High Oxygen Flow Rate Research Articles

Standard vs. targeted oxygen therapy prehospitally for chronic obstructive pulmonary disease (STOP-COPD): study protocol for a randomised controlled trial

BackgroundA high concentration of inspired supplemental oxygen may possibly cause hypercapnia and acidosis and increase mortality in patients with acute exacerbation of chronic obstructive pulmonary disease (AECOPD). Even so, patients with AECOPD are being treated with high oxygen flow rates when receiving inhalation drugs in the prehospital setting. A cluster-randomised controlled trial found that reduced oxygen delivery by titrated treatment reduced mortality—a result supported by observational studies—but the results have never been reproduced. In the STOP-COPD trial, we investigate the effect of titrated oxygen delivery compared with usual care consisting of high flow oxygen delivery in patients with AECOPD in the prehospital setting.MethodsIn this randomised controlled trial, patients will be blinded to allocation. Patients with suspected AECOPD (n = 1888) attended by the emergency medical service (EMS) and aged > 40 years will be allocated randomly to either standard treatment or titrated oxygen, targeting a blood oxygen saturation of 88–92% during inhalation therapy. The trial will be conducted in the Central Denmark Region and include all ambulance units. The power to detect a 3% 30-day mortality risk difference is 80%. The trial is approved as an emergency trial. Hence, EMS providers will include patients without prior consent.DiscussionThe results will provide evidence on whether titrated oxygen delivery outperforms standard high flow oxygen when used to nebulise inhaled bronchodilators in AECOPD treatment. The trial is designed to ensure unselected inclusion of patients with AECOPD needing nebulised bronchodilators—a group of patients that receives high oxygen fractions when treated in the prehospital setting where the only compressed gas is generally pure oxygen. Conducting this trial, we aim to improve treatment for people with AECOPD while reducing their 30-day mortality.Trial registrationEuropean Union Clinical Trials (EUCT) number: 2022-502003-30-00 (authorised 06/12/2022), ClinicalTrials.gov number: NCT05703919 (released 02/02/2023), Universal trial number: U1111-1278-2162.

Low-temperature homoepitaxial growth of β-Ga2O3 thin films by atmospheric pressure plasma-enhanced chemical vapor deposition technique

Low-temperature homoepitaxial growth of β-Ga2O3(-201) has been successfully demonstrated by the atmospheric pressure plasma-enhanced chemical vapor deposition technique. To search for low-temperature growth, temperature-dependent studies were carried out between 350 and 600 °C. A high N2 gas flow rate, low gallium source concentration, and high oxygen flow rate ratio played key roles in growing independent and homogeneous multiple nuclei of Ga2O3, leading to three-dimensional grain growth mode, single crystallinity, and the highest growth rate of ⁓0.17 µm/h at 350 °C. The highly reactive atmospheric pressure oxygen plasma actively led to epitaxial growth. The low thermal budget homoepitaxial growth is a record reduction reported thus far.

Transnasal Humidified Rapid Insufflation Ventilatory Exchange in children requiring emergent intubation (Kids THRIVE): a statistical analysis plan for a randomised controlled trial

The placement of an endotracheal tube for children with acute or critical illness is a low-frequency and high-risk procedure, associated with high rates of first-attempt failure and adverse events, including hypoxaemia. To reduce the frequency of these adverse events, the provision of oxygen to the patient during the apnoeic phase of intubation has been proposed as a method to prolong the time available for the operator to insert the endotracheal tube, prior to the onset of hypoxaemia. However, there are limited data from randomised controlled trials to validate the efficacy of this technique in children. The technique known as transnasal humidified rapid insufflation ventilatory exchange (THRIVE) uses high oxygen flow rates (approximately 2 L/kg/min) delivered through nasal cannulae during apnoea. It has been shown to at least double the amount of time available for safe intubation in healthy children undergoing elective surgery. The technique and its application in real time have not previously been studied in acutely ill or injured children presenting to the emergency department or admitted to an intensive care unit. The Kids THRIVE trial is a multicentre, international, randomised controlled trial (RCT) in children less than 16 years old undergoing emergent intubation in either the intensive care unit or emergency department of participating hospitals. Participants will be randomised to receive either the THRIVE intervention or standard care (no apnoeic oxygenation) during their intubation. The primary objective of the trial is to determine if the use of THRIVE reduces the frequency of oxygen desaturation and increases the frequency of first-attempt success without hypoxaemia in emergent intubation of children compared with standard practice. The secondary objectives of the study are to assess the impact of the use of THRIVE on the rate of adverse events, length of mechanical ventilation and length of stay in intensive care. In this paper, we describe the detailed statistical analysis plan as an update of the previously published protocol.

