Experiments were performed to study water pool boiling at atmospheric pressure on biphilic surfaces with grooves (open microchannels) produced by laser ablation and hydrophobized owing to chemisorption of fluorinated methoxysilane from vapor at a temperature of 100–110 ◦C. Surfaces with arrays of parallel grooves, as well as with arrays of grooves intersecting at right angles (groove grids with square cells), were used. The experimental data were analyzed and compared with literature and previous data. The influence of the size and location of hydrophobic regions on boiling heat transfer enhancement was studied. It has been shown that the main parameter determining the heat transfer enhancement for a surface with an array of parallel grooves is the pitch between them. For groove grids, this is also true, but only for large heat fluxes. Removal of the hydrophobizer from the grooves leads to a significant decrease in heat transfer. A comparison of the results of this study with previous data for arrays of hydrophobic cavities and arrays of hydrophobic round spots on a flat surface shows enhanced heat transfer on biphilic surfaces compared to a flat smooth surface. These surfaces are characterized by a strong dependence of heat transfer on the pitch between the hydrophobic regions. The maximum effect on heat transfer was observed on surfaces with a 3D biphilic pattern, namely on arrays of microcavities and arrays of intersecting grooves (groove grids with square cells).

Experiments were carried out on biphilic surfaces made using two technologies. The first technology was the deposition of a fluoropolymer through special masks (100 μm spots and 500 μm pitch; 50 μm spots and 200 μm pitch) onto a smooth or pre-modified (silica micrococoon arrays) copper surface. The second technology consisted in the deposition of fluorinated methoxysilane on a copper surface with arrays of caverns preliminarily created by laser ablation (caverns size of the order of 70 μm, pitch - 780 μm), as a result of which deposition the caverns became superhydrophobic. The experiments were carried out on distilled water at atmospheric pressure. For all surfaces, a significant intensification of heat transfer has been achieved, compared with a smooth copper surface. All described biphilic surfaces were compared with similar surfaces without hydrophobic treatment, that is, non-biphilic (smooth surface, arrays of micrococoons, arrays of caverns). For all surfaces, the key contribution of biphilic properties to the intensity of heat transfer is shown in comparison with other related types of processing.

The Hf–Sc–O films are synthesized by atomic layer deposition using hafnium tetrakis-diethylamide (Hf(N(C 2 H 5 ) 2 ) 4 , TDEAH), scandium tris-methylcyclopentadienyl (Sc(C 5 H 4 CH 3 ) 3 ), and water at 300 °C on (100) single crystal silicon wafers from SiO х oriented microrope arrays (OMRA). Samples are analyzed by a number of physicochemical techniques: single wave ellipsometry, X-ray photoelectron spectroscopy, X-ray diffraction, transmission and scanning electron microscopy. Growth per cycle values (a film thickness increase in one reaction step) for pure and mixed oxides are determined, phases formed in the films are characterized, the relationship between the surface morphology and the chemical composition is found, and the optical properties of the samples are investigated. The use of OMRA as wafers allows the reliable identification of the formation of an ordered δ-phase Hf 3 Sc 4 O 12 of a rhombohedral structure type and space group R3̅ .

The optical properties of noble metal nanoparticles (NPs) can be efficiently controlled by their incorporation into host matrix films. Here, we report on the fabrication of composite films of gold NPs in a silicon suboxide matrix by a novel approach using a combination of pulsed laser deposition for NP production and gas-jet, electron-beam plasma chemical vapor deposition for low-temperature (300°C) synthesis of a SiOx (x = 0.38-1.55) thin film as a matrix for the NPs. The produced nanocomposite exhibits unexpected plasmonic properties, non-monotonically dependent on the matrix thickness, due to a porous columnar matrix structure grown from the NPs with variable oxygen content along the columns. This implies that low-temperature, gold-catalyzed oxidation of silicon occurs during the structure growth. Calculations based on Mie theory show that the refractive index of the obtained SiOx matrix can be as low as 1.2 at certain film thicknesses. Mechanisms of the columnar structure formation at different deposition stages are discussed. The synthesis approach can be used for the fabrication of optical thin-film materials with controllable low refractive index.

Copper heaters were made. On the surface of these heaters the arrays of micrococoons were synthesized from silicon oxide (SiO x ) nanowires with different concentrations of micro/nanostructures and hence different average distances between them. Boiling curves were obtained for these samples and it was found that heat transfer enhancement during boiling occurs on them in comparison with a smooth copper surface. It was shown that the effect increases with decreasing concentration of micro/nanostructures and reaches a maximum for microrelief with an approximate concentration of microstructures equal to unity per square micron. It was found that surfaces with micrococoons are sufficiently stable and suitable for enhancing heat transfer during boiling.

