UNIVERSITA’ DEGLI STUDI DI PERUGIA
Dipartimento di Ingegneria Elettronica e dell’Informazione
Research topics
1. DESIGN, FABRICATION AND CHARACTERIZATION OF CMOS RADIATION ACTIVE PIXEL SENSORS
D. Passeri, P. Placidi
Collaborations: MICRON Technology Italia, Fermi National Accelerator Laboratory (FNAL), Batavia (IL), Università di Pavia e Bergamo, Sezione INFN di Perugia.
2. SENSORS AND SENSOR INTERFACE DESIGN
D. Passeri, P.Placidi, F.Rastrello, A.Scorzoni
Collaborations: CNR – IMM, Sez. di Bologna, Department of Electrical Engineering (University of South Florida), and the Morsani College of Medicine, Department of Molecular Pharmacology and Physiology (Tampa, FL), Sezione INFN di Perugia, ASL 3 Umbria (Servizio di Fisica Sanitaria), ASL 1 Umbria (S.C. Radioterapia Oncologica).
3. HIGH FREQUENCY ELECTRONIC CIRCUITS AND SYSTEMS DESIGN
F. Alimenti, L. Roselli
Collaborations: Georgia Institute of Technology-USA, University College Cork/Tyndall National Institute-Ireland, Roma Tor Vergata
4. SILICON-ON-DIAMOND TECHNOLOGY AND DEVICES
A. Scorzoni, D. Passeri
Collaborations: INFN-Firenze, INFN-Perugia
DESIGN, FABRICATION AND CHARACTERIZATION OF CMOS RADIATION ACTIVE PIXEL SENSORS
D. Passeri, P. Placidi
Subject #1: Design, fabrication and characterization of 3D CMOS VLSI vertical-scale integrated circuits.
This research has been focused on the characterization of CMOS Active Pixel Sensors fabricated in 3D vertical-scale technology. A first functional characterization of 3D monolithically stacked Active Pixel Sensors layers fabricated in Chartered/Tezzaron 130nm 3D technology for particle tracking purposes has been carried out through high focussed laser beam and radioactive sources. Beam tests at the INFN laboratories in Frascati (BTF) have been carried out as well. Good electrical contacts between bottom and top tiers have been verified: different test structures and matrix structures (5x5, 16x16, small vs. large pixel diode) have been characterized. Clear coincidence responses between bottom and top matrices have been obtained with laser stimuli. Noise analysis and X-rays calibrations with Fe and Cu fluorescence have been accomplished: encouraging results have been found in terms of S/N ratio, assessing the suitability of the adopted 3D-IC vertical scale fabrication technology and of the proposed approach for particle tracking applications. Based on these findings, the VLSI design of a new sensor prototype monolithically integrated has been accomplished, within the framework of an international consortium 3DIC led by Fermi National Accelerator Laboratory (FNAL).
Subject #2: Characterization of radiation sensors integrated in submicron CMOS VLSI technology.
Within the framework of the ongoing cooperation with Micron Technology Italy, has been continued the characterization of state of the art CMOS image sensors to assess: i) the possibility of using such image sensors in non-conventional applications (single ionizing particle detection for high energy physics experiments, X-ray dosimetry in medical applications), ii) their tolerance to radiation-induced damage. In particular, a specific activity has been dedicated to the modelling of the interaction between visible radiation and sensing element, in order to optimize the technological parameters and the design of active pixel sensors, by means of combined process- and device-level simulations. The developed models have been validated with experimental measurements possible thanks to an advanced optical workbench with IR, UV, and VISible laser heads with micro-focusing (spot size below 2 micrometers) and micro-positioning (scan step 0.21 micrometers) capabilities has been used It allows up to four sensors parallel read-out for track reconstruction and spatial resolution analysis, as well as 2D scans for surface mapping. Moreover, a detailed analysis of the radiation tolerance of CMOS VGA imager irradiated with a 24 MeV proton beam at INFN Laboratori Nazionali del Sud, up to a nominal fluence of 10E14 protons/cm2 has been carried out. We found that the detector was still working at 1013 protons/cm2, with a moderate increase of the noise (20%).
