Università degli Studi di Salerno
Dipartimento di Ingegneria Elettronica e Ingegneria Informatica
1. Modeling and characterization of material and devices for power applications
S. Bellone, L. Di Benedetto, G.D. Licciardo
Collaborations: Università Mediterranea di Reggio Calabria, CNR-IMM Unità di Bologna, KTH.
2. Architecture design for IMAGE and video processing
Collaborations: STMicroelectronics, Ansaldo STS.
3. REALIZATION AND CHARACTERIZATION OF ORGANIC SEMICONDUCTOR DEVICES
A. Rubino, M. Petrosino, R. Liguori
Collaborations: Dip. di Ing. Chimica ed Alimentare Università di Salerno, ENEA C.R. Portici, STMicroelectronics, Dip. Ing. delle Acque e Chimica Politecnico di Bari, Istituto per i materiali compositi e biomedici - C.N.R, IMAST-S.c.a.r.l., Dipartimento di Fisica Università Federico II-Napoli.
4. Noise Properties of nanocomposite materials
H. C. Neitzert
5. Ultrasound Systems for non Destructive Testing of Food Materials and Processes
Collaborations: Dip. Ing. Elettronica Università di Roma III, Dip. Ing. Industriale Università di Salerno
Modeling and characterization of material and devices for power applications
S. Bellone, L. Di Benedetto, G.D. Licciardo
The 4H polytype of Silicon Carbide (4H-SiC) appears to be the best alternative to Si for implementing semiconductor devices suited for high power applications, thanks to its higher values of thermal conductivity, saturation velocity and critical electric field. The research activity at University of Salerno has been aimed to develop analytical and circuital models of the static and switching behavior of bipolar power devices in 4H-SiC, in order to accurately account for the material peculiarities, as the partial ionization of doping, the temperature dependence, and to establish the base knowledge for designing new devices. The developed models are an important complementary tools to black-box numerical simulator since they allow to analyze separately the effects of physical parameters on the electrical performances of the devices at different operation conditions and highly support to design new devices. In this scenery, by solving the fundamental equations of semiconductors using arbitrary injections for the initial conditions of diode, a self-consistent analytical model of the switching behavior of SiC p-i-n diodes has been published, capable of describing the whole transient of the current and voltage for a wide range of physical parameters of SiC material and forward-to-reverse current ratios. The model allows to obtain, with comparable accuracy of numerical simulations, the spatial-temporal profiles of carriers, current components and electric field in the whole device, including the widening of the space charge region during the turn-off. The accuracy of the model has been verified by comparisons with numerical simulations carried out on diode structures with epilayer thickness of 5mm and 15mm respectively, which result in the expected values of forward current, at 3.5V, and breakdown voltage equal to and respectively. In addition, an analytical model of the voltage barrier height in the channel of Bipolar Static-Induction Transistors (BSIT) has been developed. The model allows to evaluate the barrier height for an arbitrary gate topology, namely for a generic gate depth, channel width, source-gate distance, doping, and is capable to predict accurately the minority and majority carrier densities at the saddle point of the channel under equilibrium conditions and gate bias. The validity of the model has been verified by comparison with numerical simulations of BSIT’s structures reported in the past by other authors and with original simulations carried out on Si and SiC JFET’s. The model turns also useful to describe the exponential behavior of the ID-VGS curves of normally-off JFET’s structures.