In this paper, the investigation of pool boiling heat transfer on biphilic micro/nanostructured surfaces is presented. An array of micrococoons from silicon oxide nanowires was synthesized on the surface of a copper heater using the gas-jet electron beam plasma chemical vapor deposition method. The biphilic properties of the surface were achieved by applying fluoropolymer spots by hot wire chemical vapor deposition. Technology of creating biphilic surfaces was developed and boiling curves were obtained for used samples. The advantages of using a biphilic surface to enhance heat transfer were demonstrated in comparison with a smooth surface and a micro-nanostructured surface without local hydrophobic fluoropolymer regions. This technology can be applied to enhance boiling heat transfer.

A new low-temperature fabrication method of SiOx-TiO2 core-shell nanowires (NWs) for photocatalytic application was suggested. In the present work, the gas jet electron beam plasma chemical vapor deposition method was used to synthesize arrays of oriented bundles (microropes) of silicon oxide NWs. Tin nanoparticles were used as catalyst for the NW growth via the "vapor-liquid-solid" mechanism at a temperature of 335 degrees C. A conformal nanocrystalline TiO2 coating was then deposited by atomic layer deposition using TiCl4 and H2O at 300 degrees C. Anatase phase formation was confirmed by Raman spectroscopy and X-ray diffraction. The photocatalytic characteristics of the fabricated arrays were demonstrated by the example of the photo-oxidation reaction of acetone vapor. Options for further development and advantages of the method such as low temperature, scalability and good compatibility of the fabrication stages are discussed.

The bonding structure and composition of amorphous silicon suboxide (a-SiOx, 0.25 < x < 0.75) thin films deposited by gas-jet electron beam plasma chemical vapor deposition were studied by Fourier transform infrared (FTIR) spectroscopy, Rutherford backscattering spectroscopy (RBS), and wavelength dispersive X-ray spectroscopy (WDS). Based on the dependence of the integrated absorption of the Si-O-Si asymmetric stretching modes normalized to the silicon atomic density on the x values evaluated by RBS, the proportionality coefficient ASiO of the Si-O-Si asymmetric stretching modes was determined to be 2 × 1019 cm−2. Details of the ASiO calculation, the dependence of the silicon atomic density on x, and the limits of integration were discussed. The significant overestimation of the x values obtained from the Si-O-Si stretching mode position in the IR spectra of the films in comparison with the actual values and the presence of a high-frequency shoulder centered at ~ 1140 cm−1 in the IR spectra indicates the inhomogeneity of the structure of the films. At the same time, the parameters of the Si-O-Si asymmetric stretching band (position and full width at half maximum) indicate the absence of a strict phase separation in the structure of the synthesized films, which are thus described by the intermediate model.

The effect of the annealing temperature on the optical and structural properties of the a-SiOx:H thin films prepared by gas jet electron beam plasma chemical vapor deposition method was studied. Annealing was carried out at 600, 700, 800, 900 and 1000 degrees C for 4 h in oxidizing atmosphere. According to FTIR spectroscopy measurements, the oxygen and hydrogen concentration in the as-deposited films was 25 at.% and 2 at.%, respectively. The SEM image showed that the as-deposited material had column structure with a large number of vertical voids. As a result of annealing, the thickness of the films decreased by approximately 1.5 times for all samples. The value of refractive index at 650 nm decreased from 2.5 to 2.0 with the increase of the annealing temperature. The E-04 optical gap decreased in comparison with the value of the as-deposited thin films for 600 degrees C and 700 degrees C, and increased for 800 - 1000 degrees C. For annealing at a temperature of 600 degrees C, the structure of the material changes insignificantly. A rearrangement in the structure of the matrix with the formation of amorphous silicon nanoclusters occurs at 700 degrees C and 800 degrees C. Annealing at the higher temperatures leads to transition from a material with amorphous nanoclusters to a material with nanocrystallites. (C) 2018 Elsevier Ltd. All rights reserved.

Polycrystalline silicon (poly-Si) thin films are fabricated by aluminum-induced crystallization (AIC) of amorphous silicon suboxide (a-SiOx, x = 0.22) at 550 °C for 20 h. AIC of a-SiO0.22 via thermal annealing of a-SiO0.22/Al bilayer structures leads to layer exchange with the formation of poly-Si films with (111) preferential orientation and high-crystalline quality-coated with a layer of a mixture of Al, Si, and O atoms with inclusions of silicon nanocrystallites. The initial a-SiO0.22/Al thickness ratio approximately equal to 1 provides the formation of a discontinuous poly-Si film with a crystallized fraction of 85%, as shown by optical microscopy.

