Search

Chemical and structural modifications occurring in homogeneous crystalline Si nanoparticles (NPs) used as anode material in Li cells are investigated. State-of-the-art high-resolution scanning transmission electron microscopy coupled with electron energy loss spectroscopy resolved at the nanoscale is exploited. It is directly highlighted by electron spectromicroscopy that, above 0.1 V versus Li, the electrochemical activity of Si electrodes involves a complex interplay between Li incorporation, electrolyte degradation, and Si reduction/oxidation. These redox processes occur upon cycling through partially reversible reactions mediated by the solid electrolyte interphase. Overall, a SiO2 amorphous layer forms in the oxidized electrodes at the Si NPs interface with the electrolyte: this oxide shell partially dissolves upon reduction to give Li2CO3 and amorphous Si. Si NPs cores are therefore eroded upon cycling as their outer layers are directly involved in a reversible oxygen shifting mechanism at the interface, whereas unreacted SiO2 accumulates cycle-by-cycle. These findings extend the comprehension of the Si pulverization mechanism in Li batteries.

Ion-beam amorphization of crystalline silicon is reviewed. All the peculiar features of the process (temperature effect, incubation fluence, superlinear behavior of the amorphous fraction as a function of the ion fluence, dose–rate effects, ion mass/energy dependence, doping influence, etc.) can be explained within the classical theory of nucleation and growth based on capillarity. Nucleation and growth rates depend on the free energy of the amorphous clusters and on the kinetics balance between damage creation at the prompt stage of each ion collision cascade and competitive re–crystallization induced by atomic jumps of long living defects at the cluster surface. The model explains the damage accumulation kinetics either in dilute or dense collision cascade. It is an extension of the theoretical approach describing the reverse process, i.e. the ion–beam assisted nucleation and growth of crystalline clusters in the amorphous material. The description is independent on the atomistic nature of the involved defects.

Well designed and safe nano drug carrier systems are an important tool in biomedical applications. The combination of two or more drugs has been used in medicine both to enhance the therapeutic effect and to decrease the side effects of drugs. Biocompatible halloysite nanotubes, that possess two different surfaces, are a suitable nanomaterial for a simultaneous carrier and release of two drugs that can exert a synergistic effect against cancer cells. In this study, three curcumin derivatives and doxorubicin were loaded by supramolecular and covalent linkage at the lumen and external surface of the halloysite nanotubes. The obtained multifunctional systems were characterized by several techniques and the kinetic release of the drugs from the lumen was also investigated. Finally, the cytotoxic effects of the multifunctional carriers were evaluated on different cancer cell lines, namely breast cancer cell lines (SUM-149 and MDA-MB-231) and acute myeloid leukemia cell lines (HL60 and HL60R). The obtained results show promising cytotoxicity activity of the hybrids which is correlated to the nanoparticles size and to the release profile of the drug supramolecularly loaded on Hal surfaces.

The burgeoning interest in two-dimensional (2D) black phosphorus (bP) contributes to the expansion of its applications in numerous fields. In the present study, 2D bP is used as a support for homogeneously dispersed palladium nanoparticles directly grown on it by a wet chemical process. Electron energy loss spectroscopy-scanning transmission electron microscopy analysis evidences a strong interaction between palladium and P atoms of the bP nanosheets. A quantitative evaluation of this interaction comes from the X-ray absorption spectroscopy measurements that show a very short Pd-P distance of 2.26 Å, proving for the first time the existence of an unprecedented Pd-P coordination bond of a covalent nature. Additionally, the average Pd-P coordination number of about 1.7 reveals that bP acts as a polydentate phosphine ligand toward the surface of the Pd atoms of the nanoparticles, thus preventing their agglomeration and inferring with structural stability. These unique properties result in a superior performance in the catalytic hydrogenation of chloronitroarenes to chloroanilines, where a higher chemoselectivity in comparison to other heterogeneous catalyst based on palladium has been observed.

