Influence Of Oxygen Partial Pressure Research Articles

Influence of oxygen partial pressure on properties of monoclinic Ga2O3 deposited on sapphire substrates

Thin monoclinic Ga2O3 films were deposited on c-plane sapphire substrates by low pressure chemical vapor deposition. The thin films were synthesized using high purity metallic gallium (Ga) and oxygen gas (O2) as precursors. The effect of oxygen volume percentage on the growth rate of thin films was observed at two growth temperatures. Within the investigated growth window, a maximum growth rate of ∼2.9 μm/h was obtained for an oxygen volume percentage of 4.8% with a growth temperature at 800 °C. The film growth rate decreased as growth temperature increased when other growth parameters were kept the same. X-ray diffraction indicates that all films have the β-Ga2O3 structure with (−201) orientation, and those deposited with higher oxygen partial pressure are thicker and have improved crystalline quality. Polarized micro-Raman scattering is consistent with small grains of (−201) β-Ga2O3 having random in-plane orientations. The large variation of the relative intensities of overlapping emission bands contributing to the broad luminescence emission extending between 1.5 and 4.5 eV (∼825 and 275 nm) suggest that deposition conditions strongly affect different defect concentrations. Films deposited at 800 °C with a higher oxygen partial pressure yielded higher resistance, which may result from the incorporation of gallium vacancies, identified as a compensating point defect affecting the electrical conductivity of bulk monoclinic Ga2O3.

TEM Study of Oxygen Partial Pressure Effect on Early LSM-YSZ Surface Interactions in Solid Oxide Fuel Cells

Abstract Long-term stability studies indicate that cathode degradation is one of the main failure mechanisms in anode-supported SOFCs. In order to better understand the microstructural degradation mechanisms of the cathode and the influence of oxygen partial pressure at relevant operating temperatures, the authors of this article acquired TEM samples from technological cells to study cation interdiffusion mechanisms and LSM-YSZ interactions, particularly in areas where LSM grains are in contact with YSZ electrolyte. Here they present and interpret the results.

The influence of oxygen partial pressure on the crack propagation of superalloy under fatigue-creep-environment interaction

We elucidate here the effect of low oxygen partial pressure on the dwell fatigue crack growth rate (DFCGR) of 718Plus alloy at high temperature. In comparison under the air and vacuum conditions with lower oxygen partial pressure, the DFCGR of 718Plus alloy reduced by three orders of magnitude at 704 °C at lower oxygen partial pressure than that of in air condition. By analysis of microstructure, oxide, and crack path under different conditions, it was considered that the oxygen-induced dynamic embrittlement (DE) was the dominant impact mechanism for fatigue crack propagation at high-temperature in 718Plus alloy. Meanwhile, the stress-accelerated grain boundary oxidation (SAGBO) mechanism also played a significant role, especially in the long step-wise period. In addition, the types of oxide formed in creep process were directly related to the oxygen partial pressure and oxidation time.

Influence of Oxygen Partial Pressure on Oxidation Reaction of Iron-bearing Materials in Iron Ore Sintering Bed

Influence of Oxygen Partial Pressure on Oxidation Reaction of Iron-bearing Materials in Iron Ore Sintering Bed

Influence of oxygen partial pressure on SmBa2Cu3O7-δ film deposited by laser chemical vapor deposition

ABSTRACT Laser chemical vapor deposition (LCVD) was applied to prepare SmBa2Cu3O7-δ (SmBCO) superconductive films on single-crystalline LaAlO3 (100) substrates. The effect of oxygen partial pressure (P O2) on the crystal orientation, microstructure, and superconducting property of SmBCO film were investigated thoroughly. The results of X-ray diffraction (XRD) and Raman showed that the crystal orientation of SmBCO film was pure c -axis orientation at the P O2 of 200 Pa, and the a- axis orientation grains gradually emerged in SmBCO film with the increase of P O2. The deposition rate, critical temperature (T c), critical current density (J c) firstly increased and then decreased with the increase of P O2. At the P O2 of 200 Pa, the SmBCO film had smooth and dense surface, the lowest FWHM of φ-scan (1.1°), the highest T c (89.2 K) and J c (2.04 MA/cm2), which indicated that SmBCO superconductive films possessed excellent crystal structure and superconducting performance.

