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We use Silvaco-TCAD tools to optimize ultrathin Cu (In1-xGax) Se2 solar cells with rear surface passivation. First of all, the single CIGS structure was performed and calibrated with the electrical and optical output of the experimental results. Based on the simulation and example results, considering the variety of carrier’s transport mechanism at the heterointerface CdS/CIGS shows a significant impact on cell performance. The proposed rear passivated ultrathin CIGS structure consists the following configuration: MgF2 (120 nm)/ZnO:Al (300 nm)/ZnO(100 nm)/CdS(50 nm)/CIGS(500 nm)/Al2O3/Ag/glass-substrate. The effect of the rear-passivated, absorber thickness (CIGS), and cell pitch on ultrathin CIGS cell performance is analyzed and studied under AM 1.5G, 1 sun illumination. This increases the model’s total implied photocurrent density from 21.1 to 29.1 mA/cm2. The simulations show that the ultrathin CIGS cell efficiencies of up to 13% can be obtained. The results from these simulations are compared with the measured characteristics of the fabricated cell. more...

Superhydrophobic surfaces on 6082 aluminum alloy substrates are tailored by low-cost chemical surface treatments coupled to a fluorine-free alkyl-silane coating deposition. In particular, three different surface treatments are investigated: boiling water, HF/HCl, and HNO3/HCl etching. The results show that the micro-nano structure and the wetting behavior are greatly influenced by the applied surface texturing treatment. After silanization, all the textured surfaces exhibit a superhydrophobic behavior. The highest water contact angle (WCA, ≈180°) is obtained by HF/HCl etching. Interestingly, the water sliding angle (WSA) is affected by the anisotropic surface characteristics. Indeed, for the HF/HCl and the HNO3/HCl samples, the WSA in the longitudinal direction is lower than the transversal one, which slightly affects the self-cleaning capacity. The results point out that the superhydrophobic behavior of the aluminum alloys surface can be easily tailored by performing a two-step procedure: (i) roughening treatment and (ii) surface chemical silanization. Considering these promising results, the aim of further studies will be to improve the knowledge and optimize the process parameters in order to tailor a superhydrophobic surface with an effective performance in terms of stability and durability. more...

Power SiC MOSFETs are going to substitute Si devices by to their significantly better performances that make them much suitable in power switching applications such as electric/hybrid vehicles. The increasingly use of these devices in critical mission profiles requires an ever-higher reliability, whereas the increase of the dissipated power during high-speed working cycling due to short current pulses leads to unavoidable thermal and mechanical stress. Here, we propose a direct method to evaluate the mechanical stress due to current pulses. This method highlights that high Power SiC-based MOSFET undergoes to almost two different thermomechanical processes with completely different time scale. The results allow a link between the thermo-mechanical stress and the device failure conditions, with special focus on the current pulses effects on metal surface, as this is a main power devices weakness. more...

The effect of surface microstructure on erosion-corrosion resistance of hydrophobic rough and smooth nickel electrodeposited coatings was investigated using on site electrochemical impedance spectroscopy in dynamic solution of 3.5 wt.% NaCl + 40 wt.% sand. Atomic force microscopy (AFM) was used to track damage initiation at the surface of the coatings during erosion-corrosion. Changes in the hydrophobic behavior of the coatings during erosion-corrosion were recorded. It was observed that the rough nickel coating was not erosion resistant and about 65% of its initial average roughness was lost after 30 min of erosion-corrosion. This loss of roughness approached to about 80% after 1 h of erosion-corrosion. The water contact angle of the rough nickel coating after two weeks of storing in the air was about 131° which decreased to about 115° after 30 min of erosion-corrosion and to about 78° after 1 h of erosion-corrosion. However, during erosion-corrosion tests, the polarization resistance of the rough nickel coating was constantly higher than that of the smooth nickel coating notwithstanding the significant loss of its surface microstructural features. more...

