Vacuum Evaporation Method Research Articles

Influence of hydrocarbon environment on electrical characteristics of Ge-As-Se-S chalcogenide glass system

The effect of propane-butane gas mixture on volt-Ampere characteristic (VAX) of thin–layer sandwich structure Al-Ge33As17S35Se15-Te obtained by thermal evaporation method in vacuum was investigated. It has been established that under the influence of gas atoms, the oscillations observed in VAX gradually decrease and disappear. This result is explained by the accumulation of neutral gas atoms into lower atomar pores. It has been shown that neutral gas atoms collected in pores lead to weakening of thermal-field ionization processes of U--centers, and to increase the speed of periodic deflection of charge carriers by these centers, which leads to an increase in the resistance of the sample.

Silver doping effect on the electrochromic performance of the WO3 thin films produced by thermal evaporation in vacuum

Ag doped WO3 thin films are successfully fabricated by thermal evaporation method in vacuum as precursor, and then annealed at 450 °C in nitrogen gases atmosphere. Cyclic voltammetry, repeating chronoamperometry, chronocolumetry and optical transmittance are recorded in 1 M LiClO4/propylene carbonate electrolyte. The color of the WO3 thin films changes from transparent to the blue under the applied potential of -1.8 and +1.9 V. XRD studies show that all the films have a polycrystalline structure of WO3. The molecular formation is also confirmed by Raman and X-Ray photoelectron spectroscopy (XPS). The EDS elemental mappings clearly confirm the homogeneous distribution of Ag, W and O elements into the WO3 network. From the optical studies, indirect band gap energy of the WO3 decreases as Ag doping level increases. The best coloration and bleaching times (2.33 and 1.25 s) are obtained for the Ag(2 %):WO3 thin films, compared to the pure WO3 (3.79 and 1.96 s). The produced WO3 films exhibit high reversibility (39.6/69.1 %), high coloration efficiency values (26.3/141.2 cm2/C), and good cycling stability. From the EIS measurements, the charge-transfer resistance is Ag(2 %):WO3 < the pure WO3 < Ag(5 %):WO3 < Ag(8 %):WO3, which means that Ag(2 %):WO3 has the biggest electrochemically active surface area. Electronic energy levels of the pure WO3 and the Ag:WO3 thin films are also given. From the Mott-Schottky studies, it is determined that the donor concentration of the materials is of the order of 1014–1015 cm−3. In the literature, there are very limited studies related to electrochromic thin films by thermal evaporation in vacuum. In this sense, the reported results in this study are promising for the electrochromic applications.

Enhanced response and recovery performance of α-hexathiophene sensors for NO2 gas by dual heterogeneous interface

Organic semiconductor gas sensors of α-hexathiophene (α-6 T) films as active layers with dual heterogeneous interface layers of p-hexabiphenyl and pentacene films are prepared by continuous vacuum evaporation method. The enhanced properties of sensors are achieved by modulating the thickness of the α-6 T films. The sensitivity of 1373 %/ ppm and a theoretical low detection limit of 361 ppb are obtained. The sensors demonstrate fast response and recovery properties of 1.05 and 1.51 min for NO2 gas of 20 ppm. The improved performance is attributed to the continuity of the interface layers and high adsorption of island-like growth. This approach is effective to improve organic sensors by introducing dual heterogeneous interface and tuning the growth of active layers.

Substantiation of wild plants used as functional ingredients in the technology of crisp grain bread

