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The influence of the SiOxFy selfmasking process on the formation of black-Silicon (b-Si) textures by maskless SF6/O2 plasma etching is of great interest with regard to the optimization of the texturing process for highly antireflective silicon. For that reason, the elemental composition of plasma textured silicon surfaces is analyzed by transmission electron microscopy and X-ray photoelectron spectroscopy. The chemical composition of a fluorine containing oxide layer on top of the surface was confirmed and determined quantitatively. A strongly reduced F content was found after ambient air exposure. A qualitative model of the chemical and physical processes caused by maskless plasma texturing was developed to explain the observed experimental results. The decrease in the F content is assumed to be caused by hydrolysis of F by air moisture, resulting in a successive desorption of HF and transformation of SiOxFy to silicon oxide. [ABSTRACT FROM AUTHOR]

Electronic states and electrical conductivity of the native oxide Si(111) surface adsorbed with an electron donor tetrakis(dimethylamino)ethylene (TDAE) were investigated using ultraviolet photoelectron spectroscopy, X-ray photoelectron spectroscopy (XPS), and independently driven four-probe conductivity measurements. The formation of positively charged TDAE species is confirmed by the downward shift of the vacuum level by 1.45 eV, the absence of HOMO level in the valence band, and observation of the positively charged state in the N 1s XPS spectra. Si 2p XPS spectra and four-probe conductivity measurements revealed that TDAE adsorption induces an increase in downward band bending and a reduction in electrical resistance of the surface, respectively. The sheet conductivity and the electron density of the surface are 1.1 μS/? and 4.6 × 109 cm-2, respectively, after TDAE adsorption, and they are as high as 350% of the original surface. These results demonstrate that the electron density of the semiconductor surface is successfully controlled by the electron donor molecule TDAE. [ABSTRACT FROM AUTHOR]

We have studied down-conversion photoluminescence (PL) from (Ce, Yb) co-doped "oxygen rich" silicon oxide films prepared by sputtering and annealing. The Ce3+ ~510nm PL is sensitive to the Ce concentration of the films and is much stronger for 3 at.% Ce than for 2 at.% Ce after annealing at 1200 °C. The PL emission and excitation spectroscopy results indicate that the excitation of Yb3+ is mainly through an energy transfer from Ce3+ to Yb3+, oxide defects also play a role in the excitation of Yb3+ after lower temperature (~800 °C) annealing. The Ce3+ 510 nm photon excites mostly only one Yb3+ 980nm photon. Temperature-dependent PL measurements suggest that the energy transfer from Ce3+ to Yb3+ is partly thermally activated. [ABSTRACT FROM AUTHOR]

The structure and thermal response of amorphous ion tracks formed along the [11̅20], [10̅10], and [0001]-directions in crystalline quartz have been investigated using small angle x-ray scattering. The radii of the ion tracks vary by about 5% (0.3 nm) for tracks along different crystallographic directions. Molecular dynamics simulations reproduce this anisotropy along the [10̅10] and [0001] directions and suggest that differences in thermal conductivity along these directions are partly responsible for this observation. Using in situ annealing, tracks along the [10̅10] and [0001] directions were shown to recrystallize during thermal annealing around 960–1020 °C with activations energies around 6 eV, while those along the [11̅20]-direction already disappeared at 640 °C with a significantly lower activation energy around 3–4 eV. [ABSTRACT FROM AUTHOR]

We explore in numerical simulation the degree to which the thermal emission in the mid-infrared (IR) range can be controlled using a lattice of plasmonic spheres. While it has been shown that a great deal of spectral control can be achieved using a single sphere, obviously no directional control exists. We propose gaining this additional directional control over the thermal emission by designing a 2D lattice of resonant spheres. In this paper, we demonstrate that directional control as well as additionally spectral control over the thermal emission is achieved with this method. We do this by simulating a 2D layer of spheres composed of SiO2 cores and a SiC shells with a polaritonic resonance in the mid-IR. We then analyze how changing the lattice geometry affects the thermal emission characteristics of the ensemble of spheres. We show that for closely spaced spheres, modest directional control is possible with the additional benefit of some spectral control. When the spheres are spaced farther apart, Bragg scattering allows for more directional control, however, the spectrum of the emission is mostly governed by the properties of a single sphere. [ABSTRACT FROM AUTHOR]

