HBr Concentration Research Articles

Inductive couple plasma reactive ion etching characteristics of TiO2 thin films

Changes in the inductively coupled plasma reactive ion etching characteristics of TiO2 thin films in response to the addition of HBr, Cl2 and C2F6 to Ar gas were investigated. As the HBr, Cl2 and C2F6 concentration increased, the etch rate increased; however, the etch profile degree of anisotropy followed a different trend. As HBr concentration increased, the greatest anisotropic etch profile was obtained at 100% HBr, while the greatest anisotropic etch profile was obtained at concentrations of 25% when etching was conducted under C2F6 and Cl2. Field emission scanning electron microscopy revealed that 25% C2F6 generated the greatest vertical etch profile; hence, etch parameters were varied at this concentration. The effects of rf power, dc-bias voltage and gas pressure on the etch rate and etch profile were also investigated. The etch rate and degree of anisotropy in the etch profile increased with increasing rf power and dc-bias voltage and decreasing gas pressure. X-ray photoelectron spectroscopy analysis of the films etched under a C2F6/Ar gas mixture revealed the existence of etch byproducts containing F (i.e. TiFx) over the film. CxFy compounds were not detected on the film surface, probably due to contamination with atmospheric carbon.

Calcium isotope fractionation in liquid chromatography with benzo-18-crown-6 resin in aqueous hydrobromic acid medium

Liquid chromatography operated in a breakthrough mode was employed to study calcium isotope fractionation in the aqueous hydrobromic acid medium. Highly porous silica beads, the inner pores of which were embedded with a benzo-18-crown-6 ether resin, were used as column packing material. Enrichment of heavier isotopes of calcium was observed in the frontal part of respective calcium chromatograms. The values of the isotope fractionation coefficient were on the order of 10−3. The observed isotope fractionation coefficient was dependent on the concentration of hydrobromic acid in the calcium feed solution; a higher HBr concentration resulted in a smaller fractionation coefficient value. The present calcium isotope effects were most probably mass-dependent, indicating that they mostly came from isotope effects based on molecular vibration. Molecular orbital calculations supported the present experimental results in a qualitative fashion. Chromatography operated in aqueous HBr media is a better system of Ca isotope separation than that operated in aqueous HCl media.

Cyclic Performance Analysis of Hydrogen/Bromine Flow Batteries for Grid‐Scale Energy Storage

AbstractThis paper explores the critical factors dominating the cycle performance of the hydrogen/bromine redox flow battery (RFB). Carbon electrode oxidation to CO2 was seen as the dominant side reaction, which can be prevented by operating the cell below 1.4 V. Crossover of bromide species from the positive to the negative electrode, especially during charge, dominates the coulombic efficiency, and can result in dissolution of the Pt catalyst if an adequate hydrogen supply is not maintained. This paper also describes the tradeoffs in voltaic, energy, and coulombic efficiencies during cycling, including the determination of the peak energy efficiency with respect to the HBr concentration and current density. Long‐term cycling demonstrates negligible cell‐component degradation over 600 cycles (≈3 months), with capacity loss caused by the bromine from the system, which can be mitigated by proper system design. The data and methodologies provided in this paper can be used to understand better the operation of this and other RFBs.

FNIRS-EEG study of focal interictal epileptiform discharges

Functional near-infrared spectroscopy (fNIRS) acquired with electroencephalography (EEG) is a relatively new non-invasive neuroimaging technique with potential for long term monitoring of the epileptic brain. Simultaneous EEG-fNIRS recording allows the spatio-temporal reconstruction of the hemodynamic response in terms of the concentration changes in oxy-hemoglobin (HbO) and deoxy-hemoglobin (HbR) associated with recorded epileptic events such as interictal epileptic discharges (IEDs) or seizures. While most previous studies investigating fNIRS in epilepsy had limitations due to restricted spatial coverage and small sample sizes, this work includes a sufficiently large number of channels to provide an extensive bilateral coverage of the surface of the brain for a sample size of 40 patients with focal epilepsies. Topographic maps of significant activations due to each IED type were generated in four different views (dorsal, frontal, left and right) and were compared with the epileptic focus previously identified by an epileptologist. After excluding 5 patients due to the absence of IEDs and 6 more with mesial temporal foci too deep for fNIRS, we report that significant HbR (respectively HbO) concentration changes corresponding to IEDs were observed in 62% (resp. 38%) of patients with neocortical epilepsies. This HbR/HbO response was most significant in the epileptic focus region among all the activations in 28%/21% of patients.