Silicon oxide (SiOx, × ≤2) nanowires were synthesized on indium (In) catalyst particles by gas-jet electron beam plasma-enhanced chemical vapor deposition through the vapor-liquid-solid (VLS) mechanism. The synthesis was carried out on substrates of different average particle sizes in the range from 42 to 710 nm. Arrays of oriented microropes of nanowires were grown on catalysts with a particle size of 42 and 79 nm. On 170 nm catalyst particles, cocoon-like structures from nanowires were formed, and on 710 nm particles, the synthesis proceeded in the same way as on an indium tin oxide (ITO) film. The chemical composition of the synthesized nanostructures was studied by Fourier transform infrared spectroscopy. Under the assumption of a uniform distribution of silicon and oxygen atoms, the nanowires were found to consist of SiOx with x = 1.9. Energy dispersive spectroscopy showed that the catalyst particles consisted of non-stoichiometric indium oxide, rather than of pure indium. Therefore, during the synthesis of silicon oxide nanowires on an indium catalyst, hydrogen should be used.

SiOx nanowires (SiOxNWs, x <= 2) were grown by gas-jet electron beam plasma chemical vapor deposition method according to the vapor-liquid-solid mechanism at different synthesis times (t(dep) = 0.5-5 min) using tin particles as a catalyst. Microropes of SiOxNWs were obtained at t(dep) of more than 1 min. The average growth rate of nanowires was about 19 nm/s. Fourier transform infrared (FTIR) spectroscopy shows that SiOxNWs synthesized at different t(dep) are very similar in chemical composition (x approximate to 2) and in the bonding network of SiOx. FTIR spectroscopy data on the chemical composition of nanowires are in good agreement with the results of X-ray energy dispersive spectroscopy (EDS) analysis. EDS mapping of silicon and oxygen indicates that the atoms are uniformly distributed in the nanowires. Also, FTIR measurements showed that a significant number of water-adsorbing silanol groups formed on the surface of the nanowires. Photoluminescence spectra of nanowires obtained at different t(dep) are typical of SiO2 and exhibit a broad band in the region 400-600 nm centered at similar to 475 nm. The contact angle for SiOxNWs is < 21 degrees and decreases to 4.4 degrees with increasing t(dep), indicating a superhydrophilic coating.

Data on the optical properties of a nanocomposite material constituted by gold nanoparticles covered with a thin film of amorphous hydrogenated silicon suboxide have been obtained for the first time. The thin film was deposited by gas-jet electron-beam plasma chemical-vapor deposition. As gold particles situated on the surface of quartz glass are covered with a thin a-SiO x : H film, their plasmonic resonance peak is shifted to longer wavelengths. The calculations made in the study demonstrated a good agreement with the experiment.

Nanostructuring of the surface is a promising technology for the processes of boiling. In this paper, we synthesized array of "microropes" from silicon oxide nanowires on the copper substrate with a silicon oxide intermediate layer by gas-jet electron beam plasma CVD method. The morphology for the synthesis time of 2 minutes 30 seconds and 5 minutes was obtained. The water droplet on the silicon oxide nanowires shows the measured contact angles 14 degrees and 10 degrees for deposition times of 5 min and 2 min 30 sec, respectively.

The boiling heat transfer on the local heaters with microstructured and nanomodified surfaces was studied. As nanomodified surfaces we used copper ones where the microropes of silicon oxide nanowires were grown. The aging of the nanomodified surface was observed after first series of experiments. It was shown that both finning and nanostructuring of the surface result in increase of heat transfer. The heat flux density of 1400 W/cm2 was reached.

Silicon oxide (SiOx) nanowires were synthesized from a monosilane-argon-hydrogen mixture on substrates of different materials (monocrystalline silicon (c-Si), glass, stainless steel, copper, and copper with a SiO2 barrier layer) coated with a tin catalyst film 60 nm thick using the gas-jet electron beam plasma chemical vapor deposition (GJ EBP CVD) method. High-density oriented arrays of microropes of SiOx nanowires were obtained on c-Si and glass substrates and a copper substrate with a SiO2 barrier layer. The fabrication of the nanowires included three steps: heating the substrate with the tin catalyst film, hydrogen plasma treatment of it, and synthesis of the structures. Heating and hydrogen plasma treatment of the tin catalyst on c-Si and glass substrates leads to a decrease in the wetting of the substrate material by tin. As a result, the morphology of the tin catalyst particles changes from semi elliptical to truncated spherical, which leads to a significant decrease in their surface density as a result of coalescence. A condition for obtaining a high-density oriented array of microropes of SiOx nanowires by the GJ EBP CVD method using a tin catalyst is the absence of chemical reaction between tin and the substrate material. (C) 2017 Elsevier Ltd. All rights reserved.

