Plasma Post-treatment Research Articles

Surface activated bonding of ALD Al2O3 films

Room temperature direct bonding of plasma enhanced ALD Al2O3 films was achieved by using surface activated bonding. ALD Al2O3 films were amorphous with C and O impurities contained. The high deposition power and H2 plasma post-treatment increased the crystallinity and hydrophilicity of ALD Al2O3 films, respectively. However, both methods increased the surface roughness of films slightly. The bond strength of ALD Al2O3 films was not changed obviously by raising the deposition power, but it experienced a slight decrease after H2 plasma post-treatment. The water in the debonding atmosphere influenced the bond strength of standard ALD Al2O3 films greatly, which was 0.54 J m−2 in humid air and 1.00 J m−2 in anhydrous N2. The bond strength in vacuum was just a little larger than that in anhydrous N2 suggesting that the trapped water at the bonding interface was less.

Optimization of metals degradation and vitrification from fly ash using Taguchi design combined with plasma pyrolysis and recycling in cement construction

Fly ash has been widely recognized as the hazardous waste due to its toxicity to environment. It should be treated properly for preventing the high contamination to the environment and generate volatile organic compounds (VOCs) from the pyrolysis treatment. The aim of this study is to investigate the most influenced parameters in elimination of elements, vitrification and destruction of volatile organic compounds (VOCs) from the fly ash via a plasma pyrolysis with the combination of Taguchi method and recycling it into the cement construction, which potentially applied in the real application. The combination of fly ash treatment with CaCO3, SiO2, Al2O3 and glass gives the high removal efficiency of VOCs at 4.653 ppm under the nitrogen plasma. Furthermore, the gas flow rate has the most significant impact on the destruction of elements based on the Taguchi analysis. The best removals of element are known as follows: Hg>Cd>Se>As>Cr>Pb>Cu. Lastly, compressive test of the cement at age 28 days with the substitution of 10% fly ash confirmed greater result on cement quality. The most influenced parameter, namely gas flow rates with the combination of flux agents are thus suggested for degrading harmful elements and VOCs. Fly ash from plasma post-treatment has the potential for replacing the cement material when used in the construction material to implemented the recycling concept.

Hydroxyl-modified Nb4C3Tx MXene@ZnIn2S4 sandwich structure for photocatalytic overall water splitting

Herein, a hydroxyl-modified MXene@ZnIn2S4 (Nb4C3Tx MXene@ZIS-OH) overall water splitting photocatalyst with a sandwich structure was prepared through an in-situ growth strategy and peroxyl plasma post-treatment. The Nb4C3Tx MXene@ZIS-OH exhibits outstanding catalytic performance, which generates the release rates of hydrogen (53.8 μmol g-1h−1) and oxygen (26.7 μmol g-1h−1) from the water under visible light irradiation. After four photocatalytic cycling, the photocatalytic overall water splitting activity of Nb4C3Tx MXene@ZIS-OH is still 95.9% of the initial activity, which indicates that Nb4C3Tx MXene@ZIS-OH exhibits excellent cycling stability. Notably, the Nb4C3Tx MXene@ZIS-OH achieves an AQY of 1.2% for the overall photocatalytic water splitting at 380 nm. The sandwich structure and matched heterointerface between high work function Nb4C3Tx MXene and ZnIn2S4 nanosheets promote the electron transport, inhibit the charge recombination, and separate the generated H2 and O2 with effectiveness. Importantly, the Finite-Difference Time-Domain (FDTD) simulation suggests the hydroxyl groups on the surface of ZnIn2S4 could increase the hydrophilicity of photocatalyst and capture the holes generated by photoexcitation, thereby promoting the separation of electron-hole pairs rapidly. This work presents a successful example of constructing overall water splitting photocatalysts by energy level regulation, structure design and functional group modification.