The radiation decomposition of water in a nano-ZrO2 + nano-SiO2 + H2O system at 300 K by the action of gamma radiation has been studied by Fourier transform IR spectroscopy. Water adsorption in the zirconium and silicon nanooxides is attributed to molecular and dissociative mechanisms. Active intermediates in this radiation-induced heterogeneous decomposition of water were detected including zirconium and silicon hydrides and hydroxyl groups. Variation in the ratio of ZrO2 and SiO2 nanopowders was shown to lead to change in their radiation catalytic activity compared to initial ZrO2. [ABSTRACT FROM AUTHOR]

We present comprehensive optical studies of recently discovered single photon sources in boron nitride, which appear in form of narrow lines emitting centres. Here, we aim to compactly characterise their basic optical properties, including the demonstration of several novel findings, in order to inspire discussion about their origin and utility. Initial inspection reveals the presence of narrow emission lines in boron nitride powder and exfoliated flakes of hexagonal boron nitride deposited on Si/SiO 2 substrates. Generally rather stable, the boron nitride emitters constitute a good quality visible light source. However, as briefly discussed, certain specimens reveal a peculiar type of blinking effects, which are likely related to existence of meta-stable electronic states. More advanced characterisation of representative stable emitting centres uncovers a strong dependence of the emission intensity on the energy and polarisation of excitation. On this basis, we speculate that rather strict excitation selectivity is an important factor determining the character of the emission spectra, which allows the observation of single and well-isolated emitters. Finally, we investigate the properties of the emitting centres in varying external conditions. Quite surprisingly, it is found that the application of a magnetic field introduces no change in the emission spectra of boron nitride emitters. Further analysis of the impact of temperature on the emission spectra and the features seen in second-order correlation functions is used to provide an assessment of the potential functionality of boron nitride emitters as single photon sources capable of room temperature operation. [ABSTRACT FROM AUTHOR]

Optical constants and micro-structure characteristics of SiO 2 films deposited by ion beam sputtering were studied. The samples were prepared on substrates of silicon and silica with different oxygen flow rates ranged from 0 sccm to 40 sccm with a step of 10 sccm. Refractive index of the samples were obtained by spectra inversion technique. It's suggested that the value of refractive index presents first decrease and then increase as the oxygen flow rate larger, and the turning point is about 30 sccm both at 0.633 μm and 10.6 μm. And the SiO 2 thin films were confirmed all amorphous structure by the XRD measurement. The proportion of hydroxyl in SiO 2 thin film were determined by XPS, which is beneficial to analyze the film defects. Also the Si-O-Si angle and vibration frequency in TO mode and LO mode were researched by FTIR spectra. [ABSTRACT FROM AUTHOR]

In this work, undoped CdSiO 3 samples with different luminescence spectra and light persistence were obtained by controlling the parameters of sol–gel synthesis. The process of monoclinic phase formation was monitored through XRD and TG-DTA measurements, combined to microstructural characterization using FTIR and SEM. The optical energy bandgap (E g ) of CdSiO 3 was estimated from Tauc equation and indicates the dependency of bandgap energy on the starting pH used for synthesis. Three main peaks could be identified from PL and XEOL spectra, at 590 nm, 490 nm and 406 nm. Their relative intensities yielded overall distinct luminescence colours, such as indigo or red. The luminescent mechanisms of CdSiO 3 related to an intrinsic defect (V Cd ) were further investigated to show its key role in the charge trapping that causes long lasting luminescence. [ABSTRACT FROM AUTHOR]

We propose and demonstrate the principle of a sub-diffraction-limited optical imaging technique for rare-earth ion crystals that preserves the ions’ homogeneous line width. Our method uses a combination of applied electric field gradients and optical pumping to create a resonant nanoscopic volume within an otherwise non-resonant macroscopic crystal. We present the concept of the Stark activation technique and perform a demonstration in Pr 3 + : Y 2 SiO 5 in which we create a 10 μm-thick absorption feature in a 1 mm thick crystal. By modeling the system we show that it is possible to increase the resolution of the technique to the 5 nm range for single Pr 3 + ions. We also discuss the physical properties that will fundamentally limit the resolution of Stark activation. Because the proposed technique simultaneously achieves high spatial and high spectral resolution it is an enabling protocol to realize technology based on single rare-earth ions and harness short-range interactions in ensembles. [ABSTRACT FROM AUTHOR]

