Thickness Impact on the Morphology, Strain Relaxation and Defects of Diamond Heteroepitaxially Grown on Ir/Al2O3 Substrates

This paper investigates the formation and propagation of defects in the heteroepitaxial growth of single-crystal diamond with a thick film achieving 500 µm on Ir (001)/Al2O3 substrate. The growth of diamond follows the Volmer–Weber mode, i.e., initially shows the islands and subsequently coalesces to closed films. The films’ strain imposed by the substrate gradually relaxed as the film thickness increased. It was found that defects are mainly located at the diamond/Ir interface and are then mainly propagated along the [001] direction from the nucleation region. Etching pits along the [001] direction formed by H2/O2 plasma treatment were used to show defect distribution at the diamond/Ir/Al2O3 interface and in the diamond bulk, which revealed the reduction of etching pit density in diamond thick-film surface. These results show the evident impact of the thickness on the heteroepitaxially grown diamond films, which is of importance for various device applications.

Synthesis, Properties and Aging of ICP-CVD SiCxNy:H Films Formed from Tetramethyldisilazane

Amorphous hydrogenated silicon carbonitride films were synthesized on Si(100), Ge(111), and fused silica substrates using the inductively coupled plasma chemical vapor deposition technique. 1,1,3,3-tetramethyldisilazane (TMDSN) was used as a single-source precursor. The effect of the precursor’s pressure in the initial gas mixture, the substrate temperature, the plasma power, and the flow rate of nitrogen gas as an additional reagent on the film growth rate, element composition, chemical bonding, wettability of film surface, and the optical and mechanical properties of a-SiCxNy:H films was investigated. In situ diagnostic studies of the gas phase have been performed by optical emission spectroscopy during the film deposition process. The long-term stability of films was studied over a period of 375 days. Fourier-transform infrared (FTIR) and X-ray energy dispersive spectroscopy (EDX), and wettability measurements elucidated the oxidation of the SiCxNy:H films deposited using TMDSN + N2 mixture. Films obtained from a mixture with argon had high stability and maintained the stability of element composition after long-term storage in ambient air.

Analysis of propagation characteristics of Rayleigh surface acoustic waves on Yb0.33Al0.67N piezoelectric films/high-velocity substrates

Piezoelectricity of YbAlN films has recently been shown to be almost as high as that of ScAlN films. YbAlN film surface acoustic wave (SAW) resonators are expected to have a high coupling factor. We theoretically investigated the propagation characteristics of first-mode Rayleigh SAWs (RSAWs) on Yb0.33Al0.67N film/high-velocity Si, sapphire, AlN, SiC, BN, and diamond substrates. The first-mode RSAWs on the YbAlN layered structures had high coupling factors, higher than those on ScAlN layered structures. An enhancement of the effective coupling factor of the first mode RSAWs was observed in polarity inverted YbAlN film/BN or diamond substrate structures.

Growth of nanoporous high-entropy oxide thin films by pulsed laser deposition

High-entropy oxides (HEO) with entropic stabilization and compositional flexibility have great potential application in batteries and catalysis. In this work, HEO thin films were synthesized by pulsed laser deposition (PLD) from a rock-salt (Co0.2Ni0.2Cu0.2Mg0.2Zn0.2)O ceramic target. The films exhibited the target’s crystal structure, were chemically homogeneous, and possessed a three-dimensional (3D) island morphology with connected randomly shaped nanopores. The effects of varying PLD laser fluence on crystal structure and morphology were explored systematically. Increasing fluence facilitates film crystallization at low substrate temperature (300 °C) and increases film thickness (60–140 nm). The lateral size of columnar grains, islands (19 nm to 35 nm in average size), and nanopores (9.3 nm to 20 nm in average size) increased with increasing fluence (3.4 to 7.0 J/cm2), explained by increased kinetic energy of adatoms and competition between deposition and diffusion. Additionally, increasing fluence reduces the number of undesirable droplets observed on the film surface. The nanoporous HEO films can potentially serve as electrochemical reaction interfaces with tunable surface area and excellent phase stability. Graphical abstract

MnBi2Se4-Based Magnetic Modulated Heterostructures

Thin films of magnetic topological insulators (TIs) are expected to exhibit a quantized anomalous Hall effect when the magnetizations on the top and bottom surfaces are parallel and a quantized topological magnetoelectric effect when the magnetizations have opposite orientations. Progress in the observation of these quantum effects was achieved earlier in the films with modulated magnetic doping. On the other hand, the molecular-beam-epitaxy technique allowing the growth of stoichiometric magnetic van der Waals blocks in combination with blocks of topological insulator was developed. This approach should allow the construction of modulated heterostructures with the desired architecture. In the present paper, based on the first-principles calculations, we study the electronic structure of symmetric thin film heterostructures composed of magnetic MnBi2Se4 blocks (septuple layers, SLs) and blocks of Bi2Se3 TI (quintuple layers, QLs) in dependence on the depth of the magnetic SLs relative to the film surface and the TI spacer between them. Among considered heterostructures we have revealed those characterized by nontrivial band topology.