Nanowires of silicon oxide SiOx (x ≤ 2) were synthesized from a mixture of monosilane and hydrogen (helium, argon) by gas‐jet electron beam plasma chemical vapor deposition (GJ EBP CVD) method with simultaneous supply of oxygen into the vacuum chamber. The synthesis was performed on monocrystalline silicon and glass substrates coated with micron‐sized particles of a tin catalyst. In particular, aligned arrays of nanowire bundles (microropes) were synthesized from a mixture of monosilane and hydrogen (argon). A bundle of amorphous silicon oxide nanowires, each of which is about 15 nm in diameter, grows from a catalyst particle. The growth rate of the microropes is about 25 nm s−1 at a synthesis temperature of 320–330 °C. The morphology of the nanostructures was investigated by transmission and scanning electron microscopy, their composition by X‐ray energy dispersive spectroscopy and optical properties by photoluminescence spectroscopy. The synthesis was carried out using the well‐known vapor–liquid–solid (VLS) mechanism. A model is proposed for the synthesis of the nanostructures by the above method, including the formation of aligned bundles of nanowires (microropes) due to nonuniform heating of the catalyst particle by directed plasma flow. The obtained nanostructures have intense photoluminescence in the visible region of the spectrum at room temperature.

Silicon oxide nanowires SiOx were synthesized by the gas‐jet electron beam plasma chemical vapor deposition method. The synthesis of nanostructures was carried out on silicon substrates with thin tin film as a catalyst. The evolution in the morphology of the obtained structures was investigated while changing the substrate temperature in the range 200–415 °C. Dense array of aligned nanowire bundles (microropes) is formed at a temperatures of 335 and 415 °C. With decrease in the temperature to 270 and 245 °C arrays of microropes transform into cocoon‐like structures of nanowires. At a temperature 200 °С, array formed almost entirely consisting of cocoon‐like structures. The results of X‐ray energy dispersive spectroscopy (EDS) of the nanowires show that the ratio of oxygen to silicon is on average Si:O = 1:2.4. At the same time, Fourier Transform Infrared spectroscopy (FTIR) analysis of the obtained nanostructures showed that the synthesized nanowires consist of SiOx with x around 2. Moreover, the composition of the structures remains practically unchanged with the variation of the substrate temperature. The IR spectra show bands due to both Si–OH bonds and water molecules. Measurements of contact angles for water showed that the nanowire film surface synthesized in this work is hydrophilic in nature. When structuring involves the oriented growth microropes, the contact angle is about 20–35°. Decreasing of the substrate temperature and formation of cocoon‐like structures leads to a decrease in the contact angle to 4–12°. The photoluminescence (PL) spectra of nanostructures synthesized at the different substrate temperatures consist of a broad band with a maximum around 2.5 eV when using laser at 325 nm as the exciting source. We assume that the composition of the nanowires is close to SiO2, and the excess of oxygen in structures composition is due to the influence of adsorbed water molecules and hydroxyl groups with the formation of Si–OH bonds. Apparently, these bonds define the photoluminescence spectrum.

Silicon oxide nanowires were synthesized from monosilane–argon–hydrogen mixture by the gas-jet electron-beam plasma chemical deposition method with simultaneous oxygen injection into the vacuum chamber. The synthesis was performed on monocrystalline silicon substrates covered with micron and nanometer tin catalyst particles. The nanowires are formed the via vapor–liquid–solid mechanism in the “catalyst-on-bottom” mode, in which many nanowires grow from one catalyst particle. The process of synthesizing nanowires on a substrate with catalyst consists of three stages: heating to synthesis temperature, hydrogen plasma treatment, and nanowire growth. In the substrate region corresponding to the jet axis, different structures are formed depending on the catalyst particle size. For catalyst particles under 100 nm, there are formed structures of chaotically oriented and interlaced bundles of silica nanowires. For catalyst particles of 0.3–1 micron, there are formed oriented arrays of cylindrically shaped nanowire bundles (“microropes”). Cocoon-like structures are formed for catalyst particles of more than 1 micron.We propose a model of nanowire growth by this method, which is based on nonuniform heating of a catalyst particle by a directed plasma flow. It was found that for synthesis of oriented microrope arrays the initial tin film thickness should be less than 100 nm and the synthesis process should include a hydrogen plasma treatment stage.