Total Working Pressure Research Articles

Role of oxygen flow rate on the structure and stoichiometry of cobalt oxide films deposited by reactive sputtering

The influence of the oxygen gas supply on the stoichiometry, structure, and orientation texture of polycrystalline cobalt oxide films was investigated in this study. The films were grown by direct current reactive magnetron sputtering using a metallic Co target and different O2 inlet flow rates (0.5–5.0 SCCM). The deposition power (80 W), the argon gas flow (40 SCCM), and the total working pressure (0.67 Pa) were kept constant during depositions. The results evidence a strong influence of the oxygen flow over the film’s stoichiometry and structure, where low oxygen flows (<2.0 SCCM) favor the formation of the rock salt CoO phase while higher oxygen flows (>2.5 SCCM) favor the spinel Co3O4 phase formation. The coexistence of monoxide and tetraoxide phases is only observed for the 2.5 SCCM oxygen flow condition. Strain effects related to the oxygen partial pressure are also observed and discussed. Computer simulations of the reactive sputtering growth supported the analysis of the film properties and its correlation to the oxygen partial pressure.

Dense VSiCN coatings deposited by filament-assisted reactive magnetron sputtering with varying amorphous phase precursor flow rates

Phase-modulated VSiCN coatings were deposited with hot filament assistance by magnetron sputtering of a vanadium target in a gas mixture of argon, nitrogen, and hexamethyldisilazane (HMDS). HMDS flow conditions and total working pressure were varied to influence coating amorphous phase content (0 at.% ≤ Si ≤ 9 at.%). Scanning electron microscopy revealed that deposition with HMDS vapor disrupted columnar growth and increased coating growth rate by as much as 27% relative to a VN 0.8 reference. Coating surface morphologies were characterized by atomic force microscopy . A transition from a nodular appearance ( R q = 8.9 nm) for the VN 0.8 coating to a pitted appearance ( R q = 2.7 nm) for the coating containing 9 at.% Si was observed. X-ray diffraction analysis and transmission electron microscopy indicated that the VSiCN coatings contained a nanocrystalline B1-VC x N y phase and an amorphous phase, whose phase fraction increased with HMDS flow. The crystallographic out-of-plane preferred orientation of the VN 0.8 coating was (220) while all VSiCN coatings were (111) textured. Coating hardness and apparent elastic modulus were measured by nanoindentation . The VSiCN coating with 3 at.% Si exhibited the highest hardness of 31.4 GPa, which was 8.8 GPa greater than the VN 0.8 coating. Coating apparent elastic modulus decreased with increasing HMDS flow from 288 GPa to 188 GPa. All coatings exhibited excellent adhesion to stainless steel substrates as evaluated by the Rockwell indentation test . The disruption of columnar growth and incorporation of Si in VSiCN coatings is a possible method of improving the high temperature wear resistance of VN-based coatings. • Deposition of dense, non-columnar VSiCN coatings is demonstrated. • Hexamethyldisilazane (HMDS) vapor is used as an amorphous phase precursor. • Granular and pitted surface topographies are obtained with R q < 3 nm. • Coating preferred orientation is (220) for the VN 0.8 reference and (111) for VSiCN. • Hardness decreases from 31 GPa to 19 GPa with increasing amorphous phase content.

Orthorhombic Ta3-xN5-yOy thin films grown by unbalanced magnetron sputtering: The role of oxygen on structure, composition, and optical properties

Direct growth of orthorhombic Ta3N5-type Ta-O-N compound thin films, specifically Ta3-xN5-yOy, on Si and sapphire substrates with various atomic fractions is realized by unbalanced magnetron sputtering. Low-degree fiber-textural Ta3-xN5-yOy films were grown through reactive sputtering of Ta in a gas mixture of N2, Ar, and O2 with keeping a partial pressure ratio of 3:2:0.1 in a total working pressure range of 5–30 mTorr. With increasing total pressure from 5 to 30 mTorr, the atomic fraction of O in the as-grown Ta3-xN5-yOy films was found to increase from 0.02 to 0.15 while that of N and Ta decrease from 0.66 to 0.54 and 0.33 to 0.31, respectively, leading to a decrease in b lattice constant up to around 1.3%. Metallic TaNx phases were formed without oxygen. For a working pressure of 40 mTorr, an amorphous, O-rich Ta-N-O compound film with a high O fraction of ~0.48, was formed, mixed with non-stoichiometric TaON and Ta2O5. By analyzing the plasma discharge, the increasing O incorporation is associated with oxide formation on top of the Ta target due to a higher reactivity of Ta with O than with N. The increase of O incorporation in the films also leads to a optical bandgap widening from ~2.22 to ~2.96 eV, which is in agreement with the compositional and structural changes from a crystalline Ta3-xN5-yOy to an amorphous O-rich Ta-O-N compound.

