifferi, L. Spinelli, A. Torricelli, and R. Cubeddu, “Fast-gated single-photon counting technique widens dynamic range and speeds up acquisition time in time-resolved measurements”, Optics Express, vol. 19, iss. 11, pp. 10735—10746, May 2011.
Parallel Photon Counting and Picosecond Timing with Silicon-SPAD based Compact Detector Modules
I. Rech, A. Gulinatti, M. Ghioni, S. Cova
In recent years there has been a growing interest in monolithic arrays of single photon avalanche diodes (SPADs) for high-sensitivity parallel fluorescence detection in life sciences. Parallel detection can lead to a significant reduction of the acquisition time in high-sensitivity measurements. Furthermore, the availability of compact monolithic array detectors can open the way to a further miniaturization of array based analytical systems. Among the potential applications of SPAD arrays, parallel fluorescence correlation spectroscopy (parallel FCS) is the most promising one. FCS is a powerful experimental technique used in studies of chemical and photophysical dynamics at the single molecule level. Single molecule sensitivity is achieved by exploiting confocal detection in order to minimize the detection volume. The performance of silicon Single Photon Avalanche Detector arrays were evaluated with a 48-element monolithic array detector. The pixels are single photon avalanche diodes (SPADs) with 50 µm diameter, ordered in a 6x8 array with 240 µm pitch. The photon detection efficiency is remarkably uniform over the array: it has a peak of 48% at 530nm and it is higher than 30% over all the visible range. Low dark counting rate (DCR) is obtained in operation at moderately low temperature (15C with thermoelectric cooling): the individual pixel DCR is 60 c/s for about 40% of the elements and it is below 5700 c/s in the rest of the array. It was verified that the afterpulsing probability is below 1% and that the optical crosstalk probability between elements is lower than 0.2%. Based on this matrix detector, we have developed a versatile and compact (20 cmx8 cmx4 cm) photon counting module that can be easily interfaced to a PC via USB link.
SPAD are nowadays widely employed also for time-correlated single photon-counting (TCSPC) measurements for time-resolved measurement of fast and weak fluorescent emissions in single molecule application. Time resolution of few tens of picoseconds is often crucial in these applications, thus limiting the choice of photodetector to either microchannel plate photomultipliers MCP-PMTs or single photon avalanche diodes SPADs with thin depleted region. In order to exploit the best performance of this kind of detector we developed a new photon timing circuit that achieves a time resolution of 35 ps full width at half maximum with single photon avalanche diodes having active area diameters up to 200 µm. The timing circuit is based on a double avalanche current sensing network that makes it particularly suited to operation at high photon counting rates. Thanks to its self-adjusting capabilities, no trimming is needed even when changing the photodetector operating conditions over a wide range.
Pubblications in 2011
1) Cammi, A. Gulinatti, I. Rech, F. Panzeri, and M. Ghioni, “Compact eight channel SPAD module for photon timing applications”, in Proc. SPIE Defense, Security and Sensing 2011 - Advanced Photon Counting Techniques V, vol. 8033, p. 80330H, Orlando (FL - USA), Apr. 25-29, 2011.
2) M. Crotti, I. Rech, and M. Ghioni, “Monolithic Time-to-Amplitude converter for TCSPC applications with 45 ps time resolution”, in Proc. PRIME 2011, 7th Conference on Ph.D. Research in Microelectronics and Electronics, pp. 21—24, Madonna di Campiglio (Italy), July 3-7, 2011.
3) M. Crotti, I. Rech, M. Ghioni, and I. Labanca, “Fully integrated time-to-amplitude converter for multidimensional TCSPC applications”, in Proc. SPIE Optics + Optoelectronics - Semiconducting Photon Counters, vol. 8072, p. 80720C, Prague (Czech Republic), Apr. 18-21, 2011.
4) X. Michalet, R. A. Colyer, G. Scalia, S. Weiss, O. H. W. Siegmund, A. S. Tremsin, J. V. Vallerga, F. Villa, F. Guerrieri, I. Rech, S. Tisa, A. Gulinatti, F. Zappa, M. Ghioni, and S. Cova, “New photon-counting detectors for single-molecule fluorescence spectroscopy and imaging”, in Proc. SPIE Defense, Security and Sensing 2011 - Advanced Photon Counting Techniques V, vol. 8033, 803316, Orlando (FL - USA), Apr. 25-29, 2011.