Oxygen partial pressure influenced stoichiometry, structural, electrical, and optical properties of DC reactive sputtered hafnium oxide films

HfO2 films have been deposited on quartz and p‐type Si (100) substrates using DC reactive magnetron sputtering technique by sputtering of hafnium target at different oxygen partial pressures. Variation of cathode potential with oxygen partial pressure was systematically studied. The influence of oxygen partial pressure on chemical composition, crystallographic structure, and optical properties of HfO2 films was systematically investigated. X‐ray photoelectron spectroscopy and energy dispersive X‐ray analysis were employed to determine the chemical composition. The films formed at oxygen partial pressure of 5 × 10−4 Torr were of stoichiometric HfO2. X‐ray diffractometer studies revealed that the films formed at 5 × 10−4 Torr were weakly crystallized with monoclinic structure. Optical bandgap of the HfO2 films increased with increasing oxygen partial pressure. Metal oxide semiconductor structures with configuration of Al/HfO2/p‐Si were fabricated and studied its dielectric and electrical properties. From these studies, it is confirmed that HfO2 film‐based metal oxide semiconductor devices formed at an optimum oxygen partial pressure of 5 × 10−5 Torr showed dielectric constant of 13 with leakage current density of 4.7 × 10−7 A/cm2.

Microstructure, optical, and photoluminescence properties of β-Ga2O3 films prepared by pulsed laser deposition under different oxygen partial pressures* *Project supported by the Guizhou Provincial Science and Technology Planning Project, China (Grant No. 2018-5781), the National Natural Science Foundation of China (Grant No. 51762010), the Guizhou Provincial Science and Technology Foundation, China (Grant Nos. 2020-1Y021 and 2020-1Y271), and the Guizhou Provincial

The β-Ga2O3 films are prepared on polished Al2O3 (0001) substrates by pulsed laser deposition at different oxygen partial pressures. The influence of oxygen partial pressure on crystal structure, surface morphology, thickness, optical properties, and photoluminescence properties are studied by x-ray diffraction (XRD), atomic force microscope (AFM), scanning electron microscope (SEM), spectrophotometer, and spectrofluorometer. The results of x-ray diffraction and atomic force microscope indicate that with the decrease of oxygen pressure, the full width at half maximum (FWHM) and grain size increase. With the increase of oxygen pressure, the thickness of the films first increases and then decreases. The room-temperature UV-visible (UV-Vis) absorption spectra show that the bandgap of the β-Ga2O3 film increases from 4.76 eV to 4.91 eV as oxygen pressure decreasing. Room temperature photoluminescence spectra reveal that the emission band can be divided into four Gaussian bands centered at about 310 nm (∼ 4.0 eV), 360 nm (∼ 3.44 eV), 445 nm (∼ 2.79 eV), and 467 nm (∼ 2.66 eV), respectively. In addition, the total photoluminescence intensity decreases with oxygen pressure increasing, and it is found that the two UV bands are related to self-trapped holes (STHs) at O1 sites and between two O2-s sites, respectively, and the two blue bands originate from at Ga1 tetrahedral sites. The photoluminescence mechanism of the films is also discussed. These results will lay a foundation for investigating the Ga2O3 film-based electronic devices.

Modifying the crystal structures of Fe2O3-doped NiO epitaxial thin films grown at room temperature by controlling the oxygen partial pressure

Herein, we investigated the influence of oxygen partial pressure (pO2) on average long- and short-range transformations in the crystal structures of ultra-smooth Fe2O3-doped NiO thin films that were epitaxially grown at room temperature. The films were deposited via pulsed laser deposition, and the oxygen content in the films was controlled by adjusting the pO2 to 1, 10-3, and 10-5 Pa. Result showed that d-spacing and lattice strain decreased with increasing pO2. The thin film grown at 10-5 Pa had a rock salt structure, whereas films grown at pO2s of 10-3 and 1 Pa had spinel structures. The local structures and valence states indicate that local Fe coordination transitioned from a distorted octahedral geometry to a tetrahedral/distorted octahedral geometry at higher pO2s. Additionally, the valence of Fe increased from Fe2+ to Fe3+, indicating structural phase transformation, which is supported by the X-ray diffraction analysis results. In contrast, the valence and local environment of Ni varied little. The structural transformation of the films was accompanied by the narrowing of the optical bandgap for direct transition and an increase in electrical resistivity.