Plasma Post‐Treatment Process‐Induced Grain Coalescence to Improve the Electron Field‐Emission Properties of Ultrananocrystalline Diamond Films

Plasma post‐treatment (PPT) process is an effective way to improve the electron field‐emission (EFE) properties of microwave plasma chemical vapor deposited ultrananocrystalline diamond (MP‐UNCD) films, while its effects on hot‐filament chemical vapor deposited UNCD (HF‐UNCD) films were not confirmed. Due to monodispersed Ta atoms existing in HF‐UNCD films, PPT process shows different effects on the structure evolution and EFE properties of HF‐UNCD films and MP‐UNCD films. CH4/N2 PPT process make diamond grains change from small spherical particles to large plate‐like aggregates with lots of stacking faults in HF‐UNCD films. This is ascribed to both the CN species in CH4/N2 plasma, which induces anisotropic growth of diamond and the monodispersed Ta atoms resulted in transition of graphite to diamond, which connect the neighboring nanosized diamond grains to a larger one and produce lots of stacking faults. The charges are easier to accumulate and emitted in the edges of the plate‐like diamond and stacking faults have lower negative electron affinity. These lower the turn‐on field from 26.3 to 12.7 V μm−1. It is different from that of MP‐UNCD films, in which only anisotropic growth occurs and forms needle‐like diamond due to CN species.

Differences in Synovial Cytokine Profile Associated with Long-Term Clinical Outcomes in Patients with Knee Osteoarthritis Undergoing Corrective Osteotomy with Platelet-Rich Plasma or Stromal Vascular Fraction Post-Treatments.

Functional outcomes and synovial fluid (SF) cytokine concentrations in response to platelet-rich plasma (PRP) or stromal vascular fraction (SVF) post-treatments following open wedge high tibial osteotomy (HTO) in 20 patients with knee osteoarthritis (OA) were examined. Six weeks after surgery, the knees of 10 patients were injected with autologous PRP (PRP subgroup), while another 10 patients were injected with autologous SVF (SVF subgroup) and monitored for 1.5 years. Pain assessment (VAS score) and functional activity (KOOS, KSS, Outerbridge, and Koshino scores) were applied. PRP subgroup performed better compared with the SVF subgroup according to KOOS, KSS, and VAS scores, while the SVF subgroup demonstrated better results according to Outerbridge and Koshino testing and produced more pronounced cartilage regeneration in the medial condyle and slowed down cartilage destruction in its lateral counterpart. SF was collected before and one week after PRP or SVF injections and tested for concentrations of 41 cytokines (Multiplex Assay). In the PRP subgroup, a significant decrease in IL-6 and CXCL10 synovial concentrations was accompanied by an increase in IL-15, sCD40L, and PDGF-AB/BB amounts. The SVF subgroup demonstrated a significant decrease in synovial TNFα, FLT-3L, MIP-1β, RANTES, and VEGF concentrations while SF concentrations of MCP-1 and FGF2 increased. Both post-treatments have a potential for increased tissue regeneration, presumably due to the downregulation of inflammation and augmentation of synovial growth factor concentrations.

Linear and non-linear optical properties of boron carbide thin films

Boron carbide films deposited by PECVD are subjected to post deposition vacuum annealing and plasma treatment for investigation of changes in the structure, linear and non-linear optical properties of the films. Deconvolution of core level XPES spectra of B1s, C1s and O1s indicates changes in the surface chemical states of the constituent atoms after post deposition treatments. Particle size estimated from XRD spectrum is found increasing from 135 to 140 nm after annealing. Envelop method is used to estimate refractive index, extinction co-efficient, and thickness from their measured optical transmission spectra in VIS-NIR region (400–1400 nm). The refractive index value is found to be 1.619, highest for the vacuum annealed boron carbide film. Direct and indirect optical bandgap remains same after vacuum annealing (Eg = 2.84), the plasma treatment causes a slight decrease in the bandgap. 5% decrease in film thickness is observed after post deposition annealing and plasma treatment owing to film densification. Energy loss in the medium measured in terms of tanδ and ELF’s reveals that the vacuum annealing of the film reduces the electromagnetic and electron energy loss in the film. Non-linear refractive index estimated using Ticha and Tichy relation exhibits similar trend as the linear refractive index spectra.

