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The experimental forward current–voltage–temperature (ID–VD–T) characteristics of Mo/4H-SiC Schottky barrier diodes are investigated by means of a careful simulation study. The simulations are in excellent agreement with measurements in the whole explored current range extending over ten orders of magnitude for temperatures from 303 K to 498 K. The diode ideality factor tends to decrease while the Schottky barrier height increases with increasing temperature. These variations are explained on the basis of the thermionic emission theory with a Gaussian distribution of the barrier height around the Mo/4H-SiC interface. The calculated Richardson constant is A* = 155.78 A cm−2 K−2 which is very close to the theoretical value of 146 A cm−2 K−2 expected for n-type 4H-SiC. The linear dependence of VD on temperature is also investigated for several bias currents. The obtained results reveal that the device is well suited for temperature-sensing applications, showing a good coefficient of determination (R2 = 0.99974 for 100 nA ≤ ID ≤ 1 mA) and a high sensitivity (S = 1.92 mV K−1 for ID = 1 μA). The temperature error between the voltage measurements and their linear best fit is lower than 1.5 K.

An analytical model is used to describe the electrical characteristics of a dual-junction tandem solar cell performing with a conversion efficiency of 32.56% under air mass 1.5 global (AM1.5G) spectrum. The tandem structure consists of a thin heterojunction top cell made of indium gallium phosphide (InGaP) on gallium arsenide (GaAs), mechanically stacked on a relatively thick germanium (Ge) substrate, which acts as bottom cell. In order to obtain the best performance of such a structure, we simulate for both the upper and lower sub-cell the current density–voltage, power density–voltage, and spectral response behaviors, taking into account the doping-dependent transport parameters and a wide range of minority carrier surface recombination velocities. For the proposed tandem cell, our calculations predict optimal photovoltaic parameters, namely the short-circuit current density (J sc ), open-circuit voltage (V oc ), maximum power density (P max ), and fill factor (FF) are J sc = 28.25 mA/cm 2 , V oc = 1.24 V, P max = 31.64 mW/cm 2 , and FF = 89.95%, respectively. The present study could prove useful in supporting the design of high efficiency dual junction structures by investigating the role of different materials and physical parameters.

The electrical characteristics of a 4H silicon carbide (4H-SiC) metal–oxide– semiconductor field-effect transistor (MOSFET) have been investigated by using a multiobjective genetic algorithm (MOGA) to overcome the existing tradeoff between main device figures of merit such as the breakdown voltage, drain current, and ON-state resistance. The aim of this work is to achieve an optimized device for a specific application. In particular, without loss of generality, we refer to a dual-implanted MOSFET (DMOSFET) dimensioned for use as a low-power transistor in direct current (DC)–DC converters for solar power optimizers. Typical blocking voltages for these transistors are around 150 V. In this investigation, both analytical and numerical models are used as objective functions in MOGA to determine a set of optimized physical and geometrical device parameters that meet the application constraints while minimizing the ON-state resistance (RON). The optimized DMOSFET exhibits an RON value of a few hundred kΩ × μm2 for different breakdown voltages in the range from 150 V to 800 V.

In this work, the reliability of different oxide/4H-SiC interfaces under high temperature and carrier-trapping conditions are investigated carefully. In more detail, the carrier-trapping and temperature effects are considered in the electrical characterization of a low breakdown 4H-SiC-based MOSFET by using in turn SiO2, Si3N4, AlN, Al2O3, Y2O3 and HfO2 as gate dielectric. A gate oxide with a high relative permittivity notably improves the transistor performance. In addition, HfO2 assures the MOSFET best immunity behaviors. The obtained results are explained in terms of the carrier channel mobility, device on-state resistance, and oxide electric field. By using HfO2, however, an increased gate leakage current is calculated. This drawback is overcome by inserting a thin interfacial layer (2 nm-thick) in the HfO2/4H-SiC MOS structure. In particular, two alternative gate stacked dielectrics, involving either SiO2 or Al2O3, have proven their effectiveness in preserving the transistor on-state figures of merit while limiting the gate leakage current in the whole explored gate voltage range. To support the prediction capabilities of the presented modeling analysis, the simulations results are compared with experimental data from literature resulting in a good agreement. Low power MOSFETs are used in several applications for which reliability and durability are as critical as performance. For example, referring to power optimizers for photovoltaic (PV) modules, which fall under the low-load and low-voltage category of DC–DC converters, these devices significantly increase the energy generated by each single PV module operating under harsh conditions and stressing environments. In addition, they have to ensure high reliability over the long term of operation.