Glancing Angle Deposition and Growth Mechanism of Inclined AlN Nanostructures Using Reactive Magnetron Sputtering

Glancing angle deposition (GLAD) of AlN nanostructures was performed at room temperature by reactive magnetron sputtering in a mixed gas atmosphere of Ar and N2. The growth behavior of nanostructures shows strong dependence on the total working pressure and angle of incoming flux. In GLAD configuration, the morphology changed from coalesced, vertical nanocolumns with faceted terminations to highly inclined, fan-like, layered nanostructures (up to 38°); while column lengths decreased from around 1743 to 1068 nm with decreasing pressure from 10 to 1.5 mTorr, respectively. This indicates a change in the dominant growth mechanism from ambient flux dependent deposition to directional ballistic shadowing deposition with decreasing working pressures, which is associated with the change of energy and incident angle of incoming reactive species. These results were corroborated using simulation of metal transport (SiMTra) simulations performed at similar working pressures using Ar and N separately, which showed the average particle energy and average angle of incidence decreased while the total average scattering angle of the metal flux arriving at substrate increased with increasing working pressures. Observing the crystalline orientation of GLAD deposited wurtzite AlN nanocolumns using X-ray diffraction (XRD), pole-figure measurements revealed c-axis &lt;0001&gt; growth towards the direction of incoming flux and a transition from fiber-like to biaxial texture took place with increasing working pressures. Under normal deposition conditions, AlN layer morphology changed from {0001} to {101¯1} with increasing working pressure because of kinetic energy-driven growth.

The Development of a Tympanic Membrane Model and Probabilistic Dose-Response Risk Assessment of Rupture Because of Blast.

There is no dose-response model available for the assessment of the risk of tympanic membrane rupture (TMR), commonly known as eardrum rupture, from exposures to blast from nonlethal flashbangs, which can occur concurrently with temporary threshold shift. Therefore, the objective of this work was to develop a fast-running, lumped parameter model of the tympanic membrane (TM) with probabilistic dose-dependent prediction of injury risk. The lumped parameter model was first benchmarked with a finite element model of the middle ear. To develop the dose-response curves, TMR data from a historic cadaver study were utilized. From these data, the binary probability response was constructed and logistic regression was applied to generate the respective dose-response curves at moderate and severe eardrum rupture severity. Hosmer-Lemeshow statistical and receiver operation characteristic analyses showed that maximum stored TM energy was the overall best dose metric or injury correlate when compared with total work and peak TM pressure. Dose-response curves are needed for probabilistic risk assessments of unintended effects like TMR. For increased functionality, the lumped parameter model was packaged as a software library that predicts eardrum rupture for a given blast loading condition.

Efeito de diferentes intervalos recuperativos sobre as respostas musculares, sanguíneas e hemodinâmicas

O treinamento com pesos é uma estratégia para controle de processos ocorridos com o envelhecimento e o período de intervalo entre as séries pode determinar a carga total de treinamento. O objetivo deste estudo foi analisar o desempenho muscular, lactato sanguíneo, índice de fadiga e variáveis hemodinâmicas em diferentes intervalos de recuperação após exercício isocinético. O estudo foi realizado com 11 indivíduos de meia idade (57.00 ± 7.2 anos) que praticavam treinamento com pesos a mais de seis meses. Os voluntários realizaram duas visitas ao Laboratório de Avaliação Física da Universidade, onde realizaram três séries de 10 repetições concêntricas com 60º/segundo na extensão e flexão de joelho em dinamômetro isocinético. Na primeira visita 60 segundos de descanso entre as séries foram realizados e na segunda visita 90 segundos. As variáveis analisadas foram pico de torque (Nm), Trabalho Total (J), Índice de Fadiga (%), Frequência Cardíaca (bpm), Pressão Arterial Sistólica e Diastólica (mmHg) e Concentração de Lactato Sanguíneo (mmol/L). Para comparação entre os dados foi utilizado a Análise de Variância (p&lt;0.05). Após análise pode-se verificar que não houve diferenças significativas entre intervalo de recuperação de 60 e 90 segundos na força muscular, índice de fadiga, concentração de lactato sanguíneo e variáveis hemodinâmicas. Conclui-se que para indivíduos que estão em processo de envelhecimento, aparentemente 60 ou 90 segundos de intervalo entre as séries ocasionam as mesmas respostas. Esse achado pode ser importante para profissionais da educação física na prescrição de exercícios.

