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The single-walled carbon nanotube-based thin films with a thickness from 11 ± 3 to 157 ± 18 nm have been formed using vacuum filtration. The thermal conductivity of the thin films as a function of thickness and temperature up to 450 K has been studied by the 3ω technique. It has been found that, in the region of 49 nm, the supplied heat from a gold strip started propagating with the high efficiency to the thin film plane. The thermal conductivity of the thin films with a thickness of 49 ± 8 nm was measured using the 3ω technique for bulk samples. It has been found that the thermal conductivity of the single-walled carbon nanotube-based thin films strongly depends on their thickness and temperature. The thermal conductivity sharply (by a factor of ~60) increases with an increase in thickness from 11 ± 3 to 65 ± 4 nm. In addition, it has been observed that the thermal conductivity of the thin film with a thickness of 157 ± 18 nm rapidly decreases from 211 ± 11 to 27.5 ± 1.4 W m–1 K–1 at 300 and 450 K, respectively.

Aluminum-doped zinc oxide thin films have been grown by atomic layer deposition at a temperature of 200°C. Using X-ray diffraction, it has been established that the ZnO:Al thin films exhibits the reflections from the (100), (002), (110), and (201) ZnO hexagonal phase planes. The (101) and (102) planes have also been detected by electron diffraction. The ZnO:Al thin films grow smooth with a root-mean-square roughness of Rq = 0.33 nm and characteristic nanocrystallite sizes of ~70 and ~15 nm without additional aluminum or aluminum oxide phases. The transmission at a wavelength of 550 nm with regard to the substrate has been found to be 96%. The refractive indices and absorption coefficients of the ZnO:Al thin films in the wavelength range of 250–900 nm have been determined. The maximum refractive indices and absorption coefficients have been found to be 2.09 at a wavelength of 335 nm and 0.39 at a wavelength of 295 nm, respectively. The optical band gap is 3.56 eV. The resistivity, Seebeck coefficient, and power factor of the ZnO:Al thin films are ∼1.02 × 10–3 Ω cm, –60 μV/K, and 340 μW m–1 K–2 at room temperature, respectively. The maximum power factor attains 620 μW m–1 K–2 at a temperature of 200°C.

This Letter presents the results of a study of the physical properties of micromesh transparent electrodes on a flexible substrate, obtained using a template in the form of silica layers subjected to controlled cracking. For the first time, a combined approach to the control of parameters of a micromesh structure (crack width and cell size) by varying the pH and the thickness of the sol layer is proposed. Using this approach, transparent electrodes with a surface resistance of 4.1 Ω/sq with a transparency of 85.7% were obtained. Micromesh electrodes are characterized by linear optical transmission in the visible and IR ranges, which opens up prospects for their use in optoelectronics.

Thin films have been produced via a spray method from commercially available single-walled carbon nanotubes (SWCNTs). A SWCNT film thickness has ranged from ~10 to ~80 nm. The SWCNT diameter has accepted values of 1.6–1.8 nm. The existence of SWCNTs longer than 10 μm is established. The optimal thickness of a SWCNT thin film is found to be ~15 nm at which the transmittance exceeds 85%. The specific resistance of SWCNT thin films goes from ~1.5 × 10–3 to ~3 × 10–3 Ohm cm at room temperature. The pioneering study of the temperature dependences of the Seebeck coefficient and surface resistance is performed for this type of SWCNT. A surface resistance is found to increase with rising temperature. Furthermore, the Seebeck coefficient of SWCNT thin films weakly depends on temperature. Its value for all samples is evaluated to be ~40 μV/K. According to the sign of the Seebeck coefficient, thin films exhibit hole-type conductivity. Moreover, the power factor of a 15-nm thin SWCNT-film decreases with a temperature increase to 140◦C from the value of approximately ~120 to ~60 μW m–1 K–2. A further rise in temperature has led to a gain in the power factor.

The results of structural and magnetic investigations of nanogranular Co–Al2O3 films formed from Co3O4/Al thin-film layered structures upon vacuum annealing are reported. The Co3O4/Al films have been obtained by sequential reactive magnetron sputtering of a metallic cobalt target in a medium consisting of the Ar + O2 gas mixture and magnetron sputtering of an aluminum target in the pure argon atmosphere. It is shown that such a technique makes it possible to obtain nanogranular Co–Al2O3 single- and multilayer thin films with a well-controlled size of magnetic grains and their distribution over the film thickness.

