Plasma Oxidation Process Research Articles

Extreme environmental micro-plasma electrolyte oxidation induced defect-rich Au nanoparticles catalyst improving the nitrophenol hydrogenation reaction

The defect-rich Au nanoparticles (NPs) catalyst on Mg surface was prepared by the micro-plasma electrolyte oxidation (MPEO) utilizing liquid nitrogen as the cooling medium. MPEO is a high-temperature plasma oxidation process that decomposes the [AuCl4]-precursor salt to form metastable state Au NPs. The rapid quenching effect of liquid nitrogen occurs during this non-equilibrium process and generates numerous defects on the Au NPs, thereby altering their electronic state. Consequently, the catalytic performance of this Au/MgO catalyst was outstanding, exceeding that of the sample prepared without using liquid nitrogen. This finding indicates that the harsh environment plays a crucial role in producing defect-rich Au NPs and improving the catalytic efficiency.

Degradation and transformation of carbamazepine in aqueous medium under non-thermal plasma oxidation process

Carbamazepine (CBZ) is a pharmaceutical compound detected in various water resources. With a view to removing this contaminant, the applicability of non-thermal plasma (NTP) oxidation process has been widely tested in recent years. This study utilized NTP from a dielectric barrier discharge reactor in the treatment of CBZ. NTP on the surface of a water sample containing 25 mg.L−1 of CBZ resulted in a removal efficiency of over 90% with an energy yield of 0.19 g. (kWh)−1. On the other hand, a rapid reduction in pH and an increase of conductivity and nitrate/nitrite ions concentration were observed during the degradation. The applied voltage amplitude significantly affected the removal efficiency and the energy yield as the degradation efficiency was 55%, 70%, and 72% respectively with an applied voltage of 8, 10, and 12 kV. The water matrices containing inorganic anions such as chloride and carbonate ions reduced the removal efficiency by scavenging the reactive species. Accordingly, a reduction in the removal efficiency was observed in tap water. The high-resolution mass spectrometry (HRMS) results revealed that both reactive oxygen and nitrogen species take part in the reaction process which yields many intermediate products including aromatic nitro-products. This study concluded that NTP can effectively degrade CBZ in both pure and tap water, but special attention must be paid to changes in the water quality parameters (pH, conductivity, and nitrate/nitrite ions) and the fate of nitro products.

(Best Paper Award) Aluminum Josephson Junction Formation on 200mm Wafers Using Different Oxidation Techniques

For superconducting quantum circuits with a large number of Qubits, reproducible components are crucial for reducing entanglement decoherence. Particularly for reliable industrial manufacturing on full-scale 200 mm' wafers, a very high uniformity level is required to ensure sufficient coherence times. In the present work the special focus was put on manufacturing Al/AlOx/Al Josephson junctions (JJ), which are the most important component of many quantum circuit. Fully Al-based CMOS-compatible JJ’s were produced using a double dry etch process. After patterning the first Al metallization several oxidation processes have been investigated.Static oxidation has been performed by first removing the native AlOx in a multi-chamber system with Ar milling. The final tunneling oxide was controlled by applying a specific pressure in the chamber under a pure O2 atmosphere. Afterwards, without breaking the vacuum, the second Al metallization has been deposited by sputtering. Oxide thicknesses between 1 and 2.5 nm were achieved. A full mapping of the process homogeneity will be given.On the other hand, a dynamic recipe controlled plasma oxidation process was performed, where the native AlOx was first removed by a H2 plasma followed by a defined reoxidation with an oxygen plasma. The resulting oxides had thicknesses up to 10 nm. The second Al metallization was again deposited by sputtering.Both oxidation processes were carefully studied to understand the initial oxidation process of the aluminum surface. Special attention was devoted to the non-destructive removal of the native AlOx with respect to the Al interface. Because the oxide thicknesses varied between 1 and 10 nm, the transition between direct and Fowler-Nordheim tunneling could be investigated. The process-stability on full scale 200 mm wafers and on chip size could be determined via test structures as well as the resistance variation of the Josephson junctions. Furthermore, the electrical properties of the different oxides could be measured and analyzed on wafer level. These studies provide insight into the structure and composition of the aluminum oxides and the applicability for Qubits.