Cogeneration system of power and h2 from black liquor through gasification and syngas chemical looping

One of the strategies to improve environmentally friendly energy harvesting can be realized by using biomass as a primary energy source for generating electricity and H2. In addition, high energy efficiency can be achieved by minimizing the exergy loss through process integration and exergy recovery. As an implementation, this study proposes a cogeneration system for black liquor (BL) to co-produce electricity and H2. The system primarily comprises of BL drying, circulating fluidized bed gasification, syngas chemical looping (SCL), and power generation. The Aspen Plus V8.8 software package is used for modelling and performing calculations of the proposed integrated system. Furthermore, thermodynamic analysis of gasification is performed by employing Gibbs energy minimization. The effects of target solid content on the required total work and compressor outlet pressure during drying and gasification with different steam-to-fuel ratios are evaluated. Moreover, the SCL process adopts three reactors, namely, the reducer, oxidizer, and combustor. Compared to the conventional processes, the integrated drying-gasification-SCL processes are significantly cleaner and more energy efficient. The proposed integrated system can achieve a net energy efficiency of about 70 %, with almost 100 % carbon capture.

The mediating effects of ICU nurses psychological capital on job stress and job satisfaction

Objective To understand the job well-being status of ICU nurses, and to explore the mediating role of psychological capital in job stress and job well-being. Methods ICU nurses' general data questionnaire, the Nurse Questionnaire Psychological Capital, Chinese Nurses' Work Stressor Scale and Work Well-Being Scale were used to investigate 224 ICU nurses in three grade a general hospitals. Results Total score of psychological capital for ICU nurses was (4.46±0.55) points, the total average working pressure was (2.14±0.37) points, the happiness score was (4.36±0.67) points. Psychological capital and job well-being were positively correlated (r=0.513, P< 0.01), job stress and job well-being was negatively correlated (r=-0.454, P< 0.05). The structural equation results showed that psychological capital played an intermediary role in the sense of ICU nurses job stress and job happiness. Conclusions Hospital nursing managers should pay more attention to the mental health of ICU nurses and lower their work stress, so as to improve the work well-being of ICU nurses and improve the quality of ICU nursing. Key words: Intensive care units; Nurses; Psychological capital; Job stress; Job well-being

Ageing effects on electrical resistivity of Nb-doped TiO2 thin films deposited at a high rate by reactive DC magnetron sputtering

We report on the long-term stability of electrical resistivity in Nb-doped TiO2 thin films grown at a high rate by a reactive DC magnetron sputtering from metallic targets. The high deposition rate is obtained by an active control of the oxygen flow during the growth process. Film microstructure and preferential orientation of the crystallites are controlled by the total working pressure in the film growth process. After a heat treatment in vacuum, the film resistivity is in a 10−3 Ω cm range and the optical transmission higher than 80% in the visible region. While the film is stable when kept under dry nitrogen, significant ageing has been observed when the material is exposed to air. In this case, the DC resistivity steadily increases and fractures form throughout the film. The ageing process is discussed in terms of the evolution of the film microstructure and/or the oxygen exchange through on the film surface. Oxygen uptake from ambient air is confined to a shallow surface region. It is possible that this mechanism triggers the formation/propagation of the fractures that predominantly contribute to the increase in film resistivity.

