Oxygen Band Research Articles

Lattice geometry controlled synthesis of Cu – Doped nickel oxide nanoparticles

NiO3+δ and Ni1−xCuxO3+δ (x = 5, 10, 20) were synthesized by solid state precipitation method, using precursors, nickel chloride and copper chloride with potassium hydroxide as an alkalizing agent. The present work reports the synthesis of copper doped nickel oxides. The phase formation, crystallinity index, crystal structure and microstructure with composition analysis were investigated with the help of various characterization techniques. The FTIR spectrum reveals that characteristic metal oxygen bands of the Ni–O stretching at 447cm−1 with crystallinity index 0.39. Phase pure, hexagonal NiO3+δ formation was identified from the XRD data. Nanosized particles with size as small as ~ 6 to 15nm for pure sample and ~ 11 to 50nm for the copper doped sample are observed from field emission scanning electron micrographs. Thermo chemical calculations such as enthalpy of reaction 77.44kJmole−1, Gibbs free energy − 639.23kJmole−1and entropy of the reaction 0.0024kJK−1mole−1 have been calculated. Specific surface area of NiO3+δ and Ni1−xCuxO3+δ (x = 5, 10, 20) is obtained by Sauter formula, i.e. ~ 292m2/g, ~ 656m2/g, ~ 557m2/g, and ~ 517m2/g respectively.

Wireless TDMA‐Based Body Area Network Platform Gathering Multibiosignals Synchronized with Patient’s Heartbeat

In the application of a body area network in medical healthcare, the process of receiving, archiving, and analyzing multibiosignals simultaneously from different devices for each body is very important. For example, to diagnose sleep apnea symptoms, a patient must sleep with dozens of devices, including electroencephalography (EEG), electrocardiogram (ECG), photoplethysmogram (PPG), peripheral oxygen saturation (SpO2), nasal cannula, and bands. Various wireless methods of body area network for acquisition and measurement of body signals have been introduced, but it is difficult to accurately diagnose various biosignals because their measurement frequencies are different from each other, and they are not guaranteed precise synchronization. Because each body biosignal is commonly synchronized with the heartbeat of the patient, precise synchronization of the heartbeat and other measuring cycles of each device is a critical attribute for analyzing the corelation of each biosignal in the body area network. However, it is difficult to guarantee the precise synchronization of multibiosignals by solely using carrier sense multiple access with collision detection‐ (CSMA/CD‐) based wireless protocols, which are mainly used in existing body area networks. This study proposes a method of creating a self‐organizing body area network based on wireless Time Division Multiple Access (TDMA) to guarantee the synchronization of multibiosignals and compare its accuracy with the CSMA/CD method.

Facile Synthesis and Characterization of ZrO₂ Nanoparticles via Modified Co-Precipitation Method.

The crystalline Zirconium oxide (ZrO2) nano particles were synthesized using optimized content of Zirconium nitrate (Zr(NO3)2·3H2O) with varying KOH concentration (0.5, 1 and 1.5 M) by co-precipitation method. The thermal history of the precursor was carefully analyzed through Thermogravimetric (TG/DTA) measurement. The as prepared samples were characterized to ensure structural, functional, morphological, compositional, chemical composition and band gap by X-ray diffractometer (XRD), Fourier transform infrared spectroscopy (FTIR), Laser Raman, scanning electron microscopy (SEM), High resolution Transverse Electron Microscopy (HR-TEM), X-ray photo electron spectroscopy (XPS), EDX, Photo luminescence spectroscopy (PL). The monoclinic structure with space group P21/c has been confirmed from XRD (JCPDS 89-9066). The Zr-O stretching vibration and Zr-O2-Zr bending vibrations were confirmed through FTIR analysis. The well dispersed particles with spherical morphology were confirmed through SEM and TEM analysis. The oxidation states of Zr, O and C were confirmed through XPS analysis. The oxygen vacancies and band gap of the particles were investigated through PL analysis.