Poly‐SiOx Passivating Contacts with Plasma‐Assisted N2O Oxidation of Silicon (PANO‐SiOx)

Passivating contacts are crucial for realizing high‐performance crystalline silicon solar cells. Herein, contact formation by plasma‐enhanced chemical vapor deposition (PECVD) followed by an annealing step is focused on. Poly‐SiOx passivating contacts by combining plasma‐assisted N2O‐based oxidation of silicon (PANO‐SiOx) with a thin film of phosphorus (n+) or boron (p+)‐doped hydrogenated amorphous silicon oxide (a‐SiOx:H) are manufactured. Postannealing is conducted for transitioning a‐SiOx:H into poly‐SiOx. The aim is to achieve a contact with low absorption and high‐quality passivation. It is demonstrated that by tuning the plasma oxidation process time and power, the PANO‐SiOx thickness and its passivation quality can be controlled. A higher SiO2 content is observed in PANO‐SiOx than in the nitric acid oxidation of silicon (NAOS‐SiOx) counterpart. PANO‐SiOx acts as a stronger diffusion barrier for both boron and phosphorus atoms compared to NAOS‐SiOx, affecting the dopant distribution during annealing. Implied open‐circuit voltages up to 751 and 710 mV for n+ and p+ flat symmetric samples, respectively, are demonstrated. With respect to standard thermally grown SiO2 tunneling oxide combined with (in/ex )situ‐doped low‐pressure chemical vapor deposition poly‐Si, this study presents a simple alternative for manufacturing passivating contact fully based on PECVD processes.

Corrosion and Wear Behavior of TiO2/TiN Duplex Coatings on Titanium by Plasma Electrolytic Oxidation and Gas Nitriding.

In this study, corrosion and wear behavior of three kinds of coatings by two processes, namely, plasma electrolytic oxidation (PEO) coatings (Ti/TiO2), gas nitriding coating (Ti/TiN), and the duplex coating (Ti/TiO2-N) by combination of PEO and gas nitriding methods were systematically investigated. X-ray diffraction tests, field-emission scanning electron microscopy, and adhesion tests are employed for the coating characterization, along with the wear and electrochemical test for evaluating the corrosion and tribological properties. The morphology and structure of the coating consist of micro-cavities known as the pancake structure on the surface. The electrolytic plasma oxidation process produces a typical annealing behavior with a low friction coefficient based on the wear test. The coating consists of nitride and nitrate/oxides titanium for nitrided samples. The surface morphology of nitrided oxide titanium coating shows a slight change in the size of the crystals and the diameter of the cavities due to the influence of nitrogen in the titanium oxide coating. The tribological behavior of the coatings showed that the wear resistance of the duplex coating (Ti/TiO2-N) and Ti/TiO2 coatings is significantly higher compared to Ti/TiN coatings and uncoated Ti samples. The polarization resistance of the Ti/TiO2-N and Ti/TiO2 coatings was 632.2 and 1451.9 kΩ cm2, respectively. These values are considerably greater than that of the uncoated Ti (135.9 kΩ cm2). Likewise, impedance showed that the Ti/TiO2-N and Ti/TiO2 coatings demonstrate higher charge transfer resistance than that of other samples due to better insulating behavior and denser structure.

Spatio-temporal profile of atomic oxygen in a 1 kHz repetition atmospheric-pressure plasma jet in He–O2–H2O mixture

