Surface morphology and electrical properties of copper thin films prepared by MOCVD

Thin copper films have been grown in a vertical MOCVD (Metal-Organic Chemical Vapor Deposition) reactor using bis(2,2,6,6-tetramethyl-3,5-heptanedionato) copper(II), Cu(thd)₂, as precursor. Deposition has been carried out in a pure hydrogen atmosphere (pressure: 3, 20 mbar) at different substrate temperatures (350–750 ° C). The films have been investigated by profilometry, four-point resistivity measurements, ESCA, AES, XRD, AFM, and Normarsky microscopy. An unusual dependence of the film thickness with deposition time has been observed. Rapid growth occurred in the first minutes resulting in badly conducting films (thickness below 1000 Å). Good electrical resistivities have been obtained above 2000 Å. AFM has been used to gain information about the surface morphology of the films with different thicknesses. The grain size and surface roughness increased with increasing film thickness. Small grains grew in the beginning and the electrical properties have been governed by the highly Ohmic bridges between the individual grains.     

Rechnergesteuerte Kalibrierung ionensensitiver Elektroden

Analytical and Bioanalytical Chemistry - Der üblichen Kalibrierung ionensensitiver Elektroden mit Hilfe von Standardlösungen wird ein rechnergesteuertes Verfahren gegenübergestellt....     

Synthesis,Crystal Structure,and Thermal Behaviour of Some New Copper Complexes with tridentate β-iminoketone ligands

The reaction of Cu(AcO)₂ · H₂O and tridentate β-iminoketone ligands yielded four new copper complexes: acetato{4-{[2-(dimethylamino)ethyl]amino}pent-3-en-2-onato}copper(II) ( 1 ), triacetato{4-{[3-(dimethylamino)-propyl]amino}pent-3-en-2-onato}dicopper(II) ( 2 ), {4-{[2-(dimethylamino)ethyl]amino}-1,1,1-trifluoropent-3-en-2-onato}( trifluoroacetato)copper(II) ( 3 ), and pentaacetato{4-{[3-(dimethylamino)propyl]amino}-1,1,1-trifluoropent-3-en-2- onato}tricopper(II) ( 4 ). All compounds were coloured and air-stable solids. The crystal structures of 1 and the dioxane adduct of 3 , μ-(1,4-dioxane)bis{{4-{[2-(dimethylamino)ethyl]amino}-1,1,1-trifluoropent-3- en-2-onato}(trifluoroacetato)copper(II)} ( 3a ), were determined. Complex 1 consists of dimeric units [{Cu(AcO)L}₂] in the solid state (L = β-iminoketonato ligand). In 3a , two [Cu(CF₃COO)L] are linked via the O-atoms of the coordinated solvent 1,4-dioxane. Compound 1 crystallized in the monoclinic space group P2₁/n with a formula unit in a cell having the dimensions a = 11.152(6)Å, b = 10.104(3)Å, c = 11.805(7)Å, and β = 99.02(4)Å, and compound 3a crystallized in the triclinic space group P1 with a formula unit in a cell having the dimensions a = 8.709(3)Å, b = 9.439(4)Å, c = 12.395(3)Å, α = 67.57(3)°, β = 77.01(2)°, and β = 84.17(3)°. Mass spectra (MS), thermal analysis (DTA/TG), and evaporation-rate measurements are reported for all compounds. The influence of fluorination on the structure and volatility will be discussed.     

Elektronenspinresonanz-, Differentialthermoanalyse- und Molekulargewichtsuntersuchungen an mechanisch beanspruchten Kunststoff-Fäden

Zusammenfassung Polyamid-6-, Polyamid-12-, Polyäthylenterephthalat-, Polyäthylen- und Polypropylenfasern werden im Meßkopf eines ESR-Spektrometers gedehnt. Aus dem Auftreten eines ESR-Spektrums während der Dehnung von Polyamid-6 wird auf die Bildung freier Radikale geschlossen, die durch Kettenbrüche in den amorphen Bereichen entstehen. Bei den anderen Substanzen tritt keine oder nur sehr geringe Radikalbildung auf. Dies wird dadurch erklärt, daß nur in Polyamid-6 die Stabilität der kristallinen Bereiche zur Bildung bis zur Bruchdehnung verspannter Kettenmolekeln in den amorphen Bereichen ausreicht. Diese Vorstellung wird durch Bestimmungen der Molekulargewichte und der Kristallinität der gedehnten Proben gestützt.