Countercurrent Flame Propagation and Quenching Behaviour in a Packed Bed of Spherical PMMA Beads in an Upward Flow of Pure Oxygen

ABSTRACT Countercurrent flame propagation and quenching behavior in a packed bed of spherical polymethyl methacrylate (PMMA) beads in an upward flow of pure oxygen was experimentally studied. Monosized PMMA beads of 2, 5, 8 or 10 mm in diameter (d) were packed in a vertical quartz tube of 35 mm ID to form a bed of 180 mm in height. In a typical experimental run, upon ignition from the top, a blue flame formed and propagated downwards. For d = 10, 8, or 5 mm, there existed a minimum oxygen flow rate (q) to sustain a quasi-steady state flame propagation, and the minimum q increased as d decreased from 10 to 5 mm. However, for d = 2 mm, it was not possible for the flame to propagate downwards irrespective of the q value. The apparent pyrolysis rate (m py) of PMMA was estimated by monitoring the bed mass loss rate, from which the nominal equivalence ratio upon flame quenching was also estimated. The equivalence ratio was found to be less than unity upon flame quenching, suggesting insufficient pyrolysis gases to sustain the combustion. The heat transfer between flame and PMMA bead was analyzed theoretically, and it was revealed that the minimum m py to sustain the quasi-steady state flame propagation inversely correlates with the PMMA particle size, and therefore a higher oxygen flow rate is required to sustain the flame propagation in a packed bed of smaller PMMA particles.

Oxygen mediated defect evolution in RF sputtered Ga2O3 thin films on p-Si substrate

Impact of oxygen concentration in governing the structural and optical properties of RF sputter Ga 2 O 3 thin film deposited on p-Si at 500 o C by controlling the oxygen flow rate (OFR) has been demonstrated in this work. To maintain the oxygen rich and oxygen poor condition, the argon (Ar) to oxygen (O 2 ) ratio systematically varied from 1:1, 1:2, to 1:0, 2:1 and, 3:1 respectively. Such OFR reliant change in crystalline quality of the grown Ga 2 O 3 thin film is investigated by X-ray Diffraction (XRD) study. The atomic force microscopy results further illustrate an increase in film roughness owing to the inevitable introducing of defects/ oxygen vacancy ( V O ) during deposition with higher OFR. The modification in material stoichiometry via generation of V O and defects in surplus of oxygen is further supported with XPS analysis. Moreover, a rising trend of optical bandgap (Eg) due to transformation from oxygen rich to oxygen poor condition was revealed by spectroscopic ellipsometery study and further correlated with the improved crystallinity of the film. A maximum Eg of 4.44 eV was obtained for the Ga 2 O 3 thin film deposited with 3:1 Ar to O 2 ratio. Finally, the photoluminescence (PL) investigation confirms a strong correlation between defects/ V O generation with OFR variation. Where, the decrease in blue band contribution in lower oxygen concentration was correlated with reduced Vo concentration via its active participation in gallium vacancy V Ga and Vo pair (V Ga +Vo) formation. Finally, the impact of OFR on the Ga 2 O 3 /Si heterojunction device property is also investigated by utilizing the current–voltage (I-V) measurements, which shows a superior device performance for film grown in oxygen poor condition owing to the presence of lower defect concentration, surface roughness, and interface states. • Oxygen mediated structural, chemical and optical transformation of Ga 2 O 3 thin film deposited on p-Si substrate at 500 o C temperature by RF sputtering. • Impact of oxygen extremes on the defect evolution of Ga 2 O 3 thin film by photoluminescence study. • The heterojunction properties of β-Ga 2 O 3 /Si are studied electrically and such heterojunctions exhibit relatively superior rectification properties. • 3:1 is the optimum Ar to O 2 ratio to achieve high quality, defect-free Ga 2 O 3 film on Si.

