Extended X-ray absorption fine structure

About: Extended X-ray absorption fine structure is a research topic. Over the lifetime, 10452 publications have been published within this topic receiving 276744 citations.

Optical Absorption in the Presence of a Uniform Field

Abstract: Expressions for the absorption coefficient in the presence of a uniform field, of semiconductors and insulators for both allowed and forbidden transitions are derived. The results are expressed in terms of Airy functions, and the limiting cases examined indicate the tunneling mechanism as a possible explanation for the experimentally observed long-wavelength tails.

Epitaxially grown La-modified BiFeO3 magnetoferroelectric thin films

Abstract: Effects of the La modification on the structure and magnetoferroelectric properties of BiFeO3 (BFO)-based films were examined. On SrTiO3 (001) planes, all the BFO-based films (for x between 0 and 0.15 in Bi1−xLaxFeO3 with the film thickness of 300 nm) were grown epitaxially along [001] direction of tetragonal symmetry. However, the La modification gradually changes the film structure from a monoclinically tilted state to a nontilted tetragonal-like state. Both extended x-ray absorption fine structure and x-ray absorption near edge structure spectra revealed the presence of a strong in-plane compressive stress. Room-temperature magnetization-field curves indicated that the saturation magnetization of these BFO-based epitaxial films increased with the degree of La modification. La-modified BFO film capacitors fabricated on SrRuO3-buffered SrTiO3 (001) substrates showed fatigue-free ferroelectric switching characteristics up to 4×1010 read∕write cycles at a frequency of 1 MHz.

Fundamental Optical Absorption in Sn S 2 and Sn Se 2

Abstract: Optical absorption in single-crystal $n$-type Sn${\mathrm{S}}_{2}$ and Sn${\mathrm{Se}}_{2}$ has been studied at 300\ifmmode^\circ\else\textdegree\fi{}K throughout the wavelength range 0.26 to 6.5 \ensuremath{\mu}. Samples suitable for optical measurements were prepared by various vapor-deposition techniques. The electrical characteristics of the samples used in the absorption measurements were as follows: for Sn${\mathrm{Se}}_{2}$, conductivity 3.6 ${(\mathrm{\ensuremath{\Omega}}\phantom{\rule{0ex}{0ex}}\mathrm{c}\mathrm{m})}^{\ensuremath{-}1}$, electron concentration ${10}^{18}$ per ${\mathrm{cm}}^{3}$, mobility 27 ${\mathrm{cm}}^{2}$/V sec; and for Sn${\mathrm{S}}_{2}$, conductivity ${10}^{\ensuremath{-}7}$ ${(\mathrm{\ensuremath{\Omega}}\phantom{\rule{0ex}{0ex}}\mathrm{c}\mathrm{m})}^{\ensuremath{-}1}$. From transmittance and reflectance measurements, the absorption coefficient and index of refraction were determined for light polarized perpendicular to the crystallographic symmetry axis. From an analysis of the data in the high-absorption region, direct-transition band gaps of 1.62 and 2.88 eV were found for Sn${\mathrm{Se}}_{2}$ and Sn${\mathrm{S}}_{2}$, respectively. A threshold for possible indirect phonon-assisted transitions was found to occur at 0.97 eV for Sn${\mathrm{Se}}_{2}$ and at 2.07 eV for Sn${\mathrm{S}}_{2}$. Photo-conductivity data for Sn${\mathrm{S}}_{2}$ are also presented.

In Situ/Operando Electrocatalyst Characterization by X-ray Absorption Spectroscopy

Abstract: During the last decades, X-ray absorption spectroscopy (XAS) has become an indispensable method for probing the structure and composition of heterogeneous catalysts, revealing the nature of the active sites and establishing links between structural motifs in a catalyst, local electronic structure, and catalytic properties. Here we discuss the fundamental principles of the XAS method and describe the progress in the instrumentation and data analysis approaches undertaken for deciphering X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectra. Recent usages of XAS in the field of heterogeneous catalysis, with emphasis on examples concerning electrocatalysis, will be presented. The latter is a rapidly developing field with immense industrial applications but also unique challenges in terms of the experimental characterization restrictions and advanced modeling approaches required. This review will highlight the new insight that can be gained with XAS on complex real-world electrocatalysts including their working mechanisms and the dynamic processes taking place in the course of a chemical reaction. More specifically, we will discuss applications of in situ and operando XAS to probe the catalyst’s interactions with the environment (support, electrolyte, ligands, adsorbates, reaction products, and intermediates) and its structural, chemical, and electronic transformations as it adapts to the reaction conditions.