Optical properties of Codium tomentosum seaweed like Bi2O3 nanostructure and its gas-sensing activity

Codium tomentosum seaweed structured Bi2O3 was prepared by anodization technique using thermally evaporated bismuth films. The present study concerns the development of an efficient CO2 sensor at room temperature by controlling the crystallinity, morphology, carrier concentration, and bang gap. Crystal structure variation was achieved by sequential annealing from 200 to 600 °C. During anodization, truncated polyhedral aggregates of bismuth particles get reformed into Codium tomentosum seaweed like nanostructures of Bi2O3. The nature of Bi2O3 semiconductor with carrier concentration has been identified from the Mott–Schottky plot. Lattice defects such as oxygen vacancies, Bi interstitials, recombination effect, and band gap values were analyzed through optical studies. The sensor study was performed at room temperature for the detection of CO2 gas in the concentration 10–100 ppm. Bi2O3 nanostructure annealed at 400 °C having amorphous nature offered the maximum response magnitude. The underlying, sensing mechanism was correlated with the experimental findings on the basis of optical properties and surface morphology.

Crystallization and solid solution attainment of samarium doped ZnO nanorods via a combined ultrasonic-microwave irradiation approach

An advanced sol-gel method is developed via combined ultrasound-microwave irradiation and utilized for the crystallization of pristine and samarium doped zinc oxide nanorods. Organic structure directing agents directed one dimensional growth and air-annealing was applied as post-thermal treatment. Microstructural, optical, and solid state survey was pursued by PXRD, FESEM, TEM, EDS, FTIR, DRS, PL, micro-Raman, H2-TPR, and ESR techniques. Phase analysis by diffraction patterns confirmed the efficacy of irradiation strategy as it improves the crystallinity degree, expedites the hexagonal close pack morphology, and conducts lattice imperfection. Accordingly, aspect ratio and electronic evolution parallel to dopant content is favored. Electron microscopy demonstrated the flake-like rearrangement of nanorods as well as a structure-related growth where a direct proportion exists between atomic packing factor in lattice and aspect ratio. Textural investigation by EDS and FTIR rejected the presence of any impurity verifying an integrated composition. Reflectance and luminescence spectra exhibited characteristic optical behavior with shifts corresponding to dopant concentration. Also, band gap energies increased with samarium addition depicting an opposite trend with respect to unit cell variation. Finally, Raman, TPR, and ESR spectra provided detailed dopant-dependent trends on the internal solid state and defect chemistry of the nanorods. In this regard, maximum shifts in E2high and E1LO phonon modes duly correlated with the vibrations of zinc and oxygen atoms, surface oxygen and bulk ZnO reduction bands, emergence and alteration of samarium centers, along with the dominance of zinc and oxygen vacancies were all resulted due to the utmost lattice imperfection in SZO1.

Atmospheric Beacons of Life from Exoplanets Around G and K Stars

The current explosion in detection and characterization of thousands of extrasolar planets from the Kepler mission, the Hubble Space Telescope, and large ground-based telescopes opens a new era in searches for Earth-analog exoplanets with conditions suitable for sustaining life. As more Earth-sized exoplanets are detected in the near future, we will soon have an opportunity to identify habitale worlds. Which atmospheric biosignature gases from habitable planets can be detected with our current capabilities? The detection of the common biosignatures from nitrogen-oxygen rich terrestrial-type exoplanets including molecular oxygen (O2), ozone (O3), water vapor (H2O), carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4) requires days of integration time with largest space telescopes, and thus are very challenging for current instruments. In this paper we propose to use the powerful emission from rotational-vibrational bands of nitric oxide, hydroxyl and molecular oxygen as signatures of nitrogen, oxygen, and water rich atmospheres of terrestrial type exoplanets “highlighted” by the magnetic activity from young G and K main-sequence stars. The signals from these fundamental chemical prerequisites of life we call atmospheric “beacons of life” create a unique opportunity to perform direct imaging observations of Earth-sized exoplanets with high signal-to-noise and low spectral resolution with the upcoming NASA missions.

