Bombardment Of High-energy Particles Research Articles

Study on the structure, growth pattern and corrosion behavior of CoCrFeNiAl high entropy alloy coatings - base on hollow cathode effect

The surface of TC18 titanium alloy was coated with a CoCrFeNiAl HEA coating using double-glow plasma surface metallurgy. The structure, phase, and growth mode of the coating were investigated, along with its electrochemical corrosion behavior. The prepared HEA coating, under the influence of the hollow cathode effect and non-equilibrium diffusion, exhibits a composite structure consisting of a deposited layer and an interdiffused layer. It demonstrates robust metallurgical bonding with the substrate, and it exhibits a hardness of 12.66 GPa and an elastic modulus of 158.52 GPa, along with exceptional hardness and high elastic modulus. The primary phase of the coating consists of an FCC solid solution, with a minor presence of Ni3Al and Al8Cr5 phases. TEM results demonstrate that hollow cathode enhanced sputtering effectively refines the grain structure on the substrate surface. The high entropy alloy coating, characterized by a significant abundance of nanocrystalline and amorphous structures, is obtained under the bombardment of high-energy particles. Gradually increasing from the interface to the deposited layer, there is an augmentation in the content of nanocrystals. The transition from the substrate to the sedimentary layer comprises three distinct regions: a surface fine crystal region, a nanocrystalline structure region, and a nanocrystalline and amorphous precipitated phase-rich region. In 3.5 wt% NaCl solution, the electrochemical corrosion rate of the coating is 1.36 × 10−1 μm·year−1, which is about ten times lower than that of the substrate. Moreover, pre-soaking forms a stable oxide film on the coating's surface, effectively preventing corrosion and demonstrating its remarkable corrosion resistance.

Aging Effect of Plasma-Treated Carbon Fiber Surface: From an Engineering Point

Dielectric barrier discharge (DBD) plasma surface modification has certain aging effect. This article studies the aging effect of plasma (DBD) on the surface modification of carbon fibers. The test results show that plasma (DBD) treatment reduces the impurity particles on the surface of carbon fibers and makes the surface texture coarser. In addition, there is no significant change. After plasma (DBD) treatment, the content of C–O–C, C–O and C=O on the surface of carbon fibers increased from 3.20%, 7.76% and 1.64% to 7.06%, 21.50 and 6.08%, respectively. This is due to the high-energy particle bombardment of the fiber surface, which forms activated carbon atoms on the surface. The free electrons of these activated carbon atoms combine with ionized oxygen in the air. However, with the passage of time, the content of C–O–C, C–O and C=O gradually decreases to 3.31%, 8.57% and 1.77%, respectively. This is because some functional groups formed on the treated carbon fiber surface are not firmly bound, and some of these functional groups containing O2 groups will combine with surrounding substances through irreversible chemical oxidation reactions to produce CO2, which leaves the carbon fiber surface as a gas. The treated carbon fibers will immediately become hydrophilic, and the water contact angle decreases from 148.71° to 0°. With the passage of time, the water contact angle gradually increases to 118.16°, and the hydrophobicity recovers.

Effect of substrate bias on structure and properties of (AlTiCrZrNb)N high-entropy alloy nitride coatings through arc ion plating

This study mainly focused on the effects of different substrate bias on the microstructure, elemental composition, mechanical and tribological properties of (AlTiCrZrNb)N coatings. (AlTiCrZrNb)N high-entropy nitride coatings with different substrate bias parameters were deposited on cemented carbide and silicon wafers using arc ion plating. The results showed that the bias voltage created a high-energy particle bombardment effect to reduce the number and volume of macroparticles brought by arc ion deposition technology; this optimized the surface quality of the coating. (AlTiCrZrNb)N coatings at different bias voltages exhibited a single-sided cubic solid solution structure. Substrate bias can significantly change the preferred orientation of coatings. As bias voltage increased from 0 V to −100 V, the preferred orientation of coatings changed from (111) to (200), and when negative voltage further increased to 200 V, the preferred orientation changed from (200) to (111). Appropriate substrate bias parameters can improve the residual stress, mechanical properties, and tribological properties of coatings. The highest hardness of the coating reached 34.85 ± 2.05 GPa. The lowest average friction coefficient was 0.26, and the lowest wear rate was 8.86 ± 1.05 × 10−6 mm3 ∙ N−1 ∙ m−1.

