Colin Georgi

Twin Polymerization at Spherical Hard Templates: An Approach to Size‐Adjustable Carbon Hollow Spheres with Micro‐ or Mesoporous Shells

Kitset hollow spheres: The combination of twin polymerization with hard templates makes hollow carbon spheres (HCSs) with tailored properties easily accessible. The thickness and pore texture of the HCS shells and also the diameter of the spherical cavity can be varied. The application potential of synthesized HCS is substantiated by an excellent cycling stability of lithium-sulfur batteries.

A cobalt layer deposition study: Dicobaltatetrahedranes as convenient MOCVD precursor systems

Low melting or liquid cobalt(0) MOCVD precursors of type [Co2(CO)6(η2-RCCR′)] (R = H, R′ = (CH3)3Si, nC4H9, nC5H11, nC6H13, nC7H15; R = nC3H7, R′ = (CH3)3Si, CH3; R = R′ = C2H5, (CH3)3Si) have been prepared by the reaction of the appropriate alkynes with Co2(CO)8. Variation of the substituents at the C,C triple bond allowed the study of their influence on the thermal behaviour and vapour pressure. These measurements showed that the cobalt(0) precursors are suitable for application within the MOCVD (Metal–Organic Chemical Vapour Deposition) process. Decomposing deposition of the cobalt precursors was realized in a home-built vertical cold-wall CVD reactor under mild conditions without any addition of co-reactants. The obtained dense and conformal cobalt layers have been characterized by SEM, EDX and XPS measurements. Depending on the precursor applied, pure cobalt films (96.7% Co) or mixtures of cobalt, carbon and cobalt oxide with varying composition with layer thicknesses of 35–90 nm were formed.

Bis(β-diketonato)- and allyl-(β-diketonato)-palladium(II) complexes: synthesis, characterization and MOCVD application

The syntheses and characterization of the palladium complexes [Pd(accp)2] (7), [Pd(acch)2] (8), [Pd(η3-CH2CMeCH2)(accp)] (11), [Pd(η3-CH2CMeCH2)(acch)] (12), [Pd(η3-CH2CtBuCH2)(accp)] (13) and [Pd(η3-CH2CtBuCH2)(acch)] (14) (accp = 2-acetylcyclopentanoate; acch = 2-acetylcyclohexanoate) are reported. These complexes are available by the reaction of Haccp (2-acetylcyclopentanone) and Hacch (2-acetylcyclohexanone) with Na2[Pd2Cl6] forming 7 and 8 or with [(Pd(η3-CH2CRCH2)(μ-Cl))2] (9, R = Me; 10, R = tBu) forming 11–14. The molecular structures of 7, 8 and 14 are discussed. Complexes 7 and 8 consist of a square-planar coordinated Pd atom with two trans-positioned bidentate β-diketonate ligands. The asymmetric unit of 14 exhibits one molecule of the palladium complex and a half molecule of water. The thermal behavior of 7, 8 and 11–14 and their vapor pressure data were investigated to show, if the appropriate complexes are suited as CVD precursors for palladium layer formation. Thermogravimetric studies showed the evaporation of the complexes at atmospheric pressure upon heating. The vapor pressure of 7, 8 and 11–14 was measured by using thermogravimetric analysis, giving vapor pressure values ranging from 0.62 to 2.22 mbar at 80 °C. Chemical vapor deposition studies were carried out applying a vertical cold wall CVD reactor. Either oxygen or forming gas (N2/H2, ratio 90/10, v/v) was used as reactive gas. Substrate temperatures of 350 and 380 °C were utilized. With 11–14 dense and conformal as well as particulate palladium films were obtained, as directed by SEM studies, whereas 7 and 8 failed to give thin films, which is probably attributed to their high thermal stability in the gas phase. For all deposited layers, XPS measurements confirmed the partial oxidation of palladium to palladium(II) oxide at 380 °C, when oxygen was used as reactive gas. In contrast, thin layers of solely metallic palladium were obtained utilizing forming gas during the deposition experiments.