Structural, morphological and electrical properties of Sm-Gd Co-doped ceria thin films for micro-solid oxide fuel cells

Thin film electrolytes of Sm and Gd doubly co-doped ceria, namely, Ce0.8Sm0.1Gd0.1O1.90 (CSGO) deposited by pulsed laser deposition (PLD) technique have been investigated. The influence of oxygen partial pressure (pO2) on structural and morphological properties of CSGO thin films deposited on Si (111) substrate was studied by X-ray diffraction (XRD), Raman spectroscopy, field emission scanning electron microscope (FESEM) and atomic force microscopy (AFM) techniques. The XRD and FESEM results showed that the films were polycrystalline cubic structure with (111) oriented columnar structure. The co-doping strategy has strongly helped to stabilize the Ce4+ state as the lattice parameter of the films did not show any significant change under the influence of pO2 in the range of 2 × 10-4-3 × 10-2 mbar. The electrical conductivity and activation energy of CSGO thin film supported on NiO-GDC10 anode were found to be 0.48 mS.cm−1 and 0.5 eV respectively. Determination of significantly lower Ce3+ concentration (27%) in CSGO film by X-ray photon electron spectroscopy (XPS) suggests that Sm-Gd co-doping has strongly suppressed the conversion of Ce4+ to Ce3+ in the overall composition.

Highly transparent IGZO-TFTs uses IGZO source and drain electrodes with a composite insulation layer structure

In this paper, the characteristic that the proper oxygen partial pressure during sputtering can change IGZO from semiconductor to conductor was used to fabricate IGZO-TFTs. Firstly, in order to determine the optimum parameters for the preparation of IGZO thin films as active layer and source/drain electrode, the influence of oxygen partial pressure on the conductivity and transmittance of IGZO thin films prepared by magnetron sputtering was studied, then a highly transparent IGZO-TFT device based on IGZO source/drain electrode was fabricated, in which an ultra-thin layer of atomic layer deposited (ALD) alumina under the original PMMA insulation layer was added to make a composite insulation layer structure. The mobility of the device is 6.07 cm2/Vs, the switching ratio is 0.87 × 104, threshold voltage and sub-threshold swing are 2.6 V and 3.5 V/decade, respectively. And the transmittance of the device in the visible light range is more than 80%, showing a good optical transmittance.

Investigation on tailoring physical properties of Nickel Oxide thin films grown by dc magnetron sputtering

We report a comprehensive study on influence of oxygen partial pressure on NiO thin films grown on glass substrates in a combined argon and oxygen ambience by reactive dc magnetron sputtering. In this present article, we have discussed the dependence of oxygen pressure on structural, chemical, morphological, optical and electrical properties of the sputtered NiO films. Glancing angle x-ray diffraction reveals that the deposited films were polycrystalline in nature with FCC phase. The preferred orientation changes from (200) to (111) in a higher O2 flow rate environment and an average particle size was estimated using Scherrer relation. The surface morphology of films was studied by using atomic force microscopy. The x-ray photoelectron spectroscopy analysis demonstrates the core level Ni 2p spectra over a range of 850 eV to 885 eV of binding energy and observed Ni 2p3/2, Ni 2p1/2 domains along with their satellite peaks. It infers the presence of both Ni+2 and Ni+3 oxidation states in the sputtered films. Additionally, Raman spectroscopy was carried out to confirm the structural defects level and crystalline nature of the films. The optical results show that deposited films were semi-transparent and the evaluated optical band gap of the material lies in the range 3.36 eV to 3.52 eV. The extracted electrical properties infer either n-type or p-type conductivity depending on the processing conditions of the films.

Oxygen partial pressure dependent UV photodetector performance of WO3 sputtered thin films

The influence of oxygen partial pressure (pO2) on the ultra-violet (UV) photodetector performance of WO3 thin films was studied. Here, the thickness of the WO3 thin films decreased from 225 nm to 150 nm with increasing the pO2 from 5% to 20%. The crystallinity of WO3 films decreased at higher pO2. The XPS analysis confirmed that the WO3 film deposited at 10% of pO2 had the more oxygen vacancies. The grain size of WO3 films decreased at higher pO2 grown conditions owing to the fragmentation of the oxide formation through the plasma. From current-voltage (I–V) measurements of WO3/Ti device, the ohmic-contact implies the formation of the metal-semiconductor junction with very less barrier height (φB) and it helps to the trapping of generated electrons for potential photodetector. Due to the higher number of incoming photons, the photocurrent was found to be increased as the power density increases. Finally, the WO3 film deposited at 10% of pO2 exhibits the higher photocurrent and quick rising time and hence this optimized thin film is suitable for UV-A photodetector.