Effect of oxygen flow rate on long-term and short-term Schottky barrier modulations in Pd/IGZO/SiO2/p+-Si memristors

In this work, we investigate the long- and short-term Schottky barrier modulations in a Pd/IGZO/SiO2/p+-Si memristor under oxygen flow rate (OFR) control. The thickness of the SiO2 layer verified using transmission electron microscopy (TEM) was found to affect resistive-switching characteristics such as the on/off ratio. A high barrier was observed corresponding to a high OFR in the thermionic emission model. In addition, we present an energy band diagram considering traps and oxygen vacancies for oxygen-rich (O-rich) and oxygen-poor (O-poor) devices. Moreover, physical parameters such as a change in barrier height, activation energy, and potentiation/depression were experimentally extracted through various pulse schemes. Experimental results reveal that an O-rich device has high accuracy with a neural network on the MNIST dataset. In this study, we optimized the resistive-switching characteristics by varying OFR as an experimental factor. Further, we provide guidelines for designing hardware-based neuromorphic systems by separating short- and long-term components.

Mutations in the nonstructural proteins of SARS-CoV-2 may contribute to adverse clinical outcome in patients with COVID-19

BackgroundFrom late March through April 2021, we experienced a cluster of patients with COVID-19, named “Cluster K”, with rapid severe illness compared with those who were infected before. MethodsPatients with COVID-19 who were enrolled in this study were divided into two groups: 66 patients from November 2020 to March 2021 (group A) and 37 patients whose infection links were traced from Cluster K (group B). The primary outcome was mortality rate, and the secondary outcome was maximal oxygen flow rate as the severity of the disease. Viral genome sequences were compared between the two groups. ResultsMortality rates were 6.1% in group A and 16.2% in group B (odds ratio: 2.97, 95% confidence interval: 0.65–15.38). The patients in group B required high oxygen flow rate (O2 ≥10 l/min) in the earlier clinical course (P = 0.029). Viral genome sequences revealed five amino acid mutations; of these, four were found on three nonstructural proteins (NSPs): one in nsp3 and nsp15, two in nsp6 (one of them is near the potential sites under positive selective pressure). Another one was on the S protein. ConclusionThis study suggests that mutations in NSPs, especially nsp6, are associated with adverse clinical outcome in patients with COVID-19.

Oxygen point defect stabilized metastable M3‐phase VO2 films

Point defects can stabilize various metastable polymorph phases of complex oxides showing unique physical properties, even though their role in the stabilization of the metastable phase is unclear. In this study, we examined the role of oxygen point defects in stabilizing a polymorph M3-VO2 phase and its transition characteristics. Raman spectroscopy revealed the M3-VO2 phase at the ambient environment for the VO2 film grown on c-Al2O3 substrate at a higher oxygen flow rate. High-resolution XRD and DFT calculation exhibited that the M3-VO2 phase was stabilized by oxygen point defect incorporated into the tetrahedral interstitial site, the most stable defect type in the monoclinic VO2 system. The M3-phase had a higher IMT temperature and a sharper IMT than the M1-phase due to the decrease in interdimer hopping energy and the small energy barrier for the IMT by the slightly zigzag V-V chain. Furthermore, the temperature-dependent Raman spectra showed the unprecedented structural phase transition from the M3-VO2 phase to the R-phase without an intermediate state. Overall, these findings provide fundamental information on the role of oxygen point defects in realizing metastable polymorph phases in promising new technological materials.

