Effect Of Oxygen Partial Pressure Research Articles

Effects of various oxygen partial pressures on Ti-doped ZnO thin film transistors fabricated on flexible plastic substrate

By applying a novel active layer of titanium zinc oxide (TiZO), we have successfully fabricated fully transparent thin-film transistors (TFTs) with a bottom gate structure fabricated on a flexible plastic substrate at low temperatures. The effects of various oxygen partial pressures during channel deposition were studied to improve the device performance. We found that the oxygen partial pressure during channel deposition has a significant impact on the performance of TiZO TFTs, and that the TFT developed under 10% oxygen partial pressure exhibits superior performance with a low threshold voltage (Vth) of 2.37 V, a high saturation mobility (μsat) of 125.4 cm2 V−1 s−1, a steep subthreshold swing (SS) of 195 mV/decade and a high Ion/Ioff ratio of 3.05 × 108. These results suggest that TiZO thin films are promising for high-performance fully transparent flexible TFTs and displays.

Laser heating and oxygen partial pressure effects on the dynamic magnetic properties of perpendicular CoFeAlO films

The impact of oxidation and laser heating on the dynamic magnetic properties of perpendicularly magnetized Co50Fe25Al25O films has been studied by time-resolved magneto-optical Kerr effect in a fs-laser pump-probe setup. We find that pump laser fluence Fp can affect the effective magnetic anisotropy field and thus the precession frequency f seriously, leading to an increased dependence of effective magnetic damping factor αeff on the external field at higher fluences. Moreover, the αeff increases with increasing the oxygen partial pressure PO2 while the uniaxial anisotropy energy Ku and Landau factor g decrease, owing to the increased proportion of superparamagnetic CoFe oxides formed by over-oxidation. By optimizing both the Fp and PO2, the intrinsic damping factor is determined to be lower than 0.028 for the perpendicular film showing a uniaxial anisotropy energy as high as 4.3×106erg/cm3. The results in this study provide a promising approach to manipulate the magnetic parameters for possible applications in spintronic devices.

Effect of oxygen partial pressure on epitaxial growth and properties of laser-ablated AZO thin films

Al-doped ZnO (AZO) thin films were grown on c-sapphire substrates by laser ablation under different oxygen partial pressures (P O2). The effect of PO2 on the crystal structure, preferred orientation as well as the electrical and optical properties of the films was investigated. The structure characterizations indicated that the as-grown films were single-phased with a wurtzite ZnO structure, showing a significant c-axis orientation. The films were well crystallized and exhibited better crystallinity and denser texture when deposited at higher P O2. At the optimum oxygen partial pressures of 10 - 15 Pa, the AZO thin films were epitaxially grown on c-sapphire substrates with the (0001) plane parallel to the substrate surface, i e, the epitaxial relationship was AZO (000 1) // Al2O3 (000 1). With increasing P O2, the value of Hall carrier mobility was increased remarkably while that of carrier concentration was decreased slightly, which led to an enhancement in electrical conductivity of the AZO thin films. All the films were highly transparent with an optical transmittance higher than 85 %.

氧分压对铟镓锌氧薄膜晶体管性能影响

氧分压对铟镓锌氧薄膜晶体管性能影响

Effects of oxygen partial pressure on the oxidation of ZrB2–SiC–graphite composites at 1800 °C

The oxidation behaviors of ZrB2–SiC–graphite composites are investigated under low partial pressure of oxygen ranging from 100Pa to 2000Pa at 1800°C. The microstructure of the oxidized specimen was analyzed using XRD, XPS, SEM and EDS. A modified volatility diagram is used to justify the development of the oxide layer in this paper. Results indicate that low oxygen partial pressures have a remarkable effect on phase composition of the surface and the microstructures of oxide layer. The higher oxygen partial pressure enhances the oxidation behavior of ZrB2–SiC–graphite composites.

