Application of spectroscopic ellipsometry for real-time control of CdTe and HgCdTe growth in an OMCVD system

A multi-wavelengthinsitu spectroscopic ellipsometer system is described. The hardware can acquire accurate ellipsometric data at 44 wavelengths in less than one second, is simple and compact, and is well suited forin-situ monitoring of chemical vapor deposition. The software used for data analysis is capable of determining the growth rate and composition of the growing layer in real time. These tools were used to study the organometallic chemical vapor deposition of CdTe, HgTe, and HgCdTe on GaAs. We could obtain the dielectric constants of these materials at the growth temperature and also the growth rate and composition of the layers in real time. Feedback control of CdTe growth was performed by connecting an analog control voltage line from the data acquisition/ analysis computer to the dimethylcadmium mass flow controller. Using dielectric constants of HgCdTe for two different compositions at the growth temperature, composition control of HgCdTe was attempted in a similar manner.     

Synthesis and characterization of conductive copper-based metal-organic framework/graphene-like composites

Metal-organic framework (MOF) incorporating conductive graphene-like layers were synthesized and characterized. The selected MOF, HKUST-1, combines high surface area, water stability, simple preparation and low costs. Graphene-like layers incorporated into the MOF structure were obtained by a two-step oxidation/reduction wet treatment of a high surface carbon black. MOF composites were produced at different carbonaceous layers content. It was shown, through a wide characterization of the samples, that the composites preserve the main features of the parent MOF, additional exhibiting a tunable electrical conductivity.     

Growth of SrTiO3 thin epitaxial films by aerosol MOCVD

SrTiO₃ thin films were prepared by aerosol metal-organic chemical vapour deposition on (001) MgO, R-plane Al₂O₃ and (001) Si single-crystal substrates. Strontium tetramethyl heptadionate and titanium n-butoxide dissolved in diethyleneglycol dimethyl ether were used as precursors. The structure of the films was investigated by X-ray diffraction and transmission electron microscopy. Epitaxial films with [001] and [111] orientation perpendicular to the substrate surface were obtained on MgO and Al₂O₃, respectively. The epitaxial films on the MgO substrate were found to be in a relaxed state with lattice parameters corresponding to the bulk values. SrTiO₃ films on the Si substrate were grown as highly textured in the [011]direction and randomly oriented in the plane parrallel to the substrate surface.     

Synthesis of Metal-containing Polymers via Ring Opening Metathesis Polymerization (ROMP). Part II: Polymers Containing Transition Metals

Following from Part I (this journal, 18(1), 2008), dedicated to main group metal containing polymers obtained by ROMP, the application of the same progressive concept to prepare polymers having this time transition metals in the side- or main-chain is here critically overviewed. These TMC polymers were produced through ROMP reactions promoted by Schrock’s Mo-carbene or the Grubbs’ Ru-carbene catalysts, the most recent and unique methodology for obtaining wished for structures. While discussing main aspects of these target-driven syntheses, as well as properties and applications of the neutral and cationic transition metal containing polymers, emphasis is laid upon organoiron macromolecules based on ferrocene scaffolds. Special attention is given to electrochemical behavior and thermal characteristics. Topics also cover polymers with other transition metals such as Co, Ni, Ru, Pd and Pt, which are important for generating zero valent metal nanoclusters in polymer films. Finally highlighted are some illustrative examples of metal-linked, metallodendrimers and hyperbranched, dendritic and star polymers.

The reaction between Pt- and Pd-cis di-chloro complexes and 4,4′-diethynylbiphenyl: synthesis and characterisation of a ‘zigzag’ metal/poly-yne polymer

The synthesis of poly-yne polymers containing transition metals inserted in the main chain has been attempted by reacting a dialkyne molecule, 4,4′-diethynylbiphenyl (or DEBP), with [PtCl₂(dppe)] and [PdCl₂(dppe)], the platinum- and palladium-cis square-planar di-chlorine complexes containing diphenylphosphine ethane (dppe) as bidentate ligand. The aim of this work was to obtain organometallic polymers ([Pt(dppe)DEBP]_n and [Pd(dppe)DEBP]_n, respectively) having an all-cis ‘zigzag’ structure, by formation of a σ-acetylide bond between the transition metal complexes and the dialkyne molecule. When [PtCl₂(dppe)] was reacted with DEBP, the formation of a chlorine-terminated [Pt(dppe)DEBP]_n oligomer was evidenced; in the reaction involving the Pd(II) complex, on the other hand, [PdCl₂(dppe)] seems to catalyse the polymerisation of DEBP via opening of the triple bond, producing a poly-DEBP polymer containing Pd(II) atoms inserted in the main chain.     