Publications in 2011
1) F. G. Della Corte, F. Pezzimenti, S. Bellone and R. Nipoti, “Numerical simulations of a 4H-SiC BMFET power transistor with normally-off characteristics”, Materials Science Forum, Vols. 679-680 (2011), pp. 621-624;2) S. Bellone, G.D. Licciardo,, “Extension of the TPA method for the exact analysis of feedback circuits in terms of the return ratio”, Environment and Electrical Engineering (EEEIC), 2011 10th International Conference on, pp.1-4, 8-11 May 2011
Architecture design for image and video processing
As part of the “Laboratorio della Campania per lo studio della Microelettronica”, together with STMicroelectronics, the Unit of Salerno is involved in the Compact Descriptors for Visual Search (CDVS) standardization process. In this context, at University of Salerno has been developed an HW module for real-time Difference-of-Gaussian (DoG) calculation, which avoid the use of external or embedded SRAM and works on data read in streaming order from raw image sensors. In addition, a HW module has been developed for real-time calculation of Context Adaptive Variable Length Coding (CAVLC). CAVLC is a lossless compression method which combines the variable length coding technique, consisting in coding high recurrent symbols with shorter codewords, with an adaptively selec-tion of these codewords on the basis of previously coded symbols. Since its inclusion in the H.264/MPEG4 AVC, the latest video coding standard approved by ITU-T, CAVLC is adopted for coding video streams employed in a wide range of applications, from webcasting to HD videos, where its good efficiency highly improves the H.264 compression ratio capability with respect to previous standards like MPEG-2, MPEG-4 and H.263.The developed encoder architecture is proposed which achieves real time execution through the utilization of different approaches in order to minimize the area cost as well as to speed up the coding efficiency also when implemented with a low-cost, low-speed FPGA platform. A large area reduction has been obtain by using the Arithmetic Table Elimination (ATE) technique in order to completely eliminate the seven tables for level coding which are usually implemented in very large embedded ROM. For those syntax elements which cannot be encoded by using arithmetical derivations, a subdivision of the traditional tables into smaller compressed tables is adopted which minimize the occupied memory space at the cost of a small circuitry for the elaboration of side information.The proposed architecture has been verified on a XILINX Spartan 3 FPGA where synthesis results give 20K equivalent gates and 63 MHz of maximum operating frequency, thus making the encoder capable of processing HDTV video frames with a resolution of 1920x1080 pixels at 30fps. These performances, although obtained without using any pipelining scheme, overcomes other architectures presented in the literature exploiting FPGA platforms and is comparable with ASIC implementations.
REALIZATION AND CHARACTERIZATION OF ORGANIC SEMICONDUCTOR DEVICES
A.Rubino, M. Petrosino, R. Liguori
The aim of the activity is the development of devices and processes that allow the performing electronic circuits on “poor substrates” as glass and plastics. These devices are realized using organic semiconductors and insulators exploiting the low temperatures of the depositions and the low cost of the processes. In particular, several typologies of Organic Thin Film Transistors (OTFT) have been realized, characterized and modeled using thin layers of pentacene as channel semiconductor and different polymers as gate insulators. The effect of the luminous stimulation at different wavelength has been analyzed focusing on the UV-light annealing, trap generation and photo-induced current. These experiments have been performed with the Portici ENEA Research Center in the fulfillment of the PHONEMA MIUR-financed project.
Publications in 2011
1) M. Petrosino, A. Rubino, “Effects of the PEDOT interface trap distribution in polymeric OLEDs”, Organic Electronics – 12 (2011) 1159-1165
2) M. Petrosino, A. Rubino, “Admittance spectroscopy of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) based organic light emitting diodes”, Journal of Applied Physics – 109 (2011) 114504
3) M. Petrosino, A. Rubino, “Admittance electrical model of polyfluorene based organic light emitting diodes”, Journal of Applied Physics – 110 (2011) 064513
Noise Properties of nanocomposite materials
H. C. Neitzert
Noise spectroscopy often gives more detailed insight into the basic electrical transport mechanisms than conventional current-voltage characterizations. As a matter of fact, the so-called “fluctuation spectroscopy” can be a very informative method to understand the kinetic processes and the dynamic behaviors of the charge carriers in the investigated systems, as already demonstrated in the case of manganite compounds. In literature, most noise related reports are regarding transistor noise in individual single-walled carbon nanotubes. There are few reports on noise spectroscopy in carbon nanotube networks (CNN). In such case the transport is often dominated by tunneling resistance, related to the nanotube-nanotube contacts in the percolation network, rather than by the resistance of the individual nanotube. We investigate in detail the noise properties of high-density polyethylene (HDPE)/multi-walled carbon nanotube composites in a temperature range between 10 and 300 K. A crossover of the conduction from a low-field to a high-field regime is found in current-voltage characteristics. In particular, the high-field regime has a strong dependence on carbon nanotube concentration. Noise measurements reveal a standard 1/f behavior due to resistance fluctuations. However, in samples with different concentration of nanotubes, an unusual temperature dependence of the noise is observed. The samples with higher percentage of nanotubes seem to be the most promising ones for devices application, since their noise level is lower in the whole investigated temperature range.