An investigation to enhance the mechanical property of high‐performance thermoplastic composite through different plasma treatment

AbstractIn this study, polyetherketone was investigated as the high‐performance thermoplastic resin for fabrication of carbon fiber reinforced polymer composite. The composites were manufactured by film‐fiber stacking process and consolidation by compression molding. The surfaces are modified with different plasma treatment (argon, nitrogen, and air) to overcome the inert nature of carbon fiber surface and subsequent changes were analyzed through atomic force microscopy, X‐ray photoelectron spectroscopy, and contact angle measurements. The effectivity of each type of plasma treatment in improvement of the surface—roughness, composition, and wettability were quantified and the subsequent effect on the mechanical properties was demonstrated by measurement of tensile properties and interlaminar shear strength (ILSS). The changes in interfacial morphology of the composite post plasma treatment have been characterized by scanning electron microscopy. From the test results, nitrogen plasma was found to most effective with a 43% increase in mean tensile strength and 25% increase in ILSS when compared to untreated composite.

Designing N-Graphene Nanowalls Via Plasma-Enabled Nitrogen Incorporation and Substitution

Surface engineering of graphene-based materials with nitrogen is a potential technique for tailoring the electrical and electronic features of the nanostructures. Surface engineered graphene can be fabricated by adsorbing foreign molecules into the graphene lattice or substitutional doping. Considering different chemical and physical doping techniques, plasma-assisted surface treatment is one of the fastest approaches to design nitrogen-incorporated graphene (N-graphene) with different nitrogen bonding configurations. However, it is still a great challenge to create N-graphene with controlled concentrations and desired configurations of nitrogen. Several studies demonstrated that the structural defects in graphene have a critical role in incorporating N-atoms, which has been well-explained by DFT theories. However, there is a lack of experimental studies to confirm the DFT theories explained for the influence of structural defects for nitrogen incorporation in graphene. In this study, we have demonstrated a systematic study on designing N-graphene with controlled concentration and configuration of nitrogen by plasma post-treatment on vertically oriented graphene nanowalls (GNWs). A low-pressure inductively coupled radio-frequency plasma is used for surface engineering with nitrogen gas as the reactive gas. The structural and morphological analysis describes a remarkable difference in the plasma surface interaction, nitrogen concentration, and nitrogen configurations in GNWs concerning the plasma treatment conditions. As the result of plasma treatment, the creation of structural defects and their healing upon prolonged treatment is determined with several spectroscopic and microscopic techniques. These results, along with the other measurements, revealed that the configurations of the nitrogen groups in graphene are highly influenced by the structural defects formed during the processes. Also, the electrical conductivity of the N-GNWs is strongly influenced by the concentration and different configurations of C-N bonding. These findings demonstrate the potential of plasma to tune the graphene lattice by controlled surface engineering in a fast and facile green approach, which can be fruitful for several future electronics and energy devices.

Regulating the Ni3+/Ni2+ ratio of NiOx by plasma treatment for fully vacuum-deposited perovskite solar cells

Inorganic p-type NiOx was considered as an idea hole-transport layer (HTL) for perovskite solar cells due to its good transmittance in visible region and outstanding chemical stability. The p-type behavior of NiOx is mainly derived from its nonstoichiometric nature and determined by the Ni cation deficiency. Thus, the synthesizing methods play an important role to the electronic properties of NiOx films. And for most of the inverted PSCs with NiOx HTL, the hole-extraction efficiency was limited by the unmatched valence band and too much surface defects of NiOx, causing poor performance of the device. To date, solution-based synthesizing methods and surface treatments were widely used for achieving high efficiencies of the PSCs. But the vacuum-based synthesizing methods and surface treatments are rarely reported. Herein, we developed a facile plasma post-treatment for the electron-beam evaporated NiOx to regulate its Ni3+/Ni2+ ratio and improve its electronic performance. By using O2 plasma treatment, we successfully enhanced the conductivity of the NiOx and optimized the charge-extraction capability. As a result, the all-vacuum deposited PSCs based on the O2 plasma-treated NiOx HTL achieved a champion PCE of 17.84%. This facile approach is expected to be further developed for fabricating high-efficiency PSCs on textured silicon solar cell.

Interface Adhesion Property and Laser Ablation Performance of GAP-PET Double-Layer Tape with Plasma Treatment.