Atomic oxygen (O) is one of the essential reactive species in plasma oxidation processes. We investigated the behavior of atomic oxygen in a 1 kHz-repetition pulsed plasma jet in atmospheric-pressure He/O2/H2O mixture. By two-photon absorption laser-induced fluorescence, the spatio-temporal profiles of O density were measured under various conditions. In the dry ([H2O] 100 ppm) condition, the rate of O production did not depend on the [O2] fraction in the range of [O2] = 275–8600 ppm. The analysis of the O-production rate indicates that the atomic oxygen in this plasma jet arises from electron-impact dissociation and quenching of O(1 D), similar to the O-production mechanism in radio-frequency plasma jet. The dependence of O-production in each discharge pulse (Δ[O]) on the discharge energy and [O2] in the plasma region at dry condition is formulated as . The decay rate of atomic oxygen was not explained by self-recombination or ozone-generation reactions; it was consistent with the reaction rate of O + OH O2 + H at [OH] = cm−3. This result suggests that the small amount of [OH] with 1013 cm−3 density is more responsible for O behavior than [O2] with large fraction of 1015 cm−3. We conducted a chemical reaction simulation considering the measured results of [O] and [OH] production, resulting in good agreement with the spatial distribution of [O]. Chemical reaction analysis revealed that the cyclic reproduction of OH via chain reaction with O and O2 is important, therefore a small amount of OH catalytically consumes atomic oxygen with two-order higher density.

Degradation and Detoxification of Remazol Blue Contaminants as a Model Textile Effluent via Advanced Nonthermal Plasma Oxidation Processes

This study explores the degradation of the reactive Remazol Blue RR (RBRR) as a model textile effluent upon its exposure to non-thermal atmospheric pressure plasma. An extensive comparative study of different combinations of the following plasma/solution treatment environments was conducted: 1) Ar plasma jet (Ar-PJ) alone; 2) Ar/O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> and Ar/N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> plasmas; 3) Ar plasma with O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> or N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> injected (INJ) in the bulk of the Ar plasma afterglow; and 4) Ar plasma with O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> or N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> bubbling (BB) in the RBRR solution. In all conditions, plasma treatment was carried out at a fixed applied voltage of 31 kV and treatment time of 10 min. The degradation efficiency of RBRR in the different plasma-treated solutions was evaluated using UV–visible spectroscopy. Optical emission spectroscopy (OES) was used to examine the generation of excited species in plasma during the degradation processes. Moreover, the concentration of plasma-induced reactive hydroxyl radicals (OH <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">•</sup> ) and hydrogen peroxide (H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) was determined spectroscopically. To further corroborate the results, the pH, conductivity, and total organic carbon (TOC) of the plasma-treated RBRR solutions were assessed. Overall, the results showed that the highest degradation efficiency (45%) was obtained upon exposure of RBRR aqueous solution to Ar plasma with N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> bubbling in the solution. The non-toxic nature of all plasma-treated solutions was confirmed by non-inhibition of bacterial growth ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Escherichia coli</i> and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Staphylococcus aureus</i> ). Overall, plasma treatment in general and Ar plasma accompanied with N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> bubbling in particular constitute an eco-friendly and very promising techniques to degrade/decolorize textile effluent.

Comparative analysis of hexamethyldisiloxane and hexamethyldisilazane plasma polymer thin films before and after plasma oxidation

AbstractThe presented study compares the structure of hexamethyldisiloxane (HMDSO) and hexamethyldisilazane (HMDSN) plasma polymer thin films with a thickness of about 30 nm before and after a plasma oxidation process, focusing on the analysis of porosity and the correlated electrolyte up‐take in the formed films. The results illustrate that the plasma oxidation treatment converts the HMDSO and HMDSN plasma polymer films progressively into SiOx‐like films. However, the underlying mechanism of the etching of CxHy groups and the condensation of intermediate Si‐OH groups leads to highly porous films. The studies show that the differences in the chemical structure and nanoporosity as measured by spectroscopic techniques could be correlated with the resulting up‐take of electrolytes in the open pores of the films.

Combinatorial effects of non-thermal plasma oxidation processes and photocatalytic activity on the inactivation of bacteria and degradation of toxic compounds in wastewater.