Research on the nutritional content of wild plant fruits in Kazakhstan, including Hawthorn fruit (Crataegus laevigata), rosehip fruit (Rose canina L. variety), sea buckthorn fruit (Hippophae rhamnoides - Altai variety), and black chokeberry fruit (Aronia melanocarpa), has determined that these fruits possess a combination of properties essential for maintaining human health, attributed to the presence of bioactive substances (BAS) and other components. The technological process for obtaining extracts and concentrates from wild-growing raw material fruit has developed. The following extraction modes were proposed: ultrasonic wave frequency 40 kHz, extraction time 30 minutes, temperature 500С, and concentration of the obtained extracts was carried out by vacuum evaporation method, using IKA RV-10 apparatus at 40-50°С and pressure 800 mbar. Found that extracts and concentrates have a higher concentration of nutritional substances when compared to the fruits themselves. Thus, the vitamin C content in hawthorn fruits was 27.8 mg, while in the extract, it was 47.84 mg, and in the concentrate – 62.19 mg. The vitamin C content in rosehip fruits, extracts, and concentrates was 578.01 mg, 811.8 mg, and 1101.3 mg, respectively. The vitamin C content in sea buckthorn fruits, extracts, and concentrates was 285.05 mg, 518.8 mg, and 640.9 mg, respectively. The vitamin C content in black chokeberry fruits, extracts, and concentrates was 86.2 mg, 128.8 mg, and 160.5 mg, respectively. A similar increase was observed for the content of vitamin E and other components. Furthermore, the obtained concentrates meet the safety parameters required by regulatory documents. A technology for producing grain crispbread using the extrusion method has developed, incorporating whole grains, groats, flavouring additives, and concentrates derived from wild fruits such as hawthorn, rosehip, sea buckthorn, and black chokeberry into the recipe.

Relationship between crystal orientation and energy storage capacity in WO3 photoelectrodes for water splitting

For photoelectrochemical water splitting, tungsten trioxide (WO3) films with a monoclinic structure were synthesized on fluorine-doped tin oxide coated glass substrates with a vacuum evaporation method. To control the WO3 film thickness from 0.42 to 5.6 μm, the crystal orientation was intergraded from the (200) crystal plane to the (002) one. In x-ray diffraction measurements, the intensity ratio of the (002) crystal plane to the (200) one was defined as rp. In the WO3 photoelectrode with higher (002)-preferred orientation, the photocurrent continued to flow even when the incident light against the photoelectrode was completely blocked after the irradiation for 60 s. This suggests that hydrogen continues to be produced owing to the electrons charged by the formation of a hydrogen tungsten bronze (HxWO3) phase. After 72 s, the photocurrent density of the WO3 photoelectrode with rp = 42 became one-tenth of the value before the incident light was blocked. This charge release time was remarkably long compared to those of the WO3 photoelectrodes with (200)-preferred orientation and non-orientation. Therefore, it was considered that the hydrogen ion diffusion through the defects in the WO3 crystals tends to occur in the [002] crystal direction. However, the improvement in the (002)-preferred orientation can facilitate the structural change from the WO3 phase to the HxWO3 one for the entire film.

Increase of coercivity and composition distribution in dysprosium-diffused NdFeB sintered magnets treated by vacuum evaporation method

This study examines the distribution of heavy rare-earth elements (HRE) and magnetic properties in sintered NdFeB permanent magnets treated with Dy vacuum evaporation grain boundary diffusion, considering variations in time and temperature. The HRE distribution and magnetic properties were analyzed using an electron probe microanalyzer (EPMA), glow discharge optical emission spectrometer (GDOES), and hysteresis loop meter. The optimal temperature gradient for achieving the best results was found to be between 850 °C and 950 °C for a duration of 10 h. This resulted in iHc of 1415 kJ/m and (BH)max of 396.2 kJ/m3, which is classified as N52H grade. In comparison, the untreated NdFeB magnets had iHc of 1105 kJ/m and (BH)max of 400.3 kJ/m3, classified as N52 M grade. The results suggest that 0.167 wt% consumption of vacuum evaporated Dy alloy can enhance the 28 % in iHc of the magnet and 5 % increase in (BH)max compared to the untreated ones. This innovative manufacturing method improves the utilization of rare heavy earth and enhances the overall magnetic properties. This material has the potential to be used in the development of low-weight rare earth-sintered NdFeB magnets with high intrinsic coercivity. This study's findings advance energy-efficient technologies such as electric vehicles and offshore wind turbines, aiding global energy conservation efforts.