This paper deals with an accurate experimental investigation of the optical sensing behavior of a microwave low-noise amplifier (LNA). The tested amplifier, employing a commercial InGaAs pHEMT has been analyzed in terms of the scattering parameters and the noise figure. The analysis has been carried out by observing how the device behavior is influenced by a continuous wave laser illumination for different optical wavelengths, power levels, and bias conditions. It has been assessed that the LNA performance is significantly influenced by the light exposure with optical effects more pronounced at higher wavelengths for a fixed incident power. Upon applying the recommended bias conditions of the sensing amplifier, the main changes consist of a degradation of the noise figure and gain. As opposite to this, an overall performance enhancement is clearly recognizable with the amplifier biased at the transistor pinch-off. The results obtained in the present work fully confirm a theoretical analysis previously carried out by employing different devices and LNA design. more...

This paper investigates recent developments in Interdigitated Back Contact (IBC) solar cell physics and technology by using ATLAS Silvaco device simulator. The work has been focused on improvement of structural and electrical properties by using zinc oxide layer to passivate the front surface of a crystalline silicon (c-Si) substrate. In a silicon cells, the device performance crucially depends on the quality of the n-ZnO/c-Si heterojunction. Simulation results for various front dielectric material, emitter doping concentration, and semiconductor material for the front surface field (FSF) layer on the considered structure are reported and analyzed. These variations have a direct impact on the electrical device characteristics. We could determine the critical parameters of the cell and optimize its main parameters to obtain the highest performance for IBC solar cell. Therefore, we present our best results obtained recently and some guidelines to improve still more the efficiency of the devices. The optimization at 300 K led to the following results Jsc = 41.89 mA/cm2, Voc = 0.727 V, FF = 85.23 %, P $_{\max }=$ 259.95 W/m-2, and η =25.99 % which are close with those found in different works. The structure simulation will simplify the manufacturing processes of solar cells; will thus reduce the costs while producing high outputs of photovoltaic conversion. Finally, we finish by a summary of the main advantages of this technology taking into account all the parameters described above. more...

Pure and titanium- or silicon-doped iron oxide fibres are synthesised by electro-spinning over conductive fluorine doped tin oxide (FTO)/glass substrates, and the effect of the type of dopant on the morphology of the fibres and the crystalline phase of the oxide is investigated by means of several complementary characterisation techniques. Results show that in the absence of dopant, highly porous fibres, consisting of interconnected polycrystalline hematite grains, are obtained. Doping with titanium does not influence the crystalline phase of the oxide, but the better packed structure of the fibres causes them to detach from the support. Silicon-doping results in a different phase of the host oxide (maghemite) and good adhesion of the fibres to the FTO/glass support. Very preliminary tests to evaluate the photo-electrochemical activity of the samples demonstrate that the photocurrent measured with Si-doped maghemite fibres is 53% higher with respect to that obtained with pure hematite fibres, as an effect of the nearly threefold increase in the donor concentration brought about by doping. This, in turn, improves the charge transfer at the interface, leading to a higher charge injection from the electrode to the electrolyte and, thus, to a greater photo-oxidation efficiency. more...

Pure and Al- and/or Ca-added ZnO fibers are synthesized by electro-spinning. Their morphological, structural and optical properties are investigated by means of several complementary characterization techniques, focusing attention on optical properties and fiber surface roughness, which are of relevance in many applications. The comparative analysis of the results obtained demonstrates that all the fibers consist of rounded polycrystalline oxide nanoparticles interconnected to each other, with the (dopant-dependent) nanoparticle size controlling their surface roughness. Non-stoichiometry affects all the samples and strongly influences their photoluminescence properties. Calcium segregates in a secondary phase forming calcite. On the contrary, aluminum well disperses within zincite as an isolated impurity, with Al 3+ ions substituting Zn 2+ ions in the ZnO lattice. Its content controls the relative exciton-to-defect emission band intensity, as well as the frequency of the main Zn O absorption peak. more...

This paper presents the effects of optical radiation on the behavior of two scaled-gate aluminum gallium nitride/gallium nitride (AlGaN/GaN) high electron mobility transistors (HEMTs). The tested devices, having a gate width of 100 and 200 &micro, m and a gate length of 0.25 &micro, m, were exposed to a laser beam with a wavelength of 404 nm (blue-ray) in order to investigate the main optical effects on the DC characteristics. Owing to the threshold shift and the charge generation, a marked increase of the gate and drain current was noticed. The occurrence of the kink effect in the absence of light exposure was identified, and a hypothesis about its origin is provided. The obtained results agree with the analysis previously carried out on gallium arsenide (GaAs)-based devices. more...