Studies on the spectral purity of copper–hydrogen bromide laser radiations

This paper presents, for the first time to the best of our knowledge, the linewidth, frequency, and stability characteristics of a copper-HBr laser. These spectral purity attributes were found to be critically linked with the electrical input power and HBr concentration, unlike that of the optical resonator. Variation in green and yellow radiation linewidths from 4 to 4.5GHz and from 6.5 to 8.8GHz, linewidth fluctuations from 50 to 150MHz and from 60 to 530MHz as well as frequency fluctuations from 10 to 100MHz and from 410 to 10MHz were observed when varying the input power and HBr concentration. These results are comprehensively analyzed in terms of isotopic shift, hyperfine splitting, line broadening, and temperature and gain distribution effects relevant to this laser.

Determination of single-ion activity coefficients of hydrogen and bromide ions in aqueous hydrobromic acid solutions based on an ionic liquid salt bridge

Single ion activity coefficients of H+ and Br− in aqueous hydrobromic acid solutions, γH+ and γBr−, have been estimated potentiometrically at 25°C with a hydrogen electrode and a silver–silver bromide electrode, respectively, based on the assumption that the change in the liquid junction potential at the interface between a sample solution and an ionic liquid salt bridge is negligibly small. The mean activity coefficients of HBr calculated from experimentally obtained values of γH+ and γBr− well agree with the literature values over the entire concentration ranges studied, 1.04 × 10−3 to 0.528molkg−1. Overall dependencies of γH+ and γBr− on ionic strength are similar to those found previously in aqueous HCl solutions, but the degree of the dependence is distinctively stronger in both γH+ and γBr−. Plots of γH+ and γBr− as a function of the ionic strength are nearly congruent with the predictions by Fraenkel's smaller-ion shell (SiS) model up to 0.05molkg−1. However, with a further increase in HBr concentration experimental γH+ and γBr− more rapidly increases and decreases, respectively, in comparison with the SiS predictions.

Aqueous bromine etching of InP: a specific surface chemistry

AbstractThe n ‐InP behaviour in HBr (0.1‐1.0 M)/Br2 (1.25 × 10‐2M) aqueous solutions is studied by AAS, XPS and SEM‐FEG. Indium AAS‐titrations of the HBr/Br2 solutions demonstrate that InP undergoes an etching mechanism whatever the HBr/Br2 formulation. The etching process is always linear with time but its rate depends on the HBr concentration. XPS analyses permit to link the apparent slow‐down of the dissolution process when decreasing the HBr molarity from 1.0 M to 0.1 M to the presence of a mixed (In,P)ox oxide layer on the surface. Therefore, the dissolution process of InP in HBr/Br2 solution appears to be ruled by the surface chemical state (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Investigation on Etch Characteristics of Nanometer-Sized Magnetic Tunnel Junction Stacks Using a HBr/Ar Plasma

The etch characteristics of CoFeB magnetic films and magnetic-tunnel-junction (MTJ) stacks masked with Ti films were investigated using an inductively coupled plasma reactive ion etching in a HBr/Ar gas mix. The etch rate, etch selectivity, and etch profile of the CoFeB films were obtained as a function of the HBr concentration. As the HBr gas was added to Ar, the etch rate of the CoFeB films, and the etch selectivity to the Ti hard mask, gradually decreased, but the etch profile of the CoFeB films was improved. The effects of the HBr concentration and etch parameters on the etch profile of the MTJ stacks with a nanometer-sized 70 x 100 nm2 pattern were explored. At 10% HBr concentration, low ICP RF power, and low DC-bias voltage, better etch profiles of the MTJ stacks were obtained without redeposition. It was confirmed that the protective layer containing hydrogen, and the surface bombardment of the Ar ions, played a key role in obtaining a steep sidewall angle in the etch profile. Fine-pattern transfer of the MTJ stacks with a high degree of anisotropy was achieved using a HBr/Ar gas chemistry.