Publications in 2011
1) Biagetti D., Marras A., Meroli S., Passeri D., Placidi P., Servoli L., Tucceri P.,Beam test results for the RAPS03 non-epitaxial CMOS active pixel sensor,NIM, A, Volume: 628, Issue: 1, February 1, 2011, pp. 230-233.
2) Ozdemir T., Meroli S., Pilicer E., Mencaroni A., Alpat B., Ozkorucuklu S., Passeri D., Placidi P., Servoli L., A combined approach to the simulation of ionizing radiation effects in silicon devices, JINST 6 T05001 doi: 10.1088/1748-0221/6/05/T05001.
3) Servoli L., Biagetti D., Meroli S., Placidi P., Passeri D., Tucceri P., Use of a standard CMOS imager as position detector for charged particles, Nuclear Physics B, Volume: 215, Issue: 1, June, 2011, pp. 228-231.
4) Servoli. L., Bizzarri F., Passeri D. Continuous measurement of radiation damage of standard CMOS imagers, Nuclear Inst. and Methods in Physics Research, A, Volume 658, 2011, pp. 137-140, doi: http://dx.doi.org/10.1016/j.nima.2011.04.059.
5) Meroli S., Passeri D. , Servoli. L., Energy loss measurement for charged particles in very thin silicon layers, Journal of Instrumentation, Volume: 6, June 2011, doi: http://10.1088/1748-0221/6/06/P06013.
6) Passeri D., Servoli L., Meroli S., Placidi P., Marras A., 2D/3D MAPS in the Tezzaron/Chartered Technology: Preliminary Characterization, 8th Front End Electronics Meeting, Bergamo (Italy), May 24-27, 2011.
SENSORS AND SENSOR INTERFACE DESIGN
D. Passeri, P.Placidi, F.Rastrello, A.Scorzoni
Collaborations: CNR – IMM, Sez. di Bologna, Department of Electrical Engineering (University of South Florida), and the Morsani College of Medicine, Department of Molecular Pharmacology and Physiology (Tampa, FL), Sezione INFN di Perugia, ASL 3 Umbria (Servizio di Fisica Sanitaria), ASL 1 Umbria (S.C. Radioterapia Oncologica).
Subject #1: Interface circuit for an ultra low power gas sensor
Motivation. Gas sensors are widely used for such applications as environmental and air quality monitoring and automotive and industrial control. Recently, particularly in view of legislative initiatives aimed at reducing the pollution and the human exposure to dangerous gases, hand-held systems for gas sensing are becoming quite important, thus pushing in the direction of the following: improving performance; minimizing size power consumption and cost of such systems.
Metal oxide (MOX) gas sensors have been proposed for several application scenarios, including the following: environmental monitoring; food quality and safety; food logistics; and safety and security. The main advantages of these solid-state devices include: low cost; low power consumption; fast response; high sensitivity; reliability; and ease of use. Temperature control up to about 450 °C is necessary for correct operation of MOX gas sensors. In fact, their operating principle depends on the interaction between the target gas molecules and the metal oxide surface, where oxygen and OH adsorption phenomena occur.
Activity and results. The first objective of this research is the design of new architecture for an electronic system devoted to controlling the operating temperature and acquisition of data from a Ultra Low Power (ULP) gas sensor [1,2]. The novelty of this system is its capability to take into account the absence of electrical insulation of the sensing layer from the heater and to exploit this feature to measure the sensing resistance. The system provides both control of the operating temperature and management of the acquired data. The readout circuit is able to measure the electrical current flowing in the sensing layer of the sensor in a range from 30 nA–60 μA with a relative error less than 0.6%. The system allows the user to measure the heater resistance related to the operating temperature of the sensor with a relative error of 1% in the range (100–300) Ω. The data acquisition system was tested by acquiring data of a three-terminal ULP gas sensor located in an automatically controlled environmental chamber. The response to two different gases, benzene, and NO2, was acquired. It was demonstrated that the range of electrical currents the system is able to manage is appropriate for the innovative ULP three-terminal sensors adopted in this paper, which have proven the capability to detect low ppb concentrations of benzene with a power dissipation as low as 8.1 mW, as well as concentrations smaller than 100 ppb of NO2 at 2.7 mW.