This paper presents an experimental investigation on the microwave performance of a GaN HEMT subject to UV light exposure. The device, having 0.25 μm gate length and 100 μm gate width, has been characterized by measuring its DC performance, linear scattering parameters, noise parameters in the 2–26 GHz frequency range, either in dark condition and under CW light exposure at 375 nm. Clear variations of the GaN HEMT performance related to the charge generation and the relevant threshold voltage shift within the semiconductor layers are recognizable in the reported results. The scattering parameters and the noise parameters are affected in a similar way as it occurs in GaAs HEMT's under optical irradiation in the visible range. A circuit model extraction has then been performed to analyze more deeply the effects of the UV exposure. The observed changes of the noise parameters might be ascribed to the effects of the increased gate conduction under illumination and have been efficiently modeled by an additional resistor between the internal gate and source terminals with an assigned noise temperature of 3053 °C. more...

Graphene quantum dots (GQD), the new generation members of graphene-family, have shown promising applications in anticancer therapy. In this study, we report the synthesis of a fluorescent and biocompatible nanovector, based on GQD, for the targeted delivery of an anticancer drug with benzofuran structure (BFG) and bearing the targeting ligand riboflavin (RF, vitamin B2). The highly water-dispersible nanoparticles, synthesized from multi-walled carbon nanotubes (MWCNT) by prolonged acidic treatment, were linked covalently to the drug by means of a cleavable PEG linker while the targeting ligand RF was conjugated to the GQD by π–π interaction using a pyrene linker. The cytotoxic effect of the synthesized drug delivery system (DDS) GQD-PEG-BFG@Pyr-RF was tested on three cancer cell lines and this effect was compared with that exerted by the same nanovector lacking the RF ligand (GQD-PEG-BFG) or the anticancer drug (GQD@Pyr-RF). The results of biological tests underlined the low cytotoxicity of the GQD sample and the cytotoxic activity of the DDS against the investigated cancer cell lines with a higher or similar potency to that exerted by the BFG alone, thus opening new possibilities for the use of this drug or other anticancer agents endowed of cytotoxicity and serious side effects. more...

Hematite (α-Fe2O3) is one of the most promising photoanode materials for photoelectrochemical (PEC) water splitting although great challenges hinder high performance. Silicon-doped α-Fe2O3 shows improved PEC activity but the relationship among dopant content and enhanced conductivity, structure, and particle morphology is only poorly understood. Here, we present a systematic study on hydrothermally grown α-Fe2O3 nanocrystals by using XRD, Raman, UV–vis spectroscopy, TEM, XPS, SQUID magnetometry, electrochemical impedance spectroscopy, and photocurrent measurements. We find that the Si content controls the morphology of α-Fe2O3 already at Si 5 at.% inducing a transition from nanostructures with ellipsoidal shape to nanowires. Si doping is effective in improving PEC activity in the case of Si1% at. sample, which shows a 20% photocurrent enhancement in comparison with pure α-Fe2O3. On the contrary, α-Fe2O3 containing Si content higher than 5 at.% presents lower PEC activity. Results are rationalized in the view of the interplay of morphological, structural, magnetic, and electronic properties in doped α-Fe2O3 thus providing general guidelines for the design of efficient photoelectrodes for solar water splitting. more...

a Cardiologia Ospedale San Vincenzo, Taormina (Me) Azienda Sanitaria Provinciale di Messina, 98039, Taormina, (Messina), Italy b Cardiologia Ospedale San Vincenzo, Taormina (Me) and Cardiologia Presidio Ospedaliero “G. Fogliani”, Milazzo (ME) Azienda Sanitaria Provinciale di Messina, Italy c Cardiochirurgia Ospedale Papardo Messina, Azienda Ospedaliera Ospedali Riuniti Papardo Piemonte, 98158 Messina, Italy more...