In this paper, a novel 4H-SiC metal–semiconductor-metal photodetector design based on Graphene electrode engineering and gold nanoparticles is proposed. The benefits of using an intense light trapping formalism to improve the optical performance of the 4H-SiC PD are investigated by means of an accurate optoelectronic model. The developed model is based on the EMT and avoids the difficulty of considering all nanoparticles. The precision assessment of the built model is carried out by comparison with the experimental data. The findings shed light on the ability of the proposed design to realize the dual task of reducing the unwanted shadowing effect and improving the absorption through Graphene electrode formalism and the Surface Plasmon Resonance effect in the 4H-SiC layer. Furthermore, to optimize the design sensing capability, the proposed model is adopted to formulate fitness functions for the multi-objective genetic algorithm. It is found that for a filling fraction of 0.02 and 7.5 nm radius, the optimized design yields 50 % increase in absorption compared to the standard designs where responsivity of 458 mA/W, PDCR of 3.05 × 106 and response time of 4.7 µs are achieved. These findings confirm the outstanding ability of the proposed design approach to boost up the PD active area for low-cost and high sensing capability, making it valuable for optoelectronic application.

The insertion of optimized Window and a back surface field (BSF) layers on an InxGa1-xN p-n basic single junction (BSJ) solar cell is the chief reason behind the reduction of front and back recombination. In this context, this work is focused on the selection of the suitable parameters including the indium (In) content, thickness and doping concentration for the InxGa1-xN inserted layers, that gives the best photovoltaic performances. At this aim, numerical simulations were performed using the computational numerical modeling TCAD Silvaco-Atlas to design, optimize the InxGa1-xN BSJ and extract the above Window and BSF parameters that enhance the BSJ performances. A short circuit current density ( J s c ) of 26.15 m A / c m 2 , an open circuit voltage ( V o c ) value of 0.904 V and a fill factor ( F F ) value of 79.67 % are obtained under AM1.5G illumination, exhibiting a maximum conversion efficiency η of 19.62 % . Other parameters like the external quantum efficiency (EQE), electric field developed, the current density-voltage (J-V) and the power density-voltage (P-V) characteristics are also calculated and plotted for the designed solar cell.

In this paper, the impact of silicon carbide intrinsic defect states, such as Z1/2 and EH6/7 centers, on the forward current–voltage curves of aluminum (Al)-implanted 4H-SiC p-i-n diodes is investigated by means of a physics-based device simulator. During the simulations, an explicit carrier trap effect due to an electrically active defect concentration produced by the Al+ ion implantation process in the anode region was also taken into account. The obtained current–voltage characteristics are compared with those measured experimentally for several samples at different current levels. It is found that intrinsic defect densities as high as the epilayer doping may lead to undesirable device properties and instability of the forward bias behavior. The diode ideality factor and the series resistance increase with the increase of defects and could be controlled by using high-purity epi-wafers. Furthermore, due to their location in the bandgap and capture cross-sections, the impact of Z1/2 centers on the device electrical characteristics is more severe than that of EH6/7 centers.