Enhanced photoluminescence characteristics in Mg doped Alq3: An insight into doping mechanism

The present paper deals with the investigations on the effect of Mg doping on the structural and photophysical properties of Alq3 thin films. Mg doped Alq3 powders, with varying Mg concentrations, are synthesized using co-precipitation method and their thin films are deposited using vacuum evaporation method. These films are subjected to different analytical analyses to study the effect of Mg doping on the structural and photophysical properties of Alq3. It has been observed that Mg is attached at the central part of the Alq3 molecules making bonds with Al, N and O atoms. In this process, Mg atoms transfer electrons to Alq3 molecules and increases the electron density in its highest occupied molecular orbital (HOMO). Increased HOMO electron density in Mg doped Alq3 results in the improvement in its photoluminescence characteristics. Highest photoluminescent characteristics are observed for Mg doped Alq3 having 1.5 % (by mole) Mg which shows almost 2-fold enhancement in photoluminescence quantum efficiency (PLQY) and 3-fold enhancement in radiative decay rate. The results obtained in this work suggest that Mg doped Alq3 films may be integrated in high performing organic light emitting devices.

Single‐Source Evaporated High‐Quality Single‐Phase Cs3Cu2I5 Scintillator Films for High Performance X‐Ray Imaging

AbstractVacuum‐evaporated metal halides (MHs) scintillator thick films have received much attention in the X‐ray imaging field due to their excellent light yield and uniform large‐area preparation. However, the inevitable heteromorphic homologs in MHs (e.g., Copper‐based MHs (Cu‐MHs): CsCu2X3∖Cs3Cu2X5) and change of film structural backbone will result in spectral hybridization (phase purity), and the film eventually detaches (lattice mismatches). Herein, a single‐source vacuum evaporation method to prepare a thick film (≈10 µm) of Cu‐MHs (as an example) scintillators is realized: 1) Presynthesis of pure phase materials by solution method with a protective agent to ensure phase purity without precise control of component ratios in evaporation process; 2) One‐shot formation of film structural backbone avoids stress accumulation and utilize the longitudinal growth characteristics of crystalline films to obtain crystal orientations with better optical outputs. Finally, the films obtained have a light yield comparable to a partially single‐crystal (53 983 photons MeV−1) and an imaging resolution (14.1 lp mm−1) comparable to the partial template method. The detection system based on the prepared Cu‐MHs scintillator thick films exhibits good response speed and linearity in response to different X‐ray radiation intensities and exposure times. The method will further drive the application of MHs is believed.

Stabilizing Single‐Source Evaporated Perovskites with Organic Interlayers for Amplified Spontaneous Emission

AbstractMetal halide perovskites are promising semiconductors with promising applications in optoelectronic and photonic technologies. When coherent emission applications are targeted, materials with lower lasing thresholds and increased stabilities must be developed to increase the performance under continuous wave optical pumping condition and finally allow the realization of the long sought‐after electrically pumped lasers. Perovskite multiple‐quantum‐wells (MQWs) can potentially ease the population inversion by confining photoexcitation within the heterostructure's wells, but their fabrication process and structural design still require a delicate optimization to make them valuable photonic platforms. Here, perovskite MQWs are fabricated based on organic semiconductors and CsPbBr3, using a facile and easily scalable sequential single‐source vacuum evaporation method. Perovskite with the organic interlayer shows radically enhanced phase stability, passivated defects, and improved radiative recombination properties. In this way, upon proper design of the heterostructure wells and barriers thicknesses, optically pumped amplified spontaneous emission can be achieved. This work reports an effective fabrication approach for perovskite MQWs, while providing a deeper understanding of their photophysical properties to foster their application as coherent light emitters.

High-throughput centrifugal evaporation for mesoporous alumina powder synthesis via evaporation-induced self-assembly (EISA).

