I. A. Tambasov

Reversible UV induced metal–semiconductor transition in In2O3 thin films prepared by autowave oxidation

We have prepared thin indium oxide films by the autowave oxidation reaction. Measurements of temperature dependence of resistivity, Hall carrier concentration and Hall mobility have been conducted in the temperature range 5–272 K. Before ultraviolet (UV) irradiation, the indium oxide film had a semiconductor-like temperature dependence of resistivity ρ and the ratio of ρ (5 K)/ρ(272 K) was very limited (∼1.2). It was found that after UV irradiation of the In2O3 film, the metal–semiconductor transition (MST) was observed at ∼100 K. To show that this MST is reversible and repeatable, two full cycles of ‘absence of MST–presence of MST’ have been done using UV irradiation (photoreduction) as the induced mechanism and exposure to an oxygen environment as the reversible mechanism, respectively. MST in transparent conducting oxide (TCO) is possibly associated with the undoped structure of metal oxide, which has some disorder of oxygen vacancies. It was suggested that reversible UV induced metal–semiconductor transition would occur in other TCOs.

Structural and optical properties of thin In2O3 films produced by autowave oxidation

Cubic-phase In2O3 films are produced by the autowave oxidation reaction. Electron microscopy and photoelectron spectroscopy of the atomic profiles show that the samples are homogeneous over the entire area and throughout the thickness, with the typical grain size being 20–40 nm. The optical and electrical properties are studied for In2O3 films fabricated at different pressures in the vacuum chamber. In the wave-length range from 400 to 1100 nm, the transparency of the films was higher than 85%; the resistivity of the films was 1.8 × 10−2 Ω cm.

Solid-state synthesis of the ZnO-Fe 3 O 4 nanocomposite: Structural and magnetic properties

The structural and magnetic properties of ZnO-Fe3O4 nanocomposites produced by the solid-state reaction Zn + 3Fe2O3 → ZnO + 2Fe3O4 upon annealing of Zn/α-Fe2O3 films under vacuum at a temperature of 450°C have been studied. Ferrimagnetic Fe3O4 clusters with an average grain size of 40 nm and a magnetization of ∼430 emu/cm3 at room temperature, which are surrounded by a ZnO layer with a large contact surface, have been synthesized. The magnetic characteristics of the ZnO-Fe3O4 nanocomposite in the temperature range of 10–300 K have been presented.

Structural and magnetic features of solid-phase transformations in Mn/Bi and Bi/Mn films

Solid-phase transformations at different annealing temperatures in Mn/Bi (Mn on Bi) and Bi/Mn (Bi on Mn) films have been studied using X-ray diffraction, electron microscopy, and magnetic measurements. It has been shown that the synthesis of the α-MnBi phase in polycrystalline Mn/Bi films begins at a temperature of ~120°C and the Mn and Bi layers react completely at 300°C. The resulting α-MnBi(001) samples have a large perpendicular magnetic anisotropy (Ku ≃ 1.5 × 107 erg/cm3) and a coercive force H > HC ~ 3 kOe. In contrast to Mn/Bi, the ferromagnetic α-MnBi phase in Bi/Mn films is not formed even at annealing processes up to 400°C and Mn clusters are formed in a Bi melt. This asymmetry in phase transformations occurs because chemosorbed oxygen existing on the surface of the Mn film in Bi/Mn films suppresses a solid-phase reaction between Mn and Bi. The analysis of the results obtained implies the existence of new low-temperature (~120°C) structural transformation in the Mn–Bi system.

High rotatable magnetic anisotropy in epitaxial L10CoPt(111) thin films

The evolution of the structural and magnetic properties in epitaxial film systems Co/Pt(111) of equiatomic composition during vacuum annealing has been presented. Annealing to the temperature of 400°C does not lead to the variation of the structural and magnetic properties of the films, which indicates the absence of considerable mixing of the Co/Pt interface. With the increase in the annealing temperature from 400 to 750°C, nanoclusters containing the main magnetically hard L10CoPt(111) phase epitaxially intergrown with the CoPt3 phase are formed. High rotatable magnetic anisotropy has been found in the prepared films. In magnetic fields above the coercive force (H > HC = 8 kOe), the easy anisotropy axis with the angle of lag taken into account can be oriented in any spatial direction. Possible mechanisms of the formation of the rotatable magnetic anisotropy have been discussed. It has been assumed that the high rotatable magnetic anisotropy makes the main contribution to the magnetic perpendicular anisotropy in CoxPt1–x films.

Solid-state synthesis, structural and magnetic properties of CoPd films

The results of the investigation of the structural and magnetic properties of CoPd films with equiatomic composition have been presented. The films have been synthesized by vacuum annealing of polycrystalline Pd/Co and epitaxial Pd/α-Co(110) and Pd/β-Co(001) bilayer samples. It has been shown that, for all samples, the annealing to 400°C does not lead to the mixing of layers and the formation of compounds. A further increase in the annealing temperature results in the formation of a disordered CoPd phase at the Pd/Co interface, which is fully completed after annealing at 650°C. The epitaxial relationships between the disordered CoPd phase and the MgO(001) substrate are determined as follows: CoPd(110)〈

Temperature-dependent Photoconductance and Optical Properties of In2O3 Thin Films Prepared by Autowave Oxidation

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