In this paper,. an accurate analytical model has been developed to optimize the performance of an Interdigitated Graphene Electrode/p-silicon carbide (IGE/p-4H-SiC) Metal semiconductor Metal (MSM) photodetector operating in a wide range of temperatures. The proposed model considers different carrier loss mechanisms and can reproduce the experimental results well. An overall assessment of the electrodes geometrical parameters’ influence on the device sensitivity and speed performances was executed. Our results confirm the excellent ability of the suggested Graphene electrode system to decrease the unwanted shadowing effect. A responsivity of 238 μA/W was obtained under 325-nm illumination compared to the 16.7 μA/W for the conventional Cr-Pd/p-SiC PD. A photocurrent to- dark-current ratio (PDCR) of 5.75 × 105 at 300 K and 270 at 500 K was distinguished. The response time was found to be around 14 μs at 300 K and 54.5 μs at 500 K. Furthermore, the developed model serves as a fitness function for the multi objective optimization (MOGA) approach. The optimized IGE/p-4H-SiC MSM-PD design not only exhibits higher performance in terms of PDCR (7.2 × 105), responsivity (430A/cm2) and detectivity (1.3 × 1014 Jones) but also balances the compromise between ultrasensitive and high-speed figures of merit with a response time of 4.7 μs. Therefore, the proposed methodology permits to realize ultra-sensitive, high-speed SiC optoelectronic devices for extremely high temperature applications.

In this paper, an analytical model for studying the effect of light trapping mechanism on tandem solar cell performance is developed. The proposed model considers diffraction grating morphology and antireflection coating of the InxGa1_xP/GaAs/Ge tandem solar cell. The main photovoltaic figures of merit of the InxGa1_xP/GaAs/Ge tandem solar cell are investigated. The obtained results prove the outstanding capability of the light trapping mechanism to improve device performance. An efficiency of 32.5% was obtained. A short circuit current density (JSC) of 28 mA/cm2, an open-circuit voltage (VOC) of 1.288 V, and a fill factor (FF) of 87.7% were calculated. In addition, the developed model serves as a fitness function to optimize the light trapping capability using a multi-objective particle swarm optimization (MOPSO) approach. The optimized tandem solar cell design exhibits higher performance characterized by JSC =35.3 mA/cm2, VOC = 1.305 V, and a conversion efficiency of 41.7% which outweighs that of the conventional planar solar cell. Therefore, the proposed design methodology efficiently minimize the reflectance via establishing an intensive light trapping mechanism at the front of both subcells and opens promising opportunities to enhance the tandem solar cell performances.

A device for wireless intraoral forces monitoring is presented. Miniaturized strain gauge sensors are used for the measurements of forces applied by tongue and lips. A sensor interface IC is able to multiplex among four sensors and a low energy transmission module, equipped with an ARM Cortex–M0 core, is used for signal elaboration and remote wireless data transmission using Bluetooth® Low Energy standard protocol. The main novelty rely in the dynamic correction of the output corrupted by the prestrain issue. Moreover, the device shows a reduced dimension and the ability to transmit data wirelessly, without the use of external cables normally used in state-of-the-art intraoral monitoring devices.

The use of 4H-SiC junction devices as effective temperature sensors is demonstrated by measuring, elaborating and comparing the experimental I- V characteristics of three different devices, namely pin and Schottky diodes and the body diode of a commercial power MOSFET. Due to the strong dependence of the I-V characteristics on temperature, the sensor performs a high sensitivity. It is shown that the correct choice of the probe current during sensing is fundamental to obtain an excellent linearity with T in the sensor response.

The experimental current-voltage- temperature ($I_{D}-V_{D-}$ T)curves of a Wl4H-SiC Schottky barrier (SB) diode are explored by means of a careful simulation analysis. Simulations show a perfect agreement with experimental results for different forward current levels. The fundamental diode parameters, such as the ideality factor and barrier height are T-dependent. In more detail, the barrier height increases while the ideality factor decreases with an increasing temperature. These behaviors are interpreted assuming the thermionic emission (TE) conduction model with a single Gaussian distribution of the SB height. The calculated Richardson constant is 148.8Ac$m^{-2}K^{-2}$. In the low-medium current regime, the diode voltage drop has a good linear dependence on T. For a bias current of 5.97 nA, the coefficient of determination is in excess of 0.9996 and the diode sensitivity is close to 2.33 mV/K corresponding to a temperature error of 1.14 K.