The evaporation-induced self-assembly (EISA) process is commonly employed to synthesise mesoporous materials, such as mesoporous alumina. Typically, recovering mesoporous alumina in powder form takes several days due to the need for controlled solvent evaporation conditions. The mesostructure obtained from the EISA process is highly sensitive to these conditions, which can sometimes hinder reproducibility. This paper presents an improved EISA method using a centrifugal evaporator, which enables the rapid recovery of mesoporous alumina powder (approximately 2 h) from multiple precursor solutions under controlled evaporation conditions. The advantages of using a centrifugal evaporator over traditional vacuum evaporation methods include: (1) the reduction of bumping and foaming due to centrifugal force; (2) resistance to evaporated gaseous HCl; and (3) the ability to evaporate multiple samples simultaneously. This enhanced EISA process is expected to accelerate the research progress of powdery mesoporous materials.

PANI/SnO2 nanoparticle, FTO/PET and Al/PET as hybrid nanocomposite soft electrodes synthesized by sol–gel, spray pyrolysis and thermal vacuum evaporation methods

PANI/SnO2 nanoparticle, FTO/PET and Al/PET as hybrid nanocomposite soft electrodes synthesized by sol–gel, spray pyrolysis and thermal vacuum evaporation methods

INFLUENCE OF THE SUBSTRATE MATERIAL ON THE STRUCTURAL PROPERTIES OF CADMIUM TELLURIDE FILMS

With the use of modernized industrial vacuum installations, a series of test samples of cadmium telluride films was produced by the method of thermal vacuum evaporation on glass substrates without a sublayer of transparent conductive oxide, with a sublayer of conductive oxide, and on molybdenum foil substrates to study the influence of the substrate material on the structural parameters of the test samples. The study of the structure was carried out by the method of X-ray diffractometric analysis, the parameters of the lattice, the sizes of the regions of coherent scattering and the texture coefficient of the film were calculated. Based on the results of research into the structural parameters of samples made on a glass substrate, the presence of a cubic phase of cadmium telluride was established. It is shown that when the temperature of the substrate increases, the texture of the samples increases and the presence of tensile stresses is observed, since the lattice period of the cubic phase is significantly higher than that of the tabular phase. For a sample obtained on a glass substrate with a layer of transparent conductive ITO oxide at a substrate temperature of 200 ОC, the presence of two hexagonal phases H1 and H2 and a cubic phase C was established. The samples obtained on a molybdenum foil substrate contain almost entirely the cubic CdTe phase only in very thin sample no. 1 traces of the hexagonal phase are present. For the first thinnest sample, only one main diffraction peak of the cubic phase is observed, which can be explained by the fact that in the initial stages of the film growth, it grows as a highly textured cubic phase with the possible presence of some hexagonal phase. From the analysis of the obtained results, it can be noted that the samples obtained on the molybdenum substrate have a lattice parameter closest to the table data - 6.482–6.483 Å. The structural differences observed between the studied samples are due to the fact that they have a different preferred orientation, which is most likely due to a change in the sputtering speed

Fabrication of Ag/PP terahertz hollow waveguide by vacuum evaporation method and transmission performance investigations

This work proposed a vacuum evaporation method in preparing an Ag/polypropylene (PP) terahertz (THz) hollow waveguide (HWG). Rray model and COMSOL were used to optimize the geometric structure parameters of the HWG. Accordingly, a 5 mm bore PP tube with a wall thickness of 360 μm was selected as the structural and dielectric tube, and a silver reflective layer was deposited onto the outer surface of the PP tube using vacuum evaporation process. The as-deposited Ag layer consists of small Ag particles (about 100 nm) which contribut to form a more uniform and smoother metal reflective layer than that could be prepared via the wet chemical method. Terahertz time-domain spectroscopy (THz-TDS) analysis confirms that the Ag/PP THz HWG exhibits a low-loss window centered at the frequency of 0.1 or 0.3 THz. The HWG sample shows low transmission losses of 2.26 dB/m at 0.1 THz and 1.23 dB/m at 0.3 THz, respectively. The THz waves could be stably transmitted through the as-fabricated Ag/PP waveguide at low (−78.5 °C) and high (65 °C) temperatures. This research opens a simple and environmentally friendly avenue for the fabrication of low-loss metal/dielectric THz HWG. It is helpful for promoting the applications of THz HWG in future THz imaging, sensing and 6G communication.