Nonlinear Generation Mechanism of EMIC Falling Tone Emissions

AbstractWe have conducted a self‐consistent hybrid simulation, successfully reproducing electromagnetic ion cyclotron (EMIC) emissions with falling tone frequencies. The hybrid simulation is implemented with a parabolic ambient magnetic field. In the simulation, strong oxygen band EMIC emissions are generated through nonlinear wave growth. The cold ion density is modulated by electrostatic structures which are induced by the forward and backward propagating oxygen band EMIC waves. Along with the growth of the oxygen band, the helium band waves also grow because of the initial linear growth followed by the nonlinear growth. The nonlinear growth of the helium band waves is affected by the cold plasma density modulation, and there appear short wave packets of helium band emissions. The short wave packets entrap energetic protons efficiently, resulting in electromagnetic proton hills in the velocity phase space. The proton hill forms a nonlinear resonant current causing the falling frequency of the EMIC waves. We find strong deformation of the velocity distribution function of the energetic protons due to the proton hill being guided by the increasing resonance velocity.

Hydrothermal synthesis of spherical NiCO2O4 nanoparticles as a positive electrode for pseudocapacitor applications

Hydrothermal method was adapted to synthesis NiCo2O4 nanoparticles by varying nickel and cobalt precursor concentration as 1:1, 1:2, and 1:3 ratios. X-ray diffraction (XRD) results revealed the spinel NiCo2O4 structure belongs to $${\rm{Fd}}\overline {\rm{3}} {\rm{m}}$$ space group system with face-centered cubic crystal structure. Raman characteristic peaks observed at 495 and 654 cm−1 explored Eg and A2g modes of spinel NiCo2O4 product. Photoluminescence (PL) results revealed the hole recombination of Ni2+/Co2+ ions from 3d-Eg and 3d-Tg electronic state of spinel NiCo2O4 material. The characteristic Fourier transform infrared spectroscopy (FTIR) metal–oxygen bands appeared at 658 and 558 cm−1 revealed the spinel-type crystal structure. SEM image revealed the NiCo2O4 spherical nanoparticles formation with an average particle size of around 500 nm. The cyclic voltammetry studies revealed the estimated average specific capacitance value of NC3 (NiCo2O4 spherical nanoparticles) as 542 F g−1 relatively higher than NC1 and NC2. The electro impendence spectroscopy results explored the small arc formation in high frequency range and very low charge transfer resistance (R ct), which resulted high conductive active materials. The estimated specific capacitance for NC3 exhibited superior galvanstatic charging and discharging (GCD) characteristics with high specific capacitance of 294 F g−1 at high current density of 1 A g−1 and revealed that the obtained electrode is suitable for supercapacitor applications. Hydrothermal synthesis using an excess of Co source leads to smaller and more uniform particle size. This particle size and the slightly larger crystallite size formed in the materials leads to the improved electrochemical performance of the particles.

Synthesis and characterization of magnetic activated carbon developed from palm kernel shells

Magnetic activated carbon (MG-AC), a solid product made by dispersing magnetic substrates on AC, is gaining attention for the removal of heavy metals from wastewater due to its favorable physico-chemical properties such as enhanced surface area and magnetic properties, respectively. However, the effects of two contrasting substrates, i.e., metal solution and metal particles, for the synthesis of MG-AC to obtain enhanced magnetic property have not been considered. The MG-AC was prepared by incorporating Fe3O4 into the AC from two different sources of iron: Fe3O4 extracted from electric arc furnace slag and from a ferric chloride/ferrous sulfate solution, to produce magnetic palm kernel shell from slag (MG-PKSS) and magnetic palm kernel shell from iron suspension (MG-PKSF), respectively. The adsorbent samples were characterized using Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis, X-ray diffraction, electron microscopy, i.e., SEM and FESEM, energy-dispersive X-ray, nitrogen adsorption, vibrating sample magnetometer. The results showed that the MG-PKSF had a greater BET surface area of 257 m2 g−1, a pore volume of 0.1124 cc g−1 and higher magnetic properties with a magnetic saturation of 49.55 emu g−1 relative to the MG-PKSS. The FTIR spectrum of the MG-PKSF illustrated the intense OH bending at 1629 cm−1 which can be attributed to the presence of oxygen in the samples. The absorption bands at 1093 and 579 cm−1 indicated the presence of C–O stretching and metal–oxygen (M–O) bands due to the interaction of iron and oxygen. Therefore, the MG-PKSF presented better characteristics for heavy metal removal from wastewater relative to the MG-PKSS, thereby suggesting that the raw material (metal solution) for impregnation played a crucial role in enhancing the quality of the MG-AC.

