Local structure of condensed zinc oxide

Abstract

The high-pressure local structure of zinc oxide has been studied at room temperature using combined energy-dispersive x-ray-diffraction and x-ray-absorption spectroscopy experiments. The structural parameter u and the lattice-parameter ratio c/a of the wurtzite phase is given as a function of pressure and compared with results from ab initio calculations based on a plane-wave pseudopotential method within the density-functional theory. It is shown that an accurate study of ZnO requires the explicit treatment of the d electrons of Zn as valence electrons. In good agreement with present calculations, our experimental data do not show any variation of u(P) in the low-pressure wurtzite phase between 0 and 9 GPa, pressure at which the phase transition to the rocksalt phase occurs. Moreover, no dramatic modification of the r-phase K-edge position up to similar to20 GPa is observed, indicating the absence of metallization. In view of all these results, theoretical models identifying the wurtzite-to-rocksalt transition as an homogeneous path are discussed

Zn K-edge XANES in nanocrystalline ZnO

“…Close results were obtained for bulk ZnO in [7] by the ab initio FMS FEFF8 code [10] within the MT-potential approximation.…”

“…Hexagonal wurtzite ZnO structure (space group C6mc), existing below 9 GPa [7], with the lattice parameters a=3.2495 Å, c=5.2069Å and u=0.345 was used in all calculations. It can be described as a number of alternating planes composed of tetrahedrally coordinated O 2-and Zn 2+ ions, stacked alternately along the c-axis.…”

Optical and Structure Analysis of ZnO:Al Film

“…The unit cell has two external lattice parameters: the basal plane (a) and uniaxial plane (c) and an internal parameter u, which describes the cation and anion positions relative to the z axis (Jaffe and Hess, 1993;Marana et al, 2008). The ZnO wurtzite structure belongs to the space group P63mc with a Bravais lattice (a = 3.250 Å and c = 5.207 Å and internal coordinate u = 0.382) (Decremps et al, 2003) and can be depicted as a zinc atom surrounded by four oxygen atoms with sp 3 -hybridization in a tetrahedron configuration along the caxis. In the ZnO this value is close to a hexagonal cell with a notional value of the c/a ratio of 1.633 (Morkoç and Özgür, 2009).…”

Electrical transport property of ZnO thin films at high H2 pressures up to 20 bar

“…We suggest that the reduction of G can be explained by the competition of polarization directions because the piezoelectric potential of ZnO depends on a bending directions; the current induced by piezoelectricity increases (decreases) as compressive (stretching) force is applied to the ZnO wire [9]. Although the pressure is applied to all directions of ZnO, the amount of change of each bond length such as Zn-O and Zn-Zn is different [16]. It causes the variation of coordination [17] and the modulation of energy bandgap [18].…”