We have further extended our compartmental model describing the spread of the infection in Italy. As in our previous work, the model assumes that the time evolution of the observable quantities (number of people still positive to the infection, hospitalized and fatalities cases, healed people, and total number of people that has contracted the infection) depends on average parameters, namely people diffusion coefficient, infection cross-section, and population density. The model provides information on the tight relationship between the variation of the reported infection cases and a well-defined observable physical quantity: the average number of people that lie within the daily displacement area of any single person. With respect to our previous paper, we have extended the analyses to several regions in Italy, characterized by different levels of restrictions and we have correlated them to the diffusion coefficient. Furthermore, the model now includes self-consistent evaluation of the reproduction index, effect of immunization due to vaccination, and potential impact of virus variants on the dynamical evolution of the outbreak. The model fits the epidemic data in Italy, and allows us to strictly relate the time evolution of the number of hospitalized cases and fatalities to the change of people mobility, vaccination rate, and appearance of an initial concentration of people positives for new variants of the virus.

Hypothesis The use of non-viral vectors for gene therapy is hindered by their lower transfection efficiency and their lacking of self-track ability. Experiments This study aims to investigate the biological properties of halloysite nanotubes-carbon dots hybrid and its potential use as non-viral vector for oral gene therapy. The morphology and the chemical composition of the halloysite hybrid were investigated by means of high angle annular dark field scanning TEM and electron energy loss spectroscopy techniques, respectively. The cytotoxicity and the antioxidant activity were investigated by standard methods (MTS, DPPH and H2O2, respectively) using human cervical cancer HeLa cells as model. Studies of cellular uptake were carried out by fluorescence microscopy. Finally, we investigated the loading and release ability of the hybrid versus calf thymus DNA by fluorescence microscopy, circular dichroism, dynamic light scattering and ζ-potential measurements. Findings All investigations performed confirmed the existence of strong electrostatic interactions between the DNA and the halloysite hybrid, so it shows promise as a multi-functional cationic non-viral vector that has also possesses intracellular tracking capability and promising in vitro antioxidant potential.

The synthesis of photoluminescent nanomaterials based on halloysite nanotubes is described. The obtained hybrid was characterized by means of TGA, FT-IR, DLS and XPS measurements; in addition its morphology was imaged by TEM and HR-TEM. The HNT hybrid also exhibited photoluminescent properties, both in solution and in the solid state, and white-light emission (0.24, 0.36; CIE coordinates) was observed. This work could be pioneering as a new strategy for manufacturing both LEDs and fluorescent tags based on HNT nanomaterials. © 2018 The Royal Society of Chemistry.

A versatile catalyst based on halloysite and zinc oxide (HNT@ZnO) was prepared, for the first time, starting from ZnO commercial bulk form as Zn precursor source, in a one-pot procedure. This strategy gives the possibility to obtain small ZnO nanoparticles loaded on the HNT surface without the use of inorganic salts which envisage the removal of undesired anions and therefore a calcination process at high temperature. It was found that the presence of halloysite improved the UV–vis spectral absorption ability of ZnO. The hybrid was successful used as photocatalyst for the methylorange and rhodamine B degradation. In addition, after eight consecutive cycles for the methylorange photodegradation, the hybrid did not exhibit significant reduction in its photocatalytic performances confirming its stability. Based on trapping experiments and calculated energy bands we also proposed a photocatalytic mechanism. Furthermore, to evaluate the versatility of the synthetized HNT@ZnO hybrid, we used it as catalyst for biodiesel production from soybean oil, too. Also, in this case, the hybrid showed good catalytic performance and recyclability.

The morphology of gold nanoparticles (AuNPs) deposited on a (100) silicon wafer by simple immersion in a solution containing a metal salt and hydrofluoric acid (HF) is altered by HF treatment both before and after deposition. The gold clusters are characterized by the presence of flat regions and quasispherical particles consistent with the layer-by-layer or island growth modes, respectively. The cleaning procedure, including HF immersion prior to deposition, affects the predominantly occurring gold structures. Flat regions, which are of a few tens of nanometers long, are present after immersion for 10 s. The three-dimensional (3D) clusters are formed after a cleaning procedure of 4 min, which results in a large amount of spherical particles with a diameter of ≈15 nm and in a small percentage of residual square layers of a few nanometers in length. The samples were also treated with HF after the deposition and we found out a general thickening of flat regions, as revealed by TEM and AFM analysis. This result is in contrast to the coalescence observed in similar experiments performed with Ag. It is suggested that the HF dissolves the silicon oxide layer formed on top of the thin flat clusters and promotes the partial atomic rearrangement of the layered gold atoms, driven by a reduction of the surface energy. The X-ray diffraction investigation indicated changes in the crystalline orientation of the flat regions, which partially lose their initially heteroepitaxial relationship with the substrate. A postdeposition HF treatment for almost 70 s has nearly the same effect of long duration, high temperature annealing. The process presented herein could be beneficial to change the spectral response of nanoparticle arrays and to improve the conversion efficiency of hybrid photovoltaic devices.

