Vapor Deposition Research Articles

Initial stages of rejuvenation of vapor-deposited glasses during isothermal annealing: Contrast between experiment and simulation.

Physical vapor deposition can prepare organic glasses with high kinetic stability. When heated, these glassy solids slowly transform into supercooled liquid in a process known as rejuvenation. In this study, we anneal vapor-deposited glasses of methyl-m-toluate for 6h at 0.98Tg to observe rejuvenation using dielectric spectroscopy. Glasses of moderate stability exhibited partial or full rejuvenation in 6h. For highly stable glasses, prepared at substrate temperatures of 0.85Tg and 0.80Tg, the 6h annealing time is ∼2% of the estimated transformation time, and no change in the onset temperature for the α relaxation process was observed, as expected. Surprisingly, for these highly stable glasses, annealing resulted in significant increases in the storage component of the dielectric susceptibility, without corresponding increases in the loss component. These changes are interpreted to indicate that short-term annealing rejuvenates a high frequency relaxation (e.g., the boson peak) within the stable glass. We compare these results to computer simulations of the rejuvenation of highly stable glasses generated by using the swap Monte Carlo algorithm. The in silico glasses, in contrast to the experiment, show no evidence of rejuvenation within the stable glass at times shorter than the alpha relaxation process.

Influence of Molybdenum Addition on the Structure, Mechanical Properties, and Cutting Performance of AlTiN Coatings

Though AlTiN coating has been intensively studied, there is still a need to develop AlTiN coating to meet the growing demand of industrial machining. One effective way to improve the performance of AlTiN coating is by adding alloying elements. In this study, AlTiN and AlTiMo coatings were deposited using multi-arc ion plating to investigate the influence of molybdenum addition on the structure, mechanical properties, and cutting performance of AlTiN coatings. Spherical droplets formed on the surfaces of both coatings, with the AlTiMoN coating exhibiting more surface defects than the AlTiN coating. The grazing incidence X-ray diffraction results revealed the formation of an (Al,Ti)N phase formed in the AlTiN and AlTiMoN coatings. Molybdenum doping in the AlTiMoN coating slightly reduced the grain size. Both coatings exhibited excellent adhesion to the substrate. The hardness (H), elastic moduli (E), H/E, and H3/E2 ratios of the AlTiMoN coating were higher than those of the AlTiN coating. The improvement in the mechanical properties was attributed to grain refinement and solution strengthening. Molybdenum doping improved the tribological properties and cutting performance of the AlTiN coatings, which was ascribed to the formation of MoO3 as a solid lubricant. These results show a path to increase the performance of AlTiN coating through molybdenum addition and provide ideas for the application of AlTiMoN coatings for cutting tools.

A Review of Nanostructure Coating Techniques to Achieve High-Precision Optical Fiber Sensing Applications

Optical fiber sensors have emerged as a critical sensing technology across various fields due to their advantages, including high potential bandwidth, electrical isolation that is safe for utilization in electrically hazardous environments, high reliability, and ease of maintenance. However, conventional optical fiber sensors face limitations in achieving high sensitivity and precision. The integration of nanostructures with advanced coating technology is one of the critical solutions to enhancing sensor functionality. This review examined nanostructure coating techniques that are compatible with optical fiber sensors and evaluated etching techniques for the improvement of optical fiber sensing technology. Techniques such as vapor deposition, laser deposition, and sputtering to coat the nanostructure of novel materials on the optical fiber sensors are analyzed. The ability of optical fiber sensors to interact with the environment via etching techniques is highlighted by comparing the sensing parameters between etched and bare optical fibers. This comprehensive overview aims to provide a detailed understanding of nanostructure coating and etching for optical fiber sensing and offer insights into the current state and future prospects of optical fiber sensor technology for sensing performance advancement, emphasizing its potential in future sensing applications and research directions.