5) I. Rech, A. Gulinatti, M. Crotti, C. Cammi, P. Maccagnani, and M. Ghioni, “Towards picosecond array detector for single-photon time-resolved multispot parallel analysis”, Journal of Modern Optics, vol. 58, iss. 3 & 4, pp. 233—243, Jan. 2011.
6) I. Rech, A. Gulinatti, C. Cammi, A. Gallivanoni, F. Panzeri, and M. Ghioni, “Parallel fluorescence photon timing module with monolithic SPAD array detector”, in Proc. SPIE Photonics West 2011 - BIOS - Single Molecule Spectroscopy and Imaging IV, vol. 7905, p. 790504-1—790504-9, San Francisco (CA - USA), Jan. 22-27, 2011.
MICROELECTROMECHANICAL SYSTEMS AND FRONT-END ELECTRONICS
A. Longoni, G. Langfelder
This research is carried on in the field of microelectromechanical systems, from material characterization to the overall system design. In particular suitable test structures are designed to study fundamental aspects of the physics behind the devices. Recent examples are analyses of fatigue in polysilicon microstructures and studies on damping phenomena under specific vacuum conditions. The results of these analyses are exploited for the design of innovative device topologies, most in the field of inertial sensors (accelerometers, gyroscopes and magnetometers) to implement a 9-axis smart inertial measurement unit (IMU). The studies in the last year specifically focused (i) on the characterization of resonant and fringe-field accelerometers and related low-power electronics; (ii) on the theoretical study and design of gyroscopes based on Silicon nano wires; and (iii) on the theoretical analysis, implementation and tests of low-power Lorentz-force based MEMS magnetometers.
Due to the strong interaction of these devices with electrostatic readout forces, special care needs to be taken also in the design of the readout electronics. On one side the group has continued the development of a low-noise, low-perturbation lock-in type characterization platform for micromachined sensors. This versatile platform can be used for device characterization (e.g. extraction of electro-mechanical parameters like the elastic stiffness, the resonance frequency, the quality factor and the pull-in voltage). On the other side the group has designed VLSI front-end circuits for resonant sensors. These circuits exploit the MEMS as the frequency-selective resonating element. The oscillation loop can be closed in different ways, two studied examples of which are a transimpedance+hard-limiter based configuration and a Pierce topology based configuration.
Pubblications in 2011
1) G. Langfelder, S. Dellea, F. Zaraga, D. Cucchi, M. Azpeitia Urquia, The dependence of fatigue in microelectromechanical systems from the environment and the industrial packaging, IEEE transactions on Industrial Electronics, Issue:99, 10.1109/TIE.2011.2151824.
2) A. Tocchio, C. Comi, G. Langfelder, A. Corigliano, A. Longoni, Enhancing the Linear Range of MEMS Resonators for Sensing Applications, IEEE Sensors Journal, Vol. 11, No. 12, December 2011, 3202-3210.
3) A. Tocchio, A. Caspani, G. Langfelder, Mechanical and Electronic Amplitude-Limiting Technique in a MEMS Resonant Accelerometer, IEEE Sensors Journal, No.99, doi: 10.1109/JSEN.2011.2177657.
4) G. Langfelder, T. Frizzi, A. Longoni, A. Tocchio, D. Manelli, E. Lasalandra, Readout of MEMS capacitive sensors beyond the condition of pull-in instability, Sens. Actuators A: Phys. 167 (2011) 374–384.
5) G. Langfelder, A. Longoni, A. Tocchio, E. Lasalandra, MEMS Motion Sensors Based on the Variations of the Fringe Capacitances, IEEE Sensors Journal, Vol. 11, No. 4, April 2011.
A. A. Corigliano, A. Ghisi, G. Langfelder, A. Longoni, F. Zaraga, A. Merassi, A microsystem for the fracture characterization of polysilicon at the micro-scale, European Journal of Mechanics A/Solids 30 (2011) 127-136.
6) A. Tocchio, A. Caspani, G. Langfelder, A. Longoni, E. Lasalandra, Resolution and Start-up Dynamics of MEMS Resonant Accelerometers, IEEE SENSORS Conference, (2011) 161–164.
7) A. Comi, A. Corigliano, G. Langfelder, A. Longoni, A. Tocchio, On the nonlinear behaviour of MEMS resonators, 12th. Int. Conf. on Thermal, Mechanical and Multiphysics Simulation and Experiments in Microelectronics and Microsystems, EuroSimE 2011.
8) A. Comi, A. Corigliano, G. Langfelder, A. Longoni, A. Tocchio, B. Simoni, A New Biaxial Silicon Resonant Micro Accelerometer, IEEE MEMS Conference, (2011), 529–532.