Chemical vapor deposition of ruthenium-based layers by a single-source approach

A series of ruthenium complexes of the general type Ru(CO)2(P(n-Bu)3)2(O2CR)2 (4a, R = Me; 4b, R = Et; 4c, R = i-Pr; 4d, R = t-Bu; 4e, R = CH2OCH3; 4f, R = CF3; 4g, R = CF2CF3) was synthesized by a single-step reaction of Ru3(CO)12 with P(n-Bu)3 and the respective carboxylic acid. The molecular structures of 4b, 4c and 4e–g in the solid state are discussed. All ruthenium complexes are stable against air and moisture and possess low melting points. The physical properties including the vapor pressure can be adjusted by modification of the carboxylate ligands. The chemical vapor deposition of ruthenium precursors 4a–f was carried out in a vertical cold-wall CVD reactor at substrate temperatures between 350 and 400 °C in a nitrogen atmosphere. These experiments show that all precursors are well suited for the deposition of phosphorus-doped ruthenium layers without addition of any reactive gas or an additional phosphorus source. In the films, phosphorus contents between 11 and 16 mol% were determined by XPS analysis. The obtained layers possess thicknesses between 25 and 65 nm and are highly conformal and dense as proven by SEM and AFM studies.

Atomic layer deposition of ultrathin Cu2O and subsequent reduction to Cu studied by in situ x-ray photoelectron spectroscopy

The growth of ultrathin (<5 nm) Ru-doped Cu2O films deposited on SiO2 by atomic layer deposition (ALD) and Cu films by subsequent reduction of the Cu2O using HCO2H or CO is reported. Ru-doped Cu2O has been deposited by a mixture of 16: 99 mol. % of [(nBu3P)2Cu(acac)] as Cu precursor and 17: 1 mol. % of [Ru(η5-C7H11)(η5-C5H4SiMe3)] as Ru precursor. The catalytic amount of Ru precursor was to support low temperature reduction of Cu2O to metallic Cu by formic acid (HCO2H) on arbitrary substrate. In situ x-ray photoelectron spectroscopy investigations of the Cu2O ALD film indicated nearly 1 at. % of carbon contamination and a phosphorous contamination below the detection limit after sputter cleaning. Systematic investigations of the reduction of Ru-doped Cu2O to metallic Cu by HCO2H or CO as reducing agents are described. Following the ALD of 3.0 nm Cu2O, the ultrathin films are reduced between 100 and 160 °C. The use of HCO2H at 110 °C enabled the reduction of around 90% Cu2O. HCO2H is found to be very effec...

Arylphosphonic acid esters as bridging ligands in coordination polymers of bismuth

Abstract The reaction of the arylphosphonic acid esters 4,4′-[(i-PrO)2P(O)]C6H4C6H4[P(O)(Oi-Pr)2] (L1), 1,3,5-[(i-PrO)2P(O)]3C6H3 (L2), and 5-t-Bu-1,3-[(i-PrO)2P(O)]2C6H3 (L3), respectively, with bismuth halides BiX3 (X=Cl, Br, I) gave seven novel bismuth coordination polymers that have been characterized by single-crystal X-ray diffraction analysis. The solid-state structures of [(BiCl3)(L1)] (1), [(BiBr3)(L1)]·0.25CH3CN (2·0.25CH3CN), [(BiI3)2(L1)]·0.25CH3CN (3·0.25CH3CN), [(BiCl3)(L2)] (4), [(BiCl3)2(L2)] (5), [(BiBr3)2 (L2)]·CH3CN (6·CH3CN), and [(BiCl3)(L3)] (7) are presented. Thermal analysis of [(BiCl3)2(L2)] (5) is indicative of a conversion of the complexes into a bismuth phosphonate by complete i-PrX elimination, whereas for [(BiBr3)2(L2)] (6), elimination of i-PrBr and BiBr3 is assumed. Compounds 1–3 form one-dimensional coordination polymers, whereas two-dimensional networks are observed for compounds 4–7.

Low-temperature chemical vapor deposition of cobalt oxide thin films from a dicobaltatetrahedrane precursor

Cobalt oxides are a promising anode material for lightweight rechargeable lithium-ion batteries. Thus, the low temperature deposition of cobalt oxide is a key-technology for the production of flexible energy storage systems enabling novel application opportunities such as wearables. To satisfy the emerging process requirements the dicobaltatetrahedrane precursor [Co2(CO)6(η2-H–CC–nC5H11)] was investigated for the low-temperature chemical vapor deposition of cobalt oxides. Oxygen, water vapor and a combination of both were examined as possible co-reactants. In particular, wet oxygen proves to be an appropriate oxidizing agent providing dense and high purity cobalt oxide films within the examined temperature range from 130 °C to 250 °C. Film growth occurred at temperatures as low as 100 °C making this process suitable for the coating of temperature-sensitive and flexible substrates.