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Summary Nylon-6, Nylon-12, polyethyleneterephthalate-, polyethylene- and polypropylene fibers are stretched in the cavity of an ESR-spectrometer. The ESR-spectra formed during stretching of Nylon-6 indicate the formation of free radicals by chain scissions in the amorphous regions. With other polymers no or only very weak ESR-signals are observed. It is suggested that the stability of crystalline regions is sufficient only for Nylon-6 to allow the formation of chains in the amorphous regions which are strained up to their breaking elongation. This is confirmed by determinations of molecular weights and crystallinities of the stretched fibers.

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Mit 17 Abbildungen und 2 Tabellen

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Herrn Prof. Dr.K.-H. Hellwege zum 60. Geburtstag gewidmet.     

Isolation of the lignan secoisolariciresinol diglucoside from flaxseed (Linum usitatissimum L.) by high-speed counter-current chromatography

High-speed counter-current chromatography was successfully used for the isolation and purification of secoisolariciresinol diglucoside, a bioactive lignan from flaxseed (Linum usitatissimum L.). The solvent system consisted of tert.-butylmethyl ether-n-butanol-acetonitrile-water (1:3:1:5). The purity and identity of the isolated compound was checked by high-performance liquid chromatography analysis in combination with mass spectrometry and NMR measurements.     

Synthesis of (S)-(+)-enantiomers of food-relevant (n-5)-monoenoic and saturated anteiso-fatty acids by a Wittig reaction

We developed an enantioselective synthesis for the food-relevant anteiso-fatty acids a15:0, a16:0, and a17:0. Different (carboxyalkyl)triphenylphosphonium bromide salts were coupled with (S)-3-methylpentanal in a Wittig reaction. Mixtures of the obtained cis-/trans-isomers were separated by Ag⁺-HPLC to give the novel cis-isomers of (S)-(+)-a15:1n-5, (S)-(+)-a16:1n-5, and (S)-(+)-a17:1n-5. Hydrogenation of the monoenoic products led to (S)-(+)-a15:0, (S)-(+)-a16:0, and (S)-(+)-a17:0, which are essential for the assessment of the bioactivity of tests with standards of anteiso-fatty acids.     

The Formosalides: Structure Determination by Total Synthesis

Total synthesis allowed the constitution of the cytotoxic marine macrolides of the formosalide family to be confirmed and their previously unknown stereostructure to be assigned with confidence. The underlying blueprint was inherently modular to ensure that each conceivable isomer could be reached. This flexibility derived from the use of strictly catalyst controlled transformations to set the stereocenters, except for the anomeric position, which is under thermodynamic control; as an extra safety measure, all stereogenic centers were set prior to ring closure to preclude any interference of the conformation adopted by the macrolactone rings of the different diastereomers. Late‐stage macrocyclization by ring‐closing alkyne metathesis was followed by a platinum‐catalyzed transannular 6‐exo‐dig hydroalkoxylation/ketalization to craft the polycyclic frame. The side chain featuring a very labile unsaturation pattern was finally attached to the core by Stille coupling.     

The Intermetallic Type-I Clathrate Na8Zn4Ge42

The new intermetallic type-I clathrate Na₈Zn₄Ge₄₂ was obtained by direct reaction of the elements, and its crystal structure was determined by means of single-crystal X-ray diffraction methods. The structure is described in space group Pm3 n (no. 223) with a = 10.6982(1) Å. A mixed Zn/Ge occupancy is found for one of the network sites (6c). Na₈Zn₄Ge₄₂ represents an air-stable electron-precise Zintl phase with exclusively Na cations located in the cavities of a polyanionic host network of four-connected Zn and Ge atoms.