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Solid-state reaction synthesis produced VO2+ -doped Li2Ba3(P2O7)2 pyrophosphate nanopowder at ambient temperature. The produced sample was characterized by powder x-ray diffraction (XRD), scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), high-resolution transmission electron microscopy (HR-TEM), Fourier-transform infrared spectroscopy (FT-IR), Raman spectroscopy, UV-visible spectroscopy, electron paramagnetic resonance (EPR), and photoluminescence (PL) techniques. Powder XRD confirmed the preservation of an orthorhombic crystal structure of the sample with an average crystallite size of 34.2 nm. In addition, lattice cell parameters and internal lattice strain were evaluated. SEM and HR-TEM images revealed that a tiny agglomeration of stone-like particles appeared in the sample and also evaluated particle size distributions. FT-IR and Raman spectra exhibited characteristic vibrational modes of phosphate (PO43−) ions along with other bands. Optical absorption spectrum of the VO2+ -doped sample exhibited three characteristic peaks at 831, 635, and 416 nm. Furthermore, crystal and tetragonal field parameters were determined as Dq = 1574, Ds = − 2903, and Dt = 664 cm−1. From the EPR spectrum, calculated spin Hamiltonian parameters were g ‖ = 1.954, g ⊥ = 1.977, A ‖ = 284 × 10−4 cm−1 and A ⊥ = 53 × 10−4 cm−1. Optical and EPR spectra revealed that VO2+ ions have tetragonal distortion octahedral site symmetry and have a moderate covalent nature with ligands. Using the PL spectrum, the CIE chromaticity coordinates were determined to be in the yellowish-green region appropriate for LEDs and lighting systems. [ABSTRACT FROM AUTHOR]

Hydrogen storage in metal hydrides is feasible since many metals react readily with hydrogen, forming a stable metal hydride. In this article, the structural, electrical, thermodynamic, phonon, and hydrogen storage properties of the perovskite hydride BaXH4 (X = Mn, Re, or Tc) in its hexagonal form are examined by combining ab initio density functional theory using the generalized gradient approximation and Perdew–Burke–Ernzerhof exchange-correlation functional. The electronic characteristics of these hydrides were analyzed through band structure, total density of states (TDOS), and partial density of states (PDOS) analysis. Maximal conductivity at the Fermi level is revealed in the TDOS and PDOS, and the results were plotted against the energy of the incident radiations. The hydrogen storage properties of the material were also considered; the value of gravimetric hydrogen storage capacity was calculated to be 2.006 wt.%, 1.2124 wt.%, and 1.6517 wt.% for BaMnH4, BaReH4, and BaTcH4, respectively. The formation energies obtained for BaMnH4 and BaTcH4were estimated to be −47.225 KJ mol−1 and −47.331 KJ mol−1, respectively, while the energy required to form BaReH4perovskite hydride was −47.705 KJ mol−1. This high formation energy indicates the compounds' enhanced stability. Consequently, it is reasonable to assert that BaMnH4, BaReH4, and BaTcH4 can be effectively employed as hydrides for hydrogen storage purposes. Furthermore, the calculated desorption temperature of the perovskite hydride BaMnH4 was found to be Tdes (K) = 361.32 K, while BaTcH4 and BaReH4 had estimated desorption temperatures of 362.13 K and 364.99 K, respectively. Notably, these values are within the recommended range of desorption temperatures (289–393 K) for practical applications, as proposed by the US Department of Energy (USDOE). This indicates that no significant barriers impede hydrogen desorption from BaXH4 compounds, making them promising candidates for hydrogen release in various practical applications. The discussion above concludes that perovskite hydrides BaXH4 (X = Mn, Re, or Tc) are suitable compounds for hydrogen storage because these materials are energetically stable and may be produced for hydrogen storage devices. [ABSTRACT FROM AUTHOR]