The nonlinear interactions between O+ ions and oxygen band EMIC waves

AbstractDuring geomagnetically active times, O+ ions from the ionosphere become an important ion component in the ring current, which changes the dispersion relations and significantly enlarges the growth rate of oxygen band electromagnetic ion cyclotron (EMIC) waves. Motivated by a large number of oxygen band EMIC wave observations in the inner magnetosphere, we study the nonlinear motions of ring current O+ ions caused by the cyclotron resonance with oxygen band EMIC waves. A dimensionless parameter R is used to characterize the competition between wave‐induced and adiabatic motions. The numerical calculations based on gyroaveraged test particle equations are performed. For typical 20 keV O+ ions at L = 5, two kinds of nonlinear processes occur simultaneously when αeq > 59° (R < 2.16): the phase trapping and phase bunching. The phase trapping tends to transport the O+ ions away from the loss cone and reduce the overall loss rate estimated from the quasi‐linear theory. Instead, phase bunching tends to increase the overall loss rate. The phase‐trapped O+ ions have chance to be accelerated drastically, reaching 750% of the initial energy. These O+ ions move forward and backward alternatively along the field lines when they are bouncing back to the equator, forming a periodic energy variation which has not been reported before. The results suggest that the oxygen band EMIC waves, which appear frequently during storms, should be considered in the ring current dynamics in terms of nonlinear acceleration and resonance scattering of ring current particles.

Impact of Atmospheric Inversion Effects on Solar-Induced Chlorophyll Fluorescence: Exploitation of the Apparent Reflectance as a Quality Indicator

In the last decade, significant progress has been made in estimating Solar-Induced chlorophyll Fluorescence (SIF) by passive remote sensing techniques that exploit the oxygen absorption spectral regions. Although the O2–B and the deep O2–A absorption bands present a high sensitivity to detect SIF, these regions are also largely influenced by atmospheric effects. Therefore, an accurate Atmospheric Correction (AC) process is required to measure SIF from oxygen bands. In this regard, the suitability of a two-step approach, i.e., first an AC and second a Spectral Fitting technique to disentangle SIF from reflected light, has been evaluated. One of the advantages of the two-step approach resides in the derived intermediate products provided prior to SIF estimation, such as surface apparent reflectance. Results suggest that errors introduced in the AC, e.g., related to the characterization of aerosol optical properties, are propagated into systematic residual errors in the apparent reflectance. However, of interest is that these errors can be easily detected in the oxygen bands thanks to the high spectral resolution required to measure SIF. To illustrate this, the predictive power of the apparent reflectance spectra to detect and correct inaccuracies in the aerosols characterization is assessed by using a simulated database with SCOPE and MODTRAN radiative transfer models. In 75% of cases, the aerosol optical thickness, the Angstrom coefficient and the scattering asymmetry factor are corrected with a relative error below of 0.5%, 8% and 3%, respectively. To conclude with, and in view of future SIF monitoring satellite missions such as FLEX, the analysis of the apparent reflectance can entail a valuable quality indicator to detect and correct errors in the AC prior to the SIF estimation.

Algorithm for Recovery of Integrated Water Vapor Content in the Atmosphere over Land Surfaces Based on Satellite Spectroradiometer Data