Improvement in vocal-cord visualization with Trachway video intubating stylet using direct oxygen flow and effective analysis of the fraction of inspired oxygen: a bench study.

The Trachway video intubating stylet device facilitates the visualization of the airways of patients from the tip of an endotracheal tube (ETT) during intubation. The major limitations of Trachway are the restricted view due to secretions and the risk of a prolonged apnea during intubation. We conducted a bench study to verify the performance of an alternative, easily applicable airway device that allows better visualization of trackways during Trachway-assisted intubation and prevents the detrimental effects of apnea-related hypoxia. We conducted a bench study to thoroughly evaluate the oral-secretion-elimination ability of a newly designed oxygen delivery device (ODD) to improve vocal-cord visualization using the three commonly used ETT sizes (i.e., 7, 7.5, and 8mm). Moreover, we measured the fraction of inspired oxygen (FiO2) under different, continuous oxygen-flow supplies (1-10L/min) during intubation. Each condition was analyzed for a 2min video-stylet-intubation period. The supplemental oxygen flow and FiO2 fraction achieved using our ODD were higher, and smaller ETTs exhibited better secretion elimination. The ODD, which can be easily coupled with Trachway stylets, enabled high-quality visualization during oxygen flows of 6-8L/min, and higher FiO2 fractions were achieved at higher oxygen flow rates. The use of the ODD improved the visualization of the airways during video stylet-assisted intubations using the additional FiO2 supply. The ODD developed in this study improves the visualization of airways with Trachway stylets and enhances the safety of intubation.

High temperature (900 °C) sliding wear of CrNiAlCY coatings deposited by high velocity oxy fuel thermal spray

Nickel based superalloy are in demand for high temperature applications and their corrosion, erosion and wear resistance have been investigated for a long time. Nickel chromium (NiCr) alloys are widely used for corrosion resistant coatings, while chromium carbide nickel chromium (CrC-NiCr) alloys are preferred for wear resistant coatings at high temperature. In this study CrNiAlCY coatings were deposited via a liquid fuelled high velocity oxy fuel (HVOF) thermal spray using two spray parameters and tested as wear resistant coatings. Effects of processing parameters on microstructure and mechanical properties of the coatings were investigated. Results showed that higher oxygen flow rates are critical for obtaining coatings with lower porosity and higher microhardness. Coating with lower porosity and higher hardness was chosen for both room temperature (~24 °C) and high temperature (900 °C) unlubricated sliding wear tests in a ball on disc setup. The coating was tested against alumina counterbody under 3 different loading conditions (10, 30 and 60 N). The wear rate of the coating was directly proportional to the applied load at room temperature. In the room temperature tests, wear debris was produced, which then oxidised and pushed away to the edges of the wear track. On the other hand, wear debris was smeared on the wear surface at high temperature tests. The surface was oxidised into Cr 2 O 3 at high temperatures, which acted as a protective layer. Although thermal softening took place at higher temperatures, wear rates under 10 and 30 N were similar to room temperature values due to the protective oxide layer formed on the top surface; however, the oxide layer under 60 N could not withstand the load, started to crack and lost its protective ability. • CrNiAlCY coatings have been produced using a liquid-fuelled HVOF thermal spray. • Effects of spray parameters on the microstructure and hardness studied. • Wear performance was investigated against the alumina counter body. • 2 Different temperature settings were used during the wear tests.

Excessive Oxygen Peroxide Model‐Based Analysis of Positive‐Bias‐Stress and Negative‐Bias‐Illumination‐Stress Instabilities in Self‐Aligned Top‐Gate Coplanar In–Ga–Zn–O Thin‐Film Transistors