In addition a system for the simultaneous dynamic control and thermal characterization of the heating and cooling phases of a micromachined ULP thermal conductivity detector has been designed [3]. The device has been electrically characterized with different Helium gas flows, via a microfluidic experimental setup. Extraction of global thermo-electric parameters, exploited for the development of an electro-thermal Spice model, has been performed directly from the experimental measurements and from 3-D electro-thermal FEM simulations of the device. The resulting Spice model agrees very well with the measurements, with a maximum error less than 0.22%.
Subject #2: Design and simulation of a 64 channel, high voltage analog interface for stimulation and acquisition of neural signals
Motivation. In recent years the activity relating to biomedical applications of electronic systems has grown considerably. Many systems are currently commercially available, from pacemaker devices to defibrillators, from implantable drug delivery systems to electro-stimulation, that support the medical community using the advantages of advanced electronics. A fast growing application field utilizing advanced electronics is invasive brain-computer-interfacing (BCI) where electrodes are typically implanted in the brain in order to extract electrochemical information and, ultimately produce a bidirectional interaction between the patient and a computer or robotic device. Systems specifications required for this kind of application can cover considerable parameter space, and our aim was to design a system able to send high bipolar voltage (up to ±50 V) pulses while reading small signals (tens or hundreds of microvolts) on the same line. The main goal that drove this project was in vitro neural stimulation and recording. Previous papers in this field describe systems able to generate voltage or current stimuli and to read a very low voltage signals, and both IC and embedded systems have been reported. While some authors focused on the acquisition (i.e. reading) of neural signals, systems for signal generation have also been reported in the literature. The main characteristic of such circuits is that they are typically limited to stimulating impulses of a few volts. This characteristic is generally due to the fact that in vitro electrical stimulation and recording of neural action potentials (AP), the electrode is in contact with an electrolytic physiological cerebrospinal fluid, and high current densities required to depolarize neural membranes can initiate the Faradaic reaction phenomena that can damage both the electrode and the living cell tissue.
This project is part of a wider collaboration that intends to realize micro electro-mechanical systems (MEMS) electrode arrays (MEA) to be used for in vitro experimentation.
Activity and results. We intended to realize a system capable of withstanding bipolar voltages impulses up to ±50 V. These values are far higher than the ±1 V that we want to produce at the electrode-solution interface, but are necessary if the micro-machined path from the stimulation source to the actual electrode or sensor is highly resistive. The value of ±50 V is not a limiting value; in fact, by changing the bipolar stimulation device, we can easily overcome the range of voltages that the analog front end (AFE) can withstand.
During this research activity we have designed and simulated a very versatile AFE suitable for many applications, including that in the field of biomedical engineering [5,6]. The complete system is composed of four 16-channel read-out and acquisition boards (encompassing protection, filtering and amplifying circuitry, multiplexing units, a variable gain amplifier and a fast ADC), of a stimulation circuit and a control logic. While the application is in the field of neurological in vitro research, this architecture is easily reconfigurable as a function of the number of electrodes and of the voltage it has to withstand.
Choosing bipolar and passive devices accordingly, the system can be configured to different bandwidths, gains and limiting voltages. This makes the system suitable for different laboratory applications such as research in the field of electro- stimulation and electro-therapy. The designed system is currently being developed and the printed circuit boards housing the AFEs, the control unit and the stimulating circuit are in the final stage of design. Once completed the electronics will be assembled and tested to compare the actual performance with the Spice simulations.