An algorithm is proposed for making charts of the distribution of water vapor in the atmosphere based on multispectral images of the earth by the Ocean and Land Color Instrument (OLCI) on board of the European research satellite Sentinel-3. The algorithm is based on multiple regression fits of the spectral brightness coefficients at the upper boundary of the atmosphere, the geometric parameters of the satellite location (solar and viewing angles), and the total water vapor content in the atmosphere. A regression equation is derived from experimental data on the variation in the optical characteristics of the atmosphere and underlying surface, together with Monte-Carlo calculations of the radiative transfer characteristics. The equation includes the brightness coefficients in the near IR channels of the OLCI for the absorption bands of water vapor and oxygen, as well as for the transparency windows of the atmosphere. Together these make it possible to eliminate the effect of the reflection spectrum of the underlying surface and air pressure on the accuracy of the measurements. The algorithm is tested using data from a prototype OLCI, the medium resolution imaging spectrometer (MERIS). A sample chart of the distribution of water vapor in the atmosphere over Eastern Europe is constructed without using subsatellite data and digital models of the surface relief. The water vapor contents in the atmosphere determined using MERIS images and data provided by earthbound measurements with the aerosol robotic network (AERONET) are compared with a mean square deviation of 1.24 kg/m2.

X-ray Photoelectron spectroscopic and Raman spectroscopic study of bayldonite from Wheal Carpenter, Cornwall, UK

Bayldonite [Cu3Pb(AsO4)2(OH)2], Wheal Carpenter (Cornwall, UK) was studied by X-ray Photoelectron Spectroscopy and Raman Microscopy. X-ray Photoelectron Spectroscopy revealed single copper, lead and arsenic positions in the crystal structure. Two oxygen bands with a 1:4 ratio were associated oxygen positions in arsenate- and hydroxyl-groups, excluding the presence of acidic arsenate groups. The relatively large difference in binding energy for the two oxygen bands was interpreted as being due to the dynamic Jahn-Teller distortion of the copper octahedral in the bayldonite crystal structure. Raman microscopy showed bands at 804 and 837 cm−1 assigned to arsenate antisymmetric stretching mode and the symmetric stretching mode. Supported by the X-ray Photoelectron Spectroscopic results the bands at 726, 761, 822 and 886 cm−1 were assigned to copper-hydroxyl modes. Bands around 497 cm−1 were assigned to the arsenate antisymmetric bending modes and around 427 cm−1 to the symmetric bending modes. The 539 cm−1 band was associated with a copper-hydroxyl stretching mode or another υ4. The region 250–400 cm−1 showed sharp bands at 313 and 328 cm−1 with weaker bands at 298 and 342 cm−1 assigned to copper-oxygen and/or lead-oxygen stretching modes.

Microwave Radiometric Complex for Studying the Thermal Structure of the Earth’s Atmosphere

We describe a microwave radiometric complex intended for remote passive monitoring of the atmospheric temperatures from the Earth’s surface. The complex consists of three spectroradiometers operating in a frequency range of 50–60 GHz, which covers the central part of the absorption band of molecular oxygen and its low-frequency slope. The radiometers have different spectral resolutions and allow one to simultaneously study the thermal structure of the surface air, the free troposphere, and the stratosphere. To ensure internal calibration of the intensity of the received atmospheric radiation, a built-in device of the modulator-calibrator type on the basis of the Schottky-barrier GaAs diodes is used. The complex is equipped with an automated system to control the measurement process, calibration, and preliminary data processing. Using the microwave sensing results, we intend to retrieve the atmospheric temperature profiles in an altitude interval of 0.05–55 km on the basis on the Bayesian approach to solving ill-posed inverse problems.

Pressure dependence of the Raman signal intensity in high‐pressure gases

At present gas analysis based on Raman, spectroscopy is actively developed. In most cases, to achieve the required Raman signal intensity, compression of the gas medium is used. However, in comparison with normal conditions, the character of motion of molecules and their electric properties change in high‐pressure gas media, thereby violating a linear dependence of the Raman signal intensity on the concentration of molecules and the gas pressure. In the present work, a theoretical model is presented that describes the Raman signal intensity as a function of the pressure of the gas medium considering the compressibility factor, the internal field factor, and the instrumental factor. To verify the model, changes in the Raman signal intensities of vibrational bands of nitrogen and oxygen in the pressure range 1–80 atm and carbon dioxide in the pressure range 1–60 atm are investigated. Under these conditions, we observe a deviation of ~3% from a linear dependence for nitrogen, ~7% for oxygen and ~80% for carbon dioxide, which is in good agreement with the theoretical model. Raman shifts, half‐widths of Q‐branches of vibrational bands ν1 (and 2ν2 for carbon dioxide) of these molecules and also ratio of integral intensities I(2ν2)/I(ν1) for carbon dioxide under these conditions are investigated. Copyright © 2016 John Wiley & Sons, Ltd.

