Rosalba Liguori

A Model of Electric Field Distribution in Gate Oxide and JFET-Region of 4H-SiC DMOSFETs

For the first time, a full analytical model of the electric field in the gate oxide of 4H-polytype silicon carbide (4H-SiC) power double-implanted MOSFET devices is shown. It takes into account all the relevant physical and geometrical parameters of the device and avoids the use of any fitting parameters. To validate the results of the full-analytical model, comparisons with numerical simulations are reported for device structures having different values of the drift doping concentration and drift thickness as well as of the junction FET (JFET)-region width. Moreover, because the model equations are in closed form, they can be used to derive an adequate JFET-region geometry by fixing the maximum electric field in the oxide and the maximum blocking voltage for a given drift region.

Multiplier-Less Stream Processor for 2D Filtering in Visual Search Applications

A new 2D convolution-based filter is presented, which is specifically designed to improve visual search applications. It exploits a new radix-3 partitioning method of integer numbers, derived from the weight partition theory, which allows substituting multipliers with simplified floating point (FP) adders, working on 32-b FP filter coefficients. The memory organization allows elaborating the incoming data in raster scan order, as those directly provided by an acquisition source, without frame buffers and additional aligning circuitry. Compared with the existent literature, built around conventional arithmetic circuitry, the proposed design achieves state-of-the-art performances in the reduction of the mapped physical resources and elaboration velocity, achieving a critical path delay of about 4.5 ns both with a Xilinx Virtex-7 field-programmable gate array and CMOS 90-nm std_cells.

Conductive adhesive based on mussel-inspired graphene decoration with silver nanoparticles

Decoration with silver nanoparticles was obtained by coating graphene with a polydopamine layer, able to induce spontaneous metallic nanoparticles formation without any specific chemical interfacial modifier, neither using complex instrumentation. The choice of dopamine was inspired by the composition of adhesive proteins in mussels, related to their robust attach to solid surfaces. The synthesis procedure started from graphite and involved eco-friendly compounds, such as Vitamin C and glucose as reducing agent and water as reaction medium. Silver decorated graphene was inserted as secondary nanofiller in the formulation of a reference conductive adhesive based on epoxy resin and silver flakes. A wide characterization of the intermediate materials obtained along the step procedure for the adhesive preparation was carried out by several techniques. We have found that the presence of nanofiller yields, in addition to an improvement of the thermal conductivity (up to 7.6 W/m · K), a dramatic enhancement of the electrical conductivity of the adhesive. In particular, starting from 3 · 102 S/cm of the reference adhesive, we obtained a value of 4 · 104 S/cm at a nanofiller concentration of 11.5 wt%. The combined double filler conductivity was evaluated by Zallens model. The effect of the temperature on the resistivity of the adhesive has been also studied.

Insights Into Interface Treatments in p-Channel Organic Thin-Film Transistors Based on a Novel Molecular Semiconductor

Organic thin-film transistors (OTFTs) were fabricated using a novel small molecule, C6-NTTN, as the semiconductor layer in several different architectures. The C6-NTTN layer was deposited via both vacuum evaporation at different substrate temperatures and via solution-processing, which yield maximum hole mobilities of 0.16 and 0.05 cm2/

Blue and white OLEDs with highly stereoregular polymers

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Interface engineering in organic thin film transistors

, respectively. Surface treatments of the substrate, insulator, and metal contacts used for OTFT fabrication employing polymer films and different self-assembled monolayers were investigated. In particular, in bottom-gate devices, the insulator surface hydrophobicity was optimized by the deposition of poly(methyl methacrylate) or hexamethyldisilazane, while in the top-gate geometry, pentafluorobenzenethiol was efficiently used to modify the substrate surface energy and to change the contact work function. Atomic force microscopy analysis was exploited to understand the relationship between the semiconductor thin-film morphology and the device electrical performance. The results shown here indicate an inverse proportionality between the mobility and the interface trap density, with parameters depending especially on semiconductor–insulator interfacial properties, and a correlation between the threshold voltage and the characteristics of the semiconductor–metal interface.

Simulation and fabrication of polarized organic photodiodes

Organic light emitting diodes (OLEDs) are fabricated using two novel polymers, isotactic and syndiotactic poly(N-pentenyl-carbazole) (i-PPK and s-PPK), as emitting layers. The electroluminescence spectra of the devices are analyzed in comparison with the photoluminescence spectra of polymer films and are related to their microstructure properties. Blue light emitting diodes are obtained, except for the i-PPK based multilayer OLED, which emits white light due to three contributions (electroplex fluorescence, excimer phosphorescence and electromer emission). The results show that the polymer tacticity strongly affects the photoconductive properties of the devices.

Comparative modeling of vertical and planar organic phototransistors with 2D drift-diffusion simulations

A novel semiconductor, the small molecule C6-NTTN, was used to fabricate organic thin film transistors (OTFTs). Different architectures and deposition techniques were employed, together with various surface treatments of the substrate, insulator and metal contacts, whose effect is analyzed through atomic force microscopy. The aim is to investigate the relationship between the process parameters and the electrical performance, with a particular attention to the quality of interfaces between active layers. The proportionality between the charge carrier mobility and the interface trap density was studied.

Enhanced visible light photocatalytic activity by up-conversion phosphors modified N-doped TiO2

Several important applications rely today on the detection of polarized light, as demonstrated by the wide range of sensing devices exploited over the years. Nevertheless, the miniaturization of such systems has been little explored. In this work, a possible solution towards the direct integration of the sensing optics within an electronic device has been established, utilizing a wire-grid polarizer in conjunction with a photodetector realized with organic semiconductors. The optical and electronic properties of the device have been studied and optimized using physically based numerical simulations. Consequently, a proof of concept of the photodetector has been demonstrated, having a polarization extinction ratio of 50 at a wavelength of 550 nm.

Light- and bias-induced effects in pentacene-based thin film phototransistors with a photocurable polymer dielectric

Vertical Organic Transistors and Phototransistors have been proven to be promising technologies due to the advantages of reduced channel length and larger sensitive area with respect to planar devices. Nevertheless, a real improvement of their performance is subordinate to the quantitative description of their operation mechanisms. In this work, we present a comparative study on the modeling of vertical and planar Organic Phototransistor (OPT) structures. Computer-based simulations of the devices have been carried out with Synopsys Sentaurus TCAD in a 2D Drift-Diffusion framework. The photoactive semiconductor material has been modeled using the virtual semiconductor approach as the archetypal P3HT:PC61BM bulk heterojunction. It has been found that both simulated devices have comparable electrical and optical characteristics, accordingly to recent experimental reports on the subject.