Dilatometric study of a strontium ferrotitanate and calcium aluminate

The effect of oxygen partial pressure on the dimensions of SrTi0.7Fe0.3O3 ± δ strontium ferrotitanate (perovskite structure) and Ca12Al14O33 ± δ calcium aluminate (mayenite structure) samples has been studied by dilatometry. The observed considerable variations in dimensions are characteristic of electronic–ionic mixed conductors with the perovskite structure. The effect observed in mayenite is substantially weaker, which can be understood in terms of specific features of its structural framework, made up of hollow, closed structural elements.

Effect of oxygen partial pressure on the composition and structure of GdBa2Cu3O7−δ by solid state reaction

GdBa2Cu3O7−δ (GdBCO or Gd123) ceramics have been successfully prepared at oxygen partial pressure () of 0.02–0.10 MPa via solid state reaction method by using Gd2O3, BaCO3 and CuO powders as raw materials, whereas GdBa2Cu3O7−δ decomposed to Gd2BaCuO5 (Gd211), Gd2O3 and barium copper oxides owing to the instability of GdBa2Cu3O7−δ at according to the stability phase diagram of GdBa2Cu3O7−δ. Effect of on the phase structure and microstructure of GdBa2Cu3O7−δ has been investigated by X-ray diffractometer and field-emission scanning electron microscopy methods. Composition and microstructure of pellets sintered at were totally different from pellets sintered at .

Microstructure, wettability, optical and electrical properties of HfO2 thin films: Effect of oxygen partial pressure

The effect of oxygen partial pressure on the microstructure, wettability, optical and electrical properties of sputtering-derived HfO2 thin films has been systematically investigated by using x-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), atomic force microscope (AFM), UV–visible spectroscopy (UV–Vis), spectroscopy ellipsometry (SE), and electrical measurements. XRD results have shown that the HfO2 thin films are all polycrystalline with monoclinic phase. Based on analysis from FTIR, a strong absorption peak centered at 1105 cm−1 has been detected, indicating the formation of the interfacial layer. Reduction in particle size and decrease in root mean square (RMS) roughness of the HfO2 thin films have been detected by SEM and AFM measurements with the increase in oxygen partial pressure. Meanwhile, the contact angle decreases and the wettability increases with increasing the oxygen partial pressure. Combined with UV–vis and SE, the optical function of HfO2 thin films as functions of oxygen partial pressure has been determined. By means of electrical measurements, evolution of electrical performance of MOS capacitor based on HfO2 gate dielectrics related with oxygen partial pressure has been investigated systematically.

A study of methane oxy-combustion characteristics inside a modified design button-cell membrane reactor utilizing a modified oxygen permeation model for reacting flows

This work studies numerically the use of a modified oxygen permeation equation in a modified button-cell ion transport membrane reactor (ITMR). The permeation equation is modified in order to account for Reynolds number variations and non-elementary surface reactions on both sides of the membrane. The near membrane zone in the ITMR is modified to create recirculation zones in the vicinity of the membrane to sustain stable flame. Air is fed to the ITMR feed side and a mixture of methane and CO2 is fed to the sweep side. The ITMR is axisymmetric and the mesh was constructed using Gambit 2.2 before importing it to the CFD fluent 12.1. A series of user defined functions (UDFs) written in C++ were compiled and hooked to fluent to solve for oxygen permeation. Effects of reactivity on oxygen permeation characteristics are investigated over wide ranges of operating parameters. Considering reacting flow conditions, the effects of sweep flow rate and feed oxygen partial pressure are investigated. The results showed that two, inner and outer, recirculation zones were created in the vicinity of the membrane with a stable flame. Significant improvements in oxygen permeation and combustion temperature are encountered utilizing the present reactor design.

