Lu Zhonglin

CRYSTAL STRUCTURE AND SPECTROSCOPIC STUDIES OF A NICKEL(II) COMPLEX OF A LIGAND CONTAINING NITROGEN-SULPHUR DONORS

Abstract A bis-ligand neutral Ni(II) complex of a Schiff base ligand derived from S-benzyldithiocarbazate and p-dimethylaminobenzyldehyde was prepared and characterized. Single crystal X-ray diffraction analysis of the nickel(II) chelate established that the Schiff base loses a proton from its tautomeric thiol form and coordinates to Ni(II) via the mercapto sulphur and β-nitrogen atoms. The geometry of the Ni(II) ion is square-planar with two equivalent Ni-N and Ni-S bonds; the two dimethylaminobenzyl rings and the coordinated plane are almost in one plane, forming an electronic delocalization system. When the complex crystallizes, benzene molecules are included in the crystal. However, there is no obvious interaction between the complex molecule and the benzene molecule. Magnetic and spectroscopic data support the square-planar structure found in the structure analysis. The complex crystallizes in the triclinic space group P1 with cell parameters a = 7.839(2), b = 10.528(4), c = 10.832(5) A, α = 100.61(2...

Structural and Electrical Properties of Single Crystalline Ga-Doped ZnO Thin Films Grown by Molecular Beam Epitaxy

High-quality Ga-doped ZnO (ZnO:Ga) single crystalline films with various Ga concentrations are grown on a-plane sapphire substrates using molecular-beam epitaxy. The site configuration of doped Ga atoms is studied by means of x-ray absorption spectroscopy. It is found that nearly all Ga can substitute into ZnO lattice as electrically active donors, a generating high density of free carriers with about one electron per Ga dopant when the Ga concentration is no more than 2%. However, further increasing the Ga doping concentration leads to a decrease of the conductivity due to partial segregation of Ga atoms to the minor phase of the spinel ZnGa2O4 or other intermediate phase. It seems that the maximum solubility of Ga in the ZnO single crystalline film is about 2 at.% and the lowest resistivity can reach 1.92 × 10−4 Ω·cm at room temperature, close to the best value reported. In contrast to ZnO:Ga thin film with 1% or 2% Ga doping, the film with 4% Ga doping exhibits a metal semiconductor transition at 80 K. The scattering mechanism of conducting electrons in single crystalline ZnO:Ga thin film is discussed.

CRYSTAL STRUCTURE AND PHOTOCHEMISTRY OF BIS(BIPYRIDINE)-BIS(4-AMINOPYRIDINE)RUTHENIUM(II)

Abstract The title complex, cis-[Ru(bpy)2(4-apy)2] (ClO4)2CH3CN (where bpy = 2,2′-bipyridine, 4-apy = 4-aminopyridine), has been synthesized and characterized. An X-ray crystal structure determination established that the coordination geometry about ruthenium(II) is distorted octahedral with four nitrogen atoms from the two bpy molecules and two pyridine nitrogen atoms from apy coordinate. Time-resolved and steady-state luminescence spectra show that the emission wavelength, quantum yield and the luminescence lifetime are quite similar to those of corresponding complexes with pyridine instead of apy, which indicates that the amino group of the apy cannot quench the luminescence. Electrochemistry in CH3CN is consistent with this result. The complex crystallines in the monoclinic space group, P21/n with cell parameters a = 10.585(2), b = 11.615(2), c = 15.992(3) A, β = 99.76(3)° and Z = 4. The structure was refined by full-matrix least-squares methods to R = 0.071 and Rw = 0.093 for 4625 reflections having ...

Structural and electrical properties of single crystalline and bi-crystalline ZnO thin films grown by molecular beam epitaxy

C-oriented ZnO epitaxial thin films are grown separately on the a-plane and c-plane sapphire substrates by using a molecular-beam epitaxy technique. In contrast to single crystalline ZnO films grown on a-plane sapphire, the films grown on c-plane sapphire are found to be bi-crystalline; some domains have a 30? rotation to reduce the large mismatch between the film and the substrate. The presence of these rotation domains in the bi-crystalline ZnO thin film causes much more carrier scatterings at the boundaries, leading to much lower mobility and smaller mean free path of the mobile carriers than those of the single crystalline one. In addition, the complex impedance spectra are also studied to identify relaxation mechanisms due to the domains and/or domain boundaries in both the single crystalline and bi-crystalline ZnO thin films.