A strong demand for even more compact and reliable power electronic devices has powered the development of advanced design techniques. A key role is played in these techniques by the reliability assessment, a procedure that estimates the expected lifetime according to given mission profiles. The reliability assessment of a low voltage MOSFET working in avalanche mode is considered in this paper through an experimental approach based on the Coffin–Manson law. Differently from previously proposed techniques, based on a thermodynamic analysis, a direct measurement of the thermal strain over the source aluminum layer is instead exploited. The consistence of the proposed technique is evaluated by comparing estimation of the progressive increment of the on -state resistance with results of endurance tests and estimation obtained from previously presented reliability models. The described technique can be applied to assess the reliability of MOSFETs in applications typical of the automotive field, where they are tasked to power inductive loads in unclamped mode. More in general, the method can be exploited to characterize the front metal of MOSFET devices subjected to power cycling, or short-circuit stress tests. more...

The electrical transport properties of a set of zinc oxide (ZnO) thin films, prepared by pulsed laser ablation, were investigated at the temperatures of 30 K and 300 K. Information about the structural and morphological properties of the samples were obtained by means of atomic force microscopy (AFM) and X-ray diffraction (XRD). A significant variation in the surface morphology and photoresponse characteristics of the ZnO thin films were observed as a function of the deposition temperature. Upon increasing the deposition temperature, the surface topography changes from a more fine-grained to a more coarse-grained structure, showing a tetragonal wurtzite crystalline structure. Time resolved photocurrent measurements showed significantly variations as function of the observed samples morphologies. A photocurrent value of about three order of magnitude larger is observed for samples showing a more coarse-grained structure with respect to the fine-grained ones. Such a result is interpreted as due to the contributions of both “bulk” and defect centers that affect the conduction mechanisms and influence both the photoconductivity values and the photoresponse speed. The observed decay times are very long with respect to films grown by other techniques, due to the reduction of the surface localized centers of defect available for recombination. In this context, the sample morphology appears to be a key parameter to control the photoconductivity in ZnO thin films. more...

a Cardiologia Ospedale San Vincenzo— Taormina (Me), Azienda Sanitaria Provinciale di Messina, 98039 Taormina, Messina, Italy b Radiologia Ospedale San Vincenzo — Taormina (Me), Azienda Sanitaria Provinciale di Messina, 98039 Taormina, Messina, Italy c UOC Oncologia Presidio di Caltagirone, Azienda Sanitaria Provinciale di Catania, Italy d Cardiologia Presidio Ospedaliero “G. Fogliani” — Milazzo (ME), Azienda Sanitaria Provinciale di Messina, Italy more...

The use of implantable cardiac devices has increased in the last 30 years. The evolution of devices in serious cardiac rhythm pathology management has led progressively to the development of devices for the treatment of bradycardia, ventricular arrhythmia, and heart failure and for the prevention of sudden cardiac arrest leading to delivery of pacemakers, implantable cardioverter defibrillators (ICDs) and cardiac resynchronization therapy (CRT) plus ICD (CRT-D) [1–22] and to the recent subcutaneous implantable cardioverter-defibrillator (S-ICD) [23–27]. Infectious complications leading also to endocarditis [1,8, 28–35] and non-infectious complications [9,21,23,36–39] often necessitating removal [1,2,8,39–45] affect patient wellbeing also leading to psychological difficulty increase [46–52] in the emerging scenario of concomitant problems and diseases [53–76]. The modern ICDs in themarket deliver a maximum energy of 35 to 41 J in relation to the model using single-coil leads or dual-coil leads. In particular patients, the electric shock delivered, cannot be sufficiently effective to suppress lifethreatening ventricular arrhythmias associated with serious diseases of the myocardium dilated cardiomyopathy (CMD) with non-compacted myocardium. In such patients, in addition to the ICD, devices may be used that facilitate cardioversion such as epicardial cardioverter defibrillation patches (Fig. 1) or a subcutaneous single-finger cardioverterdefibrillator (ICD) system (Fig. 2) [77–83]. Epicardial patches are placed at the sides of the heart through a cardiac surgery approach under general anesthesia, while subcutaneous single-finger cardioverter-defibrillator more...