The simultaneous presence of hazardous chemicals and pathogenic microorganisms in wastewater is tremendously endangering the environment and human health. Therefore, developing a mitigation strategy for adequately degrading toxic compounds and inactivating/killing microorganisms is urgently needed to protect ecosystems. In this paper, the synergetic effects of the photocatalytic activity of TiO2 and Cu–TiO2 nanoparticles (NPs) and the oxidation processes of non-thermal atmospheric pressure plasma (NTAPP) were comprehensively investigated for both the inactivation/killing of common water contaminating bacteria (Escherichia coli (E. coli)) and the degradation of direct textile wastewater (DTW). The photocatalytic NPs were synthesized using the hydrothermal method and further characterized employing field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), ultraviolet-visible diffuse reflection spectroscopy (UV-Vis DRS) and photoluminescence (PL). Results revealed the predominant presence of the typical anatase phase for both the flower-like TiO2 and the multipod-like Cu–TiO2 structures. UV-Vis DRS and PL analyses showed that the addition of Cu dopants reduced the bandgap and increased oxygen defect vacancies of TiO2. The inactivation of E. coli in suspension and degradation of DTW were then examined upon treating the aqueous media with various plasma alone and plasma/NPs conditions (Ar plasma, Ar + O2 plasma and Ar + N2 plasma, Ar plasma + TiO2 NPs and Ar plasma + Cu–TiO2 NPs). Primary and secondary excited species such as OH˙, O, H and N2* generated in plasma during the processes were recognized by in situ optical emission spectrometry (OES) measurements. Several other spectroscopic analyses were further employed to quantify some reactive oxygen species (ROS) such as OH, H2O2 and O3 generated during the processes. Moreover, the changes in the pH and electrical conductivity (EC) of the solutions were also assessed. The inactivation of bacteria was examined by the colony-forming unit (CFU) method after plating the treated suspensions on agar, and the degradation of organic compounds in DTW was further validated by measuring the total organic carbon (TOC) removal efficiency. All results collectively revealed that the combinatorial plasma-photocatalysis strategy involving Cu–TiO2 NPs and argon plasma jet produced higher concentrations of ROS and proved to be a promising one-step wastewater treatment effectively killing microorganisms and degrading toxic organic compounds.

Insight into the plasma oxidation process during pulsed laser deposition

AbstractThe dynamics of transient plasmas generated by ns laser ablation of Ag targets under various O2gas pressures (10−5–10 Pa) were investigated by implementing angle‐ and time‐resolved Langmuir probe (LP) analysis and space‐ and time‐resolved optical emission spectroscopy (OES). The effects of an O2atmosphere on silver oxide formation and the ionic kinetics and the overall plasma energy were systematically investigated. Measurements performed in the LP floating regime revealed the presence of three‐ionic structures with kinetic energies varying from 0.8 to 350 eV, which can be tailored by the addition of O2. The time‐modulated regime of electron temperature in the 0.5–3 eV observed for pressures higher than 2 Pa of O2could be explained by the formation and dissociation of silver oxide molecules. The energetic balance sustains molecular oxide formation, as confirmed by OES measurements, which revealed emission signatures of AgO (B 2Π3/2and X 2Π3/2) in the 350 nm (B 2Π3/2) and 460 nm (X 2Π3/2) spectral regions. Finally, thin films were deposited to understand the range of possibilities offered by pulsed laser deposition of Ag in O2. The morphology and atomic structure of the films were analysed for large‐scale deposition. Silver oxides were detected in the films starting from 2 Pa, while at higher values, we found mixtures of different AgxOyphases. A cauliflower‐like morphology was dominant above 5 Pa of O2atmosphere pressures, which signals the formation of the AgO phase in the deposited film. Our results demonstrate that the properties of deposited thin films are influenced by plasma properties.

Self-oxidation-formed boron oxide as a tunnel barrier in SmB6 junctions

Samarium hexaboride (SmB6) belongs to a novel class of quantum matter known as topological Kondo insulators. By utilizing planar tunneling spectroscopy, signatures of spin excitons that interact with the topological surface states have been observed. To uncover additional details about this interaction, the effect on the characteristic features by plasma cleaning and ion beam etching processes, employed to clean the SmB6 crystal surface, are examined. Additionally, the effect of the plasma oxidation process used to form the tunnel barrier is analysed. Comparing the conductance spectra to simulations based on the Blonder-Tinkham-Klapwijk model revealed that the junctions with the highest resistances also had the weakest barrier strengths. Such seemingly contradictory observations may be explained by considering a barrier containing layers of B6O or B3O in addition to B2O3. This suboxide formation appears to be most dominant at higher ion beam energies as well as lower plasma oxidation powers.