Substitution Effects on Rare-Earth Ions-Doped Nickel-Zinc Ferrite Nanoparticles

Rare-earth ions (RE3+)-doped Ni-Zn ferrite nanoparticles with a structural formula of Ni0.5Zn0.5Fe1.8RE0.2O4 (RE3+ = Nd, Ce, La and Pr) were synthesized at room temperature by a sol-gel auto-combustion method. The structural and magnetic properties of Ni-Zn ferrite samples were carried out by XRD, vibrating sample magnetometer (VSM), field emission scanning electron microscopy (FE-SEM) and FT-IR spectroscopy. XRD pattern of Ni-Zn ferrite revealed that all the diffraction planes are in agreement with cubic spinel phase and the addition of Fe2O3 phase was also observed. In the case of RE ions-doped Ni-Zn ferrite in addition to the Fe2O3 phase, very low intensity peaks corresponding to some secondary phase are also present. The average crystallite sizes were found to be from 42 to 56 nm using the Scherer formula. The lattice constant (a) values are gradually decreased from 8.378 to 8.349 A with different substitutions of RE3+ ions in the Ni-Zn ferrite samples. VSM analysis revealed that saturation magnetization values are decreased and coercivity values are increased with substitution of different RE3+ ions. FE-SEM images exhibits that particles are spherical in shape. FT-IR interpretation revealed that two main metal oxygen bands (564 and 411 cm−1) are observed in all the substituted Ni-Zn ferrite samples.

Emission spectra of noble gases and their mixtures under ion beam excitation

AbstractThe luminescence spectra of noble gases and their binary mixtures were measured using heavy ion beam excitation from a DC-60 accelerator. Spectra were measured in the range of 200–975 nm; the gas spectra were dominated by lines ofp–sandd–patomic transitions; in neon and argon, lines from atomic oxygen, N2, N2+, and OH radical bands were also observed. The ultraviolet region of the spectra was represented by a “third continuum” of noble gases. In krypton, the band of the KrO excimer molecule with a maximum at 557 nm was also observed. The maxima of the heteronuclear ionic molecules bands were located at wavelengths of 329 and 506 nm (Ar–Xe), 491 nm (Kr–Xe), and 642 nm (Ar–Kr). The relative intensities of the 2p–1stransitions of the noble gases atoms were measured and are discussed.

Effect Of Annealing On The Behavior Of Oxygen Dissolved In Germanium And Optical Properties Of Single Crystals

<p>The annealing effect in the temperature range from 350 to 450 °С on the behavior of interstitial oxygen О<sub>i</sub> dissolved in germanium and on optical properties of single crystals has been investigated by Fourier transformed infrared spectrometry. It was found that oxygen band maximum of 843 cm<sup>–1</sup> shifted toward the 856 cm<sup>−1</sup> with oxygen concentration increasing after annealing at the oxygen partial pressure ranged from 1 to 10<sup>3</sup> Pа. The annealing at lower values led to the decrease of 843 cm<sup>–1</sup> band intensity due to the formation of thermal donors (TD) on the basis of dissolved oxygen atoms О<sub>i</sub>. It was established that TD formation and the decrease of unbound oxygen concentration affected optical properties of the crystals.</p>

(Invited) Current Stage of the Investigation of the Composition of Oxygen Precipitates in Czochralski Silicon Wafers