In the field of laser ablation micro-propulsion, the property of double-layer tape has significant impact on the propulsion performance. In this paper, low temperature plasma was used to treat the surface of polyethylene terephthalate (PET) to improve its adhesion with energetic polymer. The PET surface pre- and post-plasma treatment was characterized by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM), and the enhancement mechanism of the interface adhesion was discussed. In addition, the ablation performance of the double-layer tape after the plasma treatment was studied. The results showed that the plasma etching effect increased the root mean square roughness of the PET surface from 1.74 nm to 19.10 nm. In addition, after the plasma treatment, the number of C–OH/COOH bonds and O=C–O bonds increased, which also greatly improved the adhesion between the PET and energetic polymers. In the optimization of the ablation performance, the optimal laser pulse width was about 200 μs. The optimal values of the specific impulse (Isp), impulse coupling coefficient (Cm), and ablation efficiency (η) were 390.65 s, 250.82 μN/W, and 48.01%, respectively. The optimization of the adhesion of the double-layer tape and the ablation performance lay the foundation for the engineering application of laser ablation micro-thrusters.

Structural and surface evolution of nanostructured Cu-Zn-Al catalyst designed by hybrid plasma-enhanced microwave-irradiated urea-nitrate-combustion for selective H2-production

BackgroundRecently, limited sources of fossil fuels and environmental issues have caused to expanded worldwide search for an alternative clean energy. Among these, steam methanol reforming is the most common industrial kind of mature technology to produce hydrogen. MethodsIn this regards, a series of Cu-Zn-Al catalysts were synthesized via conventional urea-nitrate combustion and hybrid plasma-enhanced microwave-irradiated urea-nitrate combustion methods. The samples were characterized using XRD, FESEM, TEM, EDX, BET, FTIR and TPR-H2 techniques. Significant findingsThe crystalline size of CuZnAl-MC-P which was treated with plasma, reduced in comparison to untreated samples. This sample had high dispersion of CuO (111), ZnO (100) and ZnO (002) crystalline facets leading to enhancement of CH3OH conversion and H2-selectivity. As determined by FESEM and EDX, the plasma significantly caused to high dispersion of active sites which led to absence of any agglomeration. These features have led to prominent catalytic performance of plasma treated catalyst. Therefore, complete conversion of methanol and CO selectivity of 0.55% have been obtained at 260 °C using CuZnAl-MC-P sample. Stable performance of CuZnAl-MC-P for 24 h revealed that application of plasma post-treatment has caused strong bonding between components of catalyst and the absence of any agglomeration or sintering of particles.

Optimizing Oxygen Plasma Treatment Time to Improve the Characteristics of a-IGZO Thin-Film Transistors and Resistive-Load Inverters

Amorphous indium–gallium–zinc oxide (a-IGZO) is a widely studied semiconductor for cutting-edge electronics applications because of its low absorbance, high charge carrier mobility, and versatility. For the practical application of a-IGZO thin films, postdeposition thermal treatment is typically applied to enhance the device’s performance. Here, we present a study on the effect of oxygen plasma posttreatment of thermally annealed, sputter-deposited a-IGZO thin films to determine the optimal treatment time using a helical plasma source. The performance of devices with a-IGZO active layers exposed to oxygen plasma for different durations is compared, and the stability under constant bias is evaluated. It is found that temporarily exposing the film surface to high-energy oxygen species can improve the charge transport properties, resulting in superior device performance such as more than tenfold increase in the ON–OFF ratio, a nearly doubling of charge carrier mobility and improved bias stress stability. However, under prolonged exposure, the device deteriorates, indicating the importance of properly designing and optimizing the fabrication processes of oxide semiconductor devices. To demonstrate the practical applicability of the transistors with optimized a-IGZO active layers, load-type inverters are prepared, and their performance is evaluated and compared quantitatively to that of a device with a pristine a-IGZO active layer.

