Reactive Evaporation Process Research Articles

Understanding the in-situ transformation of CuxO interlayers to increase the water splitting efficiency in NiO/n-Si photoanodes

The buried interface tens of nanometers beneath the solid-liquid junction is crucial for photocarrier extraction, influencing the overall efficiency of photoelectrochemical devices. Precise characterization of the interfacial properties is essential for device optimization but remains challenging. Here, we directly probe the in situ transformation of a CuxO interlayer at the NiO/n-Si interface by hard X-ray photoelectron spectroscopy. It is found that Cu(I) in the CuxO interlayer gradually transforms to Cu(II) with air exposure, forming an energetically more favorable interface and improving photoanode’s efficiency. Based on this finding, a reactive e-beam evaporation process is developed for the direct deposition of a CuO interlayer, achieving a half-cell solar-to-hydrogen efficiency of 4.56% for the optimized NiO/CuO/n-Si heterojunction photoanode. Our results highlight the importance of precision characterization of interfacial properties with advanced hard X-ray photoelectron spectroscopy in guiding the design of efficient solar water-splitting devices.

Numerical Simulation of Solvent Evaporation in a Reactive Silver Ink Droplet Deposited on a Heated Substrate.

Understanding the movement of silver ions (Ag+) in the solvent of a thermally evaporated particle-free reactive silver ink droplet is essential for optimizing the electronic inkjet printing process. In this work, a numerical study based on the Navier-Stokes equations is used to examine the microflows inside the evaporating solvent of a reactive silver ink droplet and to predict the morphology of the resultant Ag particle aggregations that form during the heat-activated processes. The droplet evaporation of the water-ethylene glycol ink solvent (H2O-(CH2OH)2) is simulated using COMSOL Multiphysics software. The model assumes that the evaporating fluid is heterogeneous due to the mass transfer of ethylene glycol molecules throughout the droplet by capillary flow. A layer of concentrated ethylene glycol forms at the fluid-substrate interface during solvent evaporation if the substrate is heated. The concentrated ethylene glycol molecules are then transported inward by the capillary action, and the resultant Ag particles, arising from the thermally driven reactions, accumulate at the bottom center of the drying droplet. The numerical simulations demonstrate that the droplet evaporation process depends on the water concentration in the solvent, substrate temperature, surface tension, and natural convection. Furthermore, the capillary flow dominates the fluid flow inside the evaporating droplet, causing some Ag particles to accumulate at the contact line, the commonly observed "coffee-ring effect". The results provide new insights into the chemical reactions that produce experimentally observed silver particle aggregations during the reactive silver ink droplet evaporation process and help establish realistic process parameters for improving the quality of inkjet-printed conductive silver films and electronic circuit microtraces.

A generalized CFD model for evaluating catalytic separation process in structured porous materials

A hybrid multiphase model is developed to simulate the simultaneous momentum, heat and mass transfer and heterogeneous catalyzed reaction in structured catalytic porous materials. The approach relies on the combination of the volume of fluid (VOF) and Eulerian–Eulerian models, and several plug-in field functions. The VOF method is used to capture the gas–liquid interface motion, and the Eulerian–Eulerian framework solves the temperature and chemical species concentration equations for each phase. The self-defined field functions utilize a single-domain approach to overcome convergence difficulty when applying the hybrid multiphase for a multi-domain problem. The method is then applied to investigate selective removal of specific species in multicomponent reactive evaporation process. The results show that the coupling of catalytic reaction and interface species mass transfer at the phase interface is conditional, and the coupling of catalytic reaction and momentum transfer across fluid–porous interface significantly affects the conversion rate of reactants. Based on the numerical results, a strategy is proposed for matching solid catalyst with operating condition in catalytic distillation application.

Low‐Temperature, Scalable, Reactive Deposition of Tin Oxide for Perovskite Solar Cells

Perovskite Solar Cells In article number 2200263, David George Lidzey and co-workers fabricated SnOx electron-extraction layers via a reactive electron-beam evaporation process from a metal source under a partial pressure of oxygen. These are then used in standard (n-i-p) architecture perovskite solar cells and achieve power conversion efficiencies up to 19.3%. The SnOx deposition process is performed onto substrates maintained at low temperature compared to similar techniques, with films not requiring any subsequent high-temperature post-deposition annealing. This demonstrates the potential compatibility of reactive electron-beam evaporation with roll-to-roll processing onto flexible polymeric substrates.