Synergistic effects on thermal growth of CuO nanowires

Growing cupric oxide (CuO) nanowires (NWs) through thermal oxidation of copper (Cu) in air is a facile and low-cost strategy. In a temperature range of 673–1073 K, single-crystal, bi-crystal NWs and cone-shaped nanostructure usually coexist. As far as the underlying mechanism is concerned, the stress-driven grain-boundary (GB) diffusion mechanism has been the most successful theory up to now. However, it did not include the influence of oxygen partial pressure and cannot explain the growth of long single-crystal CuO NWs of uniform diameters. Thus, the CuO NWs growth mechanism is yet to be fully understood. In this study, we present that synergistic effects of the Kirkendall effect, stress-driven GB diffusion, large surface free energy gap between Cu2O and CuO facets and an effective electric field along the CuO NWs originating from oxygen gradient are mainly involved in the thermal growth of CuO NWs.

22.2: The influence of Oxygen Partial Pressure on the Performance of back‐channel‐etched a‐ZTO Thin‐Film Transistors

In this work, we demonstrate that back‐channel‐etched a‐ZTO thin‐film transistors (TFTs) are close to realize industrial mass production. The effects of sputtering oxygen partial pressure on the electrical characteristics were mainly explored. Results indicated that both of sub‐threshold swing (SS) and field‐effect mobility (µsat) decreases as oxygen partial pressure increases, while threshold voltage (Vth) increases. The optimal TFTs exhibited the excellent performances: a modest µsat of 7.30 cm2/Vs, a suitable Vth of 5.29V and the SS of 0.41V/decade. Not only the variation of Vth shift (ΔVth) is +1.14 under PBS, but also ΔVth is ‐0.56 under NBS. Compared with IGZO channel layer, the promising ZTO material is abundant and non‐toxic. Therefore relevant TFTs prospectively contribute to reduce industrial production costs and environmental protection.

The effect of oxygen partial pressure on band gap modulation of Ga2O3 grown by pulsed laser deposition

The influence of oxygen partial pressure and annealing on the properties of thin films of β-Ga2O3 grown by pulsed laser deposition were studied. The Ga2O3 samples were deposited at a substrate temperature of 250 °C at an oxygen pressure of 0–50 mTorr and then annealed at a temperature of 600 °C. We observed the crystallinity of Ga2O3 enhanced with annealing and with increasing oxygen pressure. The full width at half maximum of annealed β -Ga2O3 (4¯01) peaks decreased, corresponding to the grain size increasing from 6.76 nm to 11.25 nm. The conductivity of the obtained, as-grown Ga2O3 films increased with oxygen pressure from 2.1 to 7.9 mScm−1. As a result, the conductance and the energy band gap of β-Ga2O3 without annealing were controlled by the oxygen partial pressure. This was attributed to the oxygen vacancies, based on the composition ratio between O and Ga ions. These results clearly showed that the energy band gap and conductance of β-Ga2O3 thin films could be controlled in such a way that could be utilized for high-performance photo-electronic devices.

Influence of oxygen partial pressure in In-Sn-Ga-O thin-film transistors at a low temperature

We examined the electrical properties of low-temperature-processed top-gate In-Sn-Ga-O (ITGO) thin-film transistors (TFTs) by rf/dc-sputtering with different oxygen partial pressures (PO2). As PO2 changed from 0 to 50.0%, the ITGO TFT showed various electrical characteristics such as from conductor-like behavior to transfer curves with positive-shifted threshold voltages (Vth). The TFT at PO2 of 25.0% afforded the best performance, exhibiting field-effect mobility of 14.8 cm2V−1s−1, Vth of 0.56 V, and subthreshold slope of 0.16 Vdec−1 with reasonable electrical stability for gate bias stress. From various analysis techniques, we found that the TFT characteristics and the electrical stability strongly depended on the metal-oxygen surface states of the ITGO films influenced by PO2 during the sputtering process.

Early detection of diving-related cognitive impairment of different nitrogen-oxygen gas mixtures using critical flicker fusion frequency.