The self-assembly of internally ion-paired, neutral AA/BB-type supramolecular polymers composed of complementary di-ionizable homoditopic pairs of monomers is reported. Host-to-guest double-proton transfer mediates the recognition between bis-calix[5] arenedicarboxylic acids and a, w-diaminoalkanes to yield cyclic, doughnut-shaped assem-blies with morphologies (i.e., cyclic vs. linear) that can be controlled by means of external chemical stimuli. The behavior of these intriguing aggregates, both in solution and on surfaces, has been investigated by a combination of H-1 and DOSY NMR spectroscopy, light-scattering, and atomic force microscopy. more...

The interactions between hydrochloride salts of biologically relevant amines and micelles formed by a water-soluble p-tert-butylcalix[5]arene were investigated by means of 1H NMR spectroscopy, using a combination of NOESY and DOSY techniques. DOSY measurements were conveniently employed to assess the micelle affinity towards the target guests (phenylethylamine ≈ histamine ≈ serotonin > tyramine > dopamine > norepinephrine), whereas NOESY studies revealed the approximate position of these cationic guests within the different micellar regions. In general, all the guests were located in the palisade region of the micelle, with the exception of phenethylamine and histamine, the former being bound to the micellar core as well as the palisade, the latter preferring the outer shell of the micelle. more...

A light emitting structure consisting of three coupled microcavities has been realized and studied. All three cavities contain a luminescent organic thin film of tetrakis(4-methoxyphenyl)porphyrin and they are coupled by means of two same LiF/ZnS Distributed Bragg Reflector. The entire structure is enclosed between a bottom and a top Bragg mirror with different layer number. Reflectivity spectra collected at different growing steps allow us to demonstrate the effective strong coupling between the three bare cavity modes. The reflectivity spectrum of the whole structure shows the presence of three well defined cavity dips. At normal incidence, the device emits three, well separated, peaks each one corresponding to a delocalized optical mode of the coupled system, while at higher angles the peaks result blue shift. The experimental reflectivity spectra are in good agreement with a theoretical model based on the transfer matrix method. The model is applicable to any device, therefore, once the materials to employ as emitters are established, the cavity can be designed in order to amplify just the modes that correspond to the peak wavelengths of the emission spectrum and/or to change completely the spectral shape. more...

Efficient synthetic methods to produce high‐performance electrode‐active materials are crucial for developing energy storage devices for large‐scale applications, such as hybrid supercapacitors (HSCs). Here, an effective approach to obtain controllable carbon‐encapsulated T‐Nb2O5 nanocrystals (NCs) is presented, based on the solvothermal treatment of NbCl5 in acetophenone. Two separate condensation reactions of acetophenone generate an intimate and homogeneous mixture of Nb2O5 particles and 1,3,5‐triphenylbenzene (TPB), which acts as a unique carbon precursor. The electrochemical performance of the resulting composites as anode electrode materials can be tuned by varying the Nb2O5/TPB ratio. Remarkable performances are achieved for Li‐ion and Na‐ion energy storage systems at high charge–discharge rates (specific capacities of ≈90 mAh g−1 at 100 C rate for lithium and ≈125 mAh g−1 at 20 C for sodium). High energy and power densities are also achieved with Li‐ and Na‐ion HSC devices constructed by using the Nb2O5/C composites as anode and activated carbon (YPF‐50) as cathode, demonstrating the excellent electrochemical properties of the materials synthesized with this approach. more...

Bacteria existing on the surfaces of various materials can be both a source of infection and an obstacle to the proper functioning of structures. Increased resistance to colonization by microorganisms can be obtained by applying antibacterial coatings. This paper describes the influence of surface wettability and amount of antibacterial additive (Zn) on bacteria settlement on modified SiO2-based coatings. The coatings were made by sol-gel method. The sols were prepared on the basis of tetraethoxysilane (TEOS), modified with methyltrimethoxysilane (MTMS), hexamethyldisilazane (HMDS) and the addition of zinc nitrate or zinc acetate. Roughness and surface wettability tests, as well as study of the chemical structure of the coatings were carried out. The antibacterial properties of the coatings were checked by examining their susceptibility to colonization by Escherichia coli. It was found that the addition of zinc compound reduced the susceptibility to colonization by E. coli, while in the studied range, roughness and hydrophobicity did not affect the level of bacteria adhesion to the coatings. more...