Formation of Nitrogen Doped Titanium Dioxide Surface Layer on NiTi Shape Memory Alloy.

NiTi shape memory alloys are increasingly being used as bone and cardiac implants. The oxide layer of nanometric thickness spontaneously formed on their surface does not sufficiently protect from nickel transition into surrounding tissues, and its presence, even in a small amount, can be harmful to the human organism. In order to limit this disadvantageous phenomenon, there are several surface engineering techniques used, including oxidation methods. Due to the usually complex shapes of implants, one of the most prospective methods is low-temperature plasma oxidation. This article presents the role of cathode sputtering in the formation of a titanium dioxide surface layer, specifically rutile. The surface of the NiTi shape memory alloy was modified using low-temperature glow discharge plasma oxidation processes, which were carried out in two variants: oxidation using an argon + oxygen (80% vol.) reactive atmosphere and the less chemically active argon + air (80% vol.), but with a preliminary cathode sputtering process in the Ar + N2 (1:1) plasma. This paper presents the structure (STEM), chemical composition (EDS, SIMS), surface topography (optical profilometer, Atomic Force Microscopy—AFM) and antibacterial properties of nanocrystalline TiO2 diffusive surface layers. It is shown that prior cathodic sputtering in argon-nitrogen plasma almost doubled the thickness of the produced nitrogen-doped titanium dioxide layers despite using air instead of oxygen. The (TiOxNy)2 diffusive surface layer showed a high level of resistance to E. coli colonization in comparison with NiTi, which indicates the possibility of using this surface layer in the modification of NiTi implants’ properties.

Synchronous Growth of Porous MgO and Half-Embedded Nano-Ru on a Mg Plate: A Monolithic Catalyst for Fast Hydrogen Production

Development of efficient and sustainable monolithic catalysts for NaBH4 hydrolysis remains an important goal for hydrogen cycling. In this work, the structured catalyst Ru/MgO with an on–off feature has been prepared by directly growing a nano-Ru-embedded MgO coating layer on a Mg substrate via an instant high-temperature plasma oxidation process. The porous MgO framework provides an ideal space for the access of reactants and diffusion of mass transport, which facilitates reaction triggering and the expulsion of byproducts to avoid poisoning the catalyst. Importantly, Ru nanoparticles (NPs) are monodisperse with ultrasmall particle size deriving from a concurrent rapid arcing and fast quenching. The hierarchical structured Ru NP catalysts are highly active for hydrolysis of sodium borohydride by achieving a high hydrogen generation rate (HGR) of 101,189 mL min–1 g–1 and exhibit attractive stability. In addition, it is facile to realize the “on–off” functionality based on simple separation that could accurately control the hydrogen generation, suggesting the structured catalyst to be of great potential for practical applications. This simple method opens valuable opportunities for fast synthesis of the high-quality structured catalyst and could be extended to various noble metals on oxides of valve metals with high catalytic performance.

The Influence of Temperature on the Tribological Properties of the Ti&lt;sub&gt;6&lt;/sub&gt;Al&lt;sub&gt;4&lt;/sub&gt;V Alloy Treated by Plasma Oxidation

The purpose of the plasma oxidation process is to increase the hardness, corrosion resistance and to improve the biocompatibility properties of Ti6Al4V alloys by thickening the natural oxide in the material, which is produced by this treatment. The aim of this work is to verify the effect of temperature on the thickness, hardness and wear resistance of the Ti6Al4V alloy treated with plasma oxidation. The treatment was performed using a Pulsed DC vacuum reactor, with a gas ratio of 60% Ar and 40% O2and 1.65 torr pressure for 1 hour of treatment, at temperatures of 480°C, 520°C, 670°C and 705°C. In regards to the multilayer formation of anatase and rutile, it was observed that the layer thickness increased as the treatment temperature increased. The increase of surface hardness provided by the treatment caused a considerable increase in the wear resistance of the studied material. The greatest layer thickness and surface hardness were obtained for the material treated at 705°C, but the lowest wear volume was obtained for the material treated at 520°C.