The conversion efficiency of a multi-stage RF energy harvester on a printed circuit board charge-pump, based on off-the-shelf diodes and capacitors is studied, in the UHF band, as a function of temperature. The considered temperature range varies from 25°C to 85°C, highlighting that the effects of the temperature may cause a severe degradation on the harvested power, in particular at the lowers incident power regimes. Experimental measurements are presented to show that the rectifiers quality has the biggest impact of the harvester performances. Precisely, the temperature dependent rectification ratio of silicon Schottky diodes commonly used for this application can be considered as a quality factor of the converter.

The temperature and carrier-trapping effects on the electrical characteristics of a 4H silicon carbide (4H-SiC) metal–oxide–semiconductor field effect transistor (MOSFET) dimensioned for a low breakdown voltage (BVDS) are investigated. Firstly, the impact of the temperature is evaluated referring to a fresh device (defects-free). In particular, the threshold voltage (Vth), channel mobility (µch), and on-state resistance (RON) are calculated in the temperature range of 300 K to 500 K starting from the device current–voltage characteristics. A defective MOSFET is then considered. A combined model of defect energy levels inside the 4H-SiC bandgap (deep and tail centers) and oxide-fixed traps is taken into account referring to literature data. The simulation results show that the SiO2/4H-SiC interface traps act to increase RON, reduce µch, and increase the sensitivity of Vth with temperature. In more detail, the deep-level traps in the mid-gap have a limited effect in determining RON once the tail traps contributions have been introduced. Also, for gate biases greater than about 2Vth (i.e., VGS > 12 V) the increase of mobile carriers in the inversion layer leads to an increased screening of traps which enhances the MOSFET output current limiting the RON increase in particular at low temperatures. Finally, a high oxide-fixed trap density meaningfully influences Vth (negative shifting) and penalizes the device drain current over the whole explored voltage range.

The performance of a 4H-SiC Schottky diode for thermal sensing in the wide temperature range from $T=85$ up to 443 K is presented. The linear dependence on temperature of the forward voltage drop, for different bias currents, is investigated through an analytical study of the temperature-dependent physical Schottky diode parameters. A high sensitivity of 1.18 mV/K was observed for a constant bias current of $I_{D}=80 \,\,\mu \text{A}$ . The device exhibits a good degree of linearity with a calculated root mean square error, with respect to the best-linear fitting model, lower than 2.7 mV. Moreover, the proposed sensor shows a good repeatability maintaining a stable output over more cycles of measurements, from (down to) 85 up to (from) 443 K, in a long period of time.

In this paper, we present an analytical study of the impact of light trapping and multilayer antireflection coating (ARC) on the electrical characteristics of n(a-Si:H)/i(a-Si:H)/p(c-Si)/p+(C-Si) heterojunction solar cells with intrinsic thin layer (SHJ). The developed analytical model considers a triangular texture morphology of the solar cell top surface and a double ARC layer. This model serves as a fitness function to optimize the device reliability against the interfacial traps using Grey Wolf optimization approach (GWO). The optimized solar cell reveals a high short circuit current ISC = 47.9 mA, an open circuit voltage VOC = 0.56 V, fill factor FF = 74.72% and a conversion efficiency improvement in the order of 30% over conventional planar solar cells efficiency. Not only the optimized SHJ solar cell exhibits higher performance in terms of figure of merits, but also shows superior interfacial traps reliability at the amorphous/crystalline interface. This reliability enhancement is due to a better surface texture control and intrinsic thin film layer tuning provided by GWO approach.