Subject #3: Real time active pixel dosimeter for interventional radiology
Motivation. Interventional Radiology (IR) is a well established technique in medical domain aiming to obtain a good X-ray image quality while minimizing the radiation dose absorbed by patients and staff members. From a radiation protection point of view, the involved procedures are potentially harmful for interventional radiologists and medical staff. The objective of this research activity is the development of an innovative X-ray dosimeter prototype, capable of real-time measurements, packaged in a small form-factor, with wireless communication to be used for individual operators dosimetry during IR procedures.
Activity and Results. A wearable personal dosimeter designed for use during IR procedures needs to fit several requirements, both technical and related to the context where the operators work. In order to provide a portable instrumentation we are planning to design an architecture including: a sensor featuring an Active Pixel Sensor (APS) architecture; a digital signal processing unit to assess dose information from sensor data; a control unit; a wireless interface to transmit data and collect them in a remote workspace; a Graphical User Interface to manage collected data.
The proposed real-time dosimeter relies on CMOS Active Pixel Sensor, widely used in visible imaging applications. Therefore in this year the activity has been focused on the sensor part and on its requirements. We propose the use of a CMOS Active Pixel Sensor that integrates in a single chip both the sensor and the signal processing part. Several different sensors have been tested in a standard angiographic imaging setup with a PMMA phantom used to create the scattered radiation from the X-ray beam. A precision X-ray spectrometer (AMPTEK X-123) has also been used as reference detector to compare the findings of the CMOS active pixel sensors. In some cases also a standard TLD dosimeter, calibrated to give personal dose equivalent, Hp(10), has been placed on the plastic holder in a symmetric position with respect to the X-123 spectrometer and with respect to the beam axis. Results on the characterization of CMOS active pixel sensors as diffused X-ray detectors have been reported in papers [7-12].
Publications in 2011
1) Bissi L., Cicioni M., Placidi P., Zampolli S., Elmi I., Scorzoni A., “A Programmable Interface Circuit for an Ultralow Power Gas Sensor,” IEEE Transactions on Instrumentation and Measurement, vol. 60, Issue 1, pp.282–289, vol. 60, 2011.
2) Rastrello F., Placidi P., Scorzoni A., “A System for the Dynamic Control and Thermal Characterization of Ultra Low Power Gas Sensors,” IEEE Transactions on Instrumentation and Measurement, vol. 60, issue 5, pp. 1876-1883, 2011.
3) Rastrello F., Placidi P., Scorzoni A., Cozzani E., Messina M., Elmi I., Zampolli S., Cardinali G.C., “Measurements, FEM Simulation and Spice Modeling of a Thermal Conductivity Detector,” Proc. of I²MTC 2011, May 10-12, 2011, Binjiang, Hangzhou, China, pp. 651-655.
4) Rastrello F., Placidi P., Scorzoni A., Cozzani E., Messina M., Elmi I., Zampolli S. and Cardinali G.C., “Literature Search, Design and Preliminary Simulationsof an Ion Source for FAIMS Systems,” Atti - 43° Riunione Annuale del Gruppo Elettronica, 6-8 luglio 2011, Trani (Italy).
5) Abbati L., Frewin C.L., Placidi P., Saddow S.E., Scorzoni A., “Design and simulation of a 64 channel, high voltage analog interface for stimulation and acquisition of neural signals,” Proc. of 4th IEEE International Workshop on Advances in Sensors and Interfaces (IWASI), 28-29 June 2011, Savelletri di Fasano (Italy), pp. 45–50.
6) Abbati L., Frewin C.L., Placidi P., Saddow S.E., Scorzoni A., “Design and Simulation of a 64 channel, High Voltage Analog Interface for Simulation and Acquisition of Neural Signals,” Atti - 43° Riunione Annuale del Gruppo Elettronica, 6-8 luglio 2011, Trani (Italy).