Poly(methyl methacrylate) (PMMA) polymers, both undoped and doped with nickel-doped tin sulfide (Sn0.8Ni0.2S2) and with various weight percentages of carbon nanoparticles (CNPs), were prepared using casting techniques. The structure, elemental analysis, morphology, and optical features of the obtained polymers were investigated using x-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, energy-dispersive x-ray spectroscopy, fluorescence (FL), and diffuse reflectance spectroscopy. Investigations were conducted to determine how SnS2/Ni and/or carbon nanoparticle content affects the optical properties of PMMA, including its energy band gap, refractive index, dielectric constant, linear first-order susceptibility, nonlinear third-order susceptibility, and nonlinear refractive index. The direct and indirect optical band gaps for PMMA decreased from (4.99, 4.4) eV to (4.09, 2.28) eV upon doping with SnS2/Ni and 0.25 wt.% CNPs. The effect of SnS2/Ni and/or CNPs on the frequency dependence of the dielectric properties was investigated. The FL intensity can be controlled to a desired limit by adjusting the SnS2/Ni and CNP concentrations in PMMA blends for different applications in optical devices. The emitted colors from each sample were found using the CIE 1931 chromaticity diagram. [ABSTRACT FROM AUTHOR]

Glasses of the system B2O3 – PbO – MgF2 – P2O5 – SiO2 containing different dopants from Cr2O3, MnO2, and SeO2 were prepared by the conventional melt quenching method. The prepared glasses were characterized by their ruby color caused by the effect of dopants. The amorphous nature of the prepared glasses was confirmed by x-ray diffraction (XRD). Differential thermal analysis (DTA) was used to design a heat treatment program to obtain their corresponding transparent glass–ceramic derivatives from parent glasses. Collective spectroscopic measurements were applied to evaluate the optical properties of glasses and their corresponding glass–ceramics. XRD and morphological analysis of glass–ceramics indicated the formation of two crystalline phases (PbO(B2O3)2) and (Mg2BO3F). Optical analysis confirmed the stability of the color even after heat treatment. The chromaticity coordinates indicated a deep red color related to the chromium dopant and red wine color for selenium and manganese dopants. [ABSTRACT FROM AUTHOR]

The structural, elastic, electronic, and optical properties of half-Heusler CaMgZ (Z = C, Si, Ge, Sn, Pb) compounds are investigated herein. Density functional theory based on the full-potential linearized augmented plane wave method integrated in WIEN2K is used. The PBE generalized gradient approximation (PBE-GGA) is employed for the calculation of various parameters describing the structural and elastic properties. The results of lattice parameters are comparable to other data in the literature. On the other hand, the elastic constants reveal that our five compounds meet the stability criteria. CaMgC has a ductile nature, while CaMgSi, CaMgGe, CaMgSn, and CaMgPb have a brittle nature in the cubic structure type I phase. The modified Becke–Johnson potential proposed by Tran and Blaha (TB-mBJ) is applied to improve the calculations of electronic properties. Our calculations show that the materials have semiconductor behavior, with an indirect bandgap for CaMgC, CaMgSi, CaMgGe, and CaMgSn and a direct bandgap for CaMgPb. The optical investigations reveal strong absorption in the ultraviolet range. [ABSTRACT FROM AUTHOR]

In this study, glass samples of composition 20PbO-20CaO-20Sand-(40 − x)B2O3-xCeO2, where x = 0, 2.5, 5, 7.5, and 10 in wt.% and sand = SiO2 (90.4%) + CaO (2.8%) + ZrO2 (2.3%) + Fe2O3 (2.1%), were fabricated via the ordinary melt quenching technique. The thermal and optical properties of the glasses were experimentally investigated using differential scanning calorimetry (DSC) analysis, which is measured as a function of temperature based on the difference in the amount of heat needed to raise the temperature of a sample and reference. All glasses were found to be thermally stable up to 550°C. The glass transition temperature (Tg) varied from 211°C to 219°C, crystallization temperature (Tc) varied from 303°C to 310°C, and melting point (Tm) was 577°C. The values of the indirect optical energy band gaps (EOptical, Indirect) reduced from 2.63 eV to 2.28 eV, while the direct gaps (EOptical, Direct) reduced from 5.07 eV to 4.17 eV. Urbach's energy (EU) was changed from 0.42 eV to 0.46 eV. The dielectric constant behaved similarly to the refractive index and absorption coefficient of the proposed glasses. The refractive index data were analyzed to obtain important optical information and the corresponding derivative electrical parameters, namely, the oscillator energy, dispersion energy, dielectric constant at high frequency, the dielectric loss, and the energy-loss functions. There was a remarkable increase in the optical conductivity (σopt) with increasing CeO2 content, with peaks appearing in all samples doped by CeO2 and reaching a peak maxima of about 2.72–3.10 eV. Volume energy loss (VELF) and surface energy loss (SELF) functions were increased with increasing CeO2 content, with a characteristic peak at around 3.47 eV for all proposed samples. [ABSTRACT FROM AUTHOR]