Investigation on etch characteristics of MgO thin films using a HBr/Ar plasma

Etch characteristics of MgO thin films were investigated using an inductively coupled plasma reactive ion etcher in a HBr/Ar plasma. As the concentration of HBr gas increased, the etch rate of MgO thin films gradually decreased, but the etch rate of Ti hard mask showed initial decrease and then increased with increasing HBr concentration. The etch profile of MgO films was improved with increasing HBr concentration and a high degree of anisotropy in etch profile was achieved at 30% HBr/Ar gas. Based on the etch characteristics and surface analysis by X-ray photoelectron spectroscopy, it can be concluded that the etch mechanism of MgO thin films in a HBr/Ar gas does not follow the reactive ion etch mechanism but the sputter etching mechanism with the assistance of chemical reactions on the film surfaces.

Inductively Coupled Plasma Etching of Indium Zinc Oxide Thin Films with HBr ∕ Ar Discharges

High density plasma etching of indium zinc oxide (IZO) thin films was performed in gas mix. As HBr concentration increased, the etch rate was decreased and etch profile was improved. The high degree of etch anisotropy was achieved with decreasing dc-bias voltage and increasing gas pressure. The formation of protective layer, which had a strong effect on the etch profile, was confirmed by surface analyses. The X-ray photoelectron spectroscopy revealed the formation of and compounds. It could be concluded that the etching of IZO films in plasma was governed by ion sputtering along with chemical assistance.

Kinetics of the R + HBr ⇄ RH + Br (CH 3CHBr, CHBr 2 or CDBr 2) equilibrium. Thermochemistry of the CH 3CHBr and CHBr 2 radicals

The kinetics of the reaction of the CH 3CHBr, CHBr 2 or CDBr 2 radicals, R, with HBr have been investigated in a temperature-controlled tubular reactor coupled to a photoionization mass spectrometer. The CH 3CHBr (or CHBr 2 or CDBr 2) radical was produced homogeneously in the reactor by a pulsed 248 nm exciplex laser photolysis of CH 3CHBr 2 (or CHBr 3 or CDBr 3). The decay of R was monitored as a function of HBr concentration under pseudo-first-order conditions to determine the rate constants as a function of temperature. The reactions were studied separately from 253 to 344 K (CH 3CHBr + HBr) and from 288 to 477 K (CHBr 2 + HBr) and in these temperature ranges the rate constants determined were fitted to an Arrhenius expression (error limits stated are 1σ + Student’s t values, units in cm 3 molecule −1 s −1, no error limits for the third reaction): k(CH 3CHBr + HBr) = (1.7 ± 1.2) × 10 −13 exp[+ (5.1 ± 1.9) kJ mol −1/ RT], k(CHBr 2 + HBr) = (2.5 ± 1.2) × 10 −13 exp[−(4.04 ± 1.14) kJ mol −1/ RT] and k(CDBr 2 + HBr) = 1.6 × 10 −13 exp(−2.1 kJ mol −1/ RT). The energy barriers of the reverse reactions were taken from the literature. The enthalpy of formation values of the CH 3CHBr and CHBr 2 radicals and an experimental entropy value at 298 K for the CH 3CHBr radical were obtained using a second-law method. The result for the entropy value for the CH 3CHBr radical is 305 ± 9 J K −1 mol −1. The results for the enthalpy of formation values at 298 K are (in kJ mol −1): 133.4 ± 3.4 (CH 3CHBr) and 199.1 ± 2.7 (CHBr 2), and for α-C–H bond dissociation energies of analogous compounds are (in kJ mol −1): 415.0 ± 2.7 (CH 3CH 2Br) and 412.6 ± 2.7 (CH 2Br 2), respectively.