The present work reports the fabrication of p-Si/SiO2/TiO2 and p-Si/SiO2/TiO2/ZnO heterostructures deposited by RF sputtering on p-Si substrate. The structural properties of the heterostructures were characterized by X-ray reflectivity and SIMS depth profiling. The electrical and optical properties of the heterostructures were investigated by I - V, C - V measurements and VIS spectroscopy, respectively. The measurements reveal that I - V characteristics in dark show semiconductor-insulator-semiconductor (SIS) structure properties. The I - V characteristics under illumination exhibit changes with significant increase of photocurrent due to photoassisted tunnelling and injection through SiO2/TiO2 interlayer. [ABSTRACT FROM AUTHOR]

This work presents the charge transport and electroluminescent properties of silicon rich oxide (SRO) films with ~41 at% silicon content and different thicknesses (t SRO =24, 53 and 80 nm), as dielectric layer in metal-oxide-semiconductor (MOS) capacitive structures. SRO films were thermally annealed at high temperature to induce the silicon nanoparticles (Si-nps) formation. Light emitting capacitors (LECs) with SRO thickness about 80 nm behave like a normal MOS structure with a current level at about 10 −10 to 10 –12 A (equipment sensitivity) at low electric fields. However, a high conduction state (HCS) and then a resistance switching (RS) behavior to a low conduction state is observed when the thickness of the SRO film reduces to (and below) 53 nm. When the SRO thickness reduces to 24 nm, the electric field required to obtain RS behavior increases. The presence of the HCS and RS is related with silicon diffusion from the polysilicon film, used as gate electrode, towards the SRO bulk. The silicon content within the SRO film increases by the Si diffusion as the thickness reduces allowing the formation of preferential conductive paths. Once RS is obtained, LECs emit a broad visible and near infrared (IR) electroluminescence (EL) spectra with several maximum peaks at ~455, 490, 540, 650 and 800 nm. For SRO thickness ≥ 53 nm, the most intense EL peak is the placed at 650 nm. It becomes narrower and stronger when the thickness increases to 80 nm as compared to the other ones making a uniform red EL. Nevertheless, when the SRO thickness decreases to 24 nm, an additional IR EL peak above 1000 nm is observed. This IR band is slightly stronger than that observed at 650 nm and results from the silicon substrate emission enhanced by the high current flow through thin SRO films. By other hand, two narrow spectral lines of low intensity in the deep ultraviolet region (253 and 288 nm) are observed when the thickness is above 53 nm, which are related to the resonant coherent fluorescence effect. The electrical behavior and optical power emission and its relation with the electroluminescent behavior of LECs are analyzed. [ABSTRACT FROM AUTHOR]

We report theoretical rate coefficients for the ro-vibrational excitation of SiO by collision with He. A new, three-dimensional, ab initio potential energy surface, which includes the dependence on the vibrational coordinate of SiO, has been developed for the X1A' ground electronic state of the SiO-He system. Quantum dynamics calculations were performed using the vibrational close-coupling rotational infinite order sudden (VCC-IOS) method. Collisional rate coefficients have been determined for the de-excitation of the 41 first rotational states (j = 0-40) of the first six vibrational levels (v = 0-5) of SiO, in the temperature range between 300 and 6000 K. The rotational de-excitation rate coefficients corresponding to the vibrationally elastic process SiO(v, j) → SiO(v, j') are found to be almost insensitive to the selected vibrational level. The rate coefficients for the vibrationally inelastic process SiO(v, j) → SiO(v'; j') are significantly enhanced by the kinetic temperature and, to a lesser extent, by the vibrational excitation of SiO, but they are smaller than the vibrationally elastic ones by several orders of magnitude for the whole temperature range. The agreement between the present vibrational close-coupling rotational infinite order sudden (VCC-IOS) results and the available literature data for the SiO-He colliding system is discussed [ABSTRACT FROM AUTHOR]