Cognitive impairment related to inert gas narcosis (IGN) is a threat to diving safety and operations at depth that might be reduced by using enriched air nitrox (EANx) mixtures. Using critical flicker fusion frequency (CFFF), a possible early detection of cognitive abilities/cerebral arousal impairment when breathing different oxygen (O2) fractions was investigated. Eight male volunteers performed, in random order, two dry chamber dives breathing either air or EANx40 (40% O₂-60% nitrogen) for 20 minutes (min) at 0.4 MPa. Cognition and arousal were assessed before the dive; upon arrival at 0.4 MPa; after 15 min exposure at 0.4 MPa; on surfacing and 30 min post-dive using behavioural computer-based testing psychology experiment building language (PEBL) and by CFFF while continuously recording brain oxygenation with near-infrared spectroscopy. In both breathing conditions, CFFF and PEBL demonstrated a significant inverse correlation (Pearson r of -0.90, P < 0.0001), improved cognitive abilities/cerebral arousal occurred upon arrival at 0.4 MPa followed by a progressive deterioration. Initial brain activation was associated with a significant increase in oxyhaemoglobin (HbO2) and a simultaneous decrease of deoxyhaemoglobin (HHb). The magnitude of the changes was significantly greater under EANx (P = 0.038). Since changes were not related to haemodynamic variables, HbO₂ and HHb values indicate a significant, O₂-dependent activation in the prefrontal cortex. Owing to the correlation with some tests from the PEBL, CFFF could be a convenient measure of cognitive performance/ability in extreme environments, likely under the direct influence of oxygen partial pressure, a potent modulator of IGN symptoms.

Proof of Concept Study to Assess the Influence of Oxygen Partial Pressure in Capillary Blood on SMBG Measurements.

Measurement results provided by blood glucose monitoring systems (BGMS) can be affected by various influencing factors. For some BGMS using glucose oxidase (GOx)-based test strips, one of these factors is the oxygen partial pressure (pO2) of the applied blood sample. Because assessing the potential influence of pO2 when measuring capillary blood samples is not straight-forward, we performed a proof of concept study. Influence of pO2 was investigated for two GOx-based BGMS (BGMS A and B). Measurement results of the GOx-based BGMS were compared with measurement results from a pO2-independent BGMS (BGMS C). A total of 119 samples from 60 subjects were measured, twice with BGMS C, then 6 times each with BGMS A and BGMS B or vice versa, and again twice with BGMS C. Immediately afterward, pO2 was determined. Linear regression analysis based on relative differences between results from BGMS A or BGMS B and results from BGMS C was performed to estimate the degree of pO2 influence. The relative bias between the lowest and highest pO2 values differed by 14.3% for BGMS A, indicating a pO2 influence that might be clinically relevant, and by 9.7% for BGMS B, indicating that pO2 influence may be too small to be reliably detected because of the BGMS' imprecision. This proof of concept study showed that with the procedures used, a potentially clinically relevant influence of pO2 in capillary blood samples on GOx-based BGMS could be detected. Further larger-scale studies are needed to verify this influence.

Surface oxide development on aluminum alloy 6063 during heat treatment

We report on the influence of oxygen partial pressure for the development of surface oxides covering the industrial aluminum alloy standard 6063 at temperatures ranging from room temperature to 500° C. Using an array of synchrotron‐based techniques, we followed the change in oxide thickness, chemical composition, and the lateral distribution of alloying elements. The impact of the oxygen chemical potential is most visible at high temperatures where the oxide composition changes from mostly Al based to mostly Mg based. This is in stark contrast to the ultra‐high vacuum (UHV) conditions where only a partial compositional transition is observed. The microscopy data demonstrate that in the UHV case, Mg segregation onto the surface occurs firstly at grain boundaries at 300° C and secondly at sites over the entire surface at 400° C. Further, the initial oxide thickness is 45 Å, as determined by XPS and XRR, decreases in all observed cases after heating to 300° C. At higher temperatures, however, the oxygen partial pressure highly influences the resulting oxide thickness as evident from our X‐ray reflectivity data.

Oxygen partial pressure plays a crucial role in B16 melanoma cell survival by regulating autophagy and mitochondrial functions

The oxygen partial pressure generally increases when cancerous cells become part of the blood vessels. The study was to investigate the influence of oxygen partial pressure on the apoptosis of B16 melanoma cells. Our results demonstrated that both short-term and long-term hypoxia/reoxygenation (H/R) treatment increased stress-induced intracellular reactive oxygen species (ROS). H/R treatment also increased apoptosis and autophagy in B16 cells. N-acetylcysteine (NAC), a ROS scavenger, can reduce ROS and aid survival. However, Bafilomycin A1, an autophagy inhibitor, can accelerate cell death. Thus, our work revealed that ROS and autophagy play critical roles in cellular H/R.