Spectrometers of Neutrons and Fast Atoms of Tokamak Thermonuclear Plasma Based on CVD Synthesized Diamond Single-Crystal Films

High radiation resistance, chemical inertness, the ability to operate at elevated temperatures, high mobility and efficiency of charge-carrier collection are important properties of diamond for designing detectors and spectrometers of ionizing radiation. Currently, diagnostics of neutrons and neutral particle fluxes based on diamond detectors for the ITER thermonuclear reactor are justified and developed. This work presents the results of a Raman spectroscopy and photoluminescence spectroscopy study of the electronic quality of synthesized epitaxial diamond films obtained by vapor deposition in a hydrogen and methane mixture in the ARDIS reactor on boron-doped single-crystal diamond substrates. To confirm their electronic quality, detectors have been made from films selected by spectrometric methods and the charge collection efficiency and energy resolution have been measured when irradiated with alpha particles from a 241Am source and 14.7 MeV fast neutrons from the ING-07T2 neutron generator.

Evaluation of the thermal conductivity of chromium coatings for accident tolerant fuels using thermoreflectance techniques

The deployment of Cr coatings as accident tolerant fuel cladding inside nuclear reactors necessitates a thorough understanding of their performance, including mechanical, chemical, irradiation, and thermal properties. While significant research has delved into the former, the thermal transport properties of Cr coatings, which dictates fuel temperature and impacts fuel safety, have been relatively underexplored. This work presents an investigation into the thermal conductivity of 12 µm-thick Cr coatings fabricated by multi-arc ion plating employing high-resolution frequency and spatial domain thermoreflectance techniques. Vacuum annealing was utilized to control the morphology of coatings to explore the impact of grain size. The results indicate that both as-deposited and annealed coatings, despite possessing distinct grain morphologies, exhibit thermal conductivities similar to their bulk counterparts. The influence of boundaries on thermal transport is anticipated to become prominent as the critical dimension diminishes below 0.5 μm. Future investigation is required to address the potential impact of adverse reactions, such as oxygen ingress and irradiation, on the thermal properties of Cr coatings to ensure safe and efficient operation in nuclear reactor environments.

Ge-doping in polycrystalline GaN layer through electron beam evaporator deposition with successive ammonia annealing

Ge-doping in polycrystalline GaN layer through electron beam evaporator deposition with successive ammonia annealing

Design and Corrosion Resistance Performance of Nano-Multilayer Coatings for the Protection of Breathing Gas Cylinders Used in Diving

Seamless gas cylinders for diving exhibit excellent low-temperature impact performance, lightweight characteristics, and good corrosion resistance, making them widely applicable in underwater activities. However, during use, the peeling of paint or corrosion on the surface of these cylinders poses a significant threat to their safety. In this study, environmentally friendly arc ion plating technology was used to deposit TiBN, CrAlN, and nano-multilayer coatings of CrAlN/TiBN. The surface morphology, tribological properties, and corrosion resistance of these coatings were investigated. The results indicated that both CrAlN and CrAlN/TiBN coatings possess fewer droplets, pinholes, and pits, and the cross-section of the CrAlN/TiBN coating exhibits a denser structure. The preferred orientation for TiBN was identified as TiB2 (101), while that for CrAlN was Cr(Al)N (200), with the preferred orientation for CrAlN/TiBN being TiB2 (101). The friction measurements revealed that the lowest coefficient was observed in the CrAlN/TiBN coating (0.489), followed by CrAlN (0.491) and then TiBN (0.642). Electrochemical tests conducted in artificial seawater demonstrated that the self-corrosion potential was highest for the CrAlN/TiBN coating, followed by CrAlN and lastly TiBN. The developed TiBN-based nano-multilayer coatings hold substantial application value in protecting seamless gas cylinders used in diving.

The Cr/Cr2N multilayer coating with high load-bearing capacity and thermal shock resistance

By utilizing the multi-arc ion plating (MAIP) technique, multilayer coatings with varying Cr/Cr2N ratios and uniform thicknesses were deposited onto a nitrided Cr–Ni–Mo–V steel substrate. The evolution of microstructure and mechanical properties was characterized using scanning electron microscopy, X-ray diffraction, and micro-Vickers hardness testing. The load-bearing capacity of the multilayer coatings with varying modulation ratios was comprehensively evaluated through Vickers indentation tests with a 10-kgf load, Rockwell hardness testing with a 150-kgf load, and scratch tests with loads of 60 and 100 N. The coating with a Cr/Cr2N layer modulation ratio of 0.2/0.4 μm exhibited a hardness of 1385 HV and an adhesion strength of 91 N. Under a 10 kgf load, this coating also demonstrated excellent fracture toughness, and did not exhibit any radial cracks in the Vickers indentation. Subsequently, a thermal shock test, involving quenching from 900°C water to 25°C, was conducted on the coating with the best comprehensive performance. The multilayer coating with high load-bearing capacity could withstand 52 thermal shock cycles before delamination occurred. Failure analysis further confirmed that the multilayer coating with enhanced load-bearing capacity effectively resisted thermal shock.