Nitrogen incorporation in graphene nanowalls via plasma processes: Experiments and simulations

The interest in doped and functionalized graphene nanomaterials for various applications is growing due to the development of new and simple production and treatment methods. Amongst the techniques used to treat graphene nanomaterials dry methods like plasmas or ion beams are of particular interest. In this work a low temperature plasma technique is used to incorporate nitrogen atoms into the carbon network of graphene sheets. In order to gain a better understanding of such processes material analysis techniques (NEXAFS and XPS) were combined with the results coming from molecular dynamics simulations and plasma know-how. The results show that the plasma post treatment of graphene nanowalls can be regarded as a balance between vacancy formation, functionalization, doping and crosslinking. Moreover, MD simulations provided insight into fundamental mechanisms like the formation of different bonds due to the interaction of the surface with different kind of species with variable kinetic energy. This can help to improve different types of doping/functionalization techniques using energetic species: the study reveals for example the role of N2+ species, the kinetics of vacancy formations depending on type and energy of the species, the formation of amines or graphitic nitrogen, and the role of impurities such as NHx species.

The effect of O2 plasma post-treatment on atomic layer deposited TiO2 thin films

In this study, we evaluated the changes of the properties of TiO2 thin films conducted to O2 plasma treatment at various plasma powers. The XPS analysis showed that the concentration of oxygen vacancies in the TiO2 thin films was reduced by the O2 plasma treatment. In the GIXRD analysis, it was confirmed that as the O2 plasma treatment progressed, the anatase peak intensity of TiO2 increased and a new anatase peak was detected. In addition, according to HR-TEM analysis the crystallinity became excellent. The AFM analysis showed that the roughness of the as-deposited TiO2 thin film and O2 plasma-treated TiO2 thin film were almost the same. The I–V analysis showed that the leakage current density of the 800 W O2 plasma-treated TiO2 thin film (∼10−4A/cm2) was 100 times lower than that of the as-deposited TiO2 thin film (∼10−2A/cm2). The dielectric constant of the O2 plasma-treated TiO2 thin films was approximately 24–25, which is higher than that of the as-deposited TiO2 thin film (k∼17) because of the anatase structure.

Study the electron field emission properties of silver nanoparticles decorated carbon nanotubes-based cold-cathode field emitters via post-plasma treatment

Study the electron field emission properties of silver nanoparticles decorated carbon nanotubes-based cold-cathode field emitters via post-plasma treatment

Highly Effective Microwave Plasma Post-Treatment on Tin Oxide Thin Films for the Application in Electron Transport Layer of Perovskite Solar Cells

Highly Effective Microwave Plasma Post-Treatment on Tin Oxide Thin Films for the Application in Electron Transport Layer of Perovskite Solar Cells

(Invited) Plasma Produced and Processed Multimaterials Based on Vertically Aligned Graphene Walls and Their Applications

The interest in new carbonaceous materials with large effective surfaces which are in addition highly conductive and stable is growing due to the downsizing of electrical devices and the demand for new low-cost materials. Carbonaceous materials show in in particular a great potential for applications in electrochemical devices, energy storage devices or biosensors. On the other hand, there is also an emerging need for new production methods which allow an environmentally friendly, low cost and scalable synthesis of these materials.Although there exists no miracle or unicorn method meeting all these demands, one special place in this race for new technologies are novel low temperature/cold plasma processes, which guarantee the synthesis and treatments of materials in dry processes which can go down to almost ambient temperatures.In this work, we present plasma synthesised and functionalized carbon-based nanomaterials, alone or enrobed in polymers, and their analysis. Moreover, the underlying production process will be analysed both experimentally and by means of simulations. The carbon nanomaterials are all produced by low temperature plasma procedures, and examples are given for different processes including catalyst-free or catalyst driven processes. All these processes result often in conductive nanostructures, like free-standing graphene, vertically aligned graphene nanosheets, thin films or nanoparticles. These materials are either pure carbons, hydrocarbons or nitrogen-containing carbons. In this presentation we will concentrate on nitrogen free and nitrogen containing vertically aligned graphene. Nitrogen introduction is obtained here either by the growth of the carbonaceous materials in a nitrogen-containing atmosphere or by means of plasma post-treatments. These post-treatment processes can lead to both doped and functionalized materials. A popular technique to simulate plasma-surface interactions is molecular dynamics (MD). MD simulations can provide insight into fundamental mechanisms like the formation of different kinds of bonds.The plasma produced graphene stuctures can be, (depending on the applications), additionally decorated with conductive nanoparticles or thin films. One example concerns the conformal coating or enrobing with plasma polymers, as for example plasmapolyaniline. The interplay between doping, functionalization together with enrobing/decoration is advantageous and results in different surface characteristics of interest which can be useful e.g. for the synthesis of storage devices.

