E. V. Shalaeva

Metastable phase diagram of Ti–Si–N(O) films (CSi<30 at.%)

Abstract Metastable ternary concentration diagram of phase formation in arc-deposited films Ti–Si–N(O) ( C Si T dep =300–500 K is presented in this paper along with comparison of the diagram with equilibrium isothermal cross-sections of Ti–Si–N and Ti–Si–O systems. At a temperature of 300 K and C Si >10–15 at.% a transition takes place from metastable supersaturated cubic solution TiSi x N y O z to amorphous state TiSi x N y O z . Intermediate bi-phase area (TiSi x N y O z + Ti 5 Si 3 (O,N) with heterogeneous structure, preceding forming an amorphous state, was found. In the context of the heterogeneous nucleation, kinetics of the deposition of the phases TiSi x N y O z , Ti 5 Si 3 (O,N) was analyzed. It was shown that heterogeneous microstructure of these films and concentration range (on silicon) of the forming bi-phase area is defined by energy parameters of growth kinetics of critical Ti 5 Si 3 (O,N) crystal nucleus. Applicable to the system Ti–Si–N(O) ( C Si x N y O z was considered. Amorphous structures in arc-condensed films of Ti–Si–N(O) (15 C Si x framework, and Ti–N(O) bonds are more preferable as compared to Si–N(O) bonds.

Effect of Doping with 3d Elements (Co, Ni, Cu) on the Intrinsic Defect Structure and Photocatalytic Properties of Nanostructured ZnO with Tubular Morphology of Aggregates

The precursor-derived nanostructured solid solutions Zn0.95M0.05O (M = Co, Ni, Cu) with tubular aggregates have been investigated using optical absorption spectroscopy and electron paramagnetic resonance. The dependences of the concentration of intrinsic defects Vo+ and the effective band gap on the dopant type have been determined. It has been shown using the oxidation reaction of hydroquinone dissolved in water as an example that an increase in the photocatalytic activity in the series ZnO → Zn0.95Ni0.05O → Zn0.95Co0.05O Zn0.95Cu0.05O in the ultraviolet and visible spectral regions correlates with a decrease in the band gap and with an increase in the concentration of oxygen vacancies VO+.

Structural State of β‐Solid Solution in Quenched Quasicrystal‐Forming Alloys of Al61Cu26Fe13

Electron microscopic investigations of the structural state have been carried out for the β(CsCl-type)-phase in the quenched quasicrystal-forming two-phase (ι + β) alloy Al 61 Cu 26 Fe 13 . We conclude that in the vicinity of compositions at which the icosahedral phase (i) is formed, at deviations from the composition Al 3 (Cu,Fe) 2 towards Al(Cu,Fe), the β(CsCl-type)-solid solution has a heterogeneous structure (a state similar to the diffuse incommensurable ω-phase in b.c.c.-solid solutions). This structure includes the β-matrix with fine regions of correlated ω-like displacements which in a certain way are interrelated with the τ 3 -short-range order of substitution. It is concluded that the β(CsCl-type)-phase of Al 61-x Cu 26+y Fe 13-z reveals structural signs typical for electron-stabilized solid solutions, and because of this, the β-phase demonstrates a dielectric behavior of its electronic properties. An assumption has been made that the regions with ω-displacements are involved in the structural transformation β-phase → ι-phase.

Synthesis and structure of quasi-one-dimensional zinc oxide doped with manganese

Nanotubes of manganese-doped zinc oxide Zn1 − xMnxO (0 ≤ x ≤ 0.2) were synthesized by heating the Zn1 − xMnx(HCOO)(OCH2CH2O)1/2 precursor in air at 500°C. The precursor with extended crystals was synthesized by a solvothermal method based on heat treatment of a mixture of Zn1 − xMnx(HCOO)2 · 2H2O with an ethylene glycol excess at 100–130°C. The tubular morphology of Zn1 − xMnxO particles was identified by transmission electron microscopy. Tubular quasi-one-dimensional particles were shown to have a nanodispersed polycrystalline structure, the size of separate crystallites being from 5 to 20 nm. X-ray photoelectron spectroscopy suggested that the manganese distribution on the outer surface layer of Zn1 − xMnxO nanotubes is nonuniform.

Nature of defects in nanocrystalline zinc oxide with particles of tubular morphology

Nanostructured ZnO powders with particles of tubular form were synthesized by a precursor method. A narrow symmetrical line with a g factor of 2.002 was detected in the ESR spectra of the materials. On the basis of analysis of the dependence of the line intensities on the heat treatment conditions it was concluded that the signal belongs to singly charged oxygen vacancies VO+.