Insights into surrogate respiratory droplet behaviour on inclined surfaces: Implications for disease transmission

Disease transmission via fluid ejections from infected individuals presents a significant public health challenge. The ejected droplet frequently lands on substrates with varying orientations, including horizontal, vertical, and inclined. However, the behaviour of disease-causing droplets on inclined substrates remains unexplored. Recent research has demonstrated that droplet evaporation, flow, and colloidal deposition are significantly altered when surfaces are inclined. Changes in contact angle impact evaporative flux and induce flow between the top and bottom edges of the droplet. This study examines the behaviour of simulated respiratory droplets containing NaCl, mucin, and micrometer-sized particles as pathogen surrogates, focusing on substrate inclinations of 0°, 45°, and 90° on glass surfaces. As respiratory droplets evaporate, their solute concentration rises, altering both surface tension and viscosity. The study explores the coupled effects of solute concentration variations and asymmetric evaporative flux at varying relative humidity conditions and droplet volumes. The presence of salt and mucin induces Marangoni flow, potentially altering evaporation, flow patterns, and deposition dynamics. Additionally, sedimentation flow influences crystal nucleation sites and precipitation patterns. Results reveal unprecedented crystallization dynamics on inclined substrates, with notable differences in nucleation and growth based on the angle of inclination. Optical profilometry and confocal microscopy further show that surrogate bacterial particles accumulate excessively at the bottom edge of inclined droplets, suggesting an elevated risk of pathogen survival on inclined fomites. These findings highlight the critical importance of considering substrate orientation in understanding the transmission of disease through surface-bound droplets, offering insights that could inform public health strategies.

Two‐Dimensional Layered Topological Semimetals for Advanced Electronics and Optoelectronics

AbstractDue to the outstanding physical properties and the integrated characteristics, such as the gapless band structure, high state density, high conductivity, dangling‐bond‐free surface, and tunable Fermi level, two‐dimensional layered topological semimetals (2D LTSMs) exhibit a promising application prospect for including electrode contact and terahertz detection. Despite the surging in attention, a comprehensive strategy is still crucial to meet the necessary conditions for the practical application of 2D LTSMs. According to the fermion types and the band structures, 2D LTSMs can be divided into Dirac semimetals, Weyl semimetals, and nodal‐line semimetals. This review comprehensively encapsulates the intrinsic properties, typical synthesis methods, and applications in electronics and optoelectronics about these 2D LTSMs. To establish the fundamental theory, typical crystal structures, and physical properties of different 2D LTSMs are summarized at first. The effective synthesis strategies including exfoliation, molecular beam epitaxy, and vapor deposition are analyzed systematically. Finally, the article emphasizes the exploration of applications, significant challenges, and promising development directions of 2D LTSMs, which will drive 2D LTSMs to become the promisingly leading technology for next‐generation electronic and optoelectronic systems.

Enhancing Efficiency and Stability of Inverted Perovskite Solar Cells through Solution‐Processed and Structurally Ordered Fullerene

AbstractThe electron transporting layer (ETL) used in high performance inverted perovskite solar cells (PSCs) is typically composed of C60, which requires time‐consuming and costly thermal evaporation deposition, posing a significant challenge for large‐scale production. To address this challenge, herein, we present a novel design of solution‐processible electron transporting material (ETM) by grafting a non‐fullerene acceptor fragment onto C60. The synthesized BTPC60 exhibits an exceptional solution processability and well‐organized molecular stacking pattern, enabling the formation of uniform and structurally ordered film with high electron mobility. When applied as ETL in inverted PSCs, BTPC60 not only exhibits excellent interfacial contact with the perovskite layer, resulting in enhanced electron extraction and transfer efficiency, but also effectively passivates the interfacial defects to suppress non‐radiative recombination. Resultant BTPC60‐based inverted PSCs deliver an impressive power conversion efficiency (PCE) of 25.3 % and retain almost 90 % of the initial values after aging at 85 °C for 1500 hours in N2. More encouragingly, the solution‐processed BTPC60 ETL demonstrates remarkable film thickness tolerance, and enables a high PCE up to 24.8 % with the ETL thickness of 200 nm. Our results highlight BTPC60 as a promising solution‐processed fullerene‐based ETM, opening an avenue for improving the scalability of efficient and stable inverted PSCs.