Chlorobenzene Mineralization Using Plasma/Photocatalysis Hybrid Reactor: Exploiting the Synergistic Effect

Mineralization of gaseous chlorobenzene (major VOC from cement plants) was studied in a continuous reactor using three advanced oxidation processes: (i) photocatalysis, (ii) Dielectric Barrier Discharge (DBD) plasma and (iii) DBD/TiO2-UV coupling. The work showed an overproduction of OH * and O * radicals in the reaction medium due to the interaction of Cl * and O3. A parametric study was carried out in order to determine the evolution of the removal efficiency as a function of the concentration, the flow rate and the applied voltage. Indeed, a variation of the flow rate from 0.25 to 1 m3/h resulted in a decrease in the degradation rate from 18 to 9%. Similarly, an increase in concentration from 13 to 100 mg/m3 resulted in a change in degradation rate from 18 to 4%. When the voltage was doubled from 6 to 12 kV, the degradation rate varied from 22 to 29 % (plasma) and from 53 to 75% (coupling) at 13 mg/m3. The evolution of COX and O3 was monitored during the experiments. When the voltage was doubled, the selectivity increased from 28 to 37% in the plasma alone and from 48 to 62 % in the coupled process. In addition, at this same voltage range, the amount of ozone formed varied from 10 to 66 ppm in plasma and 3 to 29 ppm in coupling. This degradation performance can be linked to a synergistic effect, which resulted in an increase in the intensity of the electric field of plasma by the TiO2 and the improvement in the performance of the catalyst following the bombardment of various high-energy particles of the plasma.

Rapid Construction of LTO/CuO Heterojunctions by Active Screen Plasma for Excellent Lithium-Ion Storage

The lower intrinsic capacity and electron/ion transfer rate of Li4Ti5O12 limit its application and commercialization in high-specific-energy batteries. In this work, Li4Ti5O12/CuO heterojunctions are constructed by depositing CuO ultrafine nanoparticles on Li4Ti5O12 nanosheets using a controllable and high-efficiency active screen plasma (ASP) technique. It is found that the rich interface and built-in electric field provided by the heterojunction enhance the electron conductivity and ionic conductivity, and density functional theory calculations confirm that the heterojunction reduces the band gap and enhances the adsorption energy for lithium ions; in the lithium storage process, the conversion reaction between CuO and lithium ions not only provides additional capacity but also the product Cu facilitates electron transport and accelerates the electrochemical process. In addition, the increase in vacancies and specific surface area due to high-energy particle bombardment contributes to the increase in conductivity and the number of active sites, and the treated sample exhibits excellent reversible capacity (182.6 mAh·g–1 at 1C), high rate performance (170.6 mAh·g–1 at 30C), and long cycle stability (136.7 mAh·g–1 after 4500 cycles at 20C) in the half-cell, and the full cell assembled with NMC811 maintained 227.4 mAh·g–1 after 700 cycles at 1C.

Transport parameters and permeation behavior of hydrogen isotopes in the first wall materials of future fusion reactors

Abstract The first wall of a future magnetic fusion device is essentially defined as the plasma-facing surface of the breeding blankets, which is supposed to be subjected to bi-directional hydrogen isotopes permeation: in one direction by edge plasma-driven permeation (PDP) of deuterium as well as tritium into blankets, and in the other direction by breed tritium gas-driven permeation (GDP) into the edge plasma. Deuterium and tritium PDP will complicate the recovery of tritium from the blanket, while tritium GDP will lead to an unwanted increase of particle recycling in the first wall region, which could even affect core confinement performance. Reduced activation ferritic/martensitic (RAFM) steels are widely proposed as candidate structural materials for the blanket of a DEMO reactor, the surface coatings made of tungsten are necessary to protect the plasma-facing wall from sputtering under high-energy particle bombardment. Therefore, the characterization of hydrogen isotopes transport through a multi-layer W + RAFM wall is of crucial importance to evaluate major reactor design issues including tritium retention, particle recycling and breeding feasibility, etc. This paper is intended to provide a review over the transport parameters of hydrogen isotopes in RAFM steels, including permeability, diffusivity, solubility and surface recombination coefficient. In addition, the present research status of hydrogen isotopes permeation and retention behavior of tungsten coated RAFM steels is briefly introduced.