The performance of two temperature sensors based on 4H-SiC diodes are investigated. Both devices show a good linear dependence on temperature of the difference between the forward bias voltages measured on two identical diodes (Schottky or p-i-n) yet biased at different constant currents. The Schottky diodes-based sensor shows a high sensitivity (S=5.11mV/K) whereas the p-i-n structure has a highly linear output proportional to the absolute temperature.

In this work different experimental current–voltage behaviours of several Al implanted 4H-SiC p–i–n diodes are investigated by means of numerical simulations in a wide range of currents and temperatures. Some devices for which recombination and tunneling are the dominant current processes at all biases are classified as “leaky” diodes. The well behaved diodes, instead, show good rectifying characteristics with a current conduction due to tunneling below 1.7 V, recombination between 1.7 V and 2.5 V, and diffusion processes above 2.5 V. At higher current regimes, a series resistance in excess of 1 mΩ cm 2 becomes the main current limiting factor. Depending on the relative weight between the contact resistances and the internal diode resistance, different temperature dependencies of the current are obtained. A good agreement between numerical and measured data is achieved employing temperature-dependent carrier lifetime and mobility as fitting parameters.

Electro-optical modulation of a 1550 nm wavelength carrier is observed and characterized in a 4H-SiC epitaxial layer which is part of a 600 V breakdown voltage commercial Schottky diode. Experimental evidence of a phase shift has been obtained within an interferometric structure, however not designed for such purposes. The amplitude modulation is induced both in dc and switching operation by means of plasma dispersion effect, and specifically by carrier depletion of the epitaxial layer, when a reverse bias is applied to the metal/4H-SiC(n)/4H-SiC(n+)/metal vertical rectifying structure. The contribution arising from the electrically induced free-carrier concentration variation yields a figure of merit $\text{V}_{\pi }\times L_{\pi }$ equal to 53.6 V $\times $ cm.

The current-voltage characteristics of a 4H-SiC MOSFET dimensioned for a breakdown voltage of 650 V are investigated by means of a numerical simulation study that takes into account the defect state distribution at the oxide-semiconductor interface in the channel region. The modelling analysis reveals that, for these low-voltage devices, the channel resistance component plays a key role in determining the MOSFET specific ON-state resistance (R ON ) under different voltage biases and temperatures. The R ON value is in the order of a few m Ω ×cm2.

Performances of temperature sensors based on Divanadium Pentoxide/4H polytype of silicon carbide, V2O5/4H-SiC, and Schottky diodes are analyzed. The devices with an active area of $1.96\times 10^{-3}$ cm2 were characterized in a temperature range between 147.22 and 396.75 K and in a current range between $1~\mu \text{A}$ and 1 mA. Measurements reveal that at a bias current of $16~\mu \text{A}$ , the diode forward voltage shows a linear dependence on the temperature, with a sensitivity of 1.86 mV/K and a temperature error of 0.64 K. Sensors have also shown a good repeatability of sensing over more cycles of measurements in the considered temperature range. Numerical simulations are performed, and device physical parameters are obtained from the best fit with experimental data. From simulation results, we show that the conduction mechanism of the sensor is affected by traps at the V2O5/4H-SiC interface, which have been modeled with an exponential tail. Moreover, device parameters, as epilayer doping concentration and thickness, have been varied in order to evaluate the variations on the sensor performances.