Ultrathin Plasma Oxide for Passivation of Phosphorus-Diffused Silicon Solar Cell Emitters

Different passivation layers on phosphorous diffused emitters have been studied. A comparison between silicon nitride (SiNx) single layer at different deposition temperatures, stacks of “outgassing” silicon oxide (that was grown during the moving in/out of the furnace in ambient air during the outgassing process) and an ultrathin SiOx layer formed by plasma oxidation capped with SiNx layers have been investigated. Optimization of plasma enhanced chemical vapor deposition (PECVD) SiNx at different deposition temperatures showed good passivation quality depending on the hydrogen content. Plasma oxidation process by a PECVD tool without utilizing a silicon source in the process gas flow is an obvious choice to form a thin SiOx as it allows the formation of a SiOx/SiNx stack in a sequence of deposition processes in the same inline PECVD tool. Such an ultrathin SiOx layer was found to not only improve the surface passivation after a fast firing process but also to maintain the excellent anti-reflection coating (ARC) property of the SiNx. Low emitter saturation current density J 0 e values of 15 fA/cm2 for planar and 24 fA/cm2 for textured surfaces for an emitter with a sheet resistivity of 161 Ω/ sq has been reached after firing at 850 °C, which is comparable with the outgassing oxide. These stacks gave an improvement of the J 0 e values with a factor of 6–9 for emitters with low surface concentration comparing to single SiNx layer.

Simultaneous measurement of local densities of atomic oxygen and ozone in pure oxygen pulsed barrier discharge under atmospheric pressure

Atomic oxygen and ozone are essential reactive species in plasma oxidation processes. Pure oxygen discharge is preferable to produce atomic oxygen and ozone while a difficulty in measuring their local densities exists. The ozone density is typically measured by UV absorption, but its resolution is insufficient for measuring the local ozone density in filamentary discharges. The atomic oxygen density can be measured by two-photon absorption laser-induced fluorescence (TALIF) method. However, ozone interference from the in situ atomic oxygen production due to ozone fragmentation by the incident UV light disturbs the TALIF measurement of the discharge-originated atomic oxygen. Therefore, compensation for ozone interference is necessary in atomic oxygen measurements. In this study, we propose a method to separate ozone interference from the discharge-originated atomic oxygen signal by focusing on different TALIF signal dependence on the laser intensity between atomic oxygen density and ozone density. By changing the laser intensity in the TALIF measurement, we separate the signal of atomic oxygen density from that of ozone interference. Under a short-gapped pulsed barrier discharge at a 3.1 mJ discharge energy, the gas temperature and the local densities of the atomic oxygen and ozone in the observed volume are estimated to be approximately 380 K, 3.8–11.3 , and 3.4 , respectively. This estimated atomic oxygen density is consistent with the absolute atomic oxygen density calibrated by the Xe-TALIF measurement. This consistency indicates that our method is applicable for absolute density measurements of atomic oxygen using ozone as the calibration reference.

Combination of plasma oxidation process with microbial fuel cell for mineralizing methylene blue with high energy efficiency

Plasma advanced oxidation process (PAOP) has great ability to break recalcitrant pollutants into small molecular compounds but suffers from poor performance and low energy efficiency for mineralizing dyeing pollutants. Combining advanced oxidation process with biodegradation process is an effective strategy to improve mineralization performance and reduce cost. In this study, a combined process using PAOP as pre-treatment followed by microbial fuel cell (MFC) treatment was investigated to mineralize methylene blue (MB). The PAOP could degrade MB by 97.7%, but only mineralize MB by 23.2% under the discharge power of 35 W for 10 min. Besides, BOD5/COD ratio of MB solution raised from 0.04 to 0.38 while inhibition on E. coli growth decreased from 85.5% to 28.3%. The following MFC process increased MB mineralization percentage to 63.0% with a maximum output power density of 519 mW m−2. The combined process achieved a mineralization energy consumption of 0.143 KWh gTOC−1 which was only 41.8% of that of PAOP. FT−IR, UV–vis and pH variation demonstrated that PAOP could break the aromatic and heterocyclic structures in MB molecule to form organic acids. Possible degradation pathways of MB were accordingly proposed based on LC–MS, GC–MS, and density functional theory calculation.