In the present work, a good-quality nickel sulfate hexahydrate (NSH) single crystal measuring 30 × 20 × 15 mm3 was grown via a slow evaporation solution technique (SEST). NSH single crystal is an inorganic material and is widely used in optical applications, UV sensors, and missile detection systems, among others. The grown crystal was characterized using powder x-ray diffraction (PXRD), UV-visible spectroscopy, microhardness test and etching analysis. Photoacoustic spectroscopy (PAS) was used to identify the thermal diffusivity of the grown crystal. The thermal diffusivity of the NSH crystal was found to be superior to that of various common nonlinear optical (NLO) materials, and is thus suitable for use in optical and sensor applications. Differential scanning calorimetry (DSC) was utilized to determine the material decomposition at a certain temperature. Thermogravimetric analysis (TGA) and differential thermal analysis (DTA) were performed to identify the melting point of the grown crystal. The dielectric analysis showed that the crystal has low dielectric loss, fewer defects, and better optical properties, and is suitable for NLO applications. Thermal analysis showed that the grown crystal can be utilized for a wide array of applications including optical communications, UV bandpass filters, UV sensors, harmonic generation, and missile detection systems. [ABSTRACT FROM AUTHOR]

In the present study, we have focused on the growth of semi-organic single crystals, as they play a vital role in the generation of a terahertz pulse and its potential applications. The single crystals of l-histidine hydrochloride monohydrate (LMHCL) were grown by slow evaporation solution growth by using deionized water as a solvent in a controlled atmosphere. Good quality crystals of the required size were obtained within 2 weeks. To estimate the lattice dimensions and get the structural information, powder x-ray diffraction (PXRD) study was performed in which we have found that the crystal belongs to the orthorhombic crystal system with space group P212121. The functional groups and the corresponding vibrational mode were confirmed using Fourier transform infrared (FTIR) and Raman spectroscopy, respectively. To study the optical properties UV–Vis transmission spectrum and photoluminescence (PL) were recorded. It was observed that the single crystal has a high value of transmission over a long range of wavelength which signifies that the crystal is a good candidate for nonlinear optical (NLO) applications. The UV cut-off wavelength is found to be 236 nm. The grown single crystals were studied by time-domain terahertz spectroscopy (THz-TDS) for photonic applications and the refractive indices were calculated and it is found that the refractive index is nearly equal to 3.4. [ABSTRACT FROM AUTHOR]

Bi1−xGdxFeO3 (BGFO) (x = 0.00 ÷ 0.15) materials were prepared by a sol-gel method. The effect of Gd doping on the structural, ferromagnetic, and ferroelectric properties of BiFeO3 (BFO) were analyzed using x-ray diffraction, Raman scattering, energy-dispersive x-ray spectroscopy, ferroelectric hysteresis loop and magnetic hysteresis loop measurements. All samples showed a rhombohedral structure of the perovskite type. The a and c lattice parameters decreased with Gd content, obeying Vegard's law, from 5.583 to 5.511 Å, and from 13.869 Å to 13.741 Å, respectively. The optical band gap (Eg) also decreased with Gd content, from 2.02 to 1.60 eV at x = 0.00 to x = 0.15, respectively. The ferroelectric and ferromagnetic properties of the BGFO materials were enhanced compared with those of the pure BFO material. Maximum saturation polarization (Ps) and saturation magnetization (Ms) values of 6.88 μC/cm2 and 0.386 emu/g were obtained. We found that the optimum Gd doping content to enhance multiferroic properties of BFO material is in range from x = 0.10 to x = 0.125. The origin of ferromagnetic and ferroelectric properties of BGFO materials were also discussed. [ABSTRACT FROM AUTHOR]

