Two new heterometallic coordination polymers, [Na4Ln12(stp)8(OH)16(H2O)12]·10H2O [Ln = Dy (1) and Ho (2)], have been prepared from monosodium 2-sulfoterephthalate (NaH2stp), dysprosium acetate, or holmium acetate. They are isostructural, possessing a [Ln12(μ3-OH)16](20+) wheel-cluster core based on four vertex-sharing cubane-like [Ln4(μ3-OH)4](8+) units. The Ln12 cores are linked by stp ligands into a three-dimensional (3D) architecture. Magnetic studies indicate that complex 1 exhibits slow relaxation of magnetization, and it can be regarded as the first 3D coordination assembly of a Dy12 cluster single-molecule magnet.
Mg-doped and In-Mg co-doped p-type GaN epilayers were grown using the metal organic chemical vapour deposition technique. The effect of In co-doping on the physical properties of p-GaN layer was examined by high resolution x-ray diffraction (HRXRD), transmission electron microscopy (TEM), Hall effect, photoluminescence (PL) and persistent photoconductivity (PPC) at room temperature. An improved crystalline quality and a reduction in threading dislocation density are evidenced upon In doping in p-GaN from HRXRD and TEM images. Hole conductivity, mobility and carrier density also significantly improved by In co-doping. PL studies of the In-Mg co-doped sample revealed that the peak position is blue shifted to 3.2 eV from 2.95 eV of conventional p-GaN and the PL intensity is increased by about 25%. In addition, In co-doping significantly reduced the PPC effect in p-type GaN layers. The improved electrical and optical properties are believed to be associated with the active participation of isolated Mg impurities.
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