Moisture Transformation in Warm Air Intrusions Into the Arctic: Process Attribution With Stable Water Isotopes

AbstractWarm Airmass Intrusions (WAIs) from the mid‐latitudes significantly impact the Arctic water budget. Here, we combine water vapor isotope measurements from the MOSAiC expedition, with a Lagrangian‐based process attribution diagnostic to track moisture transformation in the central Arctic Ocean during two WAIs, under contrasting sea‐ice concentrations (SIC). During winter with high SIC, two moisture supplies are identified. The first is Arctic moisture, locally‐sourced over the sea ice, with isotopic composition influenced by kinetic fractionation during ice‐cloud formation and vapor deposition. This moisture is rapidly overprinted by low‐latitude moisture advected poleward during WAI. In summer under low SIC, moisture is supplied through evaporation from land and ocean, with moisture removal via liquid‐cloud and dew formation. The isotopic composition reflects the influence of higher relative humidity at the evaporation sites. Given the projected increase of frequency and duration of WAIs, our study contributes to assessing process changes in the Arctic water cycle.

Surface modification and patterning of polymer thin films by plasma and adsorption behavior of proteins

The surface wettability property of hydrophobic polystyrene (PS) and hydrophilic polyethylene glycol (PEG) thin films subjected to modification by direct current plasma glow discharge is studied. The polymer films exhibited change of surface wettability on exposure to air, nitrogen, oxygen or argon plasmas. In PS films a swift modification to hydrophilic surface and subsequent steady recovery following first order kinetics are observed. The rate of modification and recovery are adjustable by adjusting the plasma ambient and parameters, and additional wet-chemical treatment using ionic solutions. In PEG films the hydrophobic wettability evolve with ageing following the first order kinetics, and is stable for long period on exposure to air ambient. Moreover, a vapor deposition like process is possible using the PEG films as source to deposit self-assembled molecular layers with hydrophobic wettability on other surfaces. Using surface modification or molecular deposition processes, the fabrication of wettability patterns in the surface of PS and PEG films, and on other surfaces by vapor transport using PEG films, and also the possibility to produce gradient wettability patterns are demonstrated. Moreover, the adsorption behavior of immuno-specific system of proteins on surface modified hydrophilic PS films is studied.

Influence of NiCrAlY coating on anti-corrosion of M951 alloy

M951 alloy is a cast nickel-based super-alloy widely used in gas turbines and aircraft engines, thus a suitable high temperature protective coating must be applied on its surface to enhance the corrosion resistance. In this research, NiCrAlY coating was deposited on M951 by arc ion plating. TGA at 1100 °C, cyclic oxidation at 1000 °C and hot corrosion in molten Na2SO4+25 wt% K2SO4 salt at 850 °C of M951 bare alloy and NiCrAlY coating specimens were investigated respectively. After TGA and cyclic oxidation, mixed oxides of NiO, NiAl2O4, Nb2O5 and Al2O3 formed on M951 surface, which spalled seriously during cyclic oxidation process. Thin, continuous and adhesive α- Al2O3 formed on the surface of NiCrAlY coating after both oxidation process. In molten Na2SO4+25 wt%K2SO4 salt at 850 °C, catastrophic corrosion occurred for the M951 alloy only after 10 hours, while thin and continuous θ- Al2O3 film formed on the surface of the NiCrAlY coating. In a word, NiCrAlY coating greatly improved the high temperature oxidation and hot corrosion resistance of the M951 superalloy. This study will further refine the oxidation and corrosion behaviors of M951 superalloy under different high temperature protective coatings and provides theoretical and experimental basis for the application of M951 superalloy in corrosive environments.