Reduced atomic shadowing in HiPIMS: Role of the thermalized metal ions

In magnetron sputtering, the ability to tailor film properties depends primarily on the control of the flux of particles impinging on the growing film. Among deposition mechanisms, the shadowing effect leads to the formation of a rough surface and a porous, columnar microstructure. Re-sputtered species may be re-deposited in the valleys of the films surface and thereby contribute to a reduction of roughness and to fill the underdense regions. Both effects are non-local and they directly compete to shape the final properties of the deposited films. Additional control of the bombarding flux can be obtained by ionizing the sputtered flux, because ions can be controlled with respect to their energy and impinging direction, such as in High-Power Impulse Magnetron Sputtering (HiPIMS). In this work, the relation between ionization of the sputtered species and thin film properties is investigated in order to identify the mechanisms which effectively influence the shadowing effect in Deep Oscillation Magnetron Sputtering (DOMS), a variant of HiPIMS. The properties of two Cr films deposited using the same averaged target power by d.c. magnetron sputtering and DOMS have been compared. Additionally, the angle distribution of the Cr species impinging on the substrate was simulated using Monte Carlo-based programs while the energy distribution of the energetic particles bombarding the substrate was evaluated by energy-resolved mass analysis. It was found that the acceleration of the thermalized chromium ions at the substrate sheath in DOMS significantly reduces the high angle component of their impinging angle distribution and, thus, efficiently reduces atomic shadowing. Therefore, a high degree of ionization in HiPIMS results in almost shadowing effect-free film deposition and allows us to deposit dense and compact films without the need of high energy particle bombardment during growth.

Stress control of reactively sputtered thick NbN film on Si wafer changing the location of the substrate Si wafer against the Nb target on a magnetron cathode

We have been developing a superconducting NbN thin film coil in a spiral trench on a Si-wafer using MEMS technology. Connecting the coils on the different wafers using waferbonding process, a cylindrical wafer stack is to be formed as a unit of a compact SMES. The critical current density of our NbN film was measured to be around 1100 A/mm2. We measured critical current Ic of 47 mA for the previously fabricated coil of the film thickness tf = 0.5 μm. Ic in the spiral coil increases with tf. However, if we make the NbN film thicker, the film is apt to have higher lateral force caused by tensile or compressive stress which can cause peeling of the film from the Si substrate. It is well known that the stress of the sputtered thin films can be controlled from tensile to compressive stress by controlling the bombardment of high energy particles including argon atoms backscattered from the target surface. Based on this knowledge, a specially designed sputter-deposition apparatus was fabricated in which the substrate can be located not only at the different target-to-substrate distances but also at several different lateral distances from the central axis of the target (off-axis lateral shift). Using this apparatus, various stress conditions could be realized which contributed to fabrication of thick NbN film spiral coil in the trench. The film stress was calculated from bending analysis of the substrate Si wafer by stylus method using Stoney’s formula. The maximum compressive stress of 2.5 GPa was measured. By an off-axis lateral shift, tf could be increased from 0.5 to 1 μm. By increasing sputtering gas pressure from 0.7 to 2 Pa, the compressive stress could be mitigated and tf could be further increased from 1.0 to 3 μm. Up to now, we measured Ic of 220 mA for a NbN spiral coil at tf around 3 μm. More detailed adjustment of the deposition condition will bring further increase in tf, and hence Ic into sight.

MECHANISM OF BIJUNCTION SEMICONDUCTOR DEVICE DAMAGE INDUCED BY HEAVY PARTICLES

The physical phenomena associated with the stopping of energetic ions in semiconductor materials have always been a subject which receives great theoretical and experimental interest. Consequently, bombardment of high energy particles and high energy gamma (γ) rays causes potential hazards to these electronic systems. These effects range from degradation of performance to functional failure that can affect the system operations. Such upsets becoming increasingly likely as electronic components are getting more sophisticated while decreasing in size and moves to larger integration. In this paper, the penetration of gamma rays, utilizing Cobalt-60 (Co-60)) into bipolar junction transistor (BJT) is being simulated using the program simulation SRIM. From the findings, it is observed that the penetration of Co-60 ions into the simulated BJT leads to production of lattice defects in the form of vacancies, defect clusters and dislocations. These can alter the material parameters and hence the functional properties of the devices.

Reconsideration of metal surface sputtering due to bombardment of high-energy argon ion particles: a molecular dynamics study

Some interesting aspects of metal surface sputtering phenomenon are numerically investigated in this work using the molecular dynamics approach. Along with that, we have carried out a critical analysis of the interaction potentials typically used for modeling. Two metallic surfaces, viz., copper, Cu(100), and nickel, Ni(100), are chosen for study that are bombarded by argon ions at various energies and angles of projection. The sputtering yield is calculated by performing molecular dynamics simulations, and the same is compared with experiments and theoretical predictions wherever possible. Furthermore, other interesting parameters like the kinetic energy, velocity, and scattering angle distribution for sputtered and incident atoms are presented and discussed. Through different case studies, the present work emphasizes on the importance of interaction model used for metal surface modeling for a realistic numerical reproduction of the complex metal surface sputtering process.