ALUMINUM OXIDE IN VACUUM CONDENSATES BASED ON COPPER

Strengthening of copper and copper alloys with aluminum oxide particles is an important technological technique. Composite materials based on copper strengthened with aluminum oxide particles have a significant operating temperature range and better mechanical properties at elevated temperatures than age-hardening alloys. However, at moderate operating temperatures, the use of age-hardening alloys remains more economically justified. The main direction in the development of composites strengthened with oxide particles is the dispersion of the strengthening phase to sizes of several or one nanometer, which will bring their mechanical properties to the level of age-hardening alloys. However, dispersion leads to a significant increase not only in strength, but also in electrical resistance. The adverse effect on the electrical conductivity of dispersed particles will decrease with a decrease in the volume fraction of oxide, bringing the electrical conductivity closer to the level of copper. Based on an analysis of the materials of scientific research devoted to the production of dispersion-strengthened Cu–Al2O3 composites, it was concluded that the most significant progress in the dispersion of oxide particles with uniform distribution in the copper matrix of the composite was achieved using the method of electron beam evaporation and simultaneous deposition (condensation) of vapors of components in vacuum (EB–PVD). Structural studies of the morphology of aluminum oxide particles in dispersion-strengthened copper composites were carried out using methods such as: X-ray fluorescence analysis, transmission electron microscopy, and energy-dispersive X-ray spectroscopy (EDS). The average size of aluminum oxide particles in the studied dispersion-strengthened composites was in the range from 1.8 to 3 nm. In the work, the dependence of the specific electrical resistance of composites (ρ) on the oxide content was investigated. It was found that a decrease in the size of oxide particles leads to an increase in the electrical resistance of the dispersion-strengthened composite. The studies of the method of electron beam evaporation and subsequent condensation in vacuum, presented in the work, confirm the possibility of further dispersion of aluminum oxide particles with simultaneous narrowing of the distribution histogram. This opens up prospects for further improvement of vacuum dispersion-strengthened copper-based composites.

Vacuum Processed Metal Halide Perovskite Light‐Emitting Diodes

AbstractMetal halide perovskite light‐emitting diodes (PeLEDs) are expected to be the next‐generation display technology due to their unique optoelectronic properties. Currently, the external quantum efficiencies of PeLEDs based on solution‐processed fabrication methods already exceed 20%. However, there are still many challenges existing in solution‐based PeLEDs that inhibit their commercialization. Recently, vacuum deposition techniques of perovskites have drawn much attention because of the ability to grow dense and uniform large‐area perovskite films with precisely controlled thickness, which is compatible with state‐of‐the‐art organic LED manufacturing processes. Despite the promising prospects of vacuum‐based PeLEDs, some challenges remain to be addressed to achieve PeLEDs with both high efficiency and high stability that are required for practical applications such as active‐matrix displays. This requires precise control of the film morphology, composition, and interface during the deposition process through fine‐tuning of the substrate temperature, deposition rate, vacuum level, precursor formulation, and post‐treatment conditions. In this review, it focuses on the key requirements for vacuum‐processed PeLEDs, highlights the recent advances in materials and devices of PeLEDs, and emphasize vacuum evaporation methods as well as the corresponding device performance. Possible approaches to improve the efficiency and the long‐term operational stability of vacuum‐processed PeLEDs are discussed.

Microstructure and Magnetism of Heavily Helium-Ion Irradiated Epitaxial Iron Films

This study reports on the microstructure and magnetism of pure iron irradiated with high doses of helium ions. Iron alloys are important structural materials used as components in fusion reactors, and a comprehensive database of their various properties has been developed. But little has been investigated on magnetic properties, in particular, the effects of high doses and helium cavities are lacking. Single-crystal iron films, with a thickness of 200 nm, were prepared using the ultra-high vacuum evaporation method. These films were then irradiated with 30 keV He+ ions at room temperature up to a dose of 18 dpa. X-ray diffraction measurements and cross-sectional transmission electron microscope observations revealed significant microstructural changes, including a large lattice expansion perpendicular to the film plane and the formation of high-density cavities after irradiation. However, the saturation magnetization and the shape of the magnetization curve showed almost no change, indicating the robustness of the magnetic properties of iron.