AbstractAn excess oxygen‐peroxide‐based model that can simultaneously analyze the positive‐bias‐stress (PBS) and negative‐bias‐illumination‐stress (NBIS) instabilities in commercial self‐aligned top‐gate (SA‐TG) coplanar indium–gallium–zinc oxide (IGZO) thin‐film transistors (TFTs) is proposed herein. Existing studies have reported that the transition of oxygen vacancy (VO) charge states from VO0 to VO2+ is the dominant physical mechanism responsible for the negative shift of threshold voltage (VTH) under NBIS. However, in this study, it is observed that both the PBS and the NBIS stabilities of IGZO TFTs deteriorate at a faster rate as the amount of oxygen increases within the channel layer, implying that the conventional VO‐related defect model is inappropriate in elucidating the PBS and NBIS instabilities of commercial SA‐TG coplanar IGZO TFTs, where the channel layers are formed under high oxygen flow rates (OFRs) to make VTH positive. On the basis of the full‐energy range subgap density of states extracted before and after each stress from IGZO TFTs with different OFRs, it is determined that the generation and annihilation of the subgap states in the excess oxygen peroxide configuration are the dominant physical mechanisms for PBS and NBIS instabilities in commercial SA‐TG coplanar IGZO TFTs, respectively.

Association of transcutaneous CO2 with respiratory support: a prospective double blind observational study in children with bronchiolitis and reactive airway disease.

The use of clinical scoring to assess for severity of respiratory distress and respiratory failure is challenging due to subjectivity and interrater variability. Transcutaneous Capnography (TcpCO2) can be used as an objective tool to assess a patient’s ventilatory status. This study was designed to assess for any correlation of continuous monitoring of TcpCO2 with the respiratory clinical scores and deterioration in children admitted for acute respiratory distress. A prospective observational study over one year on children aged 2 weeks to 5 years admitted with acute respiratory distress or failure secondary to Bronchiolitis and Reactive airway disease was performed. Continuous TcpCO2 monitoring for upto 48 h was recorded. Investigators, bedside physicians, respiratory therapists, and nurses were blinded from the transcutaneous trends at the time of data collection. Total of 813 TcpCO2 measurements at standard intervals of 30 min were obtained on 38 subjects. Subjects with abnormal TcpCO2 (> 45 mmHg) were younger (6.9 ± 5.2 vs. 23.05 ± 17.7 months,) and were more likely to be on higher oxygen flow rate (0.52 L/min/kg vs 0.46 lier/min/kg, p = 0.004) and higher FiO2 (38.4 vs 33.6, p < 0.001 using heated high flow nasal cannula. No difference was found in bronchiolitis score or PEW score in subjects with normal and abnormal TcpCO2. A small but statistically significant increase in TcpCO2 was observed at the escalation of care. Even though odds of escalation of care are higher with abnormal TcpCO2 (OR 1.92), this difference did not reach statistical significance. pCO2 can provide additive information for non-invasive clinical monitoring of children requiring varying respiratory support; however, it does not provide predictive value for escalation or de-escalation of care.

Biodegradation of polyethylene terephthalate microplastics by bacterial communities from activated sludge

AbstractThe emerging accumulation of microplastics (MPs) in global waters is of increasing concern and it is posing great health risks to both humans and aquatic species, yet suitable technologies to remove MPs are lacking. The objective of this study was to investigate activated sludge as a source of promising biocatalysts for the removal of MPs in water. Bacterial communities in activated sludge were first screened for their potential to degrade hydrolyzable plastics from polyethylene terephthalate (PET) pre‐treated at 100°C for 1 hour. The consortium grew on a mineral medium with PET MPs as the sole carbon and energy source. To further assess its degrading potential, the consortium was put through a standardized CO2 evolution test at a temperature of 30°C, pH 7‐7.5, reactor residence time 168 days, and PET concentration of 2.63 g/L. The biodegradation extent was further validated through assessment of morphological/structural changes on the PET by means of SEM, DSC, FTIR, and viscometry analyses. Upon incubation, the consortium degraded 17% of PET. The molecular weight remained unchanged, reflecting a degradation via surface erosion. Furthermore, the biodegradation was significantly enhanced at high oxygen flow rates. Two bacterial strains within the consortium were isolated and identified as Bacillus cereus SEHD031MH and Agromyces mediolanus PNP3. Both strains thrived when individually cultured with PET while only B. cereus showed enzymatic activity during a clear‐zone test. The examined bacterial strains possess a promising PET‐degrading activity that can be further investigated and applied to the elimination of MPs water/wastewater through innovative and effective technologies.

