Structural and elastic properties of defect chalcopyrite HgGa2S4 under high pressure

In this work, we focus on the study of the structural and elastic properties of mercury digallium sulfide (HgGa2S4) at high pressures. This compound belongs to the family of AB(2)X(4) ordered-vacancy compounds and exhibits a tetragonal defect chalcopyrite structure. X-ray diffraction measurements at room temperature have been performed under compression up to 15.1 GPa in a diamond anvil cell. Our measurements have been complemented and compared with ab initio total energy calculations. The axial compressibility and the equation of state of the low-pressure phase of HgGa2S4 have been experimentally and theoretically determined and compared to other related ordered-vacancy compounds. The pressure dependence of the theoretical cation-anion and vacancy-anion distances and compressibilities in HgGa2S4 are reported and discussed in comparison to other related ordered-vacancy compounds. Finally, the pressure dependence of the theoretical elastic constants and elastic moduli of HgGa2S4 has been studied. Our calculations indicate that the low-pressure phase of HgGa2S4 becomes mechanically unstable above 13.8 GPa. (C) 2013 Elsevier B. V. All rights reserved.This study was supported by the Spanish government MEC under Grants No: MAT2010-21270-C04-01/03/04 and CTQ2009-14596-C02-01, by the Comunidad de Madrid and European Social Fund (S2009/PPQ-1551 4161893), by MALTA Consolider Ingenio 2010 Project (CSD2007-00045), by Generalitat Valenciana (GVA-ACOMP-2013-1012), and by the Vicerrectorado de Investigacion y Desarrollo of the Universidad Politecnica de Valencia (UPV2011-0914 PAID-05-11 and UPV2011-0966 PAID-06-11). E.P-G., A. M., and P.R-H. acknowledge computing time provided by Red Espa ola de Supercomputacion (RES) and MALTA-Cluster. J.A.S. acknowledges Juan de la Cierva fellowship program for financial support.Gomis Hilario, O.; Santamaría-Pérez, D.; Vilaplana Cerda, RI.; Luna Molina, R.; Sans, JA.; Manjón Herrera, FJ.; Errandonea, D.... (2014). Structural and elastic properties of defect chalcopyrite HgGa2S4 under high pressure. Journal of Alloys and Compounds. 583:70-78. https://doi.org/10.1016/j.jallcom.2013.08.123S707858

Microstructural and optical properties of ZrON/Si thin films

ZrON/Si(100) layer structure formation has been produced by oxidation/nitridation of sputtered Zr metal in N2O/Ar ambient at 500–900 °C. Micromorphology and structural properties of the films have been evaluated by scanning electron microscopy, atomic force microscopy, and reflection high-energy electron diffraction. Dispersive optical properties of the ZrON/Si reflection system have been studied with spectroscopic ellipsometry. A drastic increase of SiO2-based interface layer thickness has been found at 700–900 °C

Micromorphology and spectroscopic ellipsometry of Ni(100) crystal surface

AbstractDispersion of refractive index and extinction coefficient of nickel crystal surface (100) has been determined with spectroscopic ellipsometry over spectral range λ∼250-1030 nm. The crystal surface (100) at a first stage was mechanically polished and then treated by electro-polishing to remove the damage layer

Physical and dispersive optical characteristics of ZrON/Si thin-film system

To date, the complex evaluation of physical and dispersive optical characteristics of the ZrON/Si film system has yet been reported. Hence, ZrON thin films have been formed on Si(100) substrates through oxidation/nitridation of sputtered metallic Zr in N2O environment at 500, 700, and 900 ∘C. Physical properties of the deposited films have been characterized by X-ray diffractometry (XRD), Fourier transform infrared (FTIR) spectroscopy, reflection high-energy electron diffraction (RHEED), and spectroscopic ellipsometry (SE). It has been shown that ZrON/Si thin films without optical absorption can be prepared by oxidation/nitridation reaction in N2O environment at 700–900 ∘C

The linearly polarized waveguide-fed dipole-like antenna

<div><p>The modified waveguide-fed dipole-like antenna is designed using the induced <i>emf</i> method. To excite the antenna arms, the two equal in magnitude and 180° and out-of-phase excitations are created using the standard rectangular waveguide. Since the area around the radiating arms is free of any conductors (exception for a finite ground plane), the antenna radiation is of high polarization purity. The stand-alone antenna operating near 1.7 GHz was fabricated and tested to verify the design validity. Both the far-field pattern and the return loss level show good agreement with the designed parameters. Such antenna is optimal for using as a building block in the linearly polarized assemblies as well as the stand-alone radiators.</p></div

Electronic parameters of Sr₂Nb₂O₇ and chemical bonding

X-ray photoelectron spectroscopy (XPS) measurements were carried out on a strontium pyroniobate (Sr2Nb2O7) powder sample, which was synthesized using standard solid-state method. The binding energy (BE) differences between the O 1s and cation core levels, Δ(O–Nb)=BE(O 1s)–BE(Nb 3d5/2) and Δ(O–Sr)=BE(O 1s)–BE(Sr 3d5/2), were used to characterize the valence electron transfer on the formation of the Nb–O and Sr–O bonds. The chemical bonding effects were considered on the basis of our XPS results for Sr2Nb2O7 and earlier published structural and XPS data for other Sr- or Nb-containing oxide compounds. The new data point for Sr2Nb2O7 is consistent with the previously derived relationship for a set of Nb5+-niobates that Δ(O–Nb) increases with increasing mean Nb–O bond distance, L(Nb–O). A new empirical relationship between Δ(O–Sr) and L(Sr–O) was also obtained. Interestingly, the correlation between Δ(O–Sr) and L(Sr–O) was found to differ from that between Δ(O–Nb) and L(Nb–O). Possible cause for the difference is discussed. © 2008, Elsevier Ltd