Cadmium nanoparticles (Cd-NPs) were synthesized at room temperature using Moringa oleifera plant extract as a natural reducer and stabilizer agent. Cd-NPs were characterized using adsorption/desorption, Fourier-transform infrared (FTIR) spectroscopy, UV–visible spectrophotometry, photoluminescence, x-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive x-ray spectroscopy (EDX) and differential scanning calorimetry (DSC) thermal analysis. Adsorption and desorption studies shows that Cd-NPs have a stable adsorption. The FTIR studies also confirm that the Cd-NPs coated by the organic compounds are present in the Moringa extract. XRD pattern demonstrates that amorphous and crystalline phases coexist in Cd-NPs of hexagonal structure. SEM and TEM observations also show the formation of Cd-NPs with an average size of 30–40 nm. EDX analysis reveals that the nanocomposite contains 29.85% carbon, 37.97% oxygen 27.04% cadmium, 4.41% phosphorus and 0.73 potassium. DSC analysis shows the thermal behavior of Cd-NPs. [ABSTRACT FROM AUTHOR]

In this work, the heavy aluminum doping effects on the compositional, structural, optical, dielectric and electrical properties of ZnSe thin films are investigated. It is observed that the Zn/Se compositional ratio increases with increasing Al content. The major cubic phase of ZnSe becomes more pronounced compared to the hexagonal phase. In addition, the presence of Al in the structure of ZnSe causes lattice constant contraction, decreased the grain size and increased both of the strain and defect density. Optically, the Al doping increased the light absorbability and widens both of the energy band gap and energy interbands which are present in the band gap of ZnSe films. Moreover, the Al doping into ZnSe lowers the high frequency dielectric constant and enhances the optical conductivity. On the other hand, the capacitance spectra which are studied in the frequency domain of 0.01–1.80 GHz displayed negative capacitance effect associated with resonance–antiresonance phenomena upon doping of ZnSe with Al. Such enhancements in the physical properties of ZnSe that are achieved via Al doping make the zinc selenide thin films more appropriate for electronic and optoelectronic technological applications. [ABSTRACT FROM AUTHOR]

With an aim of finding a material suitable for microelectronic applications, experiments were performed to grow erbium tartrate crystals by gel encapsulation. The crystals grow with very well-developed and remarkably flat habit faces as revealed by micro-structural studies, using optical and scanning electron microscopy. The study reveals that the most prominent faces include {001}, {100} and {010}. The crystallographic data analysis of x-ray diffraction results, supplemented by trial-and-error software, shows that the compound crystallizes in a tetragonal crystal system with non-centrosymmetric space group. The high resolution x-ray diffraction results indicating the perfection of the grown crystals are presented. Results of ultraviolet–visible near infra-red (UV–Vis–NIR) spectra leading to determination of energy band gap of 5. 56 eV are described and discussed. The refractive index of the grown material comes out to be 1.40. Comparative analysis of dielectric characteristics of the grown material is made, both for the single crystal and powder form. The material is shown to be ferroelectric with low value of dielectric constant. Behaviour of dielectric constant, dielectric loss and alternating current (ac) conductivity on frequency of the applied ac field at different temperatures is described and discussed. The results are correlated with those of optical and high resolution x-ray diffraction. The material characteristics as revealed by the study suggest that the compound has the basic qualities of a promising material for microelectronic device applications. [ABSTRACT FROM AUTHOR]

