Nikolay V. Gelfond

Preparation of thin films of platinum group metals by pulsed MOCVD. II. Deposition of Ru layers

In situ high-temperature mass spectrometry is used to analyze the thermal decomposition of Ru(acac)3 and Ru(nbd)(allyl)2 vapor and possible schemes of thermal transformations on the heated surface. By pulsed MOCVD with in situ mass spectrometric control of deposition processes ultrathin Ru layers with a thickness of several nanometers are obtained. The role of the reaction medium, precursor nature, and deposition temperature in the formation of a nanocrystalline structure of the films is revealed. Ruthenium films with a compact continuous structure are formed from Ru(acac)3 and hydrogen at a deposition temperature of 340°C and below; an increase in the temperature results in the growth of nanogranular Ru layers. Regardless of deposition conditions, from Ru(nbd)(allyl)2 granular nanocrystalline Ru layers are formed

Chemical vapor deposition of electrolyte thin films based on yttria-stabilized zirconia

Gas-tight electrolyte films are obtained by chemical vapor deposition for solid oxide fuel cells from yttria-stabilized zirconia (YSZ) with a thickness of 4–15 μm on supporting porous ceramic anodes (YSZ/NiO). Volatile metal complexes with dipivaloylmethane Zr(dpm)4 and Y(dpm)3 are used as precursors. On the basis of an analysis of thermal properties of the starting compounds, parameter ranges in deposition processes are determined. Dependences of the structure, composition, and electrical characteristics on deposition conditions are found for YSZ electrolyte films. Electrochemical solid oxide fuel cells that operate at low temperatures with an open circuit voltage of 0.98–1.08 V and specific power up to 440 mW/cm2 at 1073 K and 1200 mW/cm2 at 1173 K are constructed.

Novel N-Containing Precursors of Nickel(II) for Film Deposition by MOCVD

The synthesis of volatile nickel(II) complexes with Ncontaining ligands like R(O,N)C(CH3)CH2C(CH3)NR (R – H, radical group) was carried out in inert atmosphere. The substances were characterized by means of elemental analysis, IRand NMR-spectroscopy, melting point, mass spectrometry. The thermal behavior of the compounds in the solid state was investigated by the method of thermogravimetry and difference-scanning calorimetry (DSC) in vacuum and helium. The thermodynamic characteristics of the melting processes (m.p., ∆meltHm.p., ∆meltSm.p.) were also determined by DSC: m.p. 157.5 ± 2 and 247.2 ± 1,2oC, ∆meltHm.p. = 25 ± 2 and 41,7 ± 0,3 kDj/mol, ∆meltSm.p. = 58 ± 5 and 80,1 ± 1,2 Dj/mol K for Ni(N(Me)C(CH3)CHC(CH3)N(Me))2 and Ni(OC(CH3)CHC(CH3)NH)2 respectively. Using the Knudsen method with mass spectrometric registration of gas phase and static method with quartz zero-manometer the temperature dependences of saturated vapor pressure of complexes were studied, the standard thermodynamic parameters of enthalpy and entropy of sublimation process were determined (Fig.1). The standard thermodynamic parameters of ones of evaporation process were calculated from data on sublimation and melting processes. It was shown that complex with ketoamine ligand is more thermodynamically stable in solid state than diimine analogue whereas the last one is more volatile that O-containing compound. By means of in situ high temperature mass spectrometry the thermodecomposition process of Ni(N(Me)C(CH3)CHC(CH3)N(Me))2 vapor was studied in vacuum temperature range of destruction and gas byproducts were determined (Fig.2). At temperatures 130– 250oC the first step of decrease of ion current intensity for metal-containing ion is observed that is apparently connected with forming of oligomers on surface being accompanied by isolation of 2-methylamino-4methylimino-2-pentene to gas phase. The decomposition of just formed on surface structures is hypothetically beginning at temperatures upper 250oC and is accompanied by isolation of products pointed on Fig.2. to gas phase. On account of the analysis of temperature behavior of reaction products the scheme of mechanism of chemical transformation on heated surface was proposed. The complexes have been used as precursors for the Ni-containing film formation by Metal-Organic Chemical Vapor Deposition. The film decomposition conditions were chosen on the base of information about thermal behavior of complexes. The experiments were carried out in hydrogen at substrate temperature 320– 370oC. The films obtained were investigated by using different methods: SEM, XRD etc. 1,9 2,0 2,1 2,2 2,3 2,4 2,5 2,6 2,7 2,8 2,9 -3,5 -3,0 -2,5 -2,0 -1,5 -1,0 -0,5 0,0 0,5 1,0 1,5 2,0

Thermal Properties of Some Volatile Titanium (IV) Precursors

The tensimetric study was carried out for TTIP, Ti[OEt]4 and Ti[DMAP]4 by means of static method with a quartz membrane zero-manometer and flow method using He as gas-carrier (the compounds were assumed to vaporize in a monomolecular form) in a wide range of temperatures. Temperature dependencies of saturated vapor pressure were measured; the evaporation thermodynamic parameters have been calculated (Table 1). Data obtained for TTIP can be compared with values calculated from literature data [1, 2].