Analysis of a plasma-assisted reactive evaporation process for preparation of ZnO thin films: Modeling and experimentation

This paper focuses on modeling and simulation of a plasma-assisted reactive evaporation process. A dimensional unsteady-state model consisting of six nonlinear parabolic partial differential equations which account for the diffusive and convective mass transfer, bulk and surface reactions, non-uniform fluid flow, and plasma electron density profiles is developed. The equations are spatially discretized using finite difference methods and then numerically solved. The simulation results are validated by comparison with a commercial simulation software that computes similar equation systems. To validate the model, experimental measurements of film thickness are carried out on ZnO films deposited by plasma-assisted reactive evaporation. After 130 min of deposition time and deposition rate around 6 nm/min, the simulated results and the experimental measurements exhibit a good agreement (770 nm and 750 nm respectively), just around 2.59% discrepancy in the final thin film thickness, hence showing the high accuracy of the developed model.

Synthesis and characterization of superalloy coatings by cathodic arc evaporation

Superalloy targets were produced from Ni-(Al-C-Co-Cr-Mo-Ta-Ti-W) powders by spark plasma sintering technology. The crystalline structure of the as-produced targets was investigated by XRD analysis and compared with the evolution of phases resulting from the operation of the cathodic arc at the target (cathode) surface. Coatings were synthesized at superalloy substrates utilizing these superalloy targets in non-reactive and reactive evaporation processes. Synthesized coatings and target surfaces were compared with respect to chemical composition and crystal structure. The interface between coating and superalloy substrates was investigated by TEM. As an example, a complete layer stack was synthesized by cathodic arc evaporation starting from the superalloy substrate - superalloy coating interface to a fully oxidized superalloy coating showing epitaxial growth in the interface to the superalloy substrate.

Hybrid gas phase Ti-B-C-N coatings doped with Al

Deposition of Multicomponent hard coatings (Ti-B-C-N) on the molybdenum high-speed tool steels (AISI M52) has been achieved by mixed vapor deposition technique to improve the mechanical properties of the surface. The Ti-B-C-N coating samples were produced by a hybrid gas phase process, were in this technique, the coating materials that supplied in the gas phase were produced from powders that vaporized by thermal energy (that is, PVD- Reactive Evaporation Process), while the reactor that used to deposit Ti-Base coatings is a hot-wall chemical vapor deposition (HWCVD) system equipment. The resulting coating exhibit different amounts of the Titanium oxide phase, which is characterized by the low mechanical and thermal properties. These phases (Ti-O) will have determinant effect on the coated high speed steel tools. The alloying of transition metal nitrides and borides (TiN, BN, and TiB) with stable oxide-forming elements (for example, Cr, Al, Si and Ni) will have the effect of decreasing crystallinity, promoting nanocrystalline structure and increasing oxidation resistance. Ti-Base hard film was characterized by XRD technique, and Scanning Electron Microscopy (SEM). Mechanical characterization of the hard films has been performed by using The Ball-on-disk wear tests. With different deposition temperatures (550–950 °C) and at the same reactive gas flow rate 2.5SLPM (Standard Litter Per Minute), Al doping in the Ti-B-C-N coating has proven a great success by producing a new film microstructure (free of Ti-O phases) which contains fine fiber structure as a strengthening second phase in the Ti-B type structure with a sufficient amorphous phase (B-N) as a matrix. Maximum hardness of 4230 HV is achieved, with better thermal stability during the process of the wear test than the uncoated H.S.S samples. Also a great enhancement in the wear resistance values for this coating film (Volume loss = 1.8291*10−7 mm3) was reported.

Titanium-Base Nanostructure Coatings for AISI M52 Tool Steel by Gas-Phase Mix Process

Deposition of Multicomponent hard coatings (Ti-B-N-C) on the molybdenum high-speed tool steel (AISI M52) has been achieved by mixed vapor deposition technique to improve the mechanical properties of the surface. In this technique the coating materials that were supplied in the gas phase were produced from powders that vaporized by thermal energy (that is, PVD- Reactive Evaporation Process), while the reactor that used to deposit Ti-Base coatings is hot-wall chemical vapor deposition (HWCVD) system equipment. This combination results in technical and financial advantages. The structure of deposited Ti-Base hard film was characterized by XRD technique, Scanning Electron Microscopy (SEM), and Energy Dispersive X-ray spectroscopy (EDX). Mechanical characterization of the hard films has been performed by using Vickers micro hardness tester and The Ball-on-disk wear tests. With different reactive gas flow rates that ranged from 500 to 3000Sccm(standard Cubic Centimeter per Minute), the film showed amorphous matrix with crystalline Nano fibers of Ti-B phase which led to achieve higher hardness of 2051HV and better wear resistance with relatively good COF values of 0.61 than the uncoated tools.