Paolucci M.et al., “A real time active pixel dosimeter for interventional radiology,” Radiation Measurements Journal, vol.46, Nov.2011, pp.1271-1276.
8) Paolucci M. et al, “A Real time active pixel dosimeter for interventional radiology,” Workshop ORAMED 2011, pp. 63, 20-22 Jan. 2011, Barcelona.
9) Servoli L.et al., ”Active Pixel Sensor As Dosimetric Device For Interventional Radiology,” 2nd Int. Conf. Frontiers in Diagnostic Technologies, Abstract, 28-30 November 2011, Frascati (Italy).
10) Di Lorenzo R.et al, “Realizzazione di un dosimetro “real time” per la misura della radiazione diffusa durante procedure di radiologia interventistica,” XIV° Congresso Nazionale Tecnica, Tecnologia e Radioprotezione, Abstract, 6-10 Aprile 2011, Rimini, 2011.
11) Paolucci M. et al.”Real Time Active Pixel Dosimeter (RAPID): Realizzazione di un sistema dosimetrico a matrice attiva per radiologia interventistica,” VII° Congresso Nazionale Associazione Italiana di Fisica Medica, Abstract, Catanzaro 13-16 Settembre 2011.
12) Paolucci M.et al., “Progetto RAPID (RAPID): analisi della risposta dei sensori a matrice attiva attraverso un confronto dosimetrico con dosimetri passivi,” VII° Congresso Nazionale Associazione Italiana di Fisica Medica, Abstract, Catanzaro, 13-16 Settembre 2011.
13) Scarpignato M. et al., “Realizzazione Di Un Sistema Dosimetrico Real Time Con Trasmissione Dati Wireless Per Cardiologia Interventistica,”XXXII Congresso Nazionale della Società Italiana di Cardiologia Invasiva, Abstract, Genova 11-14 Ottobre 2011.
HIGH FREQUENCY ELECTRONIC CIRCUITS AND SYSTEMS DESIGN
F. Alimenti, L. Roselli
Subject #1: RFID and paper electronics
Motivation. The objective of the research activity is the development of ultra-low cost RFID circuits and tags having improved functionalities. To reduce costs as much as possible, the paper substrate and the inkjet printing technology have been used. To improve functionalities, the localization capability has been considered. This placing the reader in a fixed (and known) position and equipping it with a narrow-beam antenna.
Activity. Novel RFID circuits based on paper electronics and inkjet printing process have been explored in the following papers [1-3]. In particular, the design of paper substrate antennas has been considered along with an effective technology to couple them (avoiding costly galvanic contacts) with a single-chip silicon tag.
In parallel to the above activities, two additional papers have been finalized. The first paper is related to a Ku-band RF Self-IDentification (RFSID) system for autonomous logistics [4]. Such a system is a custom RFID apparatus composed by readers at fixed (and known) positions and by moving (active) tags. During the operation the tags are capable to generate an alarm signal (trigger signal) each time they crosses the antenna beam of the reader.
The second paper is related to harmonic RFID tag exploiting nanoscale materials [5]. This research is carried out in cooperation with the “Università Politecnica delle Marche”, Ancona, Italy and with the “Technical University of Munich”, Munich, Germany.
Results. A novel low-cost technology for the assembly of flexible substrate antennas and UHF RFID Si chips has bee proposed. Such a technology exploits a magnetic coupling mechanism, thus avoiding the need for galvanic contacts between the Si chip and the antenna itself. The magnetic coupling is established by a planar transformer, the primary and secondary windings of which are implemented on flexible substrate and Si chip respectively. As a result the Si chip can be assembled on the antenna with a mere placing and gluing process. First the idea has been validated by theory. Electromagnetic simulations of a square heterogeneous transformer (1.0 mm side) show a minimum loss of 0.6 dB at 900 MHz, under simultaneous matching conditions.