In this paper, the phase evolution, microstructure changes, and element diffusion for the formation of BaSnO 3 from BaCO 3 and SnO 2 were extensively investigated. It was found that BaCO 3 rapidly diffused on surface of SnO 2 at the initial stage of the reaction (approximately 700 °C), forming a uniform BaSnO 3 shell. Subsequently, BaSnO 3 grew via two different routes depending on the calcination temperature. When the reaction was carried out below 820 °C, BaSnO 3 phase further grew by diffusion of barium ions across BaSnO 3 layer to SnO 2 phase, since the BaSnO 3 interlayer prevented the direct reaction between surface BaCO 3 and SnO 2 core. Once a higher temperature above 820 °C was provided, Ba 2 SnO 4 were generated by reaction between BaCO 3 and BaSnO 3 shell. Under such circumstances, pure BaSnO 3 was obtained by diffusion of barium ions from Ba 2 SnO 4 across BaSnO 3 to SnO 2 . The rate-determining step in both cases was assigned to the diffusion of barium ions. [ABSTRACT FROM AUTHOR]

Symmetrical and unsymmetrical 3,3-di(aryl)indolin-2-ones have been synthesized by nano-SiO2 as green, heterogeneous, and reusable catalyst under solvent-free conditions at room temperature via magnetic stirring and grinding methods. A plausible mechanism of condensation has also been presented. [ABSTRACT FROM AUTHOR]

The space time evolution of electric charge induced in the dielectric layer of simulated metal insulator semiconductor structures due to irradiation with X-rays is discussed. The system of equations used as a basis for the simulation model is solved it.erat.ively by the efficient, numerical method. The obtained simulation results correlate well with the respective data presented in other scientific publications. [ABSTRACT FROM AUTHOR]

Radiative defects in thermally grown SiO2/4H-SiC(0001) structures and their location in depth were investigated by means of cathodoluminescence spectroscopy. It was found that while luminescence peaks ascribed to oxygen vacancy and nonbridging oxygen hole centers were observed both from thermal oxides grown on (0001) Si-face and C-face surfaces as with thermal oxides on Si, intense yellow luminescence at a wavelength of around 600 nm was identified only from the oxide interface on the Si-face substrate regardless of the oxide thickness and dopant type. Possible physical origins of the radiative centers localized near an oxide interface of a few nm thick are discussed on the basis of visible light emission from Si backbone structures. [ABSTRACT FROM AUTHOR]

Interaction of Whispering Gallery Modes (WGMs) with dilute spin ensembles in solids is an interesting paradigm of Hybrid Quantum Systems potentially beneficial for Quantum Signal Processing applications. Unexpected ion transitions are measured in single crystal Y2SiO5 using WGM spectroscopy with large Zero Field Splittings at 14.7 GHz, 18.4GHz, and 25.4GHz, which also feature considerable anisotropy of the g-tensors as well as two inequivalent lattice sites, indicating spins from Iron Group Ion (IGI) impurities. The comparison of undoped and Rare-Earth doped crystals reveal that the IGIs are introduced during co-doping of Eu3+ or Er3+ with concentration at much lower levels of order 100 ppb. The strong coupling regime between an ensemble of IGI spins and WGM photons have been demonstrated at 18.4 GHz and near zero field. This approach together with useful optical properties of these ions opens avenues for "spins-in-solids" Quantum Electrodynamics. [ABSTRACT FROM AUTHOR]

A smart Pickering emulsion catalytic system is constructed, which not only exhibits fivefold reaction rate enhancement effects in comparison to the conventional biphasic system but also can be facilely demulsified by tuning pH, allowing for in situ recycling nanocatalysts. [ABSTRACT FROM AUTHOR]

We study the electronic properties of phosphorus doped Si nanocrystal/SiO2 superlattices and determine the carrier concentration by transient current analysis. This is achieved by encapsulating the multilayers between two electrical insulation layers and controlling the carrier mobility by a defined layer to layer separation. A saturation of the voltage dependent ionized carrier density is observed which indicates complete substitutional dopant ionization and allows to calculate the dopant induced charge carrier density. It is found that the doping efficiency of the superlattice is only 0.12% considering the full ionization regime which explains the unusual small dopant effect on transport characteristics. [ABSTRACT FROM AUTHOR]