The interfacial structure in "giant" PbS/CdS quantum dots (QDs) was engineered by modulating the Cd:S molar ratio during in situ growth. The control of the gradient interfacial layer could facilitate hole transfer, regulate the transition from double- to single-color emission, as a consequence. These QDs are optically active close-to-the near-infrared (NIR) spectral region and are candidates as absorber materials in solar energy conversion. Photoinduced charge transfer from "giant" QDs to electron scavenger can still take place despite the ultra-thick (~5 nm) shell. The hybrid architecture based on a TiO2 mesoporous framework sensitized by the "giant" QDs with alloyed interface can produce a saturated photocurrent density as high as ~5.3 mA/cm2 in a photoelectrochemical (PEC) cell under 1 Sun illumination, which is around 2 times higher than that of bare PbS and core/thin-shell PbS/CdS QDs sensitizer. The as-prepared PEC device presented very good stability thanks to the "giant" core/shell QDs architecture with tailored interfacial layer and a further coating of the ZnS shell. 78% of the initial current density is kept after 2-h irradiation at 1 Sun. Engineering of electronic band structure plays a key role in boosting the functional properties of these composite systems, which hold great potential for H2 production in PEC devices.

Since its discovery in January 2014, phosphorene, the new 2D-material prepared by exfoliation of black phosphorus and formed only by P atoms, has attracted scientists for its fascinating electronic and optical properties.1 At variance with graphene, this new single layer material has free electron pairs onto its corrugated surface that in principle can interact with metal ions, metal-ligand fragments and organic molecules. In our labs, the surface functionalization of phosphorene with transition metal nanoparticles2 was studied, and in particular for the first time EXAFS analysis was carried out to elucidate the nature of the interaction between P atoms and metal nanoclusters. Afterwards, the application of the new nanohybrids, Pd/bP and Ni/bP, in selective catalytic hydrogenation was investigated. Acknowledgements Thanks are expressed to EC for funding the project PHOSFUN "Phosphorene functionalization: a new platform for advanced multifunctional materials" (ERC ADVANCED GRANT to M.P.). References [1] H. Liu, K. Hu, D. Yan, R. Chen, Y. Zou, H. Liu, S. Wang. Adv. Mater., 2018, 30, 1800295. [2] M. Caporali, M. Serrano-Ruiz, F. Telesio, S. Heun, G. Nicotra, C. Spinella, M. Peruzzini. Chem. Commun. 2017, 53, 10946.

Studying defect formation and evolution in MethylAmmonium lead Iodide (MAPbI3) perovskite layers has a bottleneck in the softness of the matter and in its consequent sensitivity to external solicitations. Here we report that, in a polycrystalline MAPbI3 layer, Pb-related defects aggregate into nanoclusters preferentially at the triple grain boundaries as unveiled by Transmission Electron Microscopy (TEM) analyses at low total electron dose. Pb-clusters are killer against MAPbI3 integrity since they progressively feed up the hosting matrix. This progression is limited by the concomitant but slower transformation of the MAPbI3 core to fragmented and interconnected nano-grains of 6H-PbI2 that are structurally linked to the mother grain as in strain-relaxed heteroepitaxial coupling. The phenomenon occurs more frequently under TEM degradation whilst air degradation is more prone to leave uncorrelated [001]-oriented 2H-PbI2 grains as statistically found by X-Ray Diffraction. This path is kinetically costlier but thermodynamically favoured and is easily activated by catalytic species.

