Dmitry M. Tsymbarenko

Chemical synthesis of high quality epitaxial vanadium dioxide films with sharp electrical and optical switch properties

The effective preparation method of epitaxial VO2 films on the r-Al2O3 substrates based on the MOCVD technique and post-deposition annealing is described. The composition, orientation and morphology of the films obtained were investigated by Raman spectroscopy, XRD, EBSD, XPS, SEM and AFM methods. The samples obtained demonstrate high crystal quality and excellent physical properties: sharp metal-insulator (>104 resistance change) and intensive optical reflectivity (IR and THz regions) transitions. The model of VO2 film recrystallization based on the peritectic decomposition of intergrain vanadium oxide phases is proposed.

Mixed ligand acetate, propionate, and pivalate complexes of rare earth metals with monoethanolamine: A new approach to the synthesis, composition, structure, and use for the preparation of oxide materials

Compositions of mixed ligand acetate, propionate, and pivalate complexes of rare earth metals of the cerium and yttrium groups with monoethanolamine are predetermined by the synthesis conditions and the nature of the carboxylate ligand and rare earth metal ion. Solid mixed ligand complexes [Ln(Piv)5(MEAH)][MEAH] and [Ln(Piv)3(MEA)], homoligand complexes [Ln(Piv)3] (HPiv is 2,2-dimethylpropionic (pivalic) acid), and gel-like hydroxo complexes [Ln(Carb)3–x–y(NO3)x-(OH)y(MEA)w(H2O)z] (HCarb is acetic (HAc) or propionic (HProp) acid) are isolated using original synthesis procedures involving ion pairs [MEAH]+[Carb]– (MEA is monoethanolamine). The compounds are studied by IR spectroscopy, 1H NMR spectroscopy, elemental and thermal analyses, and mass spectrometry. Specific features for the complex formation of rare earth metal pivalates with MEA are additionally studied using quantum-chemical simulation.

Yttrium tris-propionate monohydrate: Synthesis, crystal structure, and thermal stability

The complex [Y(Prop)3(H2O)]∞ (I) was prepared by treating yttrium carbonate, acetate, or acetylacetonate hydrates with propionic acid and characterized by the data of elemental analysis, IR spectroscopy, X-ray diffraction, and thermal analysis in air. Complex I has a polymeric layered structure with clear-cut structure-forming dimeric groups bridged by bidentate ligands. Only van der Waals interactions occur between the adjacent polymeric layers. In air, yttrium propionate monohydrate I is completely converted to the oxide at 600°C.

Chemical deposition of smooth nanocrystalline Y2O3 films from solutions of metal-organic precursors

A series of (Y(AcO)3·4H2O—Q—Solv) solutions (Q is monoethanolamine (MEA), diethanolamine (DEA), en, dien; Solv = MeOH, EtOH, PriOH, BuOH) was studied to choose the metal-organic precursor for surface smoothing treatment of metallic tapes by chemical deposition of nanocrystalline yttria films. Based on the results of viscosity, wetting angle, and thermal stability measurements, a solution (Y(AcO)3·4H2O—dien—PriOH) was proposed as a new metal-organic precursor. After chemical deposition of nanocrystalline yttria films about 300 nm thick on a Hastelloy C-276 metallic tape the surface roughness was reduced by a factor of 11 (from 9.0 to 0.8 nm on a surface area of 5×5 μm2).

Synthesis and crystal structures of [K(H2O)(Piv)]∞ and [K2(Phen)(H2O)2(Piv)2]∞

A method for the synthesis of potassium pivalates (trimethylacetates) from potassium tert-butoxide and pivalic acid was proposed. The complexes of the formulas [K(H2O)(Piv)]∞(I) and [K2(Phen)(H2O)2(Piv)2]∞ (II) (Piv denotes the pivalate anion and Phen denotes 1,10-phenanthroline) were obtained and characterized by elemental analysis and IR and 1H NMR spectroscopy. The crystal structures of complexes I and II were determined using X-ray diffraction. Crystal structure I has a layered motif with two nonequivalent K atoms (C.N.s 5 + 2 and 6). The coordination of phenanthroline in II gives rise to a ribbon motif, the structure containing three nonequivalent K atoms (C.N.s 6, 6 + 1, and 8).

A novel dimeric complex of barium bis(hexafluoroacetylacetonate) with triglyme: Synthesis, structure, and volatility

181 The interest in mixed ligand complexes of barium bis(hexafluoroacetylacetonate) (Ba(hfa)2) with poly glymes is caused by their high volatility and the possi bility of using them as volatile precursors in the metal organic chemical vapor deposition (MOCVD) method [1]. At present time, this method is widely used in technology of fabrication of second genera tion high temperature superconductive (HTSC) wires based on yttrium barium cuprate RBa2Cu3O7 – x [2].

Spin-State Transition, Magnetism and Local Crystal Structure in Eu1-xCaxCoO3-δ

The doping series Eu1-xCaxCoO3-δ provides a rather peculiar way to study the spin-state transitions in cobalt-based complex oxides since partial substitution of Eu3+ ions by Ca2+ ions does not increase the mean valence of cobalt but is accompanied by appearance of oxygen vacancies in the ratio δ∼ x/2. In the parent compound EuCoO3, the low spin (LS)–intermediate spin (IS) or high spin (HS) transition takes place at temperatures so high that the chemical decomposition prevents its direct observation. The substitution of Eu3+ by Ca2+ shifts the spin state transition to lower temperatures and the associated energy gap Δ in octahedrally-coordinated Co3+ ions changes from 1940 K in EuCoO3 to 1540 K in Eu0.9Ca0.1CoO2.95 and 1050 K in Eu0.8Ca0.2CoO2.9. Besides, each O2- vacancy reduces the local coordination of two neighboring Co3+ ions from octahedral to pyramidal thereby locally creating magnetically active sites which couple to dimers. These dimers form another gapped magnetic system with a very different ene...

Aluminum hydroxocarboxylates in solution deposition of planarization alumina films

Aluminum hydroxocarboxylates derived from butyric, pivalic, valeric, and isovaleric acids were synthesized and characterized. The synthesized hydroxocarboxylates were suspended in isopropanol and reacted with diethylenetriamine and monoethanolamine, which acted as hydrolyzing and complex-forming agents, to obtain precursor solutions for chemical deposition of smooth amorphous alumina films on metal substrates.

Thermodynamics of vaporization of the mixed-ligand complex of sodium dipivaloylmethanate with o-phenanthroline Na(thd)(phen)

Vaporization of the complex between sodium dipivaloylmethanate and o-phenanthroline Na(thd)(phen) is studied using the Knudsen effusion method and mass spectral analysis of the gas-phase composition. Sublimation of the compound is found to occur congruently. Saturated vapor predominantly consists of o-phenanthroline molecules C12H8N2, trimeric molecules Na3(thd)3, and a minor amount of Na4(thd)4 and Na(thd)(phen) molecules. The absolute partial pressures and enthalpies of sublimation of the gas-phase components, as well as the ΔfG0(T) of formation of the complex from Na(thd)(s) and Phen(l), are calculated. The standard enthalpy of dissociation of gaseous Na(thd)(phen) into Na3(thd)3(g) and Phen(g) is estimated.