Evolution of the Surface Structure and Functional Properties of the Electroconducting Polymer Coatings onto Porous Films

Composite systems containing electroconducting polymer coatings (polyaniline and polypyrrole) applied to porous films of semicrystalline polymers (polyethylene, polypropylene, and polyvinylidene fluoride) have been prepared. Porous supports were obtained in the process based on polymer melt extrusion with subsequent annealing, uniaxial extensions, and thermal stabilization. Conducting coatings were formed by the oxidative polymerization of the monomers directly onto the porous supports. The structure (overall porosity, permeability, pore sizes, factor of orientation) and morphology (specific surface and character of the film surface) of the supports were characterized by sorptometry, filtration porosimetry, atomic force microscopy (AFM), and X-ray scattering techniques. It was observed that the porous supports have a strongly developed relief surface which is formed in the pore formation process. It was proven by scanning electron microscopy (SEM) that the porous supports have an oriented structure, and the surface of the composites is defined by the morphology inherent in the conducting component. It was shown that these composites (porous support/conducting coating) demonstrate electric conductivity both along the surface and between surfaces. It was demonstrated that the deposition of conducting coatings leads to an increase in the water wettability of the composites compared with pronounced hydrophobic supports. The composites are characterized by good adhesion between components due to a relief film surface as well as high mechanical strength and elasticity provided by the oriented character of the supports.

Спектральные оптические свойства керамических нанопористых мембран на основе анодного оксида алюминия и покрытия из серебра в парах аммиака

Spectral optical properties of synthesized ceramic nanoporous membranes based on anodic aluminum oxide coated silver in saturated ammonia gas flow have been experimentally investigated. Based on the measured transmission spectra and detected interference part of the spectra in wavelength range from 550 to 900 nm, temporal and spectral dependencies of the effective optical thickness and its changes in non-equilibrium conditions were obtained due to adsorption of ammonia molecules on silver film surface. According to detected and measured interference maximum shifts up to 14 nm in transmission spectra of Al2O3 + Ag membranes in ammonia gas flow, the possibility of constructing a selective interferometric optical sensors with 10 − 15 min response time is shown.

Investigation of thin films for fabrication of Nb/AlN/NbN tunnel junctions and microstrip lines of NbTiN-SiO2-Al.

The surface of thin films of Nb, Al, NbTiN, SiO2, Al2O3 is investigated in this work. These films are necessary for the fabrication of high-sensitive devices of THz range. The fabrication processes of such devices are described briefly. All films were fabricated using a Kurt J. Lesker magnetron sputtering system. The study of the film surface roughness was carried out using a Bruker Ikon atomic force microscope. The surface quality of films is determined not only deposition mode, but plasma etching process also. The best values of the root-mean-square deviation of the surface profile Rq = 2 nm were obtained for the used NbTiN film with a thickness of 325 nm. Thin Al-layers that is used for tunnel barrier formation is studied. It is shown than Al films with a thickness of more than 6 nm are already continuous. The surface roughness of the single-layer and multilayer films has been studied.

Influence of different types of solvents on morphology, optical and conductive properties of PCBM films

The article deals with the influence of various types of solvents on the spectral characteristics and conductive properties of films [6,6]-methyl phenyl-C61-butyric acid, precipitated from solutions. It is clearly shown that the effect of the nature of the solvent affects the morphology of the film surface. Analysis of the spectra of the optical range showed the presence of a maximum of the absorption coefficient in the frequency range of 340-490 nm. The calculation of the optical bandgap clearly demonstrates the possibility of modernizing the atomic structure of films by using various types of solvents. A study of the current-voltage characteristics showed the presence of a photocurrent in carbon films deposited with dichloromethane, toluene, and chloroform.

Spatial aspects of spin polarization of structurally split surface states in thin films with magnetic exchange and spin-orbit interaction

A theoretical study is presented of the effect of an in-plane magnetic exchange field on the band structure of centrosymmetric films of noble metals and topological insulators. Based on an ab initio relativistic k·p theory, a minimal effective model is developed that describes two coupled copies of a Rashba or Dirac electronic system residing at the opposite surfaces of the film. The coupling leads to a structural gap at Γ and causes an exotic redistribution of the spin density in the film when the exchange field is introduced. We apply the model to a nineteen-layer Au(111) film and to a five-quintuple-layer Sb2Te3 film. We demonstrate that at each film surface the exchange field induces spectrum distortions similar to those known for Rashba or Dirac surface states with an important difference due to the coupling: At some energies, one branch of the state loses its counterpart with the oppositely directed group velocity. This suggests that a large-angle electron scattering between the film surfaces through the interior of the film is dominant or even the only possible for such energies. The spin-density redistribution accompanying the loss of the counterpart favors this scattering channel.