Transportation systems are gradually changing. Innovative solutions are provided by automotive industries, construction firms, computer-aided pavement management systems, sensor-based structural health monitoring (SHM) systems, and international regulations. This calls for efforts and studies aiming at finding a trade-off between the ever-growing request of innovation (smart cities), and the never-ending depletion of resources and energy. Energy savings in road infrastructures can be pursued through: 1) construction process optimization; 2) traffic management improvement; 3) vehicle optimization; 4) recycling and reuse of construction materials; 5) innovative materials; 6) energy harvesting; 7) smart roads; 8) maintenance and rehabilitation optimization through SHMmethods and technologies. Theobjective of the study is to set up an innovative SHM method aiming at achieving energysavings in transportation in terms of Pavement Management System (PMS) optimization.The new method here setup was implemented through an experimental investigation. Amicrophone was placed on different road pavements, impulse loads were produced by aLight weight Deflectometer, LWD, and vibro-acoustic signals were recorded and analyzedin the pursuit of assessing the structural condition of the pavement. Using this knowledge toimprove the management process of transportation infrastructures, it is expected that safer,more resilient, and less energy-consuming assets will be provided.

This paper reports about an efficient method for the numerical simulation of the electrical and optical characteristics, in both steady state and transient conditions, of free carrier injection- or depletion-based electro-optical active devices, based on the low cost technology of hydrogenated amorphous silicon (a-Si:H) and related semiconducting alloys, like a-SiC:H. In particular, our experimental results, recently achieved for low-loss, birefringence-free, single-mode waveguide-integrated phase modulators, are used to tune the many simulation parameters and validate the mixed electro-optic simulation environment. The tool is used to design a Mach–Zehnder Interferometer (MZI)-based modulator enhancing the performances of previous realized devices.

Higher efficiency in photovoltaic (PV) conversion calls for the use of small Maximum Power Point Trackers (MPPT) to be placed on board the PV modules. Such circuits require in turn power transistors with low energy losses, high switching speed and blocking voltages lower than 150 V. Thus, starting from a conventional 4H-SiC power MOSFET, a novel device for photovoltaic applications has been designed and numerically simulated in order to determine its on-state resistance (RON) for different device structures and bias voltages. The resulting value of RON is compared to that of a commercial Si-based MOSFET performing the same breakdown voltage. © 2017 IEEE.

A proportional to absolute temperature sensor (PTAT) based on V2O5/4H-SiC (divanadium pentoxide/4H polytype of silicon carbide) Schottky diodes is presented. The linear dependence between the voltage differences across two constant-current forward biased diodes on temperature has been used for thermal sensing in the wide temperature range from T=147 K up to 400 K. A sensitivity of 307 µV/K was calculated for two constant bias currents, ID1=16 µA and ID2=608 µA.

An energy harvester operating at high temperature, up to T=300 °C, is presented. In particular, a voltage doubling rectifier realized with two 4H-SiC Schottky diodes is used to rectify the AC voltage output of a piezoelectric bimorph with a Curie temperature of TC=320 °C. The rectifier efficiency is of about η∼89% and it slightly increases with temperature due to the corresponding diodes threshold voltage decrease.

The forward I-V characteristics of 4H-SiC p-i-n diodes are studied in a wide range of currents and temperatures by means of an analytical model which allows to highlight the minority current contributions in the various diode regions, namely, the highly doped regions, the neutral base and the space charge layer. By accounting for the doping dependency of the various physical parameters, as bandgap narrowing, incomplete doping activation, carrier lifetime and mobility, the model turns useful to investigate the role of the various material properties at different current levels and temperatures. The accuracy of the model is verified by comparisons with numerical simulations and experimental data in a wide range of currents and temperatures, so that this model turns very useful for better understanding the impact of technological parameters on the teady-state behavior of diodes and obtaining an accurate circuital model of diodes.