Oxygen plasma modification of carbon fiber rovings for enhanced interaction toward mineral-based impregnation materials and concrete matrices

The insufficient bond strength of carbon fibers (CFs) towards cementitious matrices limits at present their prospective application as CF-reinforcement in construction. In this investigation an oxygen plasma modification process was utilized to tailor the surface properties of CF rovings in achieving higher affinity towards mineral-based aqueous suspensions. A systematic study on various process parameters was performed to outline expedient treatment regimes. X-ray photoelectron spectroscopy, single fiber tensile tests, and Weibull-analysis delivered insights on the effects of plasma modification on the carbon fibers’ properties.Mineral-impregnated carbon fiber (MCF) reinforcement bars were produced and characterized by means of pullout tests. It was found that short plasma treatment time, high oxygen flow rates, low pressure, and long pulse duration improved the shear strengths of the MCF bonds on being extracted from the concrete matrix. Morphological analysis revealed that a higher oxygen concentration enables better wetting behavior towards the mineral matrices and, hence, yields higher bond strength.

Iridium oxide top electrodes for piezo- and pyroelectric performance enhancements in lead zirconate titanate thin-film devices

Iridium oxide films of various morphologies are produced by manipulating the reactive gas flow rate in a reactive sputtering process. This study explores the benefits of using planar and nanostructured IrOx top electrodes for Pb(Zr0.52Ti0.48)O3 (PZT) devices employed in piezoelectric and pyroelectric applications in comparison with conventional platinum electrodes. For the first time, the Young’s modulus of a planar IrOx thin film was directly measured to be 300 ± 15 GPa. The piezoelectric performance of devices with planar IrOx showed up to 245% more strain compared to those capped with a Pt electrode. Nanostructured, 2D IrOx platelet networks are observed for films deposited with high oxygen flow rates. The compatibility with various cleanroom processes, such as liftoff, ultrasonic cleaning, and deposition on etched surfaces, is tested for the IrOx nanostructured layers. These films are shown to have low optical reflectivity while retaining good PZT thin-film capacitor polarization and dielectric permittivity. An improved pyroelectric energy harvesting figure of merit by a factor of 2.5× was observed for the IrOx compared to Pt films on the same PZT material.

Carbon-templated strategy toward the synthesis of dense and yolk-shell multi-component transition metal oxide cathode microspheres for high-performance Li ion batteries

Development of efficient strategies for the synthesis of multicomponent microspheres applicable to cathodes in lithium ion batteries is in urgent need. This paper presents ‘drop and dry’ method for synthesizing dense and yolk-shell multicomponent transition metal oxide microspheres. The infiltration of ethanol solution containing several metal precursors into highly porous carbon template microspheres through repetitive drop and dry process and subsequent heat treatment under oxygen atmosphere result in dense and yolk-shell microspheres. The first target cathode material is LiMn1.5Ni0.5O4, which operates at high voltage. After infiltration of Li, Mn, and Ni salts into the pores of the carbonaceous microspheres, stepwise heat treatment under low oxygen flow rate yields dense LiMn1.5Ni0.5O4 microspheres exhibiting non-aggregation characteristics and narrow size distribution. In comparison, one-step oxidation of carbon microspheres containing metal salts under high oxygen flow rate results in yolk-shell LiMn1.5Ni0.5O4 microspheres. The dense and yolk-shell microspheres exhibit stable cycle performance and capacities of 113 and 111 mA h g−1 are delivered after 1200 cycles at 10 C rate, respectively. In addition, discharge capacities of 69 and 44 mA h g−1 for yolk-shell and dense microspheres, respectively, are delivered at a high current density of 50 C.

Pragmatic recommendations for intubating critically ill patients with suspected COVID-19.