Studying defect formation and evolution in MethylAmmonium lead Iodide (MAPbI3) perovskite layers has a bottleneck in the softness of the matter and in its consequent sensitivity to external solicitations. Here we report that, in a polycrystalline MAPbI3 layer, Pb-related defects aggregate into nanoclusters preferentially at the triple grain boundaries as unveiled by Transmission Electron Microscopy (TEM) analyses at low total electron dose. Pb-clusters are killer against MAPbI3 integrity since they progressively feed up the hosting matrix. This progression is limited by the concomitant but slower transformation of the MAPbI3 core to fragmented and interconnected nano-grains of 6H-PbI2 that are structurally linked to the mother grain as in strain-relaxed heteroepitaxial coupling. The phenomenon occurs more frequently under TEM degradation whilst air degradation is more prone to leave uncorrelated [001]-oriented 2H-PbI2 grains as statistically found by X-Ray Diffraction. This path is kinetically costlier but thermodynamically favoured and is easily activated by catalytic species., Methylammonium lead halide perovskites have great potential for optoelectronic applications but are prone to degradation. Here the authors show that degradation can occur through clustering of Pb containing defects at the grain boundaries while concurrent formation of PbI2 blocks further reactions, suggesting a strategy for passivation.

The design of new hybrid nanocomposites based on poly(2-hydroxyethylmethacrylate) (pHEMA) graphene oxide (GO) cryosponges, wherein ZnO nanolayers have been deposited to induce photocatalytic properties, is reported here. Atomic layer deposition at low temperature is specifically selected as the deposition technique to stably anchor ZnO molecules to the pendant polymer OH groups. Furthermore, to boost the pHEMA cryogel adsorption capability versus organic dyes, GO is added during the synthetic procedure. The morphology, the crystallinity, and the chemical composition of the samples are deeply investigated by scanning electron microscopy, transmission electron microscopy, X-ray diffraction analyses, Fourier transform infrared spectroscopy, and thermogravimetric analysis. Swelling properties, mechanical performance, and adsorption kinetics models of the hybrid materials are also evaluated. Finally, the adsorption and photocatalytic performance are tested and compared for all of the samples using methylene blue as a dye. Particularly, the adsorption efficiency of ZnO/pHEMA and ZnO/pHEMA-GO nanocomposites, as well as their in situ regeneration via photocatalysis, renders such devices very appealing for advanced wastewater treatment technology.

In this article, electron trapping in aluminum oxide (Al2O3) thin films grown by plasma enhanced atomic layer deposition on AlGaN/GaN heterostructures has been studied and a correlation with the presence of oxygen defects in the film has been provided. Capacitance–voltage measurements revealed the occurrence of a negative charge trapping effect upon bias stress, able to fill an amount of charge traps in the bulk Al2O3 in the order of 5 × 1012 cm−2. A structural analysis based on electron energy-loss spectroscopy demonstrated the presence of low-coordinated Al cations in the Al2O3 film, which is an indication of oxygen vacancies, and can explain the electrical behavior of the film. These charge trapping effects were used for achieving thermally stable (up to 100 °C) enhancement mode operation in AlGaN/GaN transistors, by controlling the two-dimensional electron gas depletion.

The discovery of 2D conductivity at the LaAlO3/SrTiO3 interface has been linking, for over a decade, two of the major current research fields in materials science: correlated transition-metal-oxide systems and low-dimensional systems. Notably, despite the 2D nature of the interfacial electron gas, the samples are 3D objects with thickness in the mm range. This prevented researchers so far from adopting strategies that are only viable for fully 2D materials, or from effectively exploiting degrees of freedom related to strain, strain gradient and curvature. Here a method based on pure strain engineering for obtaining freestanding LaAlO3/SrTiO3 membranes with micrometer lateral dimensions is demonstrated. Detailed transmission electron microscopy investigations show that the membranes are fully epitaxial and that their curvature results in a huge strain gradient, each layer showing a mixed compressive/tensile strain state. Electronic devices are fabricated by realizing ad hoc circuits for individual micro-membranes transferred on silicon chips. The samples exhibit metallic conductivity and electrostatic field effect like 2D-electron systems in bulk heterostructures. The results open a new path for adding oxide functionalities into semiconductor electronics, potentially allowing for ultra-low voltage gating of a superconducting transistors, micromechanical control of the 2D electron gas mediated by ferroelectricity and flexoelectricity, and on-chip straintronics.