PMMA opal crystal was prepared by a simple hybrid method, which includes sedimentation, meniscus formation and evaporation. We investigated three surfaces of this crystal by angle-resolved reflective light spectroscopy and SEM study. The angle-resolved reflective measurements were carried out in the 400–1100 nm range. We have determined the high-quality ordered surface of the crystal region. Narrow particle size distribution of the surface has been revealed. The average particle diameter obtained with SEM was nearly 361 nm. The most interesting result was that reflectivity of the surface turned out up to 98% at normal light incidence. Using a fit of dependences of the maximum reflectivity wavelength from an angle based on the Bragg–Snell law, the wavelength of maximum 0° reflectivity, the particle diameter and the fill factor have been determined. For the best surface maximum reflectivity wavelength of a 0° angle was estimated to be 869 nm. The particle diameter and fill factor were calculated as 372 nm and 0.8715, respectively. The diameter obtained by fitting is in excellent agreement with the particle diameter obtained with SEM. The reflectivity maximum is assumed to increase significantly when increasing the fill factor. We believe that using our simple approach to manufacture PMMA opal crystals will significantly increase the fabrication of high-quality photonic crystal templates and thin films.

We have synthesized ferromagnetic nanocomposite Co-Al 2 O 3 thin films via a thermite reaction between Al and Co 3 O 4 with layer geometry. The starting Al/Co 3 O 4 bilayers were obtained by the deposition of Al layers onto Co 3 O 4 films at room temperature and were annealed at temperatures between 50 and 700 °C at 50 °C intervals. Above ∼450 °C the Co 3 O 4 partially transformed into the CoO phase. The simultaneous solid-state reactions of Al with Co 3 O 4 and Al with CoO started above the initiation temperature T in ∼500 °C, which did not depend on the bilayer thickness. After annealing at 700 °C about 60% of the Co was reduced by the Al and the rest of the Co was contained in intermediate CoAl 2 O 4 shells, which separated the Co nanoparticles from the Al 2 O 3 matrix. Above 700 °C the reaction was complete and the final products were noninteracting Co nanoparticles with an average size of ∼40 nm enveloped by CoAl 2 O 4 shells, which embedded into a dielectric Al 2 O 3 matrix. The synthesized Co-Al 2 O 3 nanocomposite films possessed soft magnetic behavior and good chemical stability.

Flexible film broadband absorber based on diamond-graphite mixture and polyethylene was fabricated by hot pressing. The film thickness of the absorber was 90 μm. We have measured angular reflectivity, diffusional reflectivity and transmittance in the range 85–8000 cm −1 (117–1.25 μm) in order to determine the absorption. It was shown that room temperature pressing of mesh print with 250 μm step significantly reduces reflectivity of the absorber. The absorption was over 0.85 in the range 85–320 cm −1 (117–31.25 μm) and >0.98 in the range 320–8000 cm −1 (31.25–1.25 μm). We believe that the designed and manufactured absorber might become a promising material for optical devices where high broadband absorption and flexibility are required.

The preparation of composite transparent electrodes of poly(3, 4-ethylenedioxythiophene) polystyrene sulfonate/single-wall carbon nanotubes by the spray method is described. The influence of the successive treatment of each functional layer in acid media with different activities on the optical and electric film characteristics is considered. The composite with the surface resistance of 89 Ω/sq at the transparency of 85.3% (550 nm) on a polymer substrate is obtained.

The thin-film solid-state reaction between elemental Ge and Mn across chemically inert Ag layers with thicknesses of (0, 0.3, 1 and 2.2 µm) in Ge/Ag/Mn trilayers was studied for the first time. The initial samples were annealed at temperatures between 50 and 500 °C at 50 °C intervals for 1 h. The initiation temperature of the reaction for Ge/Mn (without a Ag barrier layer) was ~ 120 °C and increased slightly up to ~ 250 °C when the Ag barrier layer thickness increased up to 2.2 µm. In spite of the Ag layer, only the ferromagnetic Mn5Ge3 compound and the Nowotny phase were observed in the initial stage of the reaction after annealing at 500 °C. The cross-sectional studies show that during Mn5Ge3 formation the Ge is the sole diffusing species. The magnetic and cross-sectional transmission electron microscopy (TEM) studies show an almost complete transfer of Ge atoms from the Ge film, via a 2.2 µm Ag barrier layer, into the Mn layer. We attribute the driving force of the long-range transfer to the long-range chemical interactions between reacting Mn and Ge atoms.