Combined effects of NH3 and NF3 post plasma treatment on the performance of spray coated ZnO thin film transistors

We investigate the effects of NH3 and NF3 post plasma-treatment on the performance of spray-coated ZnO thin film transistors (TFTs). Both NH3 and NF3 plasma treatment are varied from 10 to 40 s. The properties of plasma treated ZnO were studied by Hall Effect measurements, UV–visible spectroscopy, photoluminescence, atomic force microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and time-of-flight secondary ion mass spectrometry. NF3 plasma treatment causes n-type doping and generates carriers by F incorporation. While, NH3 plasma can cause not only n-type doping by Hydrogen incorporation but also creates acceptor-like states by the formation of Vo–H complex and inducing Nitrogen in ZnO. Owing to the N incorporation, the threshold voltage can be controlled by NH3 plasma treatment. The appropriate NH3 and NF3 plasma treatments for 10 s each greatly enhance theperformance of ZnO TFTs, exhibiting the saturation mobility and subthreshold swing of 20.65 cm2 V−1 s−1 and 0.18 V dec–1, respectively. Therefore, it is concluded that NH3 and NF3 plasma-treatment can be a useful technique to enhance the device performance and to improve the stability of solution-processed metal-oxide TFTs.

Injection-type Denture Base Materials Surface Modification after Vapor Plasma Deposition

The purpose of this study was to investigate changes of superficial topography and wettability of two injection-type denture base materials following low pressure plasma treatment. Samples of denture base materials (Polyan and Biodentaplast) were fabricate using dedicated technology and were exposed to plasma treatment. Resin surface topography and rugosity were evaluated using SEM and AFM, while wettability was determined through contact angle measurements. Artificial saliva was the testing liquid. Initial contact angles for the two materials are close (Biodentaplast-37.60�, Polyan-36.75�). Plasma treatment halves the values of the contact angle. 30-days measurement reveals a reduced bounce-back effect (Biodentaplast-20.68�, Polyan-20.11�). Surface topography modified differently for the two materials. Rugosity increased significantly for both materials (p[0.05). Surface rugosity values pre- and post-plasma treatment respect the biological threshold of fungal adhesion. Plasma exposure increased injection-type denture base materials wettability with artificial saliva and surface roughness. Injection-type denture base materials and artificial saliva can enhance prosthetic experience of xerostomic patients.

Evaluation of the Microstructure, Tribological Characteristics, and Crack Behavior of a Chromium Carbide Coating Fabricated on Gray Cast Iron by Pulsed-Plasma Deposition.

The structural and tribological properties of a protective high-chromium coating synthesized on gray cast iron by air pulse-plasma treatments were investigated. The coating was fabricated in an electrothermal axial plasma accelerator equipped with an expandable cathode made of white cast iron (2.3 wt.% C–27.4 wt.% Cr–3.1 wt.% Mn). Optical microscopy, scanning electron microscopy, energy-dispersive spectroscopy, X-ray diffraction analysis, microhardness measurements, and tribological tests were conducted for coating characterizations. It was found that after ten plasma pulses (under a discharge voltage of 4 kV) and post-plasma heat treatment (two hours of holding at 950 °C and oil-quenching), a coating (thickness = 210–250 µm) consisting of 48 vol.% Cr-rich carbides (M7C3, M3C), 48 vol.% martensite, and 4 vol.% retained austenite was formed. The microhardness of the coating ranged between 980 and 1180 HV. The above processes caused a gradient in alloying elements in the coating and the substrate due to the counter diffusion of C, Cr, and Mn atoms during post-plasma heat treatments and led to the formation of a transitional layer and different structural zones in near-surface layers of cast iron. As compared to gray cast iron (non-heat-treated and heat-treated), the coating had 3.0–3.2 times higher abrasive wear resistance and 1.2–1208.8 times higher dry-sliding wear resistance (depending on the counter-body material). The coating manifested a tendency of solidification cracking caused by tensile stress due to the formation of a mostly austenitic structure with a lower specific volume. Cracks facilitated abrasive wear and promoted surface spalling under dry-sliding against the diamond cone.