Processing Strategies for High-Performance Schottky Contacts on n-Type Oxide Semiconductors: Insights from In2O3

Preparation of rectifying Schottky contacts on n-type oxide semiconductors, such as indium oxide (In2O3), is often challenged by the presence of a distinct surface electron accumulation layer. We investigated the material properties and electrical transport characteristics of platinum contact/indium oxide heterojunctions to define routines for the preparation of high-performance Schottky diodes on n-type oxide semiconductors. Combining the evaluation of different Pt deposition methods, such as electron-beam evaporation and (reactive) sputtering in an (O and) Ar atmosphere, with oxygen plasma interface treatments, we identify key parameters to obtain Schottky-type contacts with high electronic barrier height and high rectification ratio. Different photoelectron spectroscopy approaches are compared to characterize the chemical properties of the contact layers and the interface region toward In2O3, to analyze charge transfer and plasma oxidation processes as well as to evaluate the precision and limits of different methodologies to determine heterointerface energy barriers. An oxygen-plasma-induced passivation of the semiconductor surface, which induces electron depletion and generates an intrinsic interface energy barrier, is found to be not sufficient to generate rectifying platinum contacts. The dissolution of the functional interface oxide layer within the Pt film results in an energy barrier of ∼0.5 eV, which is too low for an In2O3 electron concentration of ∼1018 cm-3. A reactive sputter process in an Ar and O atmosphere is required to fabricate rectifying contacts that are composed of platinum oxide (PtOx). Combining oxygen plasma interface oxidation of the semiconductor surface with reactive sputtering of PtOx layers results in the generation of a high Schottky barrier of ∼0.9 eV and a rectification ratio of up to 106. An additional oxygen plasma treatment after contact deposition further reduced the reverse leakage current, likely by eliminating a surface conduction path between the coplanar Ohmic and Schottky contacts. We conclude that processes that allow us to increase the oxygen content in the interface and contact region are essential for fabrication of device-quality-rectifying contacts on various oxide semiconductors.

Physical and mechanical properties investigation of oxide coatings on titanium

This paper studies the impact of rapidly flowing impulse effect of electrolytic plasma oxidation on physical and mechanical specifications of oxide coatings through the surface modification of VT1-0 titanium alloy. The present mode allows obtaining dense coatings with high mechanical properties. The electrolytic plasma oxidation process implementation leads to a micro arc-discharge emergency in a short period through the small duration values of 250 µs anodic impulse. The achieved oxide coatings have high wearing features. Frictional testing resulted in wearing features increase in 4-15 times comparing to the sample off coating at to15 µm oxide layer thickness. Friction coefficient curves of oxide coating samples have shown no destruction of the coating to the bottom. A run-in area is recognized on the curves; sliding surfaces adapt to each other and pass to the stable friction regime. The later leads to the friction coefficient reduce and wear intensity reduction.

Studying dopant diffusion from Poly-Si passivating contacts

The diffusion of dopants from the poly-Si layer through the interfacial oxide into the crystalline silicon wafer is studied experimentally and via numerical simulation. It is found that phosphorus piles up at the poly-Si/SiOx interface but boron readily diffuses through the oxide into the silicon and thereby forms a less shallow junction which adversely affects surface passivation. Although boron diffusion was suppressed by using a nitrided oxide – realized by a plasma oxidation process – a reduction in passivation was observed due to deterioration of the interface. Via 1D and 3D process simulation it was established that diffusion through pinholes contributed little to the aggregate diffusion profiles measured by ToF-SIMS but direct diffusion through the oxide was the main diffusion mechanism. The segregation coefficient at the poly-Si/SiOx interface and the diffusivity in SiOx were determined. Using these parameters simulation-based predictions were conducted in order to pave the way for future optimization of hole-selective passivating contacts.