Effects of nitrogen and oxygen partial pressure on the structural and optical properties of ZnO:N thin films prepared by magnetron sputtering

Nitrogen doped ZnO films were prepared by magnetron sputtering. We studied the influence of nitrogen partial pressure pn and oxygen partial pressure po on the microstructure, morphology and optical properties of the thin films. The results show that different defects influence the structure and optical behavior of the films. Doping-related tensile stress turns compressive, owing to a different N-doping form in the films. Red-shift of absorption edge was observed with increasing pn and decreasing po. Band-gap narrowing is improved by increasing nitrogen substitute and oxygen vacancies.

Effects of oxygen partial pressure on the structural and optical properties of undoped and Cu-doped ZnO thin films prepared by magnetron co-sputtering

Undoped and Cu-doped zinc oxide (ZnO:Cu) films were deposited on glass substrates by magnetron sputtering at different oxygen partial pressures po. Microstructure, surface morphology, resistivity, and optical properties were systematically investigated. The results show that lower po can degrade the crystallinity, and reduce the band gap. Undoped ZnO films are not obviously influenced by po, especially at high oxygen pressure. In contrast, ZnO:Cu thin films are remarkably affected by po. This work suggests that oxygen vacancies play an important role in modifying properties and allows us to accurately modulate the band gap of the ZnO-based films.

Correlation of the resistive switching and polarization switching in zinc oxide thin films using scanning probe microscopy techniques

Abstract

Rate-determining elementary step of oxygen reduction reaction at (La,Sr)CoO3-based cathode surface

In order to give insight into the guiding principle of further improvement in surface reactivity of mixed-conducting cathode materials of solid oxide fuel cells, electrochemical impedance spectroscopy study was carried out on various LaCoO3- and (La,Sr)CoO3-based dense thin film electrodes with emphasis on the effect of oxygen partial pressure, Po2. The area specific conductivity corresponding to the surface reactivity, which is evaluated from the major impedance component appearing at low frequency range, shows a Po2-exponent of 1/2 irrespective of electrode material. After examining a series of possible elementary reaction steps in the oxygen reduction reaction, the universally observed Po2 dependence can be explained only by assuming that the rate-determining step is the reaction where surface bidentate peroxide ion reacts with an oxide ion vacancy in the cathode to yield two O− ions, one left at the surface and the other in the cathode interior. The origin of the minor impedance component often observed at higher frequency range is also discussed on the basis of its independence on Po2, which leads the authors to suggest that this impedance can be associated with the redox reaction between the surface O− and O2− in the cathode.

Oxidation of vanadium metal in oxygen plasma and their characterizations

In this report, the role of oxygen plasma on oxidation of vanadium (V) metal and the volatilization of its oxides has been studied as a function of source (V metal strip) temperature (Tss) and oxygen partial pressure (PO2). The presence of O2-plasma not only enhances the oxidation rate but also ficilitates in transport of oxide molecules from metal to substrate, as confirmed by the simultanous deposition of oxide film onto substrate. Both the oxidized metal strips and oxide films deposited on substrates are characterized separately. The structural and vibrational results evidence the presence of two different oxide phases (i.e. orthorhombic V2O5 and monocilinic V O2) in oxide layers formed on V metal strips, whereas the oxide films deposited on substrates exhibit only orthorhombic phase (i.e. V2O5). The decrease in peak intensities recorded from heated V metal strips on increasing Tss points out the increment in the rate of oxide volatilization, which also confirms by the oxide layer thickness measurements. The SEM results show the noticeable surface changes on V-strips as the function of Tss and PO2 and their optimum values are recorded to be 500 ˚C and 7.5 × 10−2 Torr, respectively to deposit maximum thick oxide film on substrate. The formation of microcracks on oxidized V-strips, those responsible to countinue oxidation is also confirmed by SEM results. The compositional study of oxide layers formed on V-strips, corroborates their pureness and further assures about the existence of mixed oxide phases. The effect of oxygen partial pressure on oxidation of V-metal has also been discussed in the present report. All the results are well in agreement to each other.

