Papers by Keyword: Extended X-Ray Absorption Fine Structure

Abstract: We have investigated the surface effect of colloidally prepared CdSe nanocrystals (NCs) with the size range of 23-40 Å on their structural properties by changing the organic capping ligands. The TOPO/HDA-passivated NCs reveal a size-dependent behavior involving an elongated axial bond R⁽¹⁾ of an atomic tetrahedron and a shrunken equatorial bonds R⁽²⁾. After treatment of the NCs with pyridine, the bond length R⁽¹⁾ decreases significantly whereas R⁽²⁾ remains unchanged relative to the TOPO/HDA-passivated NCs, suggesting that a tensile stress along the [001] direction is contributed from the surface modification. In addition, we find that the expansion ratio of the pyridine-treated NCs along the c axis depends strongly on the density of stacking faults, which provides an evidence for the relaxation of atomic positions near the interface of stacking faults.

Abstract: High-resolution synchrotron radiation x-ray absorption spectroscopy on Zn K-, Cd L3- and Te L3-edges for Cd1-xZnxTe ternary alloys with x = 0.10, 0.30, 0.50 and 0.90 are presented. A detailed analysis of the extended x-ray absorption fine structure using the IFEFFIT program, and the chemical bonds of Zn-Te are obtained, suggesting distortion of the Te sub-lattice. The x-ray absorption near-edge structure of the Zn K-, Cd L3- and Te L3-edge are investigated, and the electronic structures of Cd1-xZnxTe with various compositions are studied.

Abstract: High-resolution K-edge x-ray absorption data are presented for Mg, Zn and O of Mg_1-xZn_xO films. A detailed analysis of the extended x-ray absorption fine structure by using the IFEFFIT program is given, and the Zn form chemical bonds with O are obtained. The x-ray absorption near-edge structure of Mg, Zn and O K-edge are investigated, and the electronic structures of Mg_1-xZn_xO with various compositions are studied.

Abstract: High-resolution synchrotron radiation X-ray absorption of Si K-edge have been employed to investigate 6H-, 4H- and 3C-SiC. Detailed analyses of the extended x-ray absorption fine structure are taken by using the IFEFFIT program, and significant results on the atomic bonding are obtained from these comparative studies. The x-ray absorption near-edge structures of the Si K-edge are investigated, and the electronic structure of 3C-, 4H- and 6H-SiC are studied. In order to investigate the angular dependence, the x-ray absorption near-edge spectra were operated at 55o and 90o of the angle between the surface and the X-ray direction.

Abstract: High-resolution synchrotron radiation x-ray absorption data on Mn K- and L3-edge for semimagnetic semiconductor Zn1-xMnxTe bulk materials are presented. A detailed analysis of the extended x-ray absorption fine structure by using the IFEFFIT program, and the chemical bonds of Mn-Te are obtained. The x-ray absorption near-edge structure of the Mn K- and L3-edges are investigated, and the electronic structure of Zn1-xMnxTe with various compositions are studied.

Abstract: High concentrated hydrochloric/nitric/sulfuric acid were used to dissolve Ti(OH)4 produced with TiOSO4. It was found that, titania, from pure rutile phase to anatase-rutile mixed phase to pure anatase phase have been synthesized at low temperature in liquid media through controlling the hydrolyzation conditions. The phase composition and the special surface area of nanometer titania powder were characterized by means of XRD and BET. The K-edge fine structure of Ti atom sites of rutile TiO2 was investigated with grazing incidence reflection mode XAFS (EXAFS and XANES) spectroscopy. The well-crystal rutile TiO2 with fine particle size and high specific surface (above200m2/g) was formed at low temperature below 80°C, while the anatase TiO2 was formed at higher temperature in hydrochloric or nitric acid solution. But in sulfuric acid solution the crystal phase was always anatase at any temperatures. The EXAFS and XANES result showed that the order of the lattice, the coordination numbers of the Ti atom for the first shell, the second shell and the third shell as well as the relative intensity of K-preedge three peaks increased with the increase of the rutile TiO2 nanoparticle size.