Laser damage study of nodules in electron-beam-evaporated HfO_2/SiO_2 high reflectors

A reactive electron beam evaporation process was used to fabricate 1.064 μm HfO2/SiO2 high reflectors. The deposition process was optimized to reduce the nodular density. Cross-sectioning of nodular defects by a focused ion-beam milling instrument showed that the nodule seeds were the residual particles on the substrate and the particulates from the silica source "splitting." After optimizing the substrate preparation procedure and the evaporation process, a low nodular density of 2.7/mm2 was achieved. The laser damage test revealed that the ejection fluences and damage growth behaviors of nodules created from deep or shallow seeds were totally different. A mechanism based on directional plasma scald was proposed to interpret observed damage growth phenomenon.

Abrasive wear resistance of Ti 1 − xAl xN hard coatings deposited by a vacuum arc system with lateral rotating cathodes

In this work, a series of Ti 1 − x Al x N (0 ≤ x ≤ 0.7) coatings were deposited on high speed steel (HSS) substrates by a vacuum arc reactive evaporation process from two lateral rotating elemental titanium and aluminium cathodes in a pure nitrogen atmosphere. The composition, crystalline structure and hardness of the as-deposited coatings were analyzed by energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and nanoindentation experiments. The abrasion wear resistance of the TiAlN coatings was measured by a micro-abrasion tester with the presence of SiC water-based slurry with a concentration of 0.35 g/cm 3. It was found that with increasing the Al/Ti atomic ratio the hardness of the as-deposited TiAlN coatings initially increased up to a maximum value of about 40 GPa at around Al/Ti = 1.22, and then the coating hardness decreased rapidly with increasing aluminium content further. The abrasion wear resistance of the TiAlN coatings is evidently better, with one order of magnitude lower in the wear rate, than the bare HSS substrate. With increasing Al/Ti atomic ratio, the variation trend of the abrasion wear rate of the TiAlN coatings is generally opposite to that of coating hardness. This means the abrasion wear resistance of the TiAlN PVD hard coatings is predominately determined by the hardness of the coating materials. It was also noted that, besides the coating hardness, the composition of the TiAlN coatings also plays an important role in determining their abrasive wear resistance. The coatings in the higher Al content range (Al/Ti ≥ 1.60) exhibited an evident better abrasive wear resistance than those in the lower aluminium content range (Al/Ti ≤ 0.32) when their hardness is similar. This fact could be related to the finer microstructure of the coatings incorporated with higher aluminium content.

Complementary inverter circuits based on p-SnO2 and n-In2O3 thin film transistors

Thin film transistors (TFTs) of indium oxide (In2O3) and tin oxide (SnO2) were fabricated on SiO2 gate dielectric using reactive evaporation process. Structural investigation of the films revealed that In2O3 films were polycrystalline in nature with preferred (222) orientation and SnO2 films exhibited amorphous nature. The x-ray photoelectric spectroscopy measurements suggest that SnO2 films were oxygen rich and presume mixed oxidation states of Sn, namely Sn2+ and Sn4+. While the In2O3 based TFTs possess n-type channel conduction, SnO2 based TFTs exhibited anomalous p-type conductivity. Integration of these n- and p-type devices resulted in complementary inverter with a gain of 11.