Energy-efficient recovery of black liquor through gasification and syngas chemical looping

One of the strategies to improve environmentally friendly energy harvesting can be realized by using biomass as a primary energy source for generating electricity and H2. In addition, high energy efficiency can be achieved by minimizing exergy loss through process integration and exergy recovery. As an implementation, this study proposes a cogeneration system for black liquor (BL) to co-produce electricity and H2. The system primarily comprises BL drying, circulating fluidized bed gasification, syngas chemical looping (SCL), and power generation. The Aspen Plus V8.8 software package is used for modeling and performing calculations of the proposed integrated system. Furthermore, thermodynamic analysis of gasification is performed by employing Gibbs energy minimization. The effects of target solid content on the required total work and compressor outlet pressure during drying and gasification with different steam-to-fuel ratios are evaluated. Moreover, the SCL process adopts three reactors, namely, the reducer, oxidizer, and combustor. Compared to conventional processes, the integrated drying-gasification-SCL processes are significantly cleaner and more energy efficient. The proposed integrated system can achieve a net energy efficiency of about 70% with almost 100% carbon capture.

Electrical, optical, and structural characterization of p‐type N‐doped SnO thin films prepared by thermal oxidation of sputtered SnNx thin films

We present a study of electrical and optical properties of nitrogen‐doped tin oxide thin films deposited on glass by the DC Magnetron Sputtering method. The deposition conditions to obtain p‐type thin films were a relative partial pressure between 7% and 11% (N2 and/or O2), a total working pressure of 1.8 mTorr and a plasma power of 30 W. The deposited thin films were oxidized after annealing at 250°C for 30 minutes. X‐ray diffraction results showed that the as‐deposited thin films exhibit a Sn tetragonal structure, and after annealing, they showed SnO tetragonal structure. X‐ray photoelectron spectroscopy results showed the presence of nitrogen in the samples before and after annealing. The measured physical parameters of the thin films were optical band gap between 1.92 and 2.68 eV, resistivity between 0.52 and 5.46 Ωcm, a concentration of p‐type carriers between 1018 and 1019 cm−3, and a Hall mobility between 0.1 and 1.94 cm2V−1s−1. These thin films were used to fabricate p‐type thin film transistors.

Effect of nonthermal plasma on the properties of a resinous liner submitted to aging

Statement of problemThe properties, such as softness and viscoelasticity, of a resinous reliner can deteriorate and extrinsic elements can become incorporated, making surface protection of the reliner material essential. PurposeThe purpose of this in vitro study was to evaluate the effect of low temperature plasma on Coe-Soft resinous reliner, submitted to aging in artificial saliva for up to 180 days. Sorption, solubility, Shore A hardness, surface energy, and topographic characteristics were analyzed by scanning electronic microscopy (SEM) and energy-dispersive spectroscopy (EDS). Material and methodsForty-four specimens were fabricated and distributed in 2 groups: nonplasma reliner (control group) and reliner with plasma (plasma group). The plasma was applied with a mixture of 70% hexamethyldisiloxane, 20% O, and 10% Ar. Total work pressure was maintained at a constant 20 Pa for 30 minutes of deposition. The specimens were analyzed before and after aging in an incubator with immersion in artificial saliva for 30, 90, and 180 days. The quantitative data were submitted to 2-way ANOVA and the Tukey test (α=.05), while qualitative data were compared visually. ResultsThe control group presented lower Shore A hardness values only in the initial period, and surface energy increased with aging for both groups until 90 days. Greater sorption percentage values were encountered at 180 days in the plasma group. Greater solubility values were encountered in the control group in all periods. ConclusionsPlasma is an option for the protection of the material studied because the deposited film remained on the surface of the reliner material after aging.

Effect of sputtering parameters on the self-cleaning properties of amorphous titanium dioxide thin films

The aim of this work was to assess the effect of the direct current magnetron sputtering parameters on the photocatalytic activity and photoinduced wettability of amorphous TiO2 films. TiO2 films were deposited on glass using the direct current magnetron sputtering technique, without heating, at different total working pressures. Qualitative analysis using in situ X-ray photoelectron spectroscopy confirmed the TiO2 stoichiometry of the deposited films. Surface structure was studied as a function of working pressure using scanning electron microscopy. The hydrophilicity of the TiO2 surfaces was investigated macroscopically using measurements of the water contact angle. A threshold working pressure was observed, with a strong dependence on the film thickness. A super hydrophilic surface was observed after less than 1 h of UV irradiation. The photocatalytic activity of the films was evaluated under UV light through the degradation of methylene blue ( $$\lambda_{\hbox{max} } \approx 660\;{\text{nm}}$$ ). The effect of UV irradiation on the photocatalytic activity was rapid, strong, and dependent on film thickness and total working pressure. Fifty percent of organic compounds were photodegraded by films with a thickness of 60 nm deposited at 10 mTorr.