In this paper, we report results on a field-effect-induced light modulation at λ = 1.55 μm in a high-index-contrast waveguide based on a multisilicon-on-insulator platform. The device is realized with the hydrogenated amorphous silicon (α-Si:H) technology, and it is suitable for monolithic integration in a CMOS IC. The device exploits the free-carrier optical absorption electrically induced in the semiconductor core waveguide. The amorphous silicon waveguiding layer contains several thin dielectric films of amorphous silicon carbonitride (α-SiCN) embedded along its thickness, thus highly enhancing the absorbing action of the modulator held in the on state.

article i nfo Development of non-volatile memories based on organic soft materials is one of two main trends in industry for flash-memories. The electrical bistability of such materials makes them ideal candidates for cost-effective, fast programming switching devices. SiO2-Rose Bengal (bis-triethylammonium) hybrid thin films are reported here together with their characterizations. The technology yields well reproducible films with good current-voltage switching characteristics. Owing to their physical and chemical stability the films are suited to standard micro-photolitography technology, rendering their fabrication cost-effective.

A new temperature sensor based on a divanadium pentoxide/4H-silicon carbide (V2O5/4H-SiC) Schottky diode is presented. The realized device shows a good linear dependence vs. temperature of the voltage drop measured across the forward-biased junction. The diode performance, i.e. linearity and sensitivity, were analyzed in the temperature range from 147 K up to 400 K. Moreover, fundamental diode parameters were extracted from current-voltage characteristics.

A CMOS sensor fabricated in 0.35μm technology, specifically designed for the monitoring of High Concentration Photo-Voltaic (HCPV) modules, is presented. The microchip was designed to monitor temperature and illumination of each solar cell in a module. Temperature is measured by monitoring the base-emitter voltage of two coupled, diode connected, bipolar transistors, while the illumination sensor is an integrated p-n junction photodiode. A custom communication protocol is implemented in the chip to allow the sharing of a two-wire communication resource among the cells.

We present the design and the fabrication of an integrated hybrid optical sensor for liquid and gas sensing based on the anodic bonding technique. The device is composed by three distinct elements separately realised and then joined together: a planar SOI waveguide, a porous silicon micro-chamber and a glass slide. The presence of a liquid or gaseous substance in the reaction chamber is revealed as a change in the propagation characteristic of the guided mode. In case of exposure to methanol, the preliminary experimental results show that the propagation of the laser beam, coupled into the SOI waveguide, has been efficiently modulated. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The measurement of the power dissipated by a semiconductor device is of great importance for assessing system performance and reliability and to evaluate the overall efficiency of a power electronics systems. Efficiency measurement can be difficult when the device is highly efficient and the power losses are extremely low. Measurement errors can be introduced due to high frequency components in the waveforms. We present a calorimetric method based on a micromachined dual-sensor heat-flux measurement device that allows the estimation of the power dissipated by a semiconductor device. The system use a thermoelectric heat pump to keep the switching device at room temperature in order to minimise the heat exchanged with the ambient and improve therefore the precision of the measurement.

This work aims to investigate on the electrical, optical and gas-sensing properties of zinc oxide-based nano-wires (nwZnO) deposited on a crystalline silicon (c-Si) wafer. In particular, a comparison between the less efficient heat treatment for the analyte desorption and the photo-enhanced response will be investigated and discussed for NO 2 gas flows.

In this paper, an alternative approach for the measuring and transmission of vital parameters related to High Concentration PhotoVoltaics (HCPV) modules under illumination has been proposed, allowing recovering information from every individual cell. The valuable cell parameters such as temperature and illumination are measured with a dedicated VLSI integrated circuit (IC) that contains also an integrated 2.4 GHz transmitter with an On-Chip-Antenna (OCA) - made on the top metal layer of the same die - that sends the collected data wirelessly to a base station allowing a complete diagnostic of the module performances over the years. On-Off Keying (OOK) modulation is used to send the sensors data. The IC has been designed and realized in AMS CMOS 0.35µm technology.

A high-performance Proportional To Absolute Temperature (PTAT) sensor based on two integrated 4H-SiC Schottky diodes is presented. The linear dependence between the voltage differences across the forward-biased diodes and the temperature, in a range from 30°C up to 300°C, has been used for thermal sensing. A high sensitivity of 5.13 mV/°C at two constant bias currents has been measured.

