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The Eu3+ and Y3+ complexes of a series of 7V,W'-bis(carboxymethyl) macrocyclic ether bis(lactone) ligands derived from ethylenediaminetetraacetic acid (EDTA) were characterized in solution by using Eu3+ laser-induced luminescence and and l3C NMR spectroscopy. The complexation of EDTA was also studied for comparison purposes. These ligands form 1:1 complexes with Eu3+ at the concentrations studied (10 µ, ), with the luminescence lifetimes in H2Q and D20 providing the number of coordinated water molecules. The 1234567F0 -* 5 9D0 excitation spectra indicate that for each of the complexes two isomers are present in fast exchange on the 5D0 time scale. The spectra obtained for the macrocyclic complexes are identical with that of [EuEDTA]-, suggesting that the ether moieties of the macrocyclic ligands are not involved in direct coordination to the metal ion. These results are corroborated by the and 13C NMR spectra of the Y3+ complexes. Changes in the coordination environment of the Eu3+ ion as a function of pH and temperature were observed for each complex. These results suggest that two species, which involve different numbers of coordinated carboxylate moieties, are present in rapid interconversion in solution. The interchange rates between the two species observed in aqueous solution decreases to the slow exchange limit in methanol, allowing each species to be probed independently.

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Small valence-band offset of In 0.17 Al 0.83 N / GaN heterostructure grown by metal-organic vapor phase epitaxy Appl. Phys. Lett. 96, 132104 (2010); 10.1063/1.3368689Growth of single crystalline GaN thin films on Si(111) substrates by high vacuum metalorganic chemical vapor deposition using a single molecular precursor Single crystalline In 1−x Ga x N films containing high In content (70%-100%) were grown by metalorganic vapor phase epitaxy. A linear relation was observed between the lattice constants and gas phase Ga/ In ratios. The surface morphology changed from pyramid for InN to more planar ones for the InGaN alloys with increasing Ga content. The electron mobility decreased rapidly from 1200 cm 2 / V s for InN to less than 100 cm 2 / V s for In 0.7 Ga 0.3 N, with a carrier concentration of low-10 19 cm −3 for all the as-grown films. Using photoluminescence a single emission peak was observed at 1.4-1.6 m for the In-rich InGaN with decreasing wavelengths up to below 20% of Ga. Two peaks were observed for the In 0.80 Ga 0.20 N, however, indicating possible phase separation. The x-ray photoelectron spectroscopic measurement showed shifts to higher binding energies for both In and Ga with increasing Ga content. The estimated alloy composition, however, depended sensitively on the sputtering conditions of the samples.

We have grown single crystalline InN films on sapphire substrate using metal-organic vapor phase epitaxy (MOVPE). Electron mobility exceeding 1100 cm 2 /V sec was obtained for the as-grown films, with a donor concentration of 1-2 × 10 19 cm -3 . The observed mobility was higher than other reports using the MOVPE technique, and was comparable to the best results with similar carrier concentration using molecular beam epitaxy. Photoluminescence measurement showed a broad emission near 1.6 µm, indicating a likely narrow bandgap similar to many recent reports on InN. X-ray photoelectron spectroscopic analysis revealed little oxygen in the InN films grown.