Studying the electrical and structural properties of the interface of the gate oxide (SiO

ZnO nanowalls (NWLs) represent a non-toxic, Earth abundant, high surface-to-volume ratio, semiconducting nanostructure which has already showed potential applications in biosensing, environmental monitoring and energy. Low-cost synthesis of these nanostructures is extremely appealing for large scale upgrading of laboratory results, and its implementation has to be tested at the nanoscale, at least in terms of chemical purity and crystallographic orientation. Here, we have produced pure and texturized ZnO NWLs by using chemical bath deposition (CBD) synthesis followed by a thermal treatment at 300 °C. We examined the NWL formation process and the new obtained structure at the nanoscale, by means of scanning and transmission electron microscopy in combination with x-ray diffraction and Rutherford backscattering spectrometry. We have shown that only after annealing at 300 °C in nitrogen does the as-grown material, composed of a mixture of Zn compounds NWLs, show its peculiar crystal arrangement. The resulting ZnO sheets are in fact made by ZnO wurtzite domains (4-5 nm) that show a particular kind of texturization; indeed, they are aligned with their own c-axis always perpendicular to the sheets forming the wall and rotated (around the c-axis) by multiples of 20° from each other. The presented data show that low-cost CBD, followed by an annealing process, gives pure ZnO with a peculiarly ordered nanostructure that shows three-fold symmetry. Such evidence at the nanoscale will have significant implications for realizing sensing or catalyst devices based on ZnO NWLs.

When 2D black phosphorus meets transition metal nanoparticles: synthesis, characterization and application. Recently, a new member of the growing family of 2D materials, named phosphorene, being the P-counterpart of graphene, was successfully isolated by exfoliation of the black allotrope of the element.1 Single and few-layer black phosphorus (2D bP) have gained lot of interest being semiconductors with high carrier mobility and an in-plane structural anisotropy. Successfull applications in batteries, transistors, sensors and photonics have shown 2D bP as a promising novel nanomaterial, though the problem of ambient stability still hampers its wide use.1 Currently, we are exploring its functionalization with late transition metal nanoparticles, as Ni and Pd. Preliminary tests have shown the nanohybrid Ni/2D bP has an improved stability in ambient conditions in comparison to pristine 2D bP. This feature prompted us to use Ni/2D bP as recyclable catalyst in the hydrogenation reaction and good catalytic activity together with high selectivity were achieved.2 Acknowledgements This work was supported by an ERC Advanced Grant PHOSFUN "Phosphorene functionalization: a new platform for advanced multifunctional materials" (Grant Agreement No. 670173) to M. P. References 1.Gusmao, R.; Sofer, Z.; Pumera, M.; Angew. Chem. Int. Ed. 2017, 56, 8052. 2.Caporali, M.; Serrano-Ruiz, M.; Telesio, F.; Heun, S.; Nicotra, G.; Spinella, C.; Peruzzini, M. Chem. Commun. 2017, 53, 10946.

By means of momentum-resolved electron energy loss spectroscopy (EELS) coupled with scanning transmission electron microscopy, we have studied the dispersion relation of interband plasmonic modes in the ultraviolet in black phosphorus. We find that the dispersion of the interband plasmons is anisotropic. Experimental results are reproduced by density functional theory, by taking into account both the anisotropy of the single-particle response function, arising from the anisotropic band structure, and the damping. Moreover, our theoretical model also indicates the presence of low-energy excitations in the near-infrared that are selectively active in the armchair direction, whose existence has been experimentally validated by high-resolution EELS (HREELS) in reflection mode.