Toward Development of CdZnTe and CdMnTe Thin Film‐Based Solar Cells: Optimized Properties and a Comparative Performance Exploration

AbstractThin‐film solar cells (TFSCs) are garnering attention for their unstoppable growth as a sustainable energy source as well as their innovations and indispensability. TFSCs' efficiency has plateaued, necessitating the development of novel, practical, and inexpensive alternative energy sources. CdTe material lacks the band gap for the top layer. It can still be used as an absorber top layer in tandem photovoltaic cells by forming two new, promising materials, Cd1–xZnxTe (CZT) and Cd1–xMnxTe (CMT). Consequently, CZT and CMT based PV cells have been explored, and an attempt has been made to provide an alternative to cadmuim telluride. After exploring the physical properties of CZT and CMT thin films, CZT and CMT based photovoltaic cells were fabricated using the vacuum evaporation method. Both devices (with low absorber layer thickness, 1.05 µm) showed a power conversion efficiency of 6.67% and 6.11%, respectively. The depletion layer width and dopant densities of both photovoltaic cells were also determined by capacitance–voltage measurements. The quantum efficiencies were measured to identify the specific losses that are causing the measured short circuit current density to deviate from its ideal value. The reproducibility of the devices was also tested, and it is found to be good with an 8–12% deviation.

Functionalized Copper Phthalocyanine and Zinc Phthalocyanine as a Coating Layer on the Sensitivity of QCM-Based VOCs Sensor

&lt;p&gt;The sensitivity of a QCM-based VOCs sensor with two kinds of a metal phthalocyanine, i.e., copper phthalocyanine (CuPc) and zinc phthalocyanine (ZnPc) was examined for various VOCs. The sensitivity of the two metal phthalocyanine was determined by the compatibility of the overlapped metal orbitals (Cu(II) dan Zn(II)) and the corresponding VOCs. The CuPc and the ZnPc layer were deposited on the quartz crystal oscillator by a vacuum evaporation method. The frequency shift and the sensitivity of the sensors with the two functional layers were tested using 5 VOCs: formaldehyde, propanol, ethanol, toluene, and ketone. The CuPc sensor showed the highest sensitivity to formaldehyde. On the other hand, the ZnPc was highly sensitive to ethanol.&lt;/p&gt;

Fabrication and Characterization of Mineral Hydrophilic Antifogging Film via Vacuum Evaporation Method

Natural silicate minerals have a wide range of applications as green, non-toxic and low-cost materials. In this paper, hydrophilic anti-fog films of silicate minerals were generated via a vacuum evaporation coating method using natural feldspar minerals as raw material. Thermogravimetric analysis shows that the feldspar changes its structure during the coating process, which in turn changes the roughness of the film and improves the hydrophilicity of the film. The hydrophilicity, anti-fogging properties, optical properties and surface morphology of the films were characterized by contact angle measurements, the hydrothermal method, UV-VIS spectrophotometer and atomic force microscopy, respectively. The results show that the mineral films have excellent hydrophilicity. The best anti-fog effect was achieved at a minimum contact angle of 22.3° with water when the thickness of the film was 100 nm. The anti-fog effect gradually decreased with the increasing thickness of the film. The optical transmittance test showed that the film material had a negligible effect on the transmittance of the substrate. When the film thickness was 100 nm, the maximum optical transmittance was 92.2%. This is 4.5% higher than when the film was uncoated, which has a specific visual transmittance effect.

Особливості структури і фізико-хімічних властивостей міді, отриманої способом електронно-променевого випаровування-конденсації у вакуумі

Особливості структури і фізико-хімічних властивостей міді, отриманої способом електронно-променевого випаровування-конденсації у вакуумі