First-principles calculations of the mechanical, thermal, electronic, optical and transport behavior of CoVSn half-Heusler alloys under external pressure are investigated using density functional theory. The elastic constants and thermoelectric properties are computed using ElaStic and BoltzTrap codes, respectively. The lattice constant and bond lengths are found to decrease with increased pressure. The calculated elastic properties reveal that the CoVSn alloy is mechanically stable and anisotropic under ambient pressure. At 20 GPa, the alloy is shown to be ductile, while at all other pressures it exhibits a brittle nature. In addition, it shows decreased phonon-phonon coupling with an increase in pressure. Using the modified Becke-Johnson (mBJ) potential, it was found that the indirect (L-X) band gap values range from 0.89 eV to 1.00 eV, which agrees with previous studies. The increase in the external pressure directly increases the trend in the band gap while it decreases the static reflective index values. All our calculated optical parameters for the CoVSn alloy are shifted to a high energy level due to the external pressure. Our thermoelectric results suggest that holes are the major charge carriers in the CoVSn alloy. In light of our results, we expect promising optical and thermoelectric applications for CoVSn under pressure. [ABSTRACT FROM AUTHOR]

In this article, the structural, optical and dielectric properties of the rarely investigated Cd2S3 thin films are reported. Particularly, Cd2S3 thin films prepared by the thermal evaporation technique onto glass, and 150-nm-thick lanthanum transparent substrate studied by means of energy-dispersive structural analysis have shown that the Cd2S3 thin films are of polycrystalline nature. The hexagonal unit cell parameters, which slightly differ from that of CdS, increased upon replacement of glass with lanthanum. All the other structural parameters including the grain size, strain and defect density are accordingly affected. While the optical band gap increased when La replaces glass, the high-frequency dielectric constant decreased. On the other hand, the Drude-Lorentz modeling of the dielectric spectra has shown that the La/Cd2S3 thin films are promising materials for production of thin film transistors as they exhibit drift mobility values of ∼ 13.3 cm2/Vs. The response of the glass/Cd2S3 and La/Cd2S3 interfaces to the incident electromagnetic light is associated with hole-plasmon interactions that are limited by plasmon frequency values in the range of 0.4-8.1 GHz. Such property makes this material attractive as microwave band pass/reject filters. [ABSTRACT FROM AUTHOR]

Nano-SnS2 and Sn0.75X0.25S2 (X = Cr, Fe, Y) have been prepared by thermolysis method. Phase analysis of x-ray diffraction data confirmed the single-phase nature of all prepared samples, with some residual carbon contributing to the background. Rietveld refinement revealed high anisotropy in crystallite size, signifying a cylindrical structure for the particle shape, as confirmed by transmission electron microscopy. The refined occupancies obtained for the doped cations were found to be smaller than the nominal target doping ratio (25%). Fourier-transform infrared spectra showed presence of Sn-S bond in all samples. The energy was found to be 3.42 eV, 3.33 eV, 2.1 eV and 3.14 eV, and 3.62 eV for undoped SnS2 and when doped with Cr, Fe, and Y, respectively. Density functional theory calculations illustrated that Fe-doped SnS2 has two bandgaps [normal and intermediate (IB) bands]. Meanwhile, Sn0.75Fe0.25S2 sample showed anti-Stokes and an extra photoluminescence peak related to the newly created intermediate band (IB) inside the energy gap. On the other hand, pure SnS2 and Sn0.75X0.25S2 (X = Cr, Y) samples emitted four photoluminescence subspectra in ultraviolet, violet, and blue regions. [ABSTRACT FROM AUTHOR]

The paper reports structural, electronic, vibrational, optical, and thermodynamic properties of the cubic structure of yttrium arsenide (YAs) calculated by density functional calculations. The calculated lattice constant and electronic band gap are 6.445 Å and 2.49 eV (direct band gap at Γ point), respectively. The stability of the cubic structure of YAs is also confirmed by phonon dispersion curve. The refractive index using the complex dielectric function of cubic YAs is 2.57 in the near-ultraviolet region. The thermodynamic properties are based on the function of temperature, which is investigated using the quasi-harmonic approximation and show that the heat capacity has been become constant above room temperature at 400 K which concludes the maximum stability of phase. Our theoretical results show that the absorption spectrum of YAs has a possible application for future devices in the near-ultraviolet region as an inner layer coating under UV absorbers, which is the main interest to optoelectronic-devices such as light emission and light detectors. [ABSTRACT FROM AUTHOR]