One of the main challenges to exploit molybdenum disulfide (MoS

Nickel nanoparticles were dispersed on the surface of exfoliated black phosphorus and the resulting nanohybrid Ni/2DBP showed an improved stability respect to pristine 2D BP when kept in ambient conditions in the darkness. Ni/2DBP was applied as catalyst in the semihydrogenation of phenylacetylene and exhibited high conversion and selectivity towards styrene. These features were preserved after recycling tests revealing the high stability of the nanohybrid., Corrected misspelled author name

We investigated by means of transmission electron microscopy (TEM) the final growth stage of GaAs/AlGaAs core-shell nanowires (NWs) self-assembled by Au-catalyst assisted metalorganic vapor phase epitaxy (MOVPE). TEM observations and energy dispersive x-ray spectroscopy revealed the presence of an AlGaAs tapered region of varying chemical composition nearby the NW extreme end (i.e. between the core-shell NW trunk and the Au nanoparticle catalyst). Our findings evidence that this region exhibits an unintentional AlyGa1-yAs/AlxGa1-xAs core-shell structure, a result of the combined axial (vapor-liquid-solid, VLS) self-assembly and conventional (vapor-solid, VS) overgrowth of the material. While the VS-grown AlxGa1-xAs alloy retains the Al composition (x=0.3) of the AlGaAs shell along the NW trunk, the central AlyGa1-yAs section is made of an Al-rich (y approximate to 0.8-0.9) alloy segment formed during AlGaAs shell overgrowth, followed by a graded-alloy segment formed upon deposition of the terminating GaAs cap layer, the latter segment due to the effect of the Al reservoir left in the Au catalyst nanoparticle (NP).

One of the main challenges to exploit molybdenum disulfide (MoS2) potentialities for the next-generation complementary metal oxide semiconductor (CMOS) technology is the realization of p-type or ambipolar field-effect transistors (FETs). Hole transport in MoS2 FETs is typically hampered by the high Schottky barrier height (SBH) for holes at source/drain contacts, due to the Fermi level pinning close to the conduction band. In this work, we show that the SBH of multilayer MoS2 surface can be tailored at nanoscale using soft O-2 plasma treatments. The morphological, chemical, and electrical modifications of MoS2 surface under different plasma conditions were investigated by several microscopic and spectroscopic characterization techniques, including X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), conductive AFM (CAFM), aberration corrected scanning transmission electron microscopy (STEM), and electron energy loss spectroscopy (EELS). Nanoscale current voltage mapping by CAFM showed that the SBH maps can be conveniently tuned starting from a narrow SBH distribution (from 0.2 to 0.3 eV) in the case of pristine MoS2 to a broader distribution (from 0.2 to 0.8 eV) after 600 s O-2 plasma treatment, which allows both electron and hole injection. This lateral inhomogeneity in the electrical properties was associated with variations of the incorporated oxygen concentration in the MoS2 multilayer surface, as shown by STEM/EELS analyses and confirmed by ab initio density functional theory (DFT) calculations. Back-gated multilayer MoS2 FETs, fabricated by self-aligned deposition of source/drain contacts in the O-2 plasma functionalized areas, exhibit ambipolar current transport with on/off current ratio I-on/I-off approximate to 10(3) and field-effect mobilities of 11.5 and 7.2 cm(2) s(-1) for electrons and holes, respectively. The electrical behavior of these novel ambipolar devices is discussed in terms of the peculiar current injection mechanisms in the O-2 plasma functionalized MoS2 surface.

A Kinetic Monte Carlo scheme is applied to simulate with atomic resolution the synthesis of mono (few) layer(s) graphene (Gr) from a silicon carbide (SiC) substrate by selective evaporation of silicon (Si) atoms. The simulation computes the individual dynamics of the residual carbon (C) atoms which diffuse and reconfigure starting from the positions occupied in the SiC hexagonal lattice to the final Gr honeycomb structure. During the transition they gradually modify hybridization (from sp3 to sp2) and bond partners (from Si-C to C-C). We demonstrate that our method is able to recover the complex evolution steps of the epitaxial Gr on SiC in large systems for large time intervals. Moreover, the simulation results can be validated directly by means of comparison with experimental data when varying the material (e.g. initial surface configuration or polarity) or process (e.g. temperature and pressure) conditions.