So far, more than 1000 UV converted phosphors have been reported for potential application in white light-emitting diodes (WLEDs), but most of them (e.g., Y2O2S:Eu, YAG:Ce or CaAlSiN3:Eu) suffer from intrinsic problems such as thermal instability, color aging or re-absorption by commixed phosphors in the coating of the devices. In this case, it becomes significant to search a single-phased phosphor, which can efficiently convert UV light to white lights. Herein, we report a promising candidate of a white light emitting X2-type Y2SiO5:Eu3+,Bi3+ phosphor, which can be excitable by UV light and address the problems mentioned above. Single Bi3+-doped X2-type Y2SiO5 exhibits three discernible emission peaks at ~355, ~408, and ~504 nm, respectively, upon UV excitation due to three types of bismuth emission centers, and their relative intensity depends tightly on the incident excitation wavelength. In this regard, proper selection of excitation wavelength can lead to tunable emissions of Y2SiO5:Bi3+ between blue and green, which is partially due to the energy transfer among the Bi centers. As a red emission center Eu3+ is codoped into Y2SiO5:Bi3+, energy transfer has been confirmed happening from Bi3+ to Eu3+ via an electric dipole-dipole (d-d) interaction. Our experiments reveal that it is easily realizable to create the white or tunable emissions by adjusting the Eu3+ content and the excitation schemes. Moreover, a single-phased white light emission phosphor, X2-type Y1.998SiO5:0.01Eu3+,0.01 Bi3+, has been achieved with excellent resistance against thermal quenching and a QE of 78%. At 200 °C, it preserves >90% emission intensity of that at 25 °C. Consequent three time yoyo experiments of heating-cooling prove no occurrence of thermal degradation. A WLED lamp has been successfully fabricated with a CIE chromaticity coordinate (0.3702, 0.2933), color temperature 4756 K, and color rendering index of 65 by applying the phosphor onto a UV LED chip. [ABSTRACT FROM AUTHOR]

In this work, the optical response of graphene to hydrogen plasma treatment is investigated with spectroscopic ellipsometry measurements. Although the electronic transport properties and Raman spectrum of graphene change after plasma hydrogenation, ellipsometric parameters of the Si/SiO2/ graphene tri-layer system do not change. This is attributed to plasma hydrogenated graphene still being electrically conductive, since the light absorption of conducting 2D materials does not depend on the electronic band structure. A change in the light transmission can only be observed when higher energy hydrogen ions (30 eV) are employed, which chemically sputter the graphene layer. An optical contrast is still apparent after sputtering due to the remaining traces of graphene and hydrocarbons on the surface. In brief, plasma treatment does not change the light transmission of graphene; and when it does, this is actually due to plasma damage rather than plasma hydrogenation. [ABSTRACT FROM AUTHOR]

Radial InP/InAsP/InP heterostructure nanowires (NWs) on SiO2-mask-pattered Si substrates were reported using self-catalyzed InP NWs. Self-catalyzed growth was performed using low growth temperatures and high group-III flow rates, and vertical InP NWs were formed on the mask openings. The diameter and tapering of the self-catalyzed InP NWs were controlled by the introduction of HCl and H2S gases during the NW growth, and InP NWs that have a straight region with decreased diameter were formed. Radial InP/InAsP/InP quantum wells (QWs) were grown on the sidewall of the vertical InP NWs on Si substrates. Room-temperature photoluminescence of single NWs from the QW was clearly observed, which exhibited the potential of building blocks for vertical-type optical devices on Si substrates. [ABSTRACT FROM AUTHOR]

In this work, the optical response of graphene to hydrogen plasma treatment is investigated with spectroscopic ellipsometry measurements. Although the electronic transport properties and Raman spectrum of graphene change after plasma hydrogenation, ellipsometric parameters of the Si/SiO2/ graphene tri-layer system do not change. This is attributed to plasma hydrogenated graphene still being electrically conductive, since the light absorption of conducting 2D materials does not depend on the electronic band structure. A change in the light transmission can only be observed when higher energy hydrogen ions (30 eV) are employed, which chemically sputter the graphene layer. An optical contrast is still apparent after sputtering due to the remaining traces of graphene and hydrocarbons on the surface. In brief, plasma treatment does not change the light transmission of graphene; and when it does, this is actually due to plasma damage rather than plasma hydrogenation. [ABSTRACT FROM AUTHOR]