Improving the Brightness and Reliability of InGaN/GaN Near Ultraviolet Light-Emitting Diodes by Controlling the Morphology of the GaN Buffer Layer

A facile method for fabricating near ultraviolet light-emitting diodes (NUV LEDs) with better crystal quality and enhanced light emission is demonstrated by tuning total working pressure to modify the morphology of the buffer layer. With the conditions favoring the transition from 2-D to 3-D island growth in the GaN buffer layer, the crystal quality of the epitaxial GaN film is improved, leading to a decrease in the full-width at half-maximum of the (1 0 2) peak in $X$ -ray rocking curve measurement from 293 (arcsec) to 230 (arcsec). Scanning electron microscopy images imply the morphology of GaN grain boundaries at the buffer stage is different. The transmission electron microscopy analysis shows the edge dislocation can be bended due to the controlled morphology of buffer layer, leading to a better crystal quality of the GaN epitaxial film. Therefore, the reverse current is reduced with the reverse bias of $ - \hbox{40 V}$ . Moreover, the output power in lamp-formed NUV LEDs at a driving current of 20 mA can be enhanced by about 12%.

Pumping Rate Study of a Left Ventricular Assist Device in a Mock Circulatory System.

The aim of this work was to investigate the hemodynamic influence of the change of pump rate on the cardiovascular system with consideration of heart rate and the resonant characteristics of the arterial system when a reliable synchronous triggering source is unavailable. Hemodynamic waveforms are recorded at baseline conditions and with the pump rate of left ventricular assist device (LVAD) at 55, 60, 66, and 70 beats per minute for four test conditions in a mock circulatory system. The total input work (TIW) and energy equivalent pressure (EEP) are calculated as metrics for evaluating the hemodynamic performance within different test conditions. Experimental results show that TIW and EEP achieve their maximum values, where the pump rate is equal to the heart rate. In addition, it demonstrates that TIW and EEP are significantly affected by changing pump rate of LVAD, especially when the pump rate is closing to the natural frequency of the arterial system. When a reliable synchronous triggering source is not available for LVAD, it is suggested that selecting a pump rate equal to the resonant frequency of the arterial system could achieve better supporting effects.

Diffusion of silicon in titanium dioxide thin films with different degree of crystallinity: Efficiency of TiO2 and TiN barrier layers

Two kinds of reactively sputtered titanium dioxide films with columnar and fine-grained structures were investigated as diffusion barriers, preventing the silicon diffusion. The only differences in the deposition conditions were the oxygen percentage concentration (OC) in the discharge, kept for 10% and 30% of the total working pressure. The resulting films were found to have different thicknesses being 800 and 240 nm for 10% and 30% OC, respectively. The films were studied by X-Ray diffraction spectrometry (XRD) and their composition by Rutherford Backscattering Spectrometry (RBS). In order to describe the diffusion processes, the two batches were annealed up to temperature of 800 °C. The diffusivity from 300° to 800 °C is D(m2/s)=2.43.10−18exp[−(15kJ/mol)/(RT)] andD(m2/s)=2.36.10−18exp[−(18.4kJ/mol)/(RT)] for (10% OC) and TiO2 (30% OC), respectively. The physical meaning of the derived diffusion parameters are discussed in view of the crystalline peculiarities of the obtained films. Arrhenius plots show clearly that higher activation energy is characteristics for films with better-packed crystallites. These results are compared with known diffusion barrier layer such as TiN.

