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Title: Local structures of copper-doped ZnO films

; ;  [1]
  1. (NWU)
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
Sponsoring Org.:
OSTI Identifier:
Resource Type:
Journal Article
Resource Relation:
Journal Name: Phys. Rev. B; Journal Volume: 78; Journal Issue: (21) ; 12, 2008
Country of Publication:
United States

Citation Formats

Ma, Q., Buchholz, D.B., and Chang, R.P.H. Local structures of copper-doped ZnO films. United States: N. p., 2015. Web. doi:10.1103/PhysRevB.78.214429.
Ma, Q., Buchholz, D.B., & Chang, R.P.H. Local structures of copper-doped ZnO films. United States. doi:10.1103/PhysRevB.78.214429.
Ma, Q., Buchholz, D.B., and Chang, R.P.H. 2015. "Local structures of copper-doped ZnO films". United States. doi:10.1103/PhysRevB.78.214429.
title = {Local structures of copper-doped ZnO films},
author = {Ma, Q. and Buchholz, D.B. and Chang, R.P.H.},
abstractNote = {},
doi = {10.1103/PhysRevB.78.214429},
journal = {Phys. Rev. B},
number = (21) ; 12, 2008,
volume = 78,
place = {United States},
year = 2015,
month = 2
  • We report the local structures of a series of copper-doped zinc oxide films using polarization-dependent x-ray-absorption spectroscopy. The films were grown by pulsed-laser ablation under various conditions. The results show that films where copper exists solely as clusters are not ferromagnetic. The results also show that some of the copper-doped zinc oxide films are not ferromagnetic despite the fact that the copper substitution for zinc in the ZnO lattice is in the Cu{sup 2+} state, which provides the necessary unpaired spins for ferromagnetism. Therefore, Cu{sup 2+}/Zn{sup 2+} substitution is not the only imperative condition for ferromagnetism to occur. We presentmore » characteristics unique to the electronic and atomic structure of ferromagnetic films and argue that the increased covalence of the Cu{sub Zn}-O bond found in these films is a prerequisite for the spin alignments in a substitutionally copper-doped zinc oxide film.« less
  • Lead-free ferroelectric un-doped and doped K{sub 0.5}Na{sub 0.5}NbO{sub 3} (KNN) films with different amounts of manganese (Mn) were prepared by a chemical solution deposition method. The thicknesses of all films are about 1.6 μm. Their phase, microstructure, leakage current behavior, and electrical properties were investigated. With increasing the amounts of Mn, the crystallinity became worse. Fortunately, the electrical properties were improved due to the decreased leakage current density after Mn-doping. The study on leakage behaviors shows that the dominant conduction mechanism at low electric field in the un-doped KNN film is ohmic mode and that at high electric field is space-charge-limitedmore » and Pool-Frenkel emission. After Mn doping, the dominant conduction mechanism at high electric field of KNN films changed single space-charge-limited. However, the introduction of higher amount of Mn into the KNN film would lead to a changed conduction mechanism from space-charge-limited to ohmic mode. Consequently, there exists an optimal amount of Mn doping of 2.0 mol. %. The 2.0 mol. % Mn doped KNN film shows the lowest leakage current density and the best electrical properties. With the secondary ion mass spectroscopies and x-ray photoelectron spectroscopy analyses, the homogeneous distribution in the KNN films and entrance of Mn element in the lattice of KNN perovskite structure were also confirmed.« less
  • The crystal and magnetic structures of La{sub 0.8}Sr{sub 0.2}Fe{sub 1-x}Cu{sub x}O{sub 3-w} compounds, which exhibit coercive fields larger than any others reported for iron-based perovskites, have been analyzed at room temperature with the neutron powder diffraction technique and the Rietveld method of profile fitting. For x in the range 0.05-0.10 the material is monophasic with orthorhombic symmetry (space group Pnma), and crystallizes in the perovskite-like cell of LaFeO{sub 3}, Fe/Cu cations occupy octahedral sites, La/Sr cations are twelve-fold coordinated. For x=0.20 the material is biphasic, with a main orthorhombic phase (space group Pnma) and a secondary rhombohedral phase with spacemore » group R-3c (hexagonal setting). The structural transition from the orthorhombic to the rhombohedral phase reduces the structural distortion of the (Fe/Cu)O{sub 6} octahedron. The average bond distance (Fe/Cu)-O and the pseudo-cubic unit cell volume decrease with increasing Cu content in accordance with the presence of higher valence states of the transition metals. The magnetic structure was modeled for the monophasic samples (x=0.05 and 0.10) assuming an antiferromagnetic interaction between Fe/Cu neighboring cations (G-type): the magnetic moments order antiferromagnetically along the b-axis, with the spin direction along a-axis. The magnetic moments of the Fe/Cu atoms are {mu}{sub x}=2.66(3){mu}{sub B} and 2.43(3){mu}{sub B} for the compositions x=0.05 and 0.10, respectively. By measuring the first magnetization curve and the hysteresis loops, coexisting antiferromagnetic and weak ferromagnetic interactions were observed for all samples. - Graphical abstract: Hysteresis loops measured at room temperature of the sample with x=0.05. Highlights: Black-Right-Pointing-Pointer Iron based perovskites with the largest coercive fields. Black-Right-Pointing-Pointer Sr and Cu lanthanum ferrites as magnetic materials. Black-Right-Pointing-Pointer Doped lanthanum ferrites show antiferromagnetic and weak ferromagnetic interactions. Black-Right-Pointing-Pointer Sr and Cu lanthanum ferrites show distorted perovkite structure.« less
  • X-ray-absorption fine-structure measurements were carried out to probe the local environment surrounding Mn ions in Mn-doped nanocrystals of ZnS with different size distributions ranging from 30--35 A to 50--55 A. The interatomic distances between Mn and neighboring atoms, the coordination number, local disorder, and effective valency determined for the nanocrystals are compared with those in bulk Mn-doped ZnS. The Mn ions are found to substitute for the Zn sites in the host ZnS but with significant size-dependent local structural changes. The questions of Mn-cluster formation and the presence of Mn impurities on the surface of the nanocrystals are addressed. Near-edgemore » x-ray-absorption fine structures indicate that the effective valency of Mn ions in the nanocrystals is close to +2 with a weak size dependence. These local structures are believed to be closely related to the novel optical properties observed in this new class of semiconductors.« less