Femtosecond pulsed laser induced growth of highly transparent indium-tin-oxide thin films: Effect of deposition temperature and oxygen partial pressure

Indium-tin-oxide (ITO) thin films were deposited on glass substrates by femtosecond pulsed laser. The effects of deposition temperature and oxygen partial pressure on structural, optical, electrical and morphological properties have been investigated by XRD, UV–vis spectrometer, four-probe and SEM apparatus. The increased deposition temperature significantly enhanced the optical transparency and sheet resistance of ITO films. It had been found that there exists a minimum of the electrical sheet resistance of ITO films as the oxygen pressure increases.

Effects of oxygen partial pressure on the characteristics of magnetron-sputtered ZnMgBeO thin films

Effects of oxygen partial pressure within the Ar process plasma on the optical, structural, and electrical properties of magnetron-sputtered ZnMgBeO films were investigated in detail. It was observed that the optical energy bandgap (Eg) values of the ZnMgBeO films substantially decrease with the oxygen addition, from 5.3 to 4.3eV as the oxygen partial pressure increases from zero to one. The full-width-at-half-maximum (FWHM) values of the (0002) XRD peaks drastically decrease with the addition of a small amount of oxygen but then increase with further oxygen addition. All the films had very high sheet resistance, 1.3–1.4GΩ/□. It was also observed that the concentration of Zn within the films significantly increased with the oxygen addition, which was proposed to be mainly responsible for the observed decrease in Eg. It was also proposed that the FWHM change due to the oxygen addition may be attributable to three factors, film composition, grain size, and point defect density, as confirmed by results of TEM and XPS investigations.

The Effect of Oxygen Partial Pressure during Active Layer Deposition on Bias Stability of a-InGaZnO TFTs**Supported by the National Basic Research Program of China under Grant Nos 2010CB327504, 2011CB922100 and 2011CB301900, the National Natural Science Foundation of China under Grant Nos 11104130 and 61322112, the Natural Science Foundation of Jiangsu Province under Grant Nos BK2011556 and BK2011050, and the Priority

The effect of oxygen partial pressure (PO2) during the channel layer deposition on bias stability of amorphous indium-gallium-zinc oxide (a-IGZO) thin film transistors (TFTs) is investigated. As PO2 increases from 10% to 30%, it is found that the device shows enhanced bias stress stability with significantly reduced threshold voltage drift under positive gate bias stress. Based on the x-ray photoelectron spectroscopy measurement, the concentration of oxygen vacancies (OV) within the a-IGZO layer is suppressed by increasing PO2. Meanwhile, the low-frequency noise analysis indicates that the average trap density near the channel/dielectric interface continuously drops with increasing PO2. Therefore, the improved interface quality with increasing PO2 during the channel layer deposition can be attributed to the reduction of interface OV-related defects, which agrees with the enhanced bias stress stability of the a-IGZO TFTs.

Tuning the optoelectronic properties of amorphous MoOx films by reactive sputtering

In this letter, we report on the effect of oxygen partial pressure and sputtering power on amorphous DC-sputtered MoOx films. We observe abrupt changes in the optoelectronic properties of the reported films by increasing the oxygen partial pressure from 1.00 × 10−3 mbar to 1.37 × 10−3 mbar during the sputtering process. A strong impact on the electrical conductivity, varying from 1.6 × 10−5 S/cm to 3.22 S/cm, and on the absorption coefficient in the range of 0.6–3.0 eV is observed for the nearly stoichiometric MoO3.00 and for the sub-stoichiometric MoO2.57 films, respectively, without modifying significantly the microstructure of the studied films. The presence of states within the band gap due to the lack of oxygen is the most probable mechanism for generating a change in electrical conductivity as well as optical absorption in DC-sputtered MoOx. The large tuning range of the optoelectronic properties in these films holds strong promise for their implementation in optoelectronic devices.