In situ core‐level and valence‐band photoelectron spectroscopy of reactively sputtered tungsten oxide films

In this paper, we study tungsten oxides deposited by reactive magnetron sputtering. The total working pressure during deposition was varied in order to obtain different morphology. The effects on the electronic properties and chemical composition were studied by XPS and UPS. It was observed that, for the same argon to oxygen ratio in the gas feed, the decrease in total working pressure implies a decrease of the oxygen content in the film. In the nearly stoichiometric WO3 films, W 4f5/2 and W 4f7/2 form a distinct doublet peak. In sub‐stoichiometric films, the films do not exhibit a well‐resolved doublet and suggest multiple oxidation states of tungsten.The valence‐band spectra of the sub‐stoichiometric samples present an additional feature below the Fermi edge (~0.5 eV). This peak is assigned to W 5d1 because of the presence of W5+. It is consistent with the changes on the core‐level spectra. XPS results, UPS features, and visual aspect are in agreement and suggest that the total working pressure has a strong influence on the oxygen content and therefore on the oxidation state of tungsten in the films. Copyright © 2016 John Wiley &amp; Sons, Ltd.

Enhanced photoelectrochemical performance of {001}TiO2/{001}SrTiO3 epitaxial heterostructures

The anatase TiO2 films with controllable {001} highly reactive facets were fabricated on {001}SrTiO3 substrate with various total work pressure (TWP) by direct current facing-target magnetron sputtering (DCFTMS). X-ray diffraction (XRD), scanning electron microscopy (SEM), surface roughness tester (SRT), and X-ray photoelectron spectroscopy (XPS) were employed to confirmed the influence of different TWPs on the interface of TiO2/SrTiO3 heterostructured with epitaxial preferred growth of the anatase {001}TiO2 facet. The mechanisms of enhanced photoelectrochemical properties were explored by transient photocurrent (TP), current–potential (I–V), cyclic voltammetry (CV), polarization (Tafel), electrochemical impedance spectroscopy (EIS), and Mott–Schottky (M–S) curves, which can be ascribed to the formation of high-quality heterojunction between {001}TiO2 thin film and {001}SrTiO3 substrate, which suppress the recombination of photogenerated electron–hole pairs effectively.

Hydrogenated amorphous carbon thin films deposition by pulsed DC plasma enhanced by electrostatic confinement

Diamond-like carbon (DLC) is a metastable form of amorphous carbon with attractive properties such as high hardness, low friction, chemical inertness and high wear resistance. In this work, hydrogenated amorphous carbon (a-C:H) thin films were deposited using a plasma enhanced chemical vapor deposition technique by pulsed DC plasma with a simple, low-cost and efficient arrangement of multi-cathodes and multi-anodes in order to enhance the plasma by electrostatic confinement. The samples were characterized by Scanning Electron Microscopy, Energy Dispersive X-ray Spectroscopy, Elastic Recoil Detection Analysis, Raman Spectroscopy, and nanoindentation measurements. a-C:H thin films show an homogeneous hydrogen profile along the films deposited at −600V and −800V and variable working pressure. According to Raman spectra, both the ID/IG ratio and the G-peak position increase at higher voltages (more remarkable dependence) and lower working pressures (less remarkable dependence). Moreover, the hardness depends on working conditions such as power supply voltage and total working pressure. The electrostatic confinement enhances the deposition rates of a-C:H thin films up to values of 0.9μm·h−1, which is almost double than those previously published by pulsed DC plasma in similar conditions. The Raman spectra follow the stage 2 of an established model and this structure transition may explain the hardness behavior.

Structural and morphological evolution of aluminum nitride thin films: Influence of additional energy to the sputtering process

Aluminum nitride (AlN) thin films were deposited on SiO2/Si substrates by radiofrequency (RF) magnetron sputtering using an aluminum target. The influence of the deposition parameters – such as nitrogen concentration in the sputtering atmosphere, RF power, total working pressure and substrate bias voltage – on the structure, morphology and composition of the thin films was discussed. The structure was studied using X-ray diffraction (XRD), the morphology was studied using scanning electron microscopy (SEM) and the composition was studied using energy dispersive spectroscopy (EDS). These investigations showed that all of the films grew preferentially along the c-axis regardless of the deposition conditions, without the application of external heating, whereas the grain size and morphology strongly depended on the process parameters. Additional energy, which was supplied to the growing films by increasing the power or decreasing the working pressure, improved the crystallinity, but compressive stress was induced in the samples, thus resulting in a surface morphology evolution.