Pragmatic recommendations for intubating critically ill patients with suspected COVID-19.

Low-Voltage Metal-Oxide Thin Film Transistors Using P-Type Tin-Oxide Semiconductors.

In this paper, the effect of channel annealing and oxygen flow rate in P-type tin-monoxide (SnO) thin film transistor (TFT) was investigated to reach the process compatibility with n-type oxide-based TFT. The optimized P-type SnO TFT with a small threshold voltage of -0.1 V, a high field-effect mobility of 4 cm² V-1 s-1 and an on/off current ratio of >10² was proposed. From the experimental results, the 150 °C channel annealing revealed a metallic behavior but a semiconductor-like property at a higher 200 °C that was favorable for transistor rectification. Besides, the higher oxygen flow rate was also helpful for improving device mobility and driving current, but shows a slight increase in off-state leakage, which is unavoidable due to the increase of grain in SnO channel.

Magnetic Properties of Reactive Co-Sputtered NiFe-Oxide Samples

In this paper, we discuss the properties of reactive radio-frequency-sputtered Fe-doped NiO thin films co-sputtered at different oxygen flow rates. The films were deposited in an AJA Orion sputtering system from metallic NiFe-19 at.% targets. The deposition rate was monitored before and after deposition using a quartz crystal monitor. The deposition rate at the sample location depends strongly on the O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> flow. At lower oxygen flows, the deposition rate increases with oxygen flow caused by the oxidation of the sample. At higher oxygen flow rates, the deposition rate decreases with increasing oxygen flow. This is caused by poisoning of the targets resulting in a lower deposition rate. The oxygen content of the samples increases with the oxygen flow rate. This conclusion is supported by vibrating sample magnetometer measurements that show an increase in the magnetic moment for films sputtered at lower O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> flows. To determine the chemical state of the elements, the X-ray photoelectron spectroscopy (XPS) analysis of the samples was carried out ex situ on films capped with a Pt or Au layer. Prior to the XPS measurements, part of the cap layers but not all were removed with an Ar sputtering gun in the XPS chamber. The XPS results show that the ratio of the Ni <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</sup> -Ni <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> atoms in the film decreases with the oxygen flow. The Fe-XPS spectra of the films sputtered at different oxygen flows look very similar to each other but different from XPS studies done on oxidized permalloy by others showing that RF-sputtered NiFe-oxide is different from oxidized permalloy. The comparison of the XPS data for the samples sputtered at 20 sccm covered with Pt cap and Au cap was also done and shows smaller metallic Ni peaks for the sample capped with Au than samples capped with Pt, possibly caused by partly sputtering through the cap layer for the Pt-capped samples influencing the stoichiometry of the top layer of the NiFe-oxide.

Investigation of HfO2 Thin Films on Si by X-ray Photoelectron Spectroscopy, Rutherford Backscattering, Grazing Incidence X-ray Diffraction and Variable Angle Spectroscopic Ellipsometry

Hafnium oxide (HfO2) thin films have been made by atomic vapor deposition (AVD) onto Si substrates under different growth temperature and oxygen flow. The effect of different growth conditions on the structure and optical characteristics of deposited HfO2 film has been studied using X-ray photoelectron spectroscopy (XPS), Rutherford backscattering spectrometry (RBS), grazing incidence X-ray diffraction (GIXRD) and variable angle spectroscopic ellipsometry (VASE). The XPS measurements and analyses revealed the insufficient chemical reaction at the lower oxygen flow rate and the film quality improved at higher oxygen flow rate. Via GIXRD, it was found that the HfO2 films on Si were amorphous in nature, as deposited at lower deposition temperature, while being polycrystalline at higher deposition temperature. The structural phase changes from interface to surface were demonstrated. The values of optical constants and bandgaps and their variations with the growth conditions were determined accurately from VASE and XPS. All analyses indicate that appropriate substrate temperature and oxygen flow are essential to achieve high quality of the AVD-grown HfO2 films.