LiAlO doped with Fe was synthesized by a propellant combustion route at furnace temperature of 773 K. The phosphor was characterized using powder x-ray diffraction, optical absorption, electron paramagnetic resonance (EPR) and photoluminescence spectroscopic techniques. The optical absorption spectrum exhibits a broad band at 242 nm characteristic of charge transfer between Fe-O. On excitation with 293 nm, emission band for the Fe ion was observed at 687 nm. The CIE (International Commission on Illumination or Commission Internationale de l'Elcairage) coordinates for the system were evaluated adopting standard procedure which suggested that the system can be effective as a deep red emitting phosphor. The EPR spectrum of this phosphor exhibits a number of resonance signals characteristic of Fe ions. The resonance signals at g = 3.16, 2.27 are attributed to Fe present at tetrahedral site with an axial symmetry. The resonance signals at g = 1.98 and 1.43 are attributed to Fe ions in octahedral site with an axial symmetry. Various EPR parameters such as the number of spins, Gibbs free energy, magnetic susceptibility, Curie constant and effective magnetic moment values are calculated and compared at room temperature and 110 K. [ABSTRACT FROM AUTHOR]

GdAlO phosphor samples have been prepared by a solution combustion method. X-ray diffraction analysis revealed that the GdAlO phosphor stabilized in orthorhombic phase. The optical absorption spectrum showed bands due to Gd ions as well as defect level in the host. The excitation spectrum exhibited a dominant band with maximum at 273 nm. Upon excitation at 273 nm, ultraviolet-B (UV-B) emission with maximum at 312 nm was observed from the undoped sample, being attributed to P → S transition of Gd ion. The UV-B emission was enhanced at liquid-nitrogen temperature (77 K), most probably due to increased ground-state population according to the Boltzmann distribution law. Electron spin resonance spectra of samples at both room and liquid-nitrogen temperature exhibited resonance signals at g ≈ 2, attributed to Gd ions arranged with octahedral symmetry linked via oxygen bridges. Various magnetic and thermodynamic parameters for the phosphor system were evaluated by standard procedures. Correlation of these values with the optical properties suggested that the GdAlO phosphor can be effectively used as an UV-B light source for industrial applications at room temperature. [ABSTRACT FROM AUTHOR]

The design and characterization of the InSe/BN heterojunction were investigated by study of optical reflectance, transmittance, and absorbance spectra in the incident wavelength range 300-1100 nm. Three absorption band edges related to conduction-valence band splitting of 2.75, 1.49, and 3.90 eV were observed. These bands shifted to 1.06 eV, 2.25 eV, and 3.85 eV on preparation of the InSe/BN interface. Analysis of dielectric spectra in the frequency range 275-1000 THz revealed the presence of three main resonance peaks at 333, 308, and 280 THz for the InSe substrate and at 341, 316, and 286 THz for the InSe/BN interface. The dispersion energy of the substrate increased from 27.43 eV to 33.77 eV on preparation of the InSe/BN interface. The quality factor of the heterojunction was found to be three times greater than that of InSe. The device seems to have potential, because the results suggest use of the heterojunction in thin-film transistor and optical communication technology. [ABSTRACT FROM AUTHOR]

Amorphous indium selenide thin films have been used in the design of a microwave-sensitive Schottky barrier. The illumination effects on the capacitance spectra, on the signal quality factor, and on the capacitance ( C)-voltage ( V) characteristics of the Al/InSe/C device are investigated. Particular shifts in the amplitude and in the resonance peaks of the capacitance spectra which were studied in the frequency range of 10.0 kHz to 3.0 GHz are observed. While the photoexcitation of these devices increased the capacity level by ∼1.6 times the original magnitude, the dark quality factor, which was 2.2 × 10 at 3.0 GHz, fell to 1.2 × 10 when subjected to luminance of 14.7 klux. Analysis of the C- V curves recorded at signal power ranging from wireless local area network (LAN) levels to the maximum output power of third generation (3G) mobiles reflected high tunability of capacitance upon increasing the voltage or power. The tunability of the biased capacitance was much more pronounced in the light than in the dark. The obtained characteristics of the Al/InSe/C sensors indicate their usability in radio and microwave technology. [ABSTRACT FROM AUTHOR]