Synthesis, microstructure, and native defects of photoactive Zn 1 − x Cu x O solid solutions (0 ≤ x ≤ 0.1) with tubular aggregates

258 Design of photocatalysts based on nanosized zinc oxide for oxidation of toxic and colored organic com pounds has been a perspective direction of research in recent years [1–3]. The efficiency of such materials is determined by their composition, size, and aggregate morphology and microstructure, as well as by the existence of native structural defects. In particular, doping of ZnO with 3d metals or formation of particles of extended shape causes a considerable enhancement of the photocatalytic activity of zinc oxide and often leads to the shift of the catalytic process from the char acteristic UV to the visible spectrum [4, 7]. To fabri cate photocatalysts with enhanced functional charac teristics being active under visible light, we synthesized the Zn1 – xMxO solid solutions (M = Co, Mn, Fe, Ni) with tubular morphology of aggregates [5, 8].

Photoelectron spectroscopy and diffraction of NbOx/Nb(110) surface

Methods of X-ray photoelectron spectroscopy and diffraction were used to investigate the oxygen-induced surface structures on the Nb(110) face which were formed as a result of oxygen segregation from the volume of the crystal upon thermal annealing at 2000 K in a vacuum and/or oxygen adsorption in situ at temperatures higher than 1100 K. The niobium atoms on the crystal surface form quasi-ordered structures in the form of monatomic Nb chains surrounded by oxygen atoms and from the viewpoint of the nearest surroundings and chemical bonding they are close to the states of the metal in NbOx. The thickness of such NbOx-like structure is estimated as 0.5 nm at the degree of coverage of the surface of 50%. Two chemically nonequivalent states of oxygen at Nb(110) have been distinguished, supposedly, (1) atomic chemisorbed oxygen on the surface of Nb metal and (2) oxygen in the composition of NbOx-like clusters on the Nb(110) plane. The NbOx/Nb(110) model of the surface allows for the distortion of the structure of NbOx clusters, i.e., periodic atomic displacements of metal atoms in Nb chains by height and changes in the Nb-O bond angles.

On mutual transformations of icosahedral phase and β-solid solution with participation of ordered ω-like displacements in quenched alloys of Al61Cu26Fe13

Abstract In the rapidly-quenched alloys of Al61Cu26Fe13 characteristic orientation relationships were found between the lattice of the icosahedral phase (ι-phase) and that of the β(CsCl)-solid solution (where β-solid solution contains fine regions of ω-like displacements): [111]β || A2, [110]β || A5. It was established that at the ι-phase (dendrite)/β-solid solution (interdendritic layers) boundary areas there was a state formed with a modulated structure of the ι-phase. It is assumed that the fine regions of ordered ω-like displacements are involved in the continuous transformations (direct and reverse) ι-phase→modulated ι-structure→heterogeneous β-solid solution, going on in the boundary areas due to the strained state of quenched alloys.

Metastable TiSixNyOz films of B1-type structure prepared by the arc process

Abstract Metastable TiSi x N y O z films with the cubic B1-type structure were synthesized by arc deposition. X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and electron microprobe analysis (EMA) methods were employed to study the composition and structure of the films as a function of the arc process parameters: working gas pressure, substrate temperature and potential. It was established that silicon atoms are introduced into the B1-type structure of TiN y O z films and are located in the non-metallic sublattice. The influence of the non-metallic sublattice non-stoichiometry and oxygen impurity content on the silicon concentration in the films was discussed on the basis of the experimental data obtained and the quantum chemical calculations performed.

Structure of epitaxial δ-NbN films deposited by cathode reactive sputtering

Abstract The low-temperature (298–673 K) growth and structure of epitaxial δ-NbN thin films (100–800 A) deposited by reactive sputtering on the (100) NaCl cleavage surface have been studied by transmission electron microscopy. The films have a parallel epitaxial orientation (100)NaCl ∥ (100)NbN and contain microtwin interlayers in the (111) planes. The micro twin content dependence on the background pressure as well as on deposition rate has been found. It has been concluded that microtwins form at the initial growth stage as a result of coalescence of islands of different orientations, (100) and (111), like condensed fcc metal films. The high density of block boundaries and the distortion of coherent growth with small film thicknesses ( h ≈ 100 A ) are attributed to the high activation energy of coalescence and recrystallization processes characteristic of refractory compounds.