Enhanced electrical properties of AZO thin films grown on different substrates by using a facing-target sputtering system with hetero targets

Al-doped ZnO (AZO) films were deposited on glass, polyethylene naphthalate (PEN) and polyethylene terephthalate (PET) at room temperature by using conventional rf-magneton sputtering (CMS) and a facing-target sputtering (FTS) with hetero targets of Al2O3 and ZnO. Their structural, surface morphology, electrical and optical properties were characterized by using X-ray diffractometry (XRD), atomic force microscopy (AFM), Hall-effect measurement and ultravioletvisible spectrophotometry, respectively. The films exhibit highly c-axis preferred orientation and a closely packed nanocrystalline. Structure the FTS-films deposited on plastic substrate are found to receive much less stress due to bombardment of high-energy particles compress to the CMS-films deposited on plastic substrates, during the sputtering process, which can enhance the electrical properties and crystalline quality of the FTS-films compared with those of the CMS-films. The resistivities of the FTS-films are 6.50 × 10−4 Ω·cm on glass, 7.0 × 10−4 Ω·cm on PEN and 7.4 × 10−4 Ω·cm on PET while the values for the CMS-films are 7.6 × 10−4 Ω·cm on glass, 1.20 × 10−3 Ω·cm on PEN and 1.58 × 10−3 Ω·cm on PET.

Characteristics of Ga-Al Doped Zinc Oxide Thin Films Deposited by Facing Targets Sputtering

Gallium-aluminum doped zinc oxide (GAZO) thin film is evaluated as an alternative to ITO for use as transparent electrodes for display devices. GAZO transparent conducting thin films were deposited using a facing targets sputtering (FTS) system with a hetero-targets. The FTS system can generate high plasma density, suppress the bombardment of high-energy particles to the substrate, and reduce the working pressure and substrate temperature. The average transmittance achieved with these films was as high as 80% in the visible range. Using a working pressure of 0.4 Pa, the lowest resistivity achieved with the deposited film was 5.342 × 10−4 Ω·cm.

Sputter-cleaning of an aluminum alloy using a thermionically assisted triode plasma system

Polished aluminum alloy (6061) samples were cleaned using Ar plasma in a diode or triode plasma system. By monitoring cathode current, the changes of surface state and removal (cleaning) rate were determined and compared based on various setup. A modified mathematical model, based on Berg's reactive sputtering model, is derived and proposed to simulate the cleaning process. The results show that it is possible to sputter-clean the substrate under a triode setup with low bias and high ion bombardment rate (i.e. −500 V, triode, 1.3 Pa). This triode cleaning process was comparable with high bias and high working pressure diode process (i.e. −2500 V, diode, 3.3 Pa). Cleaning with high energy particle bombardment can create rough surface in nano-scale, although with the similar efficiency. Also, according to the regressive fitting on the cathode current–time curve, it is found that the average secondary electron yield for the oxide compound is around 0.33 if the average secondary electron yield for aluminum metal is 0.1.

Effects of the Modified TCO Sputtering Condition on ZnS/CIGS Solar Cell

The Cu(In,Ga)Se2(CIGS) thin film solar cells were fabricated using ZnS buffer layer deposited by chemical bath deposition and ZnO/Al-doped ZnO transparent conducting layers deposited by magnetron sputtering with two different configurations of target-to-substrate angle and distance in order to evaluate the effect of plasma damage on device performance. The higher efficiency was obtained from the configuration of the substrate being far away from the target center than face-to-face configuration, suggesting that the excessive bombardment of high energy particles from the plasma on the film surface is responsible for the solar cell performance degradation. It is suggested that the improved open-circuit voltage is ascribed to the increased recombination barrier height.

유도 결합 플라즈마 스퍼터 승화법을 이용한 고속증착 시스템

A sputter-sublimation source was tested for high rate deposition of protective coating of PEMFC(polymer electrolyte membrane fuel cell) with high electrical conductivity and anti-corrosion capability by DC biasing of a metal rod immersed in inductively coupled plasma. A SUS(stainless steel) tube, rod were tested for low thermal conductivity materials and copper for high thermal conductivity ones. At 10 mTorr of Ar ICP(inductively coupled plasma) with 2.4 MHz, 300 W, the surface temperature of a SUS rod reached to with a dc bias of 150 W (-706 V, 0.21 A) in 2 mins. For 10 min of sputter-sublimation, 0.1 gr of SUS rod was sputter-sublimated which is a good evidence of a high rate deposition source. ICP is used for sputter-sublimation of a target material, for substrate pre-treatment, film quality improvement by high energy particle bombardment and reactive deposition.