The oxygen precipitates formed in Czochralski (CZ) silicon wafers in consequence of the thermal treatment were investigated since many decades. The main reason why so much effort was directed towards these defects was the impact which they have on integrated circuits and properties of silicon wafer itself. Oxygen precipitates can increase the resistivity of CZ silicon, change the wafer strength and cause warpage of the wafers. It was also demonstrated that metal impurities can be effectively trapped at oxygen precipitates in the process of gettering, what is a huge advantage. All these features of the oxygen precipitates require the control of precipitation in the production process of silicon devices. However, this cannot be optimally executed if the features of oxygen precipitates like their composition are not fully known. In spite of the wide knowledge of oxygen precipitation, the composition of oxygen precipitates SiO x still remains under ongoing discussion. This is due to the different x values varying from x=1 to x=2 which can be found in the literature. In this work, we look on the current stage of the investigation on the composition of oxygen precipitates obtained with the help of different techniques. Moreover, we present our recent investigation on the composition of oxygen precipitates carried out by means of energy dispersive X-ray spectroscopy (EDX), electron energy loss spectroscopy (EELS) and Fourier transform infrared spectroscopy (FTIR). The FTIR spectra measured at liquid helium temperature will be compared with the spectra simulated on the basis of experimental results obtained by scanning transmission electron microscopy (STEM). The EDX gives direct information about the composition of oxygen precipitates. However, the analysis of the EDX spectrum requires a special calibration. This is due to the limitation of EDX for light elements like oxygen. The intensity of characteristic X-rays of oxygen depends on the thickness of TEM lamellae. Therefore, in this work we measured a thermally grown SiO2 layer at different thickness of TEM lamellae in order to determine the influence of the lamellae thickness on the intensity of oxygen characteristic X-rays. After doing this, we measured the composition of oxygen precipitates located at very thin TEM lamellae. The results shown that x is in the range between 1.8 and 1.9 (1). To make sure that the EDX results are correct EELS measurements were carried out. EELS is a complementary method to EDX. It allows to avoid the limitation of EDX in the measurement of the composition of oxygen precipitate especially in the case if the precipitate does not go through the TEM lamellae. Deconvoluting the characteristic plasmons of Si, SiO2 and suboxides in the electron energy loss spectra we found that the oxygen precipitate consist of SiO2 and it is coated by thin 2-3nm SiO layer (2). Finally, we investigated the composition of oxygen precipitates by FTIR. The absorption band of oxygen precipitates were observed in FTIR spectra measured at liquid helium temperature. The position and the shape of the bands fit very well to the simulated spectra. The simulation of the spectra was conducted on the basis of the effective medium theory (EMT) where we considered SiO2 spheroids coated by SiO layers embedded in a Si matrix. In summary, the composition of oxygen precipitates was investigated by EDX, EELS and FTIR whereby the first two methods are direct methods and the latter one is an indirect method. All methods delivered similar results. Hence, we can conclude that the oxygen precipitates consist of a SiO2 core which is coated by an SiO layer. References 1D. Kot, G. Kissinger, M. A. Schubert, M. Klingsporn, A. Huber, and A. Sattler, Phys. Status Solidi RRL 9, 405 (2015). 2G. Kissinger, D. Kot, M. Klingsporn, M.A. Schubert, A. Sattler, T. Müller, ECS J. Solid State Sci. Technol. 4 (9), N124-N129 (2015).

Gyrophase bunched ions in the plasma sheet

Gyrophase bunched ions were first detected in the upstream region of the Earth’s bow shock in the early 1980s which is formed by the microphysical process associated with reflected solar wind ions at the bow shock. Inside the magnetosphere, the results of computer simulations demonstrated that nonlinear wave-particle interaction can also result in the gyrophase bunching of particles. However, to date direct observations barely exist regarding this issue occurred inside the magnetosphere. In this paper, we report for the first time an event of gyrophase bunched ions observed in the near-Earth plasma sheet. The nongyrotropic distributions of ions were closely accompanied with the electromagnetic waves at the oxygen cyclotron frequency. The phase of bunched ions and the phase of waves mainly have very narrow phase differences (<30°) when the O+ band waves are remarkably enhanced, which indicates that the wave and particle are closely corotating. The “electric phase bunching” is considered to be a possible mechanism for the formation of the gyrophase bunched distributions in this case. The MVA analysis suggests that the oxygen band waves possess left helicity with respect to the propagation direction, which agrees with the characteristic of electromagnetic ion cyclotron waves. The observation of O+ ions composition suggests that the oxygen band waves are excited due to the enhancements of the O+ ion density. This study suggests that the gyrophase bunching is a significant nonlinear effect that exists not only in the bow shock but also in the inner magnetosphere.