Improvement of spent activated carbon regeneration by wet oxidation processes

Activated carbons saturated with p-nitrophenol were regenerated under subcritical conditions by means of wet oxidation, analyzing the effect of temperature (160–200°C) and oxygen partial pressure (3–12bar). The research intended to achieve two main objectives: (a) to restore the carbons adsorption performance and (b) to get insight about the p-nitrophenol oxidation process and how it can be influenced by the presence of the adsorbent.Based on the contaminant oxidation mechanisms, which was defined as a series of radical processes, a kinetic model was developed. The model was created by COMSOL MULTIPHYSICS software, and allowed obtaining characteristical parameters. Further comparison between theoretical and experimental results showed the suitability of the model in the whole range of experimental domain. Subsequent application of this model to regeneration experiments confirmed the need of developing a new model in the latter case, since the presence of carbon involved a significant modification of kinetic parameters, which was related to the catalyzing action of the adsorbent.It was also found that both temperature and pressure affect the p-nitrophenol degradation process as well as porosity regain of the carbons. Values of p-nitrophenol regeneration efficiency up to 87% for the highest values of temperature and oxygen partial pressure.

Ionic Conductivity of the Epitaxial Li0.33La0.55TiO3 Solid Electrolyte Thin Films

Solid-state lithium batteries composed of solid electrolytes with high ionic conductivity and high stability has several advantages such as improved safety, increased energy and power density and absence of leakage problems compared to the conventional Li ion batteries containing organic liquid electrolytes. Among the most investigated ionic conductions, Li0.33La0.55TiO3 (LLTO) is reported to have the highest bulk ionic conductivity at room temperature (RT) (order of 10-3 S/cm).1,2 Ionic conductivity of amorphous LLTO and epitaxial Li0.17­La0.61TiO3 films grown on Al2O3 and Nb:SrTiO3 substrates are reported to be in the order of 10-6 and 10-4 S/cm respectively at RT. 1,2 Ionic conductivity of epitaxial LLTO films and impacts of the Ti valence change on the electrical and structural properties have not yet been clearly studied. In the present case, we report on the ionic conductivity and the effect of oxygen partial pressure during the growth of LLTO epitaxial film grown on SrTiO3 (STO) (100) and (111) substrates and explore some distinct conductivity behavior. Epitaxial LLTO films (150 nm thick) on STO (100) and (111) substrates were prepared via pulsed laser deposition (PLD) employing KrF laser at 800 oC in 10, 50, 100 and 200 mTorr oxygen partial pressures. Structural and orientation of the films were characterized employing Bruker X-ray diffractometer (XRD) and scanning transmission electron microscopy (STEM). Thin lamellas of the samples for surface and cross sectional transmission electron microscope (TEM) studies were prepared by cutting with focused ion beam. The lamellas were studied with TEM operated at 300 kV. Impedance measurements were carried out on all the films at the temperature range of RT – 250o C employing an impedance analyzer. XRD and TEM studies (Fig.1 (a)) shows that the films grown on STO (100) and (111) substrates exhibits epitaxial (100) and (111) orientations with perovskite tetragonal structure. RT ionic conductivity of LLTO films grown on STO (100) and STO (111) substrates decrease from 3.12 x 10-4 to 3.10 x 10-5 S/cm and 1.8 x 10-4 to 2.6 x 10-5 S/cm with increasing oxygen partial pressure (during the film growth) from 10 to 200 mT respectively (Fig. 1(b)). Conductivity of all the LLTO films increases exponentially with increasing temperature. Activation energy (Eg) for all the films were calculated from the temperature dependent conductivity measurements employing the Arrhenius relationship σ = σ0 exp (-Eg/KBT), where KB is Boltzmann constant. Eg value for all the films are seen to be around 0.34 eV, agreeing well with the reported bulk grain activation energy values. LLTO films grown at 10 mT are seen to have conductivity close to the bulk conductivity (in the order of 10-4S/cm) and indicates that these films can be used as a solid electrolyte in high power all solid-state batteries.