Context. L1157-mm powers a molecular outflow that is well-known for its shock-induced chemical activity in several hot-spots. Aims. We have studied the molecular emission toward L1157-mm searching for a jet component responsible for these spots. Methods. We used the IRAM 30 m telescope to observe the vicinity of L1157-mm in several lines of SiO. Results. The SiO(5-4) and SiO(6-5) spectra toward L1157-mm present blue and red detached components about 45 km s-1 away from the ambient cloud. These extremely high-velocity (EHV) components are similar to those found in the L1448 and IRAS 04166+2706 outflows and probably arise from a molecular jet driven by L1157-mm. Observations of off-center positions indicate that the jet is unresolved in SiO(5-4) (<11"). Conclusions. The EHV jet seen in SiO probably excites L1157-B1 and the other chemically active spots of the L1157 outflow. [ABSTRACT FROM AUTHOR]

The dependence of light losses in nanodimensional coatings obtained by sol-gel technology on the viscosity of film-forming solutions and on their light absorption at wavelengths of 315, 364, and 400 nm has been considered. It is shown that the number of inclusions and light losses in the coatings are proportional to the viscosity of the solutions. The absence of a reliable correlation between the viscosity and light losses in a film-forming solution is accounted for by the deviation of the shape of the particles from a spherical one. Using computer modeling, it has been established that the average size of particles in a coating does not exceed 5 nm and their arrangement is friable. The light losses in the coatings studied are sensitive to the content of oxides in a film-forming solution and the rate of its deposition onto the substrate. [ABSTRACT FROM AUTHOR]

The hydropyrolytic method was used to prepare samples of tin dioxide films without the doping additive, and also tin dioxide films with additives containing copper oxides and copper with gold. It was shown that by using doping additives it is possible to effectively control the ratio of the area of the film surface to its volume and, consequently, the adsorption ability of the sensor material. [ABSTRACT FROM AUTHOR]

Context. The SiO molecule is formed through interstellar shocks and is often used as a tracer of high-velocity shocks from protostellar outflows. However, recent studies have suggested that low-velocity shocks in the interstellar medium can be responsible for a significant amount of SiO emission observed in star-forming regions. Aims. We aim to investigate the existence of SiO emission that may or may not be associated with outflow shocks, within several massive dense clumps (MDCs), and explore how the SiO luminosities compare with the outflow properties estimated using CO. Methods. We used observations of SiO (2-1) from the Plateau de Bure Interferomètre, towards a sample of six MDCs in Cygnus-X, and compared them to the CO high-velocity outflow emission, and to the velocity shears found in these regions. Results. We find that most molecular outflows are detected in both SiO and CO, although there are some cases of CO outflows with no SiO counterpart. The data also shows narrow line SiO emission (σv ≲ 1:5 km s-1) which, in some cases, appears to be unrelated to outflows. The kinematics of this narrow emission often differs from those found by other high-density tracers such as H13CO+, and its extent varies from rather compact (∼0:03 pc) to widespread (∼0:2 pc).We find that the least centrally concentrated clumps with the least massive protostellar cores have the most widespread narrow SiO emission. The fraction of the total SiO luminosity that is not associated with outflows is highly variable in the different MDCs (from 10% to 90%); this might be a problem when extrapolating outflow properties from SiO luminosities without resolving individual outflows. Conclusions. In line with previous evidence of SiO emission associated with low-velocity shocks, we propose an evolutionary picture to explain the existence and distribution of narrow SiO line profiles. In this scenario, the least centrally condensed MDCs are at an early stage where the SiO emission traces shocks from the large-scale collapse of material onto the MDC. This could be the case of CygX-N40, a MDC with a low-mass protostar at its centre, a weak outflow, and where 90% of the SiO emission is narrow and arises from the outskirts. As the MDC collapses, the SiO emission becomes more confined to the close surroundings of cores, tracing the post-shock material from the infalling MDC against the dense cores, such as in the small-scale converging flows of CygX-N3, N12, and N48. At later stages, when single massive protostars are formed, as for instance in CygX-N53 and N63, the SiO luminosity is largely dominated by powerful outflows, and the weaker narrow component shows perhaps the last remnants of the initial collapse. [ABSTRACT FROM AUTHOR]