The formation of carbon dioxide in molecular cores by a non-energetic route

The formation of CO2 in quiescent molecular cores has long been of interest to astrochemists as CO2 is one of the most abundant solid phase molecules present in the interstellar medium. Previous studies have concentrated, for the most part, on formation mechanisms involving high energy particle or UV bombardment of ices, to mimic the influence of cosmic rays on solid phase species in the outer, lower density regions of molecular clouds. However, condensed phase CO2 is also observed in the inner, denser regions of clouds, where less UV radiation penetrates. To date, very few studies have been made of CO2 formation in the absence of energetic particles.

On the onset of void ordering in metals under neutron or heavy-ion irradiation

Formation of void lattices is observed in a number of metals and alloys under high-energy particle bombardment. The conditions were derived for destabilisation of homogeneous void arrangement using an approach developed for the description of lane formation in pedestrian crowds. The model is based on the Foreman's mechanism of void alignment due to one-dimensionally migrating clusters of self-interstitial atoms. The results show that spatial correlations between voids should exist above some very small size, unless correlations with other defects prevail. It is shown that spatial correlations of voids with dislocations and second-phase precipitates should also evolve and provide a powerful driving force for further swelling.

플렉시블 디스플레이 적용을 위한 ITO:Ce/PET 박막의 물성평가

ITO and ITO:Ce films were deposited by DC magnetron sputtering using an ITO (<TEX>$SnO_2$</TEX>: 10 wt%) and <TEX>$CeO_2$</TEX> doped ITO (<TEX>$CeO_2$</TEX>: 0.5, 3.0, 4.0 and 6.0 wt%) ceramic targets, respectively, on unheated polyethylene terephthalate (PET) substrates. The lowest resistivity <TEX>$6.7{\times}10^{-4}{\Omega}cm$</TEX> was obtained from ITO:Ce film deposited using <TEX>$CeO_2$</TEX> (3.0 wt%) doped ITO target. On hte other hand, ITO:Ce (0.5wt%) film has the excellent mechanical durability which was evaluated by bending test. This result was attributed to the higher binding energy of <TEX>$CeO_2$</TEX> compared to <TEX>$SnO_2$</TEX> and <TEX>$In_2O_3$</TEX>. Therefore, <TEX>$CeO_2$</TEX> atoms have a small displacement caused by the bombardment of high energy particles, and it attribute to the increase in adhesion caused by decrease in internal stress. The average transmittance of the films was more than 80% in the visible region.

A study of deposition of ITO films on organic layer using facing target sputtering in Ar and Kr gases

In this study, the effects of sputtering gases on the damage to an organic layer (aluminum (III) bis(2-methyl-8-quninolinato)-4-phenylphenolate (BAlq)) were investigated in the deposition of indium–tin oxide (ITO) films by using a facing target sputtering (FTS) system. Only a small improvement in the PL intensity of the BAlq layer was observed when the sputtering gas was changed from Ar to Kr gas. It was also found that suppression of the high-energy γ-electron bombardment to the substrate is very important to reduce the damages in the BAlq layers. In addition, a remarkable improvement in the PL intensity was observed by the increase in the sputtering gas pressure from 0.3 to 1.3 Pa. These results suggest that bombardment of reflected neutral gas atoms is not the main source of the damage that BAlq layer has, but the bombardment of high-energy sputtered atoms plays an important role for the remnant damages caused by the sputter-deposition of the ITO film at a low gas pressure, since the decrease in the PL intensity was almost totally suppressed by increasing the sputtering gas pressure above 1.1 Pa. Finally, low-damage sputter-deposition of ITO film with low resistivity on BAlq layer was achieved by completely suppressing the bombardment of high-energy particles, including γ-electrons, negative oxygen ions and high-energy sputter-emitted particles.

High-Efficiency and High-Operational-Stability Top-Emitting Organic Light-Emitting Diodes Using Antioxidant Buffer Layer

We have succeeded in developing top-emitting organic light-emitting diodes (OLEDs) with high efficiency and high operational stability using an antioxidant buffer layer. V2O5 was selected as the antioxidant buffer layer to suppress the degradation of the organic materials of OLEDs caused by active oxygen during buffer layer deposition and the damage caused by the bombardment of high-energy particles during transparent electrode sputtering. The top-emitting device with a V2O5 buffer layer had the same current density–voltage (J–V) characteristics as the bottom-emitting device with the same material system. The quantum efficiency of the top-emitting device was about 5%, the same as that of the bottom-emitting device. The time required for luminance to drop to 90% of the initial value of the top-emitting device was over 700 h, which is longer than that of the bottom-emitting device (300 h). From X-ray photoelectron spectroscopy (XPS) analysis of the interface between organic materials and V2O5, it was determined that there was no degradation of organic materials under V2O5.