Publications in 2011
1) R. Di Giacomo, H. C. Neitzert, L. Vertuccio, A. Sorrentino and S. Sabbatino, “Application of Epoxy/Carbon Nanotube Composites as Microwave Absorber at Frequencies up to 25 GHz”, Proceedings of the AISEM 2010, Sensors and Microsystems: Lecture Notes in Electrical Engineering, vol. 91, Chapter 74, 455-459, 2011.
2) C. Barone,D. Imparato, S. Pagano, L. Vertuccio, A. Sorrentino and H. C. Neitzert, “Electrical Noise Characterization of Epoxy/MWCNT Composites”, Proceedings of the AISEM 2010, Sensors and Microsystems: Lecture Notes in Electrical Engineering, vol. 91, Chapter 6, 49-53, 2011.
3) C. Barone, S. Pagano, and H. C. Neitzert, “Transport and noise spectroscopy of MWCNT/HDPE composites with different nanotube concentrations”,J. Appl. Phys., vol 110, 113716, 2011.
Ultrasound Systems for non Destructive Testing of Food Materials and Processes
Ultrasonic based devices have been applied to control many industrial processes for a number of decades. Nowadays, these technologies are emerging as well-suited methods to test food materials and to monitor food processes, fulfilling important quality requirements of non-invasiveness, non-destructiveness and easy automation. In the literature various ultrasonic methods have been proposed for the determination of various components of a liquid solution. All methods are based on the measurement of the sound propagation velocity in the test solutions and the determination of liquid density. The possibility of obtaining a theoretical relation between density and ultrasonic propagation velocity, was discarded being aware of the lack of a representative model for liquid mixtures and solutions. An ultrasonic technique for monitoring the alcoholic wine fermentation was proposed: a piezoelectric transducer (Tx) excited by a tone burst, is used to transmit an acoustic wave in the liquid sample and another transducer (Rx) to receive the propagated wave; by comparing the transmitted and received signals the attenuation and the propagation velocity in the liquid are measured. As first step some model solutions of saccharose in water and ethanol in water are examined in order to investigate the method applicability and resolution: it is concluded that the propagation velocity varies with the solvents' concentration and a resolution of 1% can be obtained; on the contrary the attenuation gives not useful information. The measures on must in fermentation put in evidence the possibility of monitoring the state of the process starting from the evaluation of the ultrasound propagation velocity; in fact the variation of this parameter follows an interpretable outline: in particular it decreases with the progressing of the fermentation, i.e. while saccharose is transformed in alcohol. The comparison between the velocity behavior and the chemical analysis during the fermentation process, let us to assert that the variation of the propagation velocity is exclusively due to the decreasing of the saccharose concentration.
Publications in 2011
1) N. Lamberti, G. Caliano, A. Iula, A. S. Savoia: “A High Frequency Cmut Probe for Ultrasound Imaging of Fingerprints”, SENSORS & actuators, part. A, vol. 172, pp. 561–569, 2011.
2) N. Lamberti, “A Piezoelectric Actuator, Based on a Langevin-Type Transducer, for Dermatological Aesthetic Applications”, BIODEVICES 2011, pp. 163–167.
3) A. Iula, N. Lamberti, A. Savoia, G. Caliano, “Fluid film force control in lubricated journal bearings by means of a travelling wave generated with a piezoelectric actuators’ system”, 2011 International Congress on Ultrasonics Proceedings.
4) G. Caliano, N. Lamberti, A. S. Savoia, A. Iula, “A Track-pad Device Based on a Piezoelectric Bimorph”, 2011 IEEE Ultrasonics Symp.
5) A. Bagolini, M. Boscardin, A. Picciotto, P. Bellutti, N. Lamberti, G. Caliano, A. Savoia, “Low temperature surface micromachining with metal sacrificial layer: development of materials and process for Reverse cMUT fabrication”, 10th MUT Workshop, June 2011.