Co–ZrO 2 ferromagnetic nanocomposite thin films were successfully synthesized using a new thermite reaction between Zr and Co 3 O 4 in layer geometry. The initial Zr/Co 3 O 4 bilayers were obtained by the deposition of Zr layers onto Co 3 O 4 films at room temperature. The process of mixing at the Zr/Co 3 O 4 interface and synthesis of fine-crystalline Co and amorphous ZrO 2 phases started at a temperature above the initiation temperature T in ∼250 °С which did not depend on the bilayer thickness. For the bilayer thickness more than 300 nm high-temperature fcc-Co and cubic c-ZrO 2 (or tetragonal t-ZrO 2 ) phases were formed. For the bilayer thickness less than ∼50 nm stable low-temperature hexagonal hcp-Co and monoclinic m-ZrO 2 phases were also present in the reaction product. A partial transformation from Co 3 O 4 to CoO occurred after annealing at 300 °С. The secondary reaction between CoO and Zr started soon after Co 3 O 4 had been converted to the CoO phase. After annealing at 500 °С more than 80% of Co was reduced and the final product contained Co nanoparticles above and below the superparamagnetic critical size embedded into a dielectric ZrO 2 matrix. The synthesized Co–ZrO 2 nanocomposite films possessed soft magnetic behavior, high magnetization and good chemical stability.

The dispersions of semiconducting (sc-) and metallic (m-) SWCNTs with purity more than 98 and 86%, correspondingly, were obtained by using the aqueous two-phase extraction method. The unseparated (un-) SWCNTs contained ~3/4 of semiconducting and ~1/4 of metallic nanotubes. Thin films based on unseparated, semiconducting and metallic SWCNTs were prepared by vacuum filtration method. An Atomic Force Microscopy (AFM) and a Transmission Electronic Microscopy (TEM) were used to investigate the thin film microstructure. The thin SWCNT film transmittance was measured in the wavelength range of 300–1500 nm. Thermoelectric properties were carried out in the temperature range up to 200 °C. The largest Seebeck coefficient was observed for thin films based on semiconducting SWCNTs. The maximum value was 98 μV/K under the temperature of 170 °C. The lowest resistivity was 7.5·10−4·Ohm·cm at room temperature for thin un-SWCNT films. The power factor for m-SWCNT and un-SWCNT films was 47 and 213 μW m−1 K−2, correspondingly, at room temperature and 74 and 54 μW m−1 K−2 at 200 °C, respectively. For a thin sc-SWCNT film the maximum power factor was 2.8 μW m−1 K−2 at 160 °C. The un-SWCNT film thermal conductivity coefficient was 5.63 and 3.64 W m−1 K−1 and a thermoelectric figure of merit was 0.011 and 0.016 at temperatures of 23 and 50 °C, respectively.

Текст статьи не публикуется в открытом доступе в соответствии с политикой журнала. 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. Твердофазные превращения в зависимости от температуры отжига в Mn/Bi (Mn на Bi) и Bi/Mn ( Bi на Mn) пленках исследовались с использованием рентгеновской дифракции, электронной микроскопии и магнитных измерений. Показано, что синтез альфа-MnBi фазы в поликристаллических Mn/Bi пленках начинается при при температуре 120 К и при 300 К слои Mn и Bi реагируют полностью. Полученные образцы альфа-MnBi(001) обладали большой перпендикулярной анизотропией и большой коэрцитивной силой H>Hc =3 kЭ. В отличие от Mn/Bi в пленках Bi/Mn даже при отжигах до 400 С ферромагнитная альфа-MnBi фаза не образовывалась, а наблюдалось образование кластеров Mn в расплаве Bi. Данная асиметрия в фазовых превращениях объясняется существованием в пленке Bi/Mn на поверхности Mn хемосорбционного кислорода, который подавляет твердофазную реакцию между Mn и Bi. На основании анализа результатов проведенныъх исследований предполагается существование низкотемпературного (120 С) структурного превращения в Mn-Bi-системе.

The negative magnetoresistance of thin In 2 O 3 films, obtained by an autowave oxidation reaction, was detected within a temperature range of 4.2–80 K. The magnetoresistance was –1.35% at a temperature of 4.2 K and an external magnetic field of 1 T. A weak localization theory was used to explain the negative magnetoresistance and to determine the phase-coherence length in a temperature range of 4.2–80 K. The phase-coherence length was found to oscillate as the temperatures increased to around 30 K. From the maximum and minimum values of the oscillation of the phase-coherence length, it was suggested that the In 2 O 3 film has two structure characteristic parameters. Transmission electron microscopy showed the structure of the thin In 2 O 3 film to have structural features of a «crystal phase – amorphous phase». It was found that the crystalline phase characteristic size was consistent with the maximum phase-coherence length and the amorphous phase characteristic size was consistent with the minimum phase-coherence length. It has been suggested that the temperature measurements of the magnetoresistance and the theory of weak localization can be used to evaluate the structural features of nanocomposite or nanostructured thin films.