Widely used electronic components and optical materials are made up of a variety of inorganic materials, such as nitrides, carbides, oxides, sulfides, fluorides, selenides, diamond, silicon, and GaAs. The surfaces of these materials are known to be very difficult to bond with low-melting-point solders. A direct and powerful bonding on these surfaces has been obtained in air, without using any flux, by using low-temperature solders containing rare earth (RE) alloying elements. The nature of the bonding is based on chemical reactions at the interface, and hence, strong bonds are obtained. The Sn-3.5%Ag-2.5%Lu (by weight) solder and the Au-19.5%Sn-2%Lu solder, for example, exhibit interfacial-bond strengths in excess of 6.9–13.8 MPa. They can be useful for providing direct, ohmic-electrical contacts and interconnects in a variety of electronic assemblies and for producing dimensionally stable and reliable bonding in optical fiber, laser devices, or thermal-management assemblies. [ABSTRACT FROM AUTHOR]

Optoelectronic modulation spectroscopy (OEMS) has been used to reveal defect states in 4H-SiC. Pairs of magnitude and phase spectra have been used to infer whether they were electron or hole traps. Eleven discrete trap responses have been observed, eight were assigned as electron traps and three as hole traps. Five of these had been observed previously using optical admittance spectroscopy (OAS). An electron trap at 1.20 eV gave the most prominent response with a distinctive signature indicating that these traps were spatially delocalized with an extent of at least 1.35 nm, possibly associated with an extended defect structure. An unresolved continuum of be the superimposed response of an electron and hole trap at closely similar energies. Cosistency has been demonstrated with previous work using DLOS and OAS. [ABSTRACT FROM AUTHOR]

Hydrogenated a-Si, whose properties can be modified by impurity doping, can be produced either by decomposition of silane or by reactive sputtering of Si in an argon-hydrogen plasma. This article reviews advances made during the past few years in the preparation and characterization of films produced by the second method. The basic deposition conditions are summarized. The conclusions of analytical studies (photo-emission, infrared spectroscopy, and volumetric measurements of evolved gases), regarding the amount of hydrogen and its bonding configuration in the network, are outlined. The optical, carrier transport, photoconductivity and photoluminescence properties as a function of hydrogen content and doping are described. Electron drift mobilities, deduced from steady state and transient photoconductivity are presented. The transport and recombination properties are discussed with existing models of amorphous semiconductors, and are found to be consistent with atomic relaxations, i.e. polaronic effects. [ABSTRACT FROM AUTHOR]

The mutual solubility of GeTe and PbTe was inves-tigated using x-ray techniques. An immiscibility region between PbGeTe to almost pure GeTe was found to exist at room temperature. Complete solubility does exist at and above 600°C but it was found that quenched supersaturated alloys were quite unstable upon heating to as low as 200°C, decomposing to GeTe and Pb/GeTe phases. [ABSTRACT FROM AUTHOR]

Single crystals of thallium vanadium sulphide (TlVS) up to 2 cm in length were grown from melts using the Stockbarger technique. This material has acoustic velocities as low as 8.73 × 10 cm/sec for bulk shear waves and 8.7 × 10 cm/sec for surface (Rayleigh) waves. In a sample oriented (001)Λ(110), k was found to be 1.39%, and the temperature coefficient of delay −54 ppm for surface waves. The optical transmission is from 0.75 to 10.5 µm, and the indices of refraction range from 3.156 at 0.749 µm to 2.808 at 5.26 µm. These properties make it an attractive candidate for use in acousto-optic and acoustic surface-wave devices. [ABSTRACT FROM AUTHOR]