Effect of Hydrogen Coverage on Elastic and Optical Properties of Silicene: A First-Principle Study

The structural, electronic, and optical properties of hydrogenated silicene have been investigated using first-principles DFT calculations. In comparison to pristine silicene, the hydrogenated silicene exhibits high stability, reduced anisotropy, and less birefringence. In the visible range, hydrogenated silicene exhibits a constant refractive index than silicene. The elastic and optical parameters: Young’s modulus (Y), poisson’s ratio (ν), bulk modulus (B), shear modulus (G), dielectric constant ε(0), refractive index n(0), conductivity threshold (Eth), birefringence Δn(0), and plasmon energy (ħωp) were calculated for the first time for various hydrogen occupancy levels. The estimated parameters are agree well with the experimental and reported values that are available.

Crossing the light line

We ask the question “what happens to Bloch waves in gratings synthetically moving at near the speed of light?”. First we define a constant refractive index (CRI) model in which Bloch waves remain well defined as they break the light barrier, then show their dispersion rotating through 360° from negative to positive and back again. Next we introduce the effective medium approximation (EMA) then refine it into a 4-wave model which proves to be highly accurate. Finally using the Bloch waves to expand a pulse of light we demonstrate sudden inflation of pulse amplitude combined with reversal of propagation direction as a luminal grating is turned on.

The Effect of Annealing Temperature on Structural and Solid State Properties of Aluminium Zinc Oxide (AlZnO) Deposited by Chemical Bath technique

In this work, we studied the effect of annealing temperature on the structural and solid state properties of AlZnO thin films using Chemical bath deposition technique. The thin films grown was annealed at various temperatures of 100oC, 150oC to 200oC The morphological and structural properties were studied using XRD and SEM, while the optical properties were studied using UVVIS Spectroscopy from where the bad gap, dielectric constant, refractive index, extinction coefficient and optical conductivity were deduced from the theoretical equations.From the result, it is observed that there is effect of annealing temperature on these properties such that the grain size and x-ray characteristics depicted different characteristics at these various temperatures.

Manufacturing and investigation of physical properties of polyacrylonitrile nanofibre composites with SiO2, TiO2 and Bi2O3 nanoparticles

The aim of this study was to produce nanocomposite polymer fibres, consisting of a matrix of polyacrylonitrile (PAN) and a reinforcing phase in the form of SiO2/TiO2/Bi2O3 nanoparticles, by electrospinning the solution. The effect of the nanoparticles and the electrospinning process parameters on the morphology and physical properties of the obtained composite nanofibres was then examined. The morphology of the fibres and the dispersion of nanoparticles in their volume were examined using scanning electron microscopy (SEM). All of the physical properties, which included the band gap width, dielectric constant and refractive index, were tested and plotted against the concentration by weight of the used reinforcing phase, which was as follows: 0%, 4%, 8% and 12% for each type of nanoparticles. The width of the band gap was determined on the basis of the absorption spectra of radiation (UV–vis) and ellipsometry methods. Spectroscopic ellipsometry has been used in order to determine the dielectric constant, refractive index and the thickness of the obtained fibrous mats.

Synthesis and Application of 1-[(2-methyl-3-benzothiophene)]-2-[2-methyl-5-(1,3-dioxolane)-3-thienyl]perfluorocyclopentene

A new unsymmetrical photochromic diarylethene 1-[(2-methyl-3-benzothiophene)]-2-[2-methyl-5-(1,3-dioxolane)-3-thienyl] perfluorocyclopentene (1o) has been synthesized. In the meantime, its photochromic, kinetics and fluorescence properties were investigated in detail. The results showed this compound exhibited reversible photochromism, undergoing reversible cyclization and cycloreversion reactions upon alternating irradiation with UV and visible light in solution [1]. The two isomers differ from each other not only in their absorption spectras, but also in many changes of various physical and chemical properties, such as dielectric constant, refractive index, as well as oxidation/reduction potential, etc [2]. Diarylethene 1 changed the color from colorless to pink upon irradiation with 297 nm UV light, in which absorption maxima were observed at 516 nm in acetonitrile.

Terahertz Time Domain, Raman and Fourier Transform Infrared Spectroscopy of Acrylamide, and the Application of Density Functional Theory

We present terahertz time domain spectra of acrylamide in the frequency range from 0.2 to 2 THz with nearly constant refractive index having an average value of 1.33 and an absorption coefficient. Raman (95–3000 cm−1) and FTIR (450–4000 cm−1) spectra also show good agreement with density functional theory (DFT) B3LYP 6-311G++ (3df 3pd) calculations except C-H and N-H stretching frequencies even after scaling with scale factor of 0.9679. We use MOLVIB to rescale such frequencies to match experimental values.

Transmission Fourier Transform Infra-red Spectroscopy Investigation of Structure Property Relationships in Low-k SiOxCy:H Dielectric Thin Films

ABSTRACTIn order to understand the structure property relationships for inorganic low dielectric constant (i.e. low-k) materials, transmission Fourier Transform-Infrared (FTIR) spectroscopy has been utilized to study the local bonding structure in various plasma enhanced chemically vapor deposited low-k materials in the SiOxCy:H phase diagram. The FTIR measurements were combined with additional mechanical, electrical, and optical property measurements to elucidate the structure property relationships for these materials. The combined measurements show that increased incorporation of terminal methyl bonding results in a decrease in network bonding that manifests itself in a reduction in mass density, dielectric constant, refractive index, Young’s modulus and many other important material properties.