Multimodal measurement of brain activity using fNIRS and fMRI

Event Abstract Back to Event Multimodal measurement of brain activity using fNIRS and fMRI Uzay E. Emir1* 1 CMRR, University of Minnesota, United States Investigating principles of the human brain activity requires a multimodal approach since multimodal investigation of blood oxygenation level-dependent (BOLD) functional magnetic resonance imaging (fMRI) signal using functional near infrared spectroscopy (fNIRS) may give further insight to the underlying physiological principles and the detailed transient dynamics of the vascular response. Local paramagnetic deoxy-hemoglobin (reduced hemoglobin, HbR) is the source of BOLD signals. HbR concentration changes cause MRI signal changes by altering the local susceptibility of blood around the vessels. However, fMRI as an indirect measurement does not provide a detailed understanding of the underlying physiology, since the BOLD signal is sensitive to all spatial scales of vessels and combined effects of several physiological parameters such as cerebral blood flow (CBF), cerebral blood volume (CBV) and cerebral metabolic rate of oxygen (CMRO2). fNIRS provides detailed biochemical specificity in the form of HbR and oxy-hemoglobin (HbO) concentration changes. While fNIRS offers a unique opportunity to track the concentration changes of these two molecules within a micro vascular space with high temporal resolution, it suffers from limited penetration depth and low spatial resolution. Thus, a multimodal measurement approach using fNIRS and fMRI may synergize and overcome these limitations. Conference: 10th International Conference on Cognitive Neuroscience, Bodrum, Türkiye, 1 Sep - 5 Sep, 2008. Presentation Type: Oral Presentation Topic: Symposium 13: Potentials and Limitations of Multi-modal Neuroimaging Citation: Emir UE (2008). Multimodal measurement of brain activity using fNIRS and fMRI. Conference Abstract: 10th International Conference on Cognitive Neuroscience. doi: 10.3389/conf.neuro.09.2009.01.059 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 28 Nov 2008; Published Online: 28 Nov 2008. * Correspondence: Uzay E Emir, CMRR, University of Minnesota, Minneapolis, United States, uzay@cmrr.umn.edu Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Uzay E Emir Google Uzay E Emir Google Scholar Uzay E Emir PubMed Uzay E Emir Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Inductively coupled plasma reactive ion etching of ZnO films in HBr/Ar plasma

The etching characteristics of ZnO thin films were examined in an HBr/Ar gas mix using an inductively coupled plasma reactive ion etching system. The etch rate and etch profile were systematically investigated as a function of gas concentration. In addition, the effects of etch parameters such as coil rf power, dc-bias voltage, and gas pressure were studied. As the HBr concentration increased, the etch rate of the ZnO films gradually decreased while the etch profile was improved. Surface analyses including X-ray photoelectron spectroscopy and atomic force microscopy were employed to elucidate the etch mechanism of ZnO in an HBr/Ar chemistry.

Inductively Coupled Plasma Reactive Ion Etching of GeSbTe Thin Films in a HBr/Ar Gas

ABSTRACT Inductively coupled plasma reactive ion etching of GeSbTe (GST) thin films with a photoresist mask was performed using a HBr/Ar gas mixture. The etch rate of GST films increased up to 20% HBr concentration and began to decrease with further increase of HBr concentration. The etch profiles were improved with increasing HBr gas concentration. In particular, clean and vertical etch profiles were achieved at 80∼ 100% HBr gas concentrations. As the coil rf power and dc-bias voltage increased, the etch rates increased. The gas pressure had little influence on the etch rate. The good etch profiles were obtained at high coil power, low dc-bias and high gas pressure. The x-ray photoelectron spectroscopy analysis reveals that Te showed highest reactivity with HBr gas chemistry. A high degree of anisotropic etching of GST films was achieved using HBr/Ar gas mixture at the optimized etch conditions.