Synthesis of Fatty Acid Esters of Selected Higher Polyols Over Homogeneous Metallic Catalysts

Studies on the synthesis of esters of natural origin fatty acids (oleic acid) and a branched synthetic isostearic acid derived from oleic acid with commercially available selected higher polyols in the presence of homogeneous metallic catalysts have been carried out. The effects of the synthesis temperature, molar ratio and the catalysts amount have also been studied. It was shown that higher fatty acid conversion and selectivity to tri‐ and tetraesters were obtained for organotin catalyst Fascat 2003, which was used as the esterification catalyst. Anti‐wear test confirmed good tribological properties of the obtained esters.     

Preparation and chemical properties of π-conjugated poly(1,10-phenanthroline-3,8-diyl)s with crown ether subunits

π-Conjugated polymers consisting of 1,10-phenanthroline units and crown ether subunits (Poly-1, Poly-2, and Poly-3) were prepared by dehalogenation polycondensation of the corresponding dibromo monomers using a zero-valent nickel complex as a condensing agent. They were characterized by elemental analysis, ¹H NMR and UV–Vis spectroscopies, and cyclic voltammetry (CV). They were partly soluble in CHCl₃, and the number average molecular weight of the soluble part of Poly-2, which had 15-crown-5 subunits, was estimated to be 5300. The polymers exhibited UV–Vis peaks at approximately λ_max = 360 nm, which was reasonable. Complexation with [Ru(bpy)₂]²⁺ and alkaline metal ions made the polymer soluble in organic solvents. The complexation of [Ru(bpy)₂]²⁺ to the 1,10-phenanthroline unit proceeded quantitatively, and the [Ru(bpy)₂]²⁺ complexes exhibited CV curves characteristic of [Ru(N-N)₃]²⁺ complexes.     

Photochemical preparation of aluminium oxide layers via vacuum ultraviolet irradiation of a polymeric hexanoato aluminium complex

By means of photochemical conversion of thin layers of a polymeric hexanoato aluminium complex as the precursor, thin aluminium oxide layers were prepared onto silicon wafers. The precursor compound was synthesized and characterized by several analytical techniques like NMR, FTIR, XPS, ICP, and found to be a polymeric aluminium-containing coordination compound which has been proposed to be a hydroxo-bridged aluminium chain with pendant hexanoyl side-chains ascertained as catena-poly[{di(κ-O,O-hexanoato)aluminium}(μ-hydroxo)] (PHAH). Thin layers deposited from a solution of PHAH in toluene onto silicon wafers were irradiated using VUV radiation from a xenon excimer lamp. The layers were characterized by XPS, XRD, XRR, and spectroscopic ellipsometry. VUV radiation with a radiant exposure of E = 36 J cm⁻² led to almost carbon-free amorphous layers with a composition close to that of alumina having a density of about 2.1 g cm⁻³. Thus, using the example of a polymeric aluminium complex, the potential of the photochemical conversion of metal complexes into oxides could be shown as an alternative method, in addition to sol–gel techniques, for the generation of thin plane metal-oxide layers at normal temperature and pressure.     

Synthesis and Microstructural Investigations of Organometallic Pd(II) Thiol-Gold Nanoparticles Hybrids

In this work the synthesis and characterization of gold nanoparticles functionalized by a novel thiol-organometallic complex containing Pd(II) centers is presented. Pd(II) thiol, trans, trans-[dithiolate-dibis(tributylphosphine)dipalladium(II)-4,4′-diethynylbiphenyl] was synthesized and linked to Au nanoparticles by the chemical reduction of a metal salt precursor. The new hybrid made of organometallic Pd(II) thiol-gold nanoparticles, shows through a single S bridge a direct link between Pd(II) and Au nanoparticles. The size-control of the Au nanoparticles (diameter range 2–10 nm) was achieved by choosing the suitable AuCl₄ ⁻/thiol molar ratio. The size, strain, shape, and crystalline structure of these functionalized nanoparticles were determined by a full-pattern X-ray powder diffraction analysis, high-resolution TEM, and X-ray photoelectron spectroscopy. Photoluminescence spectroscopy measurements of the hybrid system show emission peaks at 418 and 440 nm. The hybrid was exposed to gaseous NO _x with the aim to evaluate the suitability for applications in sensor devices; XPS measurements permitted to ascertain and investigate the hybrid –gas interaction.