On the other hand, results have been also obtained on the design of antennas for RFID tags, these operating in the low microwave frequency range. Paper substrate material and inkjet printing process have been used to guarantee mechanical flexibility and ultra-low production costs. A new antenna design methodology has been developed with the purpose to minimize the amount of both substrate material and conductive ink. The first goal is achieved by reducing, for a given frequency, the antenna size. The second goal, instead, is pursued by studying the surface current density distribution along the antenna and removing the metal material where such a current is negligible. The above methodology has been applied to several designs ranging from a windshield sticker tag to an RFID-SAW antenna. Finally a 3.5 GHz crossed-dipole tag, based on the frequency-doubling mechanism, is reported along with a possible modification to enable wireless sensing. The experimental characterization of these prototypes validates the proposed design methodology opening, in the mean time, the possibility for ultra-low cost mass production of RFID tag devices based on paper materials. The above 3.5 GHz crossed-dipole tag, based on the frequency-doubling mechanism, has also been studied from a theoretical point of view. As a first, fundamental step, organic diodes (based on p3HT or pentacene semiconductors) have been considered.
Subject #2: SoC microwave radiometers and applications
Motivation. The objective of the research topic is twofold, i.e. the design of a System-on-Chip microwave radiometers (i.e. integrated on silicon) and their application to both space-based instruments and real-life problems. Real-life problems are related to (but not limited to) the automatic fire detection, a research line that has strongly be studied in last years.
Activity. In the frame of this research subject three papers have been finalized. The first contribution is deals with the capability of radiometers to detect fire spots, even if they are masked by obstacles non transparent to optical or IR radiation [6]. In particular, an extensive simulation work has been carried out on radiometric imaging applied to forest environments. The developed study considers system parameters (antenna beam-width, radiometric resolution, etc.) as well as real fires and forest canopy models.
Another activity that has been carried-out is the development of System-on-Chip (SoC) millimeter-wave radiometers for space applications [7,8]. To this purpose the detailed system analysis of a 31.4 GHz radiometer for Earth observation has been completed. The selected technology is the 0.25 μm Si/SiGe BiCMOS process from IHP. This choice is motivated by the space-qualification of the above process, qualification that is under development at the IHP foundry. The schematic-level designs of the cascode LNA have been completed also accounting for a circuitry that compensate the thermal drift of the amplifier gain, a very important feature in radiometry.
Results. With respect to real-life radiometers applications, the passive microwave imaging of a forest environment has been studied. For the early detection of fires, a single-channel ground-based radiometer (operating at 12.65 GHz) is considered. The simulation of images sensed in the presence of fire spots under different environmental and operative conditions have been determined by means of a custom numerical model. Scenarios where fires are not visible and IR sensors are not useful with respect to a microwave imager have been investigated in deep, such as in the presence of vegetation canopy optically masking fire sources and smoke plumes in the early stage. These simulations have been assessed limits and capabilities of microwave imaging for the identification of little fires masked by forest areas.
Then the work has been focused on SoC millimeter-wave radiometer for space-based instruments. A Ka-band two stages LNA has been designed (at the schematic-level) exploiting the 250nm SiGe BiCMOS technology from IHP foundry. This selection is motivated by the space qualification of the above process, which is in-progress at IHP. An automatic lyout drawing tool has been developed to speed-up the 3D Electro-Magnetic simulation and equivalent-circuit extraction of silicon-integrated inductors. The final simulations of the designed LNA show a power of about 24 dB at 31.4 GHz with a noise figure around 4 dB. In addition the LNA is equipped with an active biasing circuitry capable to compensate for temperature variations. The task of such a bias network is to slightly vary the quiescent current as a function of temperature in order to keep constant the small-signal gain of the amplifier. This is a key-point in radiometer design since gain fluctuations directly impact on the sensor resolution. To cancel for the temperature dependence of the gain, we used the TSSR (Temperature-Sensing Semiconductor Shunt Resistor) technique, which involves the use of an integrated resistor with a negative temperature coefficient.