Tantalum carbide etch characterization in inductively coupled Ar∕Cl2∕HBr plasmas

The etching properties of tantalum carbide (TaC) in inductively coupled Ar∕HBr∕Cl2 plasmas are investigated in this article. Both etching experiments on patterned and blanket wafers and an integrated plasma equipment-feature scale computational model are utilized in this investigation. Results show that TaC etching is adequately described by the classical reactive ion etching mechanism, whereby etching occurs due to the synergistic effect of Cl or Br atoms and energetic ions. TaC etches faster in the presence of Cl relative to Br. The TaC etch rate is small in gas mixtures containing 5% of Cl2 or HBr and 95% of Ar, and it increases considerably as Cl2 or HBr concentration is increased. Although this etch rate increase is partially due to the availability of more Cl or Br, the chemical nature of chlorine (Cl2+,Cl+) or bromine (Br+) ions also plays a strong role. The TaC etch rate increases little if Cl2 or HBr fraction in Ar∕Cl2 or Ar∕HBr gas mixture, respectively, is increased beyond 25%. The TaC etch rate increases with rf bias power under all conditions. Scanning electron micrographs of TaC films etched using a patterned mask show that TaC sidewalls are tapered at about 77°±3° and the angle does not change appreciably with gas mixture or rf bias power. It is determined that an angle dependent ion etching yield captures well the observed trends in TaC sidewall slope.

The Influence of Cortical Maturation on the BOLD Response: An fMRI Study of Visual Cortex in Children

We performed blood oxygenation level-dependent (BOLD) functional MR imaging in 11 children younger than 5 y of age and 10 children older than 5 y of age. All but five of the children in the older age group were tested under light anesthesia. We examined the cerebral oxidative metabolism (CMRO(2)) associated with the processing of a flashed and a reversing checkerboard stimulus. These stimuli had been shown in a previous study to induce identical vascular responses. The reversing checkerboard activated twice the neuronal population of the flashed checkerboard, doubling the CMRO(2) associated with it. We compared the extent of activation for the positive BOLD response and found that it did not differ between the different age groups. We estimated the oxidative metabolism by examining the change in the local deoxyhemoglobin (HbR) concentration using Delta R2*. Because both stimuli induced the same vascular response, any increase in oxygen requirement would have to be met by the identical blood volume. Increasing CMRO(2) will therefore result in an increase in the oxygen extraction fraction (OEF), which raises the local HbR concentration. In the younger children, both checkerboard stimuli produced identical, high HbR concentrations. In the older children, the HbR concentration to the flashed stimulus was significantly lower than to the reversing stimulus. We conclude that, for identical stimuli, the oxidative energy requirement associated with the cortical processing is higher in young children than in older children because the presence of superfluous synaptic connections in the immature visual system activates a larger neuronal population.

How much luxury is there in 'luxury perfusion'? An analysis of the BOLD response in the visual areas V1 and V2.

We re-analyzed the functional magnetic resonance imaging data from a study involving awake, adult, human volunteers in order to examine the influence of vascular density on the blood oxygenation level-dependent (BOLD) response. We employed a flashed and reversing stimulus paradigm where the latter stimulated twice the number of receptive fields and with it doubled the neuronal metabolic load (CMRO2) compared to the former stimulus. The blood flow increase to these stimuli was identical, so that differences in the BOLD response are due to differences in the oxygen extraction fraction. By comparing the BOLD response in human striate cortex (V1) and its neighbor, extra-striate area V2 to the two stimuli, we were able to determine the influence of the higher vascular density of striate cortex on the BOLD response. In striate cortex, the extent of activation, as measured by the number of activated voxels, was larger for the flashed than for the reversing stimulus. In extra-striate area V2, no such difference in the extent of activation was noted. Gauging the local concentration of HbR using deltaR2*, we found it to be significantly lower for the flashed than for the reversing checkerboard. We estimated the HbR concentration in extra-striate area V2 to be double that of striate cortex independent of the stimulus presented. A frequency distribution of the deltaR2* values for the flashed and reversing checkerboard revealed a shift consistent with an increase in the HbR concentration between areas V1 and V2. The metabolically most demanding stimulus, the reversing checkerboard was associated with the highest HbR concentration and with the largest number of voxels with a negative BOLD response.

