Ultraviolet photoelectron spectroscopy of nano In clusters Schottky barriers on sputtered InP

Plasmon peaks along with Auger P_LVV peak have been observed in the ultraviolet photoelectron spectra (UPSs) of InP after 5 min of sputtering with 0.5 kV Ar⁺ ions. Plasmon and Auger peaks are not observed in UPS of un-sputtered InP surface with native oxides of In and P. Filled electron energy levels are not observed near the Fermi level from 5 min sputtered InP surface due to increase of ionization potential of nano In clusters.     

Density functional theoretical study of the structural, electronic and lattice dynamical properties of platinum pernitride

In the framework of density functional theory, the structural, electronic and lattice dynamical properties of platinum pernitride have been investigated using the plane wave pseudopotential within the GGA and LDA functional for treating the effects of exchange correlation implemented in PWSCF and ABINIT packages. The computed lattice constant and bulk modulus agree well with the experiment and other theoretical calculations. Both packages and correlation functional agree well on the lattice constant within the deviation of about 1.6%. The bulk modulus has been quite successfully predicted by LDA. The electronic structure and DOS of platinum pernitride show a narrow gap and confirms semiconducting nature of this compound. The lattice dynamical calculation shows that the platinum nitride in pyrite structure (platinum pernitride) is dynamically stable. The zone center phonon frequencies particularly the Raman active phonons agree well with the experimental Raman data in the case of GGA implemented in PWSCF. The pressure variation of Raman active modes shows a linear variation; however, at higher pressure the variation is fast.     

Effect of viscous dissipation on natural convection flow between vertical parallel plates with time-periodic boundary conditions

This article investigates the natural convection flow of viscous incompressible fluid in a channel formed by two infinite vertical parallel plates. Fully developed laminar flow is considered in a vertical channel with steady-periodic temperature regime on the boundaries. The effect of internal heating by viscous dissipation is taken into consideration. Separating the velocity and temperature fields into steady and periodic parts, the resulting second order ordinary differential equations are solved to obtain the expressions for velocity, and temperature. The amplitudes and phases of temperature and velocity are also obtained as well as the rate of heat transfer and the skin friction on the plates. In presence of viscous dissipation, fluids of relatively small Prandtl number has higher temperature than the channel plates and as such, heat is being transferred from the fluid to the plate.     

Features of the formation of silicon nanocrystals upon the annealing of SiO<Subscript>2</Subscript> layers implanted with Si ions

The effect of annealing on the ion-beam synthesis of silicon nanocrystals in Si layers was investigated by low-frequency Raman scattering (RS). The occurrence of crystal nuclei in a matrix of glass results in an additional contribution to density of the acoustic vibrational states associated with the surface vibrational modes of nanocrytals. The low-frequency RS caused by interaction of light with acoustic vibration modes of nanoparticles is an effective method of research. The low-frequency Raman spectra show that the samples do not have a smooth distribution of nanoparticle size, but have two specific sizes of nanoparticles, 3 and 6 nm.     

TAGE iterative algorithm and nonpolynomial spline basis for the solution of nonlinear singular second order ordinary differential equations

In the present paper, we discuss three point difference method based on nonpolynomial spline basis for the second order ordinary differential equation. Difference schemes are derived for linear and nonlinear case and are used to solve via two parameter alternating group explicit iterative algorithm. The schemes have a fourth and second order of uniform convergence for the choice of the parameters involved in the method. Computational results are presented comparing the two methods in terms of accuracy and execution times. The results indicate the advantage of using parallel implementation of the new method.     

Constrains in gamma spectrometry analysis of fallout <Superscript>137</Superscript>Cs in coastal marine environment of Arabian sea in India

In this study, an accurate faster gamma spectrometry method for measuring the low level activity concentrations of ¹³⁷Cs using in situ pre-concentration technique on copper ferrocyanide cartridge was standardized. Due to unavailability of reference standard in the copper ferrocyanide matrix, efficiency calibration curves were plotted using RGU and RGTh reference standards. To harmonize the difference in density of standard and sample the required density correction factors for photo peak efficiency were generated. The in situ pre-concentration technique followed by gamma-ray spectrometry was applied for activity determination in surface seawater from eight locations in the coastal marine environment of Arabian Sea. The mean activity concentration of ¹³⁷Cs ranged between 0.71 and 0.91 Bq/m³. Higher activity concentrations were observed at location with latitude, longitude of 21.6°N, 69.57°E as compared to concentration observed at location with latitude, longitude 16.98°N, 73.25°E. The observed concentrations were found to be in range of data reported in Asia–Pacific Marine radioactive database (ASPARMARD). The results will fill up the gaps in the existing database. The generated data will be useful for monitoring fresh input of anthropogenic radionuclide into coastal marine environment for post Fukushima environmental assessment.     

Structural,dielectric and photoluminescence properties of co-precipitated Zn-doped SnO2 nanoparticles

Zn-doped SnO₂ nanoparticles were prepared by the chemical co-precipitation route. X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses of these prepared nanoparticles were carried out for structural and morphological studies. All the samples have been found to have tetragonal rutile structure of the polycrystalline SnO₂ having crystallite size in the range 13–25 nm. TEM micrographs show agglomeration of nanoparticles in all the samples. At a particular temperature, the dielectric constant of all the samples has been found to decrease with increasing frequencies which may be due to rapid polarization processes occurring in SnO₂ nanoparticles. The ac conductivity, σ (ω), has been found to vary with frequency according to the relation σ (ω) ∝ ω^S. The value of S has been found to be temperature dependent, decreasing with increasing frequency which suggests that a hopping process is the most likely conduction mechanism in these nanoparticles. The room temperature photoluminescence (PL) spectra of the undoped and Zn-doped SnO₂ nanoparticles consist of the near band-edge ultraviolet (UV) emission and the defect related visible emissions. The origin of emission peaks in the visible region is attributed to oxygen-related defects that are introduced during growth.     

Controlling laser spectra in a phaseonium photonic crystal using maser

We study the control of quantum resonances in photonic crystals with electromagnetically induced transparency driven by microwave field. In addition to the control laser, the intensity and phase of the maser can alter the transmission and reflection spectra in interesting ways, producing hyperfine resonances through the combined effects of multiple scattering in the superstructure.     

Phase separation in Na–K liquid alloy

The quasi-chemical expression for weakly interacting binary alloy has been applied to obtain energy parameters and their temperature derivatives for Na–K liquid alloy at 384?K. These energy parameters have then been used to calculate thermodynamic functions, such as free energy of mixing, heat of mixing, entropy of mixing and microscopic functions, such as concentration fluctuation in long wavelength limit, Warren–Cowley short-range order parameter, ratio of mutual and self-diffusion coefficients. The analysis reveals that the energy parameters are temperature dependent and the Na–K liquid alloy at 384?K is a weakly interacting homocoordination system. The observed thermodynamic properties of Na–K alloy in molten state have successfully been explained by assuming Na₂K complex on the basis of the quasi-chemical formalism for a weakly interacting system.