This paper presents an investigation of the morphological and structural properties of graphene (Gr) grown on SiC(000-1) by thermal treatments at high temperatures (from 1850 to 1950 °C) in Ar at atmospheric pressure. Atomic force microscopy and micro-Raman spectroscopy showed that the grown Gr films are laterally inhomogeneous in the number of layers, and that regions with different stacking-type (coupled or decoupled Gr films) can coexist in the same sample. Scanning transmission electron microscopy and electron energy loss spectroscopy shoed that a nm-thick C-Si-O amorphous layer is present at the interface between Gr and SiC. Basing on these structural results, the mechanisms of Gr growth on the C-face of SiC under these annealing conditions and the role of this disordered layer in the suppression of epitaxy between Gr and the substrate have been discussed.

This study focuses and discusses the effects of temperature and humidity on electrospun conductive nanofibers, made with different polymer blends, deposited directly on interdigitated electrodes. The selected conductive polymers were based on blends of polyaniline emeraldine salt form and three different carrier hosting polymers: polyvinilpyrrolidone, polystyrene, and polyethylene oxide respectively. The obtained fibrous layers were investigated by the electrical measurements and morphological analysis (scanning electron microscopy). The study was made on the correlation between the electrical changes and morphological discrepancies due to temperature treatment. Moreover, this article reports the effects of relative humidity variations on electrical parameters. Since polyaniline is a well-known sensing material for different gases and volatile organic compounds, this study could be considered a supportive study for employing of the mentioned polymer blends as chemical interactive materials in gas sensor applications.

Studying the electrical and structural properties of the interface of the gate oxide (SiO2) with silicon carbide (4H-SiC) is a fundamental topic, with important implications for understanding and optimising the performances of metal-oxide-semiconductor field effect transistor (MOSFETs). In this paper, near interface oxide traps (NIOTs) in lateral 4H-SiC MOSFETs were investigated combining transient gate capacitance measurements (C-t) and state of the art scanning transmission electron microscopy in electron energy loss spectroscopy (STEM-EELS) with sub-nm resolution. The C-t measurements as a function of temperature indicated that the effective NIOTs discharge time is temperature independent and electrons from NIOTs are emitted toward the semiconductor via-tunnelling. The NIOTs discharge time was modelled also taking into account the interface state density in a tunnelling relaxation model and it allowed us to locate traps within a tunnelling distance of up to 1.3 nm from the SiO2/4H-SiC interface. On the other hand, sub-nm resolution STEM-EELS revealed the presence of a non-abrupt (NA) SiO2/4H-SiC interface. The NA interface shows the re-arrangement of the carbon atoms in a sub-stoichiometric SiOx matrix. A mixed sp(2)/sp(3) carbon hybridization in the NA interface region suggests that the interfacial carbon atoms have lost their tetrahedral SiC coordination.

We investigate the degradation path of MAPbI(3) (MA=methylammonium) films over flat TiO2 substrates at room temperature by means of X-ray diffraction, spectroscopic ellipsometry, X-ray photoelectron spectroscopy, and high-resolution transmission electron microscopy. The degradation dynamics is found to be similar in air and under vacuum conditions, which leads to the conclusion that the occurrence of intrinsic thermodynamic mechanisms is not necessarily linked to humidity. The process has an early stage, which drives the starting tetragonal lattice in the direction of a cubic atomic arrangement. This early stage is followed by a phase change towards PbI2. We describe how this degradation product is structurally coupled with the original MAPbI(3) lattice through the orientation of its constituent PbI6 octahedra. Our results suggest a slight octahedral rearrangement after volatilization of HI+CH3NH2 or MAI, with a relatively low energy cost. Our experiments also clarify why reducing the interfaces and internal defects in the perovskite lattice enhances the stability of the material.

In this paper, the electronic transport in epitaxial graphene (EG) grown on the Si face of 8° off-axis 4H-SiC has been investigated, using both electrical characterization of macroscopic devices and conductive atomic force microscopy (CAFM). In particular, current measurements on linear transmission line model (TLM) structures with different orientations showed a current transport anisotropy related to steps orientation, with the resistance of EG in the direction orthogonal to the steps ~2× higher than in the parallel direction. Two dimensional morphology and current maps in EG over the stepped SiC surface were obtained by CAFM and revealed a local resistance increase of EG over the (11-2n) facets with respect to the (0001) basal planes. This effect allows to account for the observed macroscopic current transport anisotropy and can be explained in terms of a different interface nature between EG and SiC on the two faces, leading to a locally different substrate induced doping of EG.