Soaking seeds of Lens culinaris with 28‐homobrassinolide increased nitrate reductase activity and grain yield in the field in India

SummarySurface‐sterilised seeds of Lens culinaris cv. Pusa‐6 were soaked in 0 M, 10−6 M, 10−8 M or 10−10 M aqueous solutions of 28‐homobrassinolide (HBR) for 4 h, 8 h or 12 h and planted in the field in a sandy loam soil. Plants were sampled 60, 90 and 120 days after sowing (DAS). Soaking with HBR decreased root length and nodule number per plant but increased nitrate reductase activity (E.C.1.6.6.1). Soaking with HBR also increased grain yield at the final harvest 140 DAS. The greatest increase was obtained with an HBR concentration of 10−8 M.

Kinetics of the R + HBr ⇄ RH + Br (R = CH2Br, CHBrCl or CCl3) equilibrium. Thermochemistry of the CH2Br and CHBrCl radicals

The kinetics of the reaction of the CH2Br, CHBrCl or CCl3 radicals, R, with HBr have been investigated separately in a heatable tubular reactor coupled to a photoionization mass spectrometer. The CH2Br (or CHBrCl or CCl3) radical was produced homogeneously in the reactor by a pulsed 248 nm exciplex laser photolysis of CH2Br2 (or CHBr2Cl or CBrCl3). The decay of R was monitored as a function of HBr concentration under pseudo-first-order conditions to determine the rate constants as a function of temperature. The reactions were studied separately over a wide ranges of temperatures and in these temperature ranges the rate constants determined were fitted to an Arrhenius expression (error limits stated are 1σ + Student’s t values, units in cm3 molecule−1 s−1): k(CH2Br + HBr) = (7.5 ± 0.9) × 10−13 exp[−(2.53 ± 0.13) kJ mol−1/RT], k(CHBrCl + HBr) = (4.9 ± 1.1) × 10−13 exp[−(8.2 ± 0.3) kJ mol−1/RT] and k(CCl3 + HBr) < (6 ± 1) × 10−15 at 787 K. The kinetics of the reverse reactions, Br + R′H → HBr + R′ (R′ = CH2Br or CHBrCl), were taken from the literature and also calculated by ab initio methods at the MP2(fc)/6-31G(d,p)//MP2(fc)/6-31G(d,p) level of theory in conjunction with the thermodynamic transition state theory to calculate the entropy and the enthalpy of formation values of the radicals studied. The thermodynamic values were obtained at 298 K using a second-law method. The results for entropy values are as follows (units in J K−1 mol−1): 263 ± 7 (CH2Br) and 294 ± 6 (CHBrCl). The results for enthalpy of formation values at 298 K are (in kJ mol−1): 171.1 ± 2.7 (CH2Br) and 143 ± 6 (CHBrCl). The C–H bond strength of analogous halomethanes are (in kJ mol−1): 427.2 ± 2.4 (CH3Br) and 406.0 ± 2.4 (CH2BrCl). Thermodynamic properties of the CH2Br radical were calculated by statistical thermodynamic methods over the temperature range 100–1500 K.

Fourier transform infrared analysis of gas composition in low-volume light bulbs.

Fourier transform infrared spectroscopy has been used for in situ analysis of HBr, CH3Br, and CO within light bulbs at different stages of burning time. The interference fringes originated in the quartz walls of the bulbs have been eliminated by different methods. The NIPALS procedure yielded higher S/N ratio than the fringe-elimination method applied. The CO and HBr showed time-dependent concentration changes during the burning period. The maximum CO concentration (approximately 6 ppm) was detected after 30-50 s of burning time, and then it practically burned out after 5 h. The HBr concentration increased in the first 3 min of burning, and then its concentration stabilized at a 10-15 ppm level. After 5 s of illumination, the CH3Br concentration became undetectable.