We study the molecular structureand aromaticity in a series ofexperimental and new in silico designed five-membered heterometallacycleswith general formula M(XC3H3)(PH3)2, where M = OsH3, OsCl3, OsCl2, RuCl2, RhCl2or IrCl2andX = NH, O, S, CH–, or CH+. The electrondelocalization of the five-membered rings in these complexes is analyzedusing the induced magnetic field, NICS, and MCI descriptors of aromaticity.Our results indicate that the five-membered rings in all complexeswith X = NH, O, S, and CH–have a low aromatic characterdenoted by nonintense diatropic behavior and low MCI values. Five-memberedrings in complexes with X = CH+are clearly paratropicand antiaromatic according to MCI values with the exception of M =OsCl3. The reason for this exception is discussed. [ABSTRACT FROM AUTHOR]

Nanolithography by local oxidation of dodecyl-terminated silicon using a scanning probe microscope is a practical method for the generation of silicon oxide nanostructures on a well-defined substrate. We report on the functionalization of such structures by the selective binding of the cationic dye cresyl violet by electrostatic interactions. The bound dye molecules could be optically excited and showed a clear luminescence emission. Additionally to the fluorescence light from monomers, an additional blue-shifted emission was found. This emission is an indication of the formation of charge-transfer complexes between the cationic dye molecules and anions in the oxide nanostructures. AFM topography and fluorescence image of selectively cresyl violet modified silicon oxide nanostructures on alkyl-terminated silicon surfaces. [ABSTRACT FROM AUTHOR]

We present a numerical analysis of the response of arc-induced long-period fiber gratings (LPFGs) under ambient refractive-index changes using standard fibers with SiO as cladding material and different GeO concentration in the SiO-GeO doped core. We obtain that the LPFG-sensitivity is increased using lower GeO concentrations and it follows a parabolic behavior. Also, we identify two linear regimes using an external index of 1.37: for GeO concentrations between 2 and 3.5 mol %, the LPFG-sensitivity changes with a rate of 3.614 nm per mole fraction of GeO, while for higher concentrations the sensitivity changes with a rate of 1.39 nm/mol %. Additionally, for fibers with 2 mol% of GeO, the sensitivity calculated is comparable to this obtained in previous works using corrugated and tapered LPFGs in SMF28 fibers. These results are of interest for the design of improved LPFG-sensors. [ABSTRACT FROM AUTHOR]

To develop a better understanding of the physical properties and microstructures of the termite hill soils, we have carried out studies on the soil samples collected from two locations: near Dehradun, Uttarakhand and near Hauz Khas, New Delhi. Their elemental composition and microstructure were studied using different instrumentation techniques, such as powder X-ray diffraction, field emission scanning electron microscopy, transmission electron microscope (TEM) and energy-dispersive analysis of X-ray (EDAX). α-Quartz (SiO2) was present in both the samples, while the sample collected from Hauz Khas, Delhi also contained β-cristobalite phase of SiO2. TEM–EDAX showed that termite hill soil consisted of silica (quartz), aluminium oxide, manganese oxide and iron oxide along with small percentage of potassium and calcium. Our studies highlight the potential to generate α-quartz from all termite hills. It is also possible to obtain the less common β-cristobalite form of silica in certain termite mounds. [ABSTRACT FROM AUTHOR]

A bilayer resistive switching memory device with an inserted porous silicon oxide layer is investigated in this letter. Compared with single Zr:SiOx layer structure, Zr:SiOx/porous SiOx structure outperforms from various aspects, including low operating voltages, tighter distributions of set voltage, higher stability of both low resistance state and high resistance state, and satisfactory endurance characteristics. Electric field simulation by comsolTM Multiphysics is applied, which corroborates that intensive electric field around the pore in porous SiOx layer guides the conduction of electrons. The constraint of conduction path leads to better stabilization and prominent performance of bilayer resistive switching devices. [ABSTRACT FROM AUTHOR]

