S. A. Soldatenko

Silicide formation during heat treatment of thin Ni-Pt and Ni-Pd solid-solution films and Pt/Ni bilayers on (111)Si

It is shown that isothermal heat treatment of (Ni-Pt)/Si and Pt/Ni/Si heterostructures leads to the formation of oriented Ni-and Pt-based silicide solid solutions. Owing to the three equivalent azimuth orientations in the basic lattice orientation relationship for the Si-Ni1−xPtxSi system, the resulting silicides have a nanocrystalline substructure. The stability of the substructure is due to the optimal interfacial lattice match and near-special grain-boundary misorientations. The silicide phases Ni1−xPtxSi and Pt1−yNiySi (or Ni1−xPdxSi and Pd1−yNiySi) may undergo segregation, having the same lattice orientation. In both systems, the segregation is associated with the predominant Ni diffusion. The second component (Pt) is shown to stabilize the orthorhombic Ni-based silicide and to prevent NiSi2 formation. Photon processing accelerates diffusion and leads to the formation of phase-pure Ni1−xPtxSi solid solutions.

Orientation, substructure, and optical properties of rutile films

The orientation, optical properties, and substructure of rutile films prepared by thermal and pulsed photon-assisted oxidation of single-crystal Ti films were investigated by transmission electron microscopy, optical spectroscopy, and high-energy electron diffraction. Crystallographic orientation relationships at the contact between titanium and rutile were established, and the energy band gap was determined. It was shown that the luminescence intensity decreased significantly with decreasing grain size from the submicrolevel to nanolevel.

Absorption spectra of TiO2 thin films synthesized by the reactive radio-frequency magnetron sputtering of titanium

The optical absorption spectra of TiO2 thin films with different phase compositions (anatase, rutile-brookite, anatase-rutile-brookite) are studied. The films are produced by the reactive radio-frequency magnetron sputtering of titanium in different atmospheres. It is shown that, on the assumption of the additivity of the contributions of each phase to the general spectrum with the fraction of the phase in the layer known, it is possible to use the method of subtraction of the spectra of individual phases. The fundamental absorption spectra of all of the crystal modifications detected in the multiphase films by structural studies are separated out, and the edges of the optical transitions in all of the phase components are established.

Effect of flash lamp annealing on solid-state reactions in (111)Si-Ni-Pt heterostructures

The effects of flash annealing with xenon arc lamps (λ = 200–1200 nm) and isothermal annealing for 30 min on the phase composition, orientation, and substructure of Pt(25 nm)-Ni(20 nm)-(111)Si(0.38 mm)-Ni(20 nm)-Pt(25 nm) heterostructures have been studied by transmission electron microscopy. The results indicate that solid-state reactions proceed more rapidly on the side under irradiation in comparison with the opposite side. Flash lamp annealing reduces the temperature threshold for silicide formation by 100–150°C.

Structure of heterosystems formed by a SnO2 film and island metal (Ag, Au, or Pd) condensate

We have studied the phase composition and microstructure of thin tin(IV) oxide films surfacemodified with silver, gold, and palladium nanoislands. Using high-energy electron diffraction, we have shown for the first time that the thermal oxidation of the Sn films leads to the formation of nanocrystalline multiphase SnO2 films in which the major phase is orthorhombic. Also present are (in order of decreasing content) tetragonal and cubic phases. Blocks of SnO2(O) subgrains with 〈101〉 texture contain dislocations and stacking faults, which are interpreted as layers of the tetragonal phase. It has been shown that vacuum condensation makes it possible to modify the surface of SnO2 films with noble metals and obtain homogeneous nanoisland coatings characterized by a unimodal, uniform island size distribution.

Orientation and microstructure of chemoepitaxial ZrO2 films

The orientation and microstructure of ZrO2 films produced by oxidizing oriented thin Zr films have been studied by transmission electron microscopy and high-energy electron diffraction. The results demonstrate that biaxial textures of the oxide are governed by the textures of the parent zirconium film. We have established a set of orientation relationships between the Zr and ZrO2 lattices. The nanocrystalline structure of the oxide is due to the fact that there are several equivalent orientations within one Zr grain (multiple-orientation chemoepitaxy). Using high-resolution transmission electron microscopy, we detected twin boundaries, stacking faults, and intragranular dislocations.

Structure and mechanical properties of Ag–Cu films prepared by vacuum codeposition of Au and Cu

We have studied in detail the structure formation process in Ag–Cu films in the course of vacuum deposition of the metals, followed by thermal annealing, and compared the hardness values of nanocrystalline Ag, Cu, and Ag–Cu films. Under equivalent deposition conditions, the hardness of the Ag–Cu films produced by codeposition of the metals exceeds that of the Ag and Cu films. The high hardness of the mixedphase Ag–Cu films is due to their amorphous–nanocrystalline structure. We have determined the limiting grain size above which plastic deformation follows a dislocation mechanism.

Orientation and substructure of chemoepitaxial rutile films

The orientation and substructure of rutile films obtained by oxidation of oriented Ti films are investigated by transmission electron microscopy and high-energy electron diffraction. It is shown that the textures of the oxide are defined by the textures of the initial metal film. A set of orientation relations between the crystal lattices of titanium and rutile is established, and the optimal orientation relation is determined. The dislocation substructure of the high-angle 90° boundaries in TiO2 films is revealed. The size and orientation mismatch at this boundary is compensated by the grain boundary lattice dislocations.

Phase composition, orientation, and substructure of iridium silicide films on silicon

The phase composition, orientation, and substructure of iridium silicide films produced by electron-beam evaporation of Ir on (001) and (111) Si at substrate temperatures from 300 to 1000°C were studied by electron microscopy and diffraction. The results demonstrate that the sequence of silicide formation upon Ir deposition onto heated substrates is the same as upon heat treatment of Ir films deposited at room temperature. It is shown that oriented growth of Ir3Si5 and IrSi0.7 is possible. The IrSi3 /Si interface is shown to be, to some extent, coherent, with the lattice mismatch being accommodated by dislocations in some directions and by elastic strain in other directions. The likely mechanism for the formation of a dislocation structure at the IrSi3 /Si interface is discussed.

Formation of composite scaffolds based on chitosan and calcium phosphate

Composite materials based on chitosan and calcium phosphates with the structure and properties close to those of natural human tissues were developed. The possibility of formation of biological apatite, i.e., octacalcium phosphate, was demonstrated. The increase in the strength characteristics was caused by crystallization of the octacalcium phosphate phase on the surface of the material pore space. The materials resemble the extracellular matrix of the body in their structure and composition and can find wide use in the regenerative medicine as a scaffold for osteogenic factors.