Metalorganic chemical vapor deposition of GaAsN epilayers: microstructures and optical properties

In this article, we investigate the parameters used in the MOCVD growth of GaAsN epilayers on GaAs substrates and some of their microstructures and optical properties. The N incorporation was found to mainly depend on the growth temperature and the fractional 1,1-dimethylhydrazine molar flow. A thin highly strained interface layer was observed between GaAsN and GaAs, which, contrary to previously published results, was not N enriched. The low-temperature (10 K) photoluminescence spectra were composed of several emissions that we attribute to a combination of interband transition and transitions involving localized defect states. (C) 2004 Elsevier B.V. All rights reserved.

Structural characteristics of GaSB / GaAs nanowire heterostructures grown by metal-organic chemical vapor deposition

Highly lattice mismatched (7.8%) GaAs/GaSb nanowire heterostructures were grown by metal-organic chemical vapor deposition and their detailed structural characteristics were determined by electron microscopy. The facts that (i) no defects have been found in GaSb and its interfaces with GaAs and (ii) the lattice mismatch between GaSb/GaAs was fully relaxed suggest that the growth of GaSb nanowires is purely governed by the thermodynamics. The authors believe that the low growth rate of GaSb nanowires leads to the equilibrium growth. (c) 2006 American Institute of Physics.

Dimeric allylpalladium(II) complexes with pyrazolate bridges: Synthesis, characterization, structure and thermal behaviour

The synthesis, characterization and thermal behaviour of some new dimeric allylpalladium (II) complexes bridged by pyrazolate ligands are reported. The complexes [Pd(mu-3, 5-R'(2)pz)(eta(3)-CH2C(R)CH2)](2) [R = H; R'= CH(CH3)(2) (1a); R = H, R' = C(CH3)(3) (1b), R = H; R' = CF3 (1c); R = CH3, R' = CH(CH3)(2) (2a); R = CH3, R' = C(CH3)(3) (2b); and R = CH3, R' = CF3 (2c)] have been prepared by the room temperature reaction of [Pd(eta(3)-CH2C(R)CH2)(acac)](acac = acetylacetonate) with 3,5-disubstituted pyrazoles in acetonitrile solution. The complexes have been characterized by NMR (H-1, C-13{H-1}), FT-IR, and elemental analyses. The structure of a representative complex, viz. 2c, has been established by single-crystal X-ray diffraction. The dinuclear molecule features two formally square planar palladium centres which are bridged by two pyrazole ligands and the coordination of each metal centre is completed by allyl substituents. The molecule has non-crystallographic mirror symmetry. Thermogravimetric studies have been carried out to evaluate the thermal stability of these complexes. Most of the complexes thermally decompose in argon atmosphere to give nanocrystals of palladium, which have been characterized by XRD, SEM and TEM. However, complex 2c can be sublimed in vacuo at 2 mbar without decomposition. The equilibrium vapour pressure of 2c has been measured by the Knudsen effusion technique. The vapour pressure of the complex 2c could be expressed by the relation: In (p/Pa)(+/- 0.06) = -18047.3/T + 46.85. The enthalpy and entropy of vapourization are found to be 150.0 +/- 3 kJ mol(-1) and 389.5 +/- 8 J K-1 mol(-1), respectively. (c) 2005 Elsevier B.V. All rights reserved.

Influence of nanowire density on the shape and optical properties of ternary InGaAs nanowires

We have synthesized ternary InGaAs nanowires on (111)B GaAs surfaces by metal-organic chemical vapor deposition. Au colloidal nanoparticles were employed to catalyze nanowire growth. We observed the strong influence of nanowire density on nanowire height, tapering, and base shape specific to the nanowires with high In composition. This dependency was attributed to the large difference of diffusion length on (111)B surfaces between In and Ga reaction species, with In being the more mobile species. Energy dispersive X-ray spectroscopy analysis together with high-resolution electron microscopy study of individual InGaAs nanowires shows large In/Ga compositional variation along the nanowire supporting the present diffusion model. Photoluminescence spectra exhibit a red shift with decreasing nanowire density due to the higher degree of In incorporation in more sparsely distributed InGaAs nanowires.