We study semi-regular arrays of Au nanoparticles (NP) obtained via UV laser irradiation of thin Au films on glass substrate. The NP structures are prepared from films of a thickness up to 60 nm produced by discharge sputtering or pulsed laser deposition, and annealed by nanosecond laser pulses at 266 or 308 nm, respectively, at fluencies in the range of 60-410 mJ/cm. For the rare- and close-packed NP structures, consistent description of optical properties is derived from microscopic observation, measurements of the absorption, and Raman spectra, and modeling of the near-field intensity distributions. The absorption bands centered at 540-570 nm are ascribed to resonant absorption of the surface plasmons. For the band positions, half widths, and intensities, the dependence on the NP shape (partial spheres), size, size distribution, and also excitation energy is observed. The structures are characterized by markedly reduced dephasing times of ∼3 fs. It is shown, that laser annealing of thin Au films provides reliable and cost effective method for controlled preparation of semi-regular NP arrays favorable for photonic applications. [ABSTRACT FROM AUTHOR]

A commonly marketed handheld Raman spectrometer showed excellent possibilities in being used as a key instrument for unambiguous identification of gemstones mounted in the sceptre of the Faculty of Science of Charles University in Prague from the mid-20s of the 20th century. Numerous SiO2 forms including chalcedonies intermixed with moganites (e.g. moss agates and carnelians), amethysts, citrines as well as garnets (pyrope-almandines) were identified. The estimation of the garnet type was based on obtained Raman parameters. The individual minerals constituting the lapis lazulis could not be discerned because of very high fluorescence they exhibited in the fingerprint region of the Raman spectrum, nevertheless the positions of the observed peaks in the 1000-2000 cm-1 area were in very good agreement with the values of commercially available lapis lazuli pigment. The noble metals of the sceptre were studied by means of X-ray fluorescence analysis, which confirmed the presence of silver alloys and gilding. The comparison of silver alloys' semiquantitative analysis with the expected fineness, denoted by the hallmarks, indicated silvering. This has been later confirmed by the newly discovered restoration documentation. Portable handheld Raman and X-ray fluorescence instruments represent an ideal tool for studying historical artefacts, where an in situ investigation in museums or similar sites is obligatory. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Amorphous silicon (a-Si:H) / micro-crystalline silicon (μc-Si:H), "micromorph" tandem solar cells have been investigated using a detailed electrical - optical model. Although such a tandem has good light absorption over the entire visible spectrum, the a-Si:H top cell suffers from strong light-induced degradation (LID). To improve matters, we have replaced a-Si:H by hydrogenated polymorphous silicon (pm-Si:H), a nano-structured silicon thin film with lower LID than a-Si:H. But the latter’s low current carrying capacity necessitates a thicker top cell for current-matching, again leading to LID problems. The solution is to introduce a suitable intermediate reflector (IR) at the junction between the sub-cells, to concentrate light of the shorter visible wavelengths into the top cell. Here we assess the suitability of N-type micro-crystalline silicon oxide (μc-SiOx:H) as an IR. The sensitivity of the solar cell performance to the complex refractive index, thickness and texture of such a reflector is studied. We conclude that N-μc-SiOx:H does concentrate light into the top sub-cell, thus reducing its required thickness for current-matching. However the IR also reflects light right out of the device; so that the initial efficiency suffers. The advantage of such an IR is ultimately seen in the stabilized state since the LID of a thin top cell is low. We also find that for high stabilized efficiencies, the IR should be flat (having no texture of its own). Our study indicates that we may expect to reach 15% stable tandem micromorph efficiency. [ABSTRACT FROM AUTHOR]

The flexible design of decoupling and matching networks for coupled antennas is introduced. The network includes three parts: circuits for impedance transformation, an element for odd-mode decoupling and conventional matching networks. It is found that all three parts are determined by one parameter of the ABCD matrix of the impedance transformation circuit. Thus a large variety of circuits with different element values can be used for decoupling which relaxes the practical design constraints. [ABSTRACT FROM AUTHOR]

Demonstrated is a nonvolatile memory device based on a SiO2/GaN/ AlGaN/GaN heterostructure in which the upper GaN layer acted as a storage node. Charges were stored in and released from the upper GaN layer by applying positive and negative gate biases, respectively. The top SiO2 layer acted as a blocking layer. The threshold voltage shift was ~ 3 V between the program and erase modes and the retention characteristics were very stable over 10000 s. [ABSTRACT FROM AUTHOR]