Titanium nitride coatings to inner wall of narrow tube

Titanium nitride (TiN) shows considerable hydrogen impermeability and is expected as a hydrogen-impermeable coating of cladding tubes for metal hydride fission fuel. The TiN coating production by the plasma process is very complicated because the cladding tube is not wide enough to create stable plasma. In this study, a simple reactive evaporation process was employed for the coating process of TiN films on the inner wall of a narrow tube. The films were thermally deposited on stainless steel sheets as the substrate and were coiled around the inner wall of silica glass tubes. A Ti wire twisted with a Mo filament was used for the evaporant. As a result, thin films with gold color were obtained. From the XRD measurement of the films, distinct diffraction patterns of TiN phase were observed. A reactivity of N2 gas molecules with Ti atoms in Ti-N film formation was measured quantitatively. The reaction probability of N2 molecules rN2 is defined as the ratio of the N2 absorption rate AN2 on Ti to the rate of N2 impingement ZN2. Reactive evaporation process showed 013 . 0 2 ≅ N r . It was 1/5

Realization of In2O3 thin film transistors through reactive evaporation process

In 2 O 3 thin films have been grown by reactive evaporation of indium in ambient oxygen. The films were structurally characterized by x-ray diffraction (XRD) and atomic force microscopy techniques. The results of XRD revealed that the films were polycrystalline in nature with preferred (222) orientation. The as-grown films were subjected to various annealing treatments to modulate the conductivity of the films for thin film transistors (TFTs). TFTs fabricated on SiO2 gate dielectric exhibited an on/off ratio of 104 and a field-effect mobility of 27cm2∕Vs. High on-state current makes them potential candidates for flat-panel display devices.

Titanium nitride coatings to inner wall of narrow tube

Titanium nitride TiN has considerable hydrogen impermeability and is expected as a prevention coating of hydrogen gas parmiation for a cladding tube of metal hydride fission fuel. The TiN coating produced with plasma process is very complicated because the cladding tube is not wide enough to create stable plasma. A simple reactive evaporation process was selected for coationg process of TiN films to inner wall of narrow tube or stainless steal tube. The films were thermally deposited on stainless steel sheets coiled around inner wall of silica glass tubes. Nitrogen as a reactive gas was introduced into the vacuum chamber with pressure range of 5.0×10-2 Pa ∼ 3.0×10-1 Pa. Thin films with gold color were obtained. From XRD measurement of films, distinct diffraction patterns of TiN phase were observed. A reactivity of N2 gas molecules with Ti atoms in Ti-N film formation has measured quantitatively. The reaction probability of N2 molecules rN2 is defined as the ratio of the absorbing rate of N2 on Ti surface AN2 to the rate of N2 impingement ZN2. Reactive evaporation process exhibits the highest N2 reaction probability rN2 ≅ 0.05. It was the similar value of rN2 with Ti film prepared by ARE plasma processes.

Deposition of indium nitride films by activated reactive evaporation process – a feasibility study

Indium nitride (InN) films are deposited by ‘activated reactive evaporation (ARE)’ process using parallel plate coupled nitrogen plasma (radio frequency source of 13.56 MHz) and evaporation of pure indium powder by resistive heating. Depositions are carried out by varying RF plasma power, on n-type silicon 〈1 0 0〉 substrate, maintained at room temperature, at a nitrogen gas pressure of 1.06 × 10 −1 Pa (8 × 10 −4 Torr). The film's crystallinity was examined by X-ray diffraction (XRD) and topography by scanning electron microscope (SEM). The diffraction pattern shows polycrystalline nature of the deposited films with characteristics of hexagonal structure. XRD peak intensity increases with increase in power. SEM observations show a smooth and pinhole free surface having improved quality of film with hexagonal structure as the power is increased from 60 to 120 W. Primary X-ray photoelectron spectroscopy (XPS) results show binding energies of the In 3d levels and N 1s level matching well with that of stoichiometric InN. Further, the refractive index of the films, measured by ellipsometry, is in the range of η = 2.79–2.91 with the variation of plasma power, which is in good agreement with the standard value for indium nitride ( η = 2.9). These results indicate the feasibility of using, ‘activated reactive evaporation (ARE)’ process for indium nitride depositions on silicon 〈1 0 0〉 substrates maintained at room temperature.

Oxygen partial pressure dependence of the structural properties of CdO thin films deposited by a modified reactive vacuum evaporation process