Correlation of Seebeck coefficient and selenization temperature in CuSe thin films grown on glass substrate

Copper selenide is emerging as a promising thermoelectric material that has the ability to harvest electricity from heat. In the present research work, copper selenide thin films were grown on glass substrate using thermal evaporation deposition technique. The phase transition from cubic to hexagonal structure was achieved by the selenization of grown samples at different temperatures (250, 300 and 350 °C) for 2 h. The phase, morphology and thermoelectric properties of the selenized CuSe thin films were studied using different characterization techniques. It was observed that the structural, morphological, and thermoelectric properties of the samples were modulated by varying the selenization temperature. XRD results suggested that as grown sample possessed a cubic phase but it transformed into hexagonal phase by selenization process. It was observed that Seebeck coefficient, electrical conductivity and power factor were modulated with the selenization temperature with maximum value of power factor (3.0 × 10−5±0.5 W m−1C−2) was obtained at optimal selinization temperature.

Integral LOCA experiments to study FFRD behavior of high burnup nuclear fuels

This paper introduces the Integral Loss Of Coolant (LOCA) facility (i-LOCA) established at Seoul National University. The facility was designed to investigate the integral fuel behavior of Light Water Reactors during LOCA, encompassing aspects such as cladding oxidation, ballooning and burst, reflood quenching, secondary hydriding, and fuel pellet dispersal. Integral LOCA experiments were carried out using three types of surrogate ZrO2 pellets, representing various segment burnups: cylindrical pellets with no fuel fragmentation (<55 GWd/MTU), mixed fragments of different sizes simulating ∼68 GWd/MTU (D = 0.3, 0.5, 1.0, 2.0, 3.0, and 5.0 mm with the same mass fraction), and small single powdered fragments simulating ultra-high burnup fuel (D = 0.5 mm, ∼94 GWd/MTU). Zr-Nb-Sn, Zr-1.1Nb, and Cr-coated (15 μm, Arc Ion Plating) Zr-1.1Nb ATF cladding were employed, with rod internal pressures ranging from 1 MPa to 7 MPa. The burst size and hoop strain exhibited significant variations depending on the type of surrogate pellets used, with larger burst sizes and hoop strains observed for smaller average diameters of surrogate pellets due to the effect of azimuthal and axial temperature distribution. Fuel dispersal was influenced by rod internal pressure, burst size, and the size of pellet fragments. Only pellet fragments smaller than the burst hole width underwent dispersal upon fuel burst, while larger fragments blocked the dispersal of smaller fragments. The rapidly escalating average dispersal fraction of single powder compared to mixed powder indicated a threshold burnup for fuel dispersal between 69–94 GWd/MTU. Cladding inner oxidation length was influenced by burst hole size and remaining fuel pellets. The results of inner oxidation confirmed the validity of the U.S. NRC’s assumption regarding the length of inner wall oxidation. The tested 15 μm Cr-coated cladding tubes, produced using the arc ion plating method, exhibited no significant differences in burst geometry, fuel dispersal, inner oxidation, and secondary hydriding when compared to the uncoated reference cladding.

Nitrogen doping of cuprous oxide films: A surface science perspective

Nitrogen doping of Cu2O films grown on Au(111) and Pt(111) supports was explored by a variety of surface-science techniques, including electron-diffraction, X-ray photoelectron-spectroscopy (XPS), scanning tunneling microscopy and photoluminescence spectroscopy (PL). The films were prepared by Cu vapor deposition and high-pressure oxidation at 50 mbar O2. Nitrogen was inserted by adding N2 to the reactive gas or via sputter doping. Only the latter resulted in a clear N1s signal in XPS, compatible with the insertion of N-atoms at O substitutional sites. The N-doping caused an overall degradation of the oxide lattice and suppressed the formation of the (√3×√3)R30° surface reconstruction observed on pristine Cu2O(111). Moreover, the oxide Fermi level shifted from the valence-band top into the band gap, indicative for a reduced p-type conductivity of the sample upon doping. The N-dopants featured low thermal stability and largely desorbed at around 500 K, leaving behind a pronounced 850 nm PL peak due to O vacancy emission. Our findings indicate that the N-atoms initially occupy O substitutional sites but get removed easily at moderate temperature, casting doubts whether N-doping is a suitable pathway to improve the conductance and luminescence behavior of Cu2O.