Room-Temperature Ferromagnetic ZnMnO Thin Films Synthesized by Plasma Enhanced Chemical Vapour Deposition Method

Room-temperature ferromagnetic Mn-doped ZnO films are grown on Si (001) substrates by plasma enhanced chemical vapour deposition (PECVD). X-ray diffraction measurements reveal that the Zn1−xMnxO films have the single-phase wurtzite structure. X-ray photoelectron spectroscopy indicates the existence of Mn2+ ions in Mn-doped ZnO films. Furthermore, the decreasing additional Raman peak with increasing Mn-doping is considered to relate to the substitution of Mn ions for the Zn ions in ZnO lattice. Superconducting quantum interference device (SQUID) measurements demonstrate that Mn-doped ZnO films have ferromagnetic behaviour at room temperature.

Synthesis, crystal structure and equilibrium studies on the bidentate amine adducts of bis(S-methyl-β-N-(4-methyloxyphenyl) methylendithiocarbazide)nickel(II) complex

Abstract The crystal structure of the 1,10-phenanthroline bis(S-methyl-β-N-(4-methyloxyphenyl)methylendithiocarbazide)nickel(II) adduct, (Ni(SN)2phen) [SN = S-methyl-β-N-(4-methyloxyphenyl)methylendithiocarbazide, phen = phenanthroline], has been determined by single crystal X-ray diffraction. The nickel atom is in an octahedral environment, surrounded by two chelating SN ligands and one chelating phen molecule. The nitrogen atoms from phen are in the cis configuration. The other chelating diamines adducts of the parent complex (Ni(SN)2) were also studied, where the chelating diamnies are 5-nitro-1,10-phenanthroline(NO2phen), 2,2′-bipyridine (bipy), 4,4′-methyl-2,2′-bipyridine (Mebipy). The equilibria were determined by UV-vis spectrometry in dichloromethane. The coordination ability of the added ligands were influenced by substitute groupings and steric factors. From the structure and addition equilibrium studies, the possible addition mechanisms are also discussed.

Activation of room-temperature ferromagnetism in Mn doped ZnO thin films by N codoping

Mn doped ZnO films with and without N codoping have been fabricated by oxidative annealing of sputtered Zn:Mn and Zn 2 N 3 :Mn films on silicon substrates in flowing O 2 ambient. It was found that the ZnO:Mn films show very weak ferromagnetic behavior, while for those with N codoping, significant ferromagnetism with a moderate saturation magnetization of about 0.23—0.61 μ B per Mn 2+ ion was observed at room temperature. It suggests that significant ferromagnetism in ZnO:Mn films could be activated by N codoping. The results indicate that holes are favorable for ferromagnetic ordering of the doped Mn 2+ ions in ZnO, in agreement with the recent theoretical studies.

Effect of hydrogenation time on magnetic and electrical properties of polycrystalline Si 0.956 Mn 0.044 :B thin films

This paper reports that polycrystalline Si0.956 Mn0.044:B films have been prepared by cosputtering deposition followed by rapid thermal annealing for crystallization. The polycrystalline thin films were treated by hydrogen plasma excited with approach of radio-frequency plasma enhanced chemical vapour deposition for different time of 10 minutes, 15 minutes and 40 minutes. After hydrogenation, the structural properties of the films do not show any change, while both the saturation magnetization and the hole concentration in the films increase at first, then decrease with the increase of hydrogenation time. The obvious correlation between the magnetic properties and the transport properties of the polycrystalline Si0.956 Mn0.044:B films suggests that a mechanism of hole-mediated ferromagnetism is believed to exist in Si-based diluted magnetic semiconductors.