Thin films of cadmium oxide were thermally deposited on glass substrates at partial pressures of oxygen, pO 2 in the range 1.33×10 −2 to 0.133 Pa at a substrate temperature of 160 °C. Energy dispersive analysis of X-ray fluorescence (EDAX) revealed that the CdO films deposited at pO 2 value of 4.00×10 −2 Pa were nearly stoichiometric. X-ray diffractometry (XRD) confirmed the polycrystalline nature of the film structure. All the films showed an fcc structure of the NaCl-type, as the dominant phase. The films exhibited preferred orientation along the (1 1 1) diffraction plane. The texture coefficients calculated for the various planes at different oxygen partial pressures ( pO 2) indicated that the maximum preferred orientation of the films occurred along the (1 1 1) plane at an oxygen partial pressure of 4.00×10 −2 Pa. This was interpreted in terms of oxygen chemisorption and desorption processes. The lattice parameters determined from the diffraction peaks were in the range 4.655–4.686 Å. The average lattice parameter a 0 found by extrapolation using the Nelson–Riley function was 4.696 Å. Both the lattice parameter and the crystallite size were found to increase with increased partial pressure of oxygen. On the other hand, the strain and dislocation density were found to decrease as the partial pressure of oxygen was raised. A maximum (80%) in the optical transmittance at λ=600 nm and minimum in the electrical resistivity (9.1×10 −4 Ω cm) of the films occurred at an optimum partial pressure of oxygen of 4.00×10 −2 Pa. The results are discussed.

Optical characterisation of thin film cadmium oxide prepared by a modified reactive thermal evaporation process

The optical transmission spectra of transparent conducting cadmium oxide (CdO) thin films deposited by a modified reactive evaporation process onto glass substrates have been measured. The interference fringes were used to calculate the refractive index, thickness variation, average thickness and absorption coefficient of the films. The influence of the partial pressure of oxygen (PO2), during film deposition on the transmittance, optical constants and bandgap of the films is studied. The observation of an optimum value of PO2­ (= 0.040 Pa) at which the transmission is maximum is considered to be a particularly significant result. So, too, is the result that the width of the bandtail has a minimum at the optimum PO2 value. Key words: CdO Films, Optical Transmittance, Evaporation (Global Journal of Pure and Applied Sciences: 2003 9(4): 567-574)

Thickness-dependent metal–insulator transition in V2O3 ultrathin films

In this study, V2O3 ultrathin films about 5–20 nm thick were prepared on Al2O3 (0001) substrates through a reactive evaporation process. Auger electron spectroscopy and x-ray photoelectron spectroscopy have been used in situ to characterize their compositions and chemical states. Electric resistance measurements show that V2O3 films transform from metallic to semiconducting with the decrease of film thickness, which results from the a1g level rising because the lattice mismatch between the substrate and the film expands the c/a parameter ratio. No temperature-induced metal–insulator transition (like that in bulk V2O3) was observed in V2O3 thin films at low temperature. We conclude that stress plays a major role in suppressing the temperature-induced metal–insulator transition.

Characterization of indium nitride films deposited by activated reactive evaporation process

Indium nitride films are deposited in the presence of nitrogen plasma by ‘activated reactive evaporation (ARE)’ process on silicon substrate maintained at room temperature. Indium powder was evaporated by resistive heating in the presence of nitrogen plasma excited by a radio frequency (RF) power source (13.56 MHz). The refractive index of 2.91 obtained by ellipsometry, was in good agreement with that of the standard value of indium nitride ( η=2.9). Observation of the films by scanning electron microscope shows a smooth and pinhole-free surface and the diffraction pattern reveals the polycrystalline nature with characteristics of hexagonal structure. In3d 5/2, In3d 3/2 and N1s levels X-ray photoelectron spectra are observed at binding energies of 443.4 eV, 451.8 eV and 396.5 eV, respectively, indicating the formation of indium nitride. Fourier transform infrared spectrum of the deposited film shows the presence of InN bond. These results indicate the feasibility of the ARE process for the deposition of indium nitride on silicon 〈100〉 substrate maintained at room temperature.

Micro-mechanical properties of ion-plated carbon nitride thin films

Carbon nitride films have been synthesized by using several processes of film deposition techniques including plasma-CVD, sputtering and ion-beam deposition, etc., according to outstanding properties of the super-hard cubic or beta-type C 3N 4 compound. We also prepared the carbon nitride films with magnetically enhanced plasma ion-plating method. The carbon nitride films were deposited on Si substrate through the reactive evaporation process in carbon vapor and nitrogen plasma. The mechanical properties of the films deposited under various conditions have been surveyed and their nano-indentation characteristics have been especially investigated. The hardness of the films showed comparatively low values approximately 2–8 GPa. The hardness of films was lower than that of silicon substrate. However, the films have shown a large amount of elastic recovery on unloading, even if they did not have any resistance for penetration on loading.