Deposition of refractory coatings on carbon fibers from volatile Hf-containing precursors

The possibility to modify the carbon fiber surface by refractory hafnium compounds via chemical vapor deposition of volatile metal-organic complexes is studied. Thermodynamic modeling is applied to calculate the CVD diagram of the Hf-C-O-F-H system within a 25–1200°C temperature range, 10−1–10 Torr pressure range, and 0–2000 hydrogen/precursor vapor ratio. It is demonstrated that the deposition should be carried out at the maximum hydrogen flow and the minimum total pressure in the system. SEM and AFM techniques are used to examine the morphology and topography of the coatings on the fibers. Continuous coatings that are uniform in length and diameter of monofilaments and are tightly bound to them are obtained.

Chemical Composition and Structure of Thin Films Produced by Chemical Vapor Deposition

This paper reports results from studies of the chemical composition and structure of semiconducting, dielectric, and metallic films produced from molecular precursors by the chemical vapor deposition method. A study was made of films of zinc sulfides, mixed copper, cadmium, and zinc sulfides, boron nitride, carbonitride, silicon carbonitride, and iridium films. It is shown that the use of metal compounds with different ligands (zinc and manganese) enables production of zinc sulfide films in which manganese ions are uniformly incorporated into the zinc sulfide crystal lattice to substitute zinc at the lattice sites. For the films of simple and mixed cadmium, copper, and zinc sulfides, the film structure depends on the type of substrate. The thin layers of mixed cadmium and zinc sulfides are asubstitution solution with a hexagonal structure. The thin layers of boron nitride produced from borazine exhibit a nanocrystalline structure and are a mixture of cubic and hexagonal phases. Composite layers were produced from alkylamine boranes and their mixtures with ammonia. Depending on synthesis conditions, the layers are mixtures of hexagonal boron nitride, carbide, and carbonitride or pure boron nitride. Using silyl derivatives of asymmetric dimethylhydrazine containing Si—N and C—N bonds in the starting molecule, we produced silicon carbonitride films whose crystal habit belongs to a tetragonal structure with lattice parameters a = 9.6 Å and c = 6.4 Å. The iridium films obtained by thermal decomposition of iridium tris‐acetylacetonate(III) on quartz substrates in the presence of hydrogen have a polycrystalline structure with crystallite sizes of 50 to 500 Å. A method for determining grain‐size composition was proposed, and grain shapes for the iridium films were analyzed. The influence of substrate temperature on the internal microstructure and growth of the iridium films is demonstrated. At the iridium–substrate interface, a transition layer forms, whose composition depends on the substrate material and deposition conditions.

Structure of platinum coatings obtained by chemical vapor deposition

To the best of our knowledge, it is the first time that the method of chemical vapor deposition (MOCVD) with platinum(II) bis(acetylacetonate) (Pt(acac)2) is used to obtain platinum coatings on the cathodes and anodes of the electrodes for pacemakers. The deposition processes are carried out under reduced pressure in the presence of oxygen. The phase and elemental composition, structure, and morphology of the coatings are examined by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). Platinum coatings with a columnar structure are prepared in the temperature range 280-340°C. An increase in the deposition temperature leads to a change in the structure of the coatings and reduction in their thickness. Cyclic voltammetry (CV) is used to estimate the specific capacities of the platinum coatings on the cathodes and anodes, the maximum values of which are 426 mC/cm2 and 1160 mC/cm2, respectively.

Crystallochemical study of ruthenium(III) tris-dipivaloylmethanate

The structure of ruthenium(III) dipivaloylmethanate is determined by single crystal X-ray diffraction at temperature of 150 K. The crystallographic data for C33H57O6Ru are as follows: a = 9.6119(11) Å, b = 17.4603(19) Å, c = 21.519(2) Å, β = 95.187(2)°, C2/c space group, V = 3596.7(7) Å3, Z = 4, dcalc = = 1.202 g/cm3, R = 0.0642. The structure is molecular, the metal atom coordinates six oxygen atoms of three ligands of β-diketone. The Ru–O distances are in the range of 1.99 Å to2.03 Å. The complexes have a distorted single layer hexagonal packing with the Ru…Ru distances being 9.84 Å within the layer, and 10.93 Å between the layers.