Simulated particle evolution within a winter storm: contributions of riming to radar moments and precipitation fallout

Abstract. Remote sensing radars from airborne and spaceborne platforms provide critical observations of clouds to estimate precipitation rates across the globe. The ability of these radars to detect changes in precipitation properties is advanced by Doppler measurements of particle fall speed. Within mixed-phase clouds, precipitation mass and its fall characteristics are especially sensitive to the effects of riming. In this study, we quantified these effects and investigated the distinction of riming from aggregation in Doppler radar vertical profiles using quasi-idealized particle-based model simulations. Observational constraints of a control simulation were determined from airborne in situ and remote sensing measurements collected during the Investigation of Microphysics and Precipitation for Atlantic Coast-Threatening Snowstorms (IMPACTS) for a wintry–mixed precipitation event over the northeastern United States on 4 February 2022. From the upper boundary of a one-dimensional column, particle evolution was simulated through vapor deposition, aggregation, and riming processes, producing realistic Doppler radar profiles. Despite a modest observed amount of supercooled liquid water (0.05 g m−3), riming accounted for 55 % of the ice-phase precipitation mass, cumulatively increasing reflectivity by 44 % and Doppler velocity by 68 %. Independent evaluation of process-based sensitivities showed that, while radar reflectivity is comparably sensitive to either riming- or aggregation-based particle morphology, the Doppler velocity profile is uniquely sensitive to particle density changes during riming. Thus, Doppler velocity profiles advance the diagnosis of riming as a dominant microphysical process in stratiform clouds from single-wavelength radars, which has implications for quantitative constraints of particle properties in remote sensing applications.

Design and fabrication of highly efficient antireflective coating in MWIR on germanium using ion-assisted e-beam deposition

We present the design, fabrication, and characterization of a multilayer anti-reflective (AR) coating on a Germanium (Ge) substrate for mid-wavelength infrared (MWIR) applications using the ion-assisted electron-beam evaporation (IAPVD) technique. The AR coating structure comprises five layers of thin films, alternating between low (nL) and high (nH) refractive index materials, specifically silicon dioxide (SiO2) and Ge. The total thickness of the multilayer structure is maintained below 2 μm. The design was meticulously optimized for the 3.6–4.9 μm MWIR range using OptiLayer software, achieving an impressive average transmission of 99.492 % and an average reflectance of merely 0.508 % over a broadband spectral width of 1300 nm. Following the fabrication process using the IAPVD technique, the empirical results demonstrated an average transmission of 98.56 % and a reflectance value of 0.177 % within the 3.6–4.9 μm range. A strong correlation was observed between the simulated and the fabricated results, with a deviation of only 0.331 % on the reflectance value, proving the accuracy and reliability of the design and fabrication process. This work introduces a highly efficient solution for AR coatings on Ge surfaces, enhancing the performance of electro-optical applications in the MWIR region. To the best of our knowledge, the newly designed Ge/SiO2 multilayer structure and the results achieved have not been previously documented in the literature, and offer substantial improvements in transmission efficiency and reflectance reduction for Ge-based optical systems.

A Review on Preparation of Palladium Oxide Films

Fabrication aspects of PdO thin films and coatings are reviewed here. The work provides and organizes the up-to-date information on the methods to obtain the films. In recent years, the interest in Pd oxide for different applications has increased. Since Pd can be converted into PdO, it is instructive to pay attention to the preparation of the pure and the alloyed Pd films, heterostructures, and nanoparticles synthesized on different substrates. The development of PdO films is presented from the early reports on coatings’ formation by oxidation of Pd foils and wires to present technologies. Modern synthesis/growth routes are gathered into chemical and physical categories. Chemical methods include hydrothermal, electrochemical, electroless deposition, and coating methods, such as impregnation, precipitation, screen printing, ink jet printing, spin or dip coating, chemical vapor deposition (CVD), and atomic layer deposition (ALD), while the physical ones include sputtering and cathodic arc deposition, laser ablation, ion or electron beam-induced deposition, evaporation, and supersonic cluster beam deposition. Analysis of publications indicates that many as-deposited Pd or Pd-oxide films are granular, with a high variety of morphologies and properties targeting very different applications, and they are grown on different substrates. We note that a comparative assessment of the challenges and quality among different films for a specific application is generally missing and, in some cases, it is difficult to make a distinction between a film and a randomly oriented, powder-like (granular), thin compact material. Textured or epitaxial films of Pd or PdO are rare and, if orientation is observed, in most cases, it is obtained accidentally. Some practical details and challenges of Pd oxidation toward PdO and some specific issues concerning application of films are also presented.