An autonomous RFID sensor platform is designed and implemented using off-the-shelf discrete components. It includes a dipole antenna to wirelessly transmit the stored data to a reader according to the EPCglobal Class-1 Gen2 standard. The rectifier operates with received power as low as −10dBm. The microcontroller dissipates below 500nW in sleep mode, allowing an optimal energy harvesting and storage from the RF source. The input impedance is dynamically adapted to respond over a range of input power and loads. The collected power is used to write the data captured by sensors into the user memory of an RFID tag at a user selectable rate. The results demonstrate the feature of the system to perform operations up to a distance of 1.5 m from an RF energy source of 30dbm, thus it is a suitable candidate for use in passively powered sensor networks.

A voltage doubler rectifier for hostile environments, in particular at high temperatures, is presented. The system consists of a clamper section and a single diode rectifier working at higher temperatures with respect to the conventional operating thermal domain of silicon electronics. Both sections are realized with integrated 4H-SiC Schottky diodes. The rectified output amplitude signal voltage increases with the temperature due to the corresponding diode threshold voltage lowering.

The compatibility of porous silicon and anodic bonding technologies for the realization of sensing micro-components in lab-on-chip applications is demonstrated. In particular, we have developed and tested an innovative anodic bonding process: voltage, time and temperature have been properly matched in order not to affect the properties of the transducing material, which can be strongly modified by thermal treatments through oxidation. Two devices for chemical and biological sensing have been designed, fabricated and tested. The results obtained are very promising, especially regarding further integration of porous silicon and glass with optical and microelectromechanical instruments.

The design of an amorphous silicon based Mach-Zehnder electro-optic modulator integrated into a two-dimensional (2D) photonic crystal (PhC) has been designed for wavelengths of ~1.55 μ m. The numerical analysis has been performed by using a finite-difference time domain (FDTD) based simulation tool. The design of the PhC-based MZ Modulator relies on the exploitation of the refractive index tunability of the hydrogenated amorphous silicon (a-Si:H) for the fabrication of PhC waveguides requiring minimum critical technological processes.

Adding computational and sensing capabilities to the new generation of passive UHF RFID tags has contributed to overcome the idea of considering them as mere identification transponders. These new functionalities give smart RFID tags the chance to be included in the global network of interconnected objects envisioned by the Internet of Things (IoT) paradigm. However, to fully enable RFID tags to participate in machine-to-machine (M2M) communications, RFID systems still lack an important feature, namely the capability of exchanging unicast messages between tags. In this paper, we propose an effective approach to enable real-time bidirectional communications among tags belonging to an RFID Local Area Network (i.e., under the coverage area of the same reader). The presented solution is based on the main idea of utilizing the User Memory of the tag as a virtual channel for transferring messages, and the tag reader as a message forwarder. As a proof-of-concept for our proposal, a novel smart RFID tag able to exploit the RFID radio interface for bidirectional real-time communications with other tags is designed, and experimental measures on the deployed testbed are discussed.

An high-resolution CMOS temperature sensor with high linearity in the range from 20°C to 90°C is presented. The circuit uses substrate bipolars as temperature transducers. The temperature sensor consists of two building blocks: a Proportional To Absolute Temperature (PTAT) voltage generator and a differential amplifier. The second block is necessary to obtain reasonable voltage level that can be either read with a simple setup using it as analog input for an ADC. The simulation predictions are confirmed with experimental data resulting from the IC fabricated in a standard 0.35µm CMOS technology.

The thermo-optic coefficient (TOC) of hydrogenated amorphous silicon (a-Si:H) has been measured in the temperature range 30–200 °C, at the communication wavelength of 1.55 μm . The experimental data have been fitted using a single oscillator model that takes into account the shape of e2-spectrum of the amorphous semiconductor. The extracted parameters significantly extend, and are consistent with, the few data reported in the literature. An interesting analogy with crystalline silicon (c-Si) is also found and discussed.