Publications in 2011
1) F. Alimenti, M. Virili, G. Orecchini, P. Mezzanotte, V. Palazzari, M.M. Tentzeris, L. Roselli, ”A New Contactless Assembly Method for Paper Substrate Antennas and UHF RFID Chips,” IEEE Trans. Microwave Theory and Techniques, vol. 59, pp. 627-637, Mar. 2011.
2) G. Orecchini, V. Palazzari, A. Rida, F. Alimenti, M.M. Tentzeris, L. Roselli, ”Design and Fabrication of Ultra-Low Cost Radio Frequency Identification Antennas and Tags Exploiting Paper Substrates and Inkjet Printing Technology”, IET Microwave Antennas and Propagation, vol. 5, pp. 993-1001, Jul. 2011.
3) F. Alimenti, G. Orecchini, M. Virili, V. Palazzari, P. Mezzanotte, L. Roselli, ”Design of Paper-Substrate Dipole Antennas Magnetically Coupled to UHF RFID Silicon Chips ”, IEEE International Microwave Workshop Series on RFID-Technology and Applications, Barcelona (E), pp. 219-222, Sep. 2011.
4) V. Palazzari, F. Alimenti, G. Orecchini, P. Mezzanotte, L. Roselli, ”A Ku-band RF Self Identification (RSFID) System for Autonomous Logistics ”, in 5th European Conference on Antennas and Propagation (EuCAP), Roma (I), pp. 2028-2030, Apr. 2011.
5) L. Pierantoni, D. Mencarelli, T. Rozzi, F. Alimenti, L. Roselli, P. Lugli, ”Multyphisics Analysis of Harmonic RFID Tag on Paper with Embedded Nanoscale Material ”, in 5th European Conference on Antennas and Propagation (EuCAP), Roma (I), pp. 3009-3010, Apr. 2011.
6) S. Bonafoni, F. Alimenti, G. Angelucci, G. Tasselli, ”Microwave Radiometry Imaging for Forest Fire Detection: a Simulation Study”, Progress In Electromagnetics Research, vol. 112, pp. 77-92, Jan. 2011.
7) L. Aluigi, F. Alimenti, L. Roselli, ”Automatic Design and 3D Electromagnetic Simulation of Sub-nH Spiral Inductors ”, in Progress In Electromagnetics Research Symposium, Marrakesh (Morocco), pp. 1719-1722, Mar. 2011.
8) L. Aluigi, F. Alimenti, L. Roselli, ”Design of Ka-Band LNA for SoC Space-Based Millimeter-Wave Radiometers”, IEEE International Microwave Workshop Series on Millimeter Wave Integration Technologies, Barcelona (E), pp. 156-159, Sep. 2011.
SILICON-ON-DIAMOND TECHNOLOGY AND DEVICES
A. Scorzoni, D. Passeri
We have compared two poly diamond detectors of the same batch material but with surface electrodes manufactured with different techniques, the classical Ti-Au and the laser graphitization without metal covering. The graphitization has been done by using a nanosecond laser at 1064 nm. The two detectors when exposed to a 90Sr beta source show small differences mostly in charge collection which however are ascribable to the reduction of volume thickness due to the graphitization process. However this limitation is due to the experimental set-up used in this work and does not seem to be an intrinsic limitation of the laser technique.
We must go ahead in the experimentation but the conclusion is the feasibility of the laser graphite contacts on diamond to collect particle signals and its flexibility not only for the buried SoD contacts of CHIPSODIA devices but also for wider applications.
Publications in 2011
1) G. Parrini, F. Fabbrizzi, S. Lagomarsino, L. Nunziati, S. Sciortino, A. Scorzoni, “Laser graphitization for polarization of diamond sensors”, presentation at the 10th International Conference on Large Scale Applications and Radiation Hardness of Semiconductor Detectors, Proceedings of Science, Firenze, Italy, July 6-8, 2011.