Concentrations Of Neutral Particles Research Articles

Mechanism of Improving Etching Selectivity for E-Beam Resist AR-N 7520 in the Formation of Photonic Silicon Structures

The selectivity of the reactive ion etching of silicon using a negative electron resist AR-N 7520 mask was investigated. The selectivity dependencies on the fraction of SF6 in the feeding gas and bias voltage were obtained. To understand the kinetics of passivation film formation and etching, the type and concentration of neutral particles were evaluated and identified using plasma optical emission spectroscopy. Electron temperature and electron density were measured by the Langmuir probe method to interpret the optical emission spectroscopy data. A high etching selectivity of 8.0 ± 1.8 was obtained for the etching process. The optimum electron beam exposure dose for defining the mask was 8200 pC/m at 30 keV.

The Influence of Small F2, H2, and HF Additives on the Concentration of Active Particles in Tetrafluoromethane Plasma

A comparative study of the effect of small (up to 20%) substituting additives F2, H2, and HF on the kinetics and stationary concentrations of neutral particles in 50% CF4 + 50% Ar plasma under the typical conditions of reactive ion etching (RIE) of silicon and its compounds is carried out. It is shown that the vari-ation of the CF4/F2 and CF4/H2 ratios leads to opposite, interrelated, and nonadditive changes in the con-centrations of fluorine atoms and fluorocarbon radicals. This provides wide ranges of regulation of the etch-ing rate and polymerization capacity with the minimal disturbance of the parameters of the electronic and ionic components of the plasma. In contrast, the CF4/HF relation has the minimal effect on the rate of sur-face polymerization, but noticeably changes the concentration of fluorine atoms. Thus, there is a selective effect on the rate of the heterogeneous chemical reaction.

Atmospheric waves disturbances from the solar terminator according to the VLF radio stations data

The perturbations from the solar terminator in the range of acoustic-gravity waves (AGWs) periods from 5 min to 1 h were analysed with the use of measurements of VLF radio signals amplitudes on the European radio path GQD–A118 (Great Britain–France). These observations provide information on the propagation of waves at altitudes near the mesopause (∼90 km), where VLF radio waves are reflected. On the considered radio path a systematic increase in fluctuations in the amplitudes of radio waves was observed within a few hours after the passage of the evening terminator. For April, June, October 2020 and February 2021 events, the distribution of the number of wave perturbations with large amplitudes over AGWs time periods has been studied. Our results show that the evening terminator for different seasons is dominated by waves in the range of periods of 15–20 min. The amplitudes of the AGWs from the terminator at the heights of the mesosphere (fluctuations in the concentration of neutral particles, velocity components and vertical displacement of the volume element) are approximately determined by the fluctuations of the amplitudes of the VLF radio signals. The amplitudes of the AGWs on the terminator are 12–14% in relative concentration fluctuations, which correspond to the vertical displacement of the atmospheric gas volume of 1.1–1.3 km. Based on the analysis of the AGW energy balance equation, it was concluded that the waves predominantly propagate in a quasi-horizontal direction at the terminator. The possibility of studying the long-term changes in the mesosphere parameters using fluctuations in the amplitudes of VLF radio waves at the terminator is shown.

Quantitatively controlled electrophoretic deposition of nanocrystal films from non-aqueous suspensions

This study presents a novel method to correlate the mass and charge transfer kinetics during the electrophoretic deposition of nanocrystal films by using a purpose-built double quartz crystal microbalance combined with simultaneous current-measurement. Our data support a multistep process for film formation: generation of charged nanocrystal flux, charge transfer at the electrode, and polarization of neutral nanocrystals near the electrode surface. The polarized particles are then subject to dielectrophoretic forces that reduce diffusion away from the interface, generating a sufficiently high neutral particle concentration at the interface to form a film. The correlation of mass and charge transfer enables quantification of the nanocrystal charge, the fraction of charged nanocrystals, and the initial sticking coefficient of the particles. These quantities permit calculation of the film thickness, providing a theoretical basis for using concentration and voltage as process parameters to grow films of targeted thicknesses.

Analysis of acoustic-gravity waves in the mesosphere using VLF radio signal measurements

A simple method has been proposed to determine acoustic-gravity wave (AGW) characteristics at lower ionosphere (mesosphere) heights by measuring VLF radio signal amplitudes. For relatively short radio paths (less than ∼ 1500 km long) we obtained the simple relations for estimation of AGW neutral density fluctuation and for vertical displacement of an elementary volume of atmospheric gas. The proposed method has been verified by using VLF radio wave amplitude measurements on several radio paths. AGW properties based on these measurements are approximately calculated at heights of radio signal reflection. The relative fluctuation of 3%–6% of neutral particle concentration and elementary volume displacement of 0.6–1.2 km have been obtained. These results are in good agreement with AGW theory in the Earth atmosphere.

Analysis of Acoustic-Gravity Waves in the Mesosphere Using VLF Radio Signal Measurements

A simple method has been proposed to determine acoustic-gravity wave (AGW) characteristics at lower ionosphere (mesosphere) heights by measuring VLF radio signal amplitudes. For relatively short radio paths (less than ~ 2000 km long) it has been obtained the simple relations for estimation of AGW neutral density fluctuation and for vertical displacement of an elementary volume of atmospheric gas. The proposed method has been verified by using VLF radio wave amplitude measurements on several radio paths. AGW properties based on these measurements are approximately calculated at heights of radio signal reflection. The relative fluctuation of 3—6 % of neutral particle concentration and elementary volume displacement of 0.6--1.2 km have been obtained. These results are in good agreement with AGW theory in the Earth atmosphere.

The Influence of Supersonic Gas Stream on Spatial Structure of Glow Discharge

This work investigates into the properties of longitudinal glowing discharge in supersonic gas stream between central body and reducer. It has been established that the properties of discharge spatial localization, intensity of radiation, formation of near-electrode areas directly depend on arrangement of supersonic stream. This work analyzes the properties of gas stream in expanding area of supersonic nozzle, pressure recovery in reducer. It has been experimentally established that gas circulation at supersonic speed in the area of glowing discharge makes it possible to control the distribution of concentration of neutral particles in interelectrode space as well as localization of near-electrode zones and positive glow.

Internal characteristics of distribution of glow discharge at supersonic speed gas flow in the positive column area

A discharge device providing the ability to create an area in the interelectrode space with a controlled concentration of neutral particles due to the supersonic flow arrangement has been developed and implemented. The possibility to control the internal discharge parameters distribution by supersonic gas flow arrangement in a limited area of the glow discharge is shown experimentally.

Features of the Kinetics of Bulk and Heterogeneous Processes in CHF3 + Ar and C4F8 + Ar Plasma Mixtures

We carry out a comparative study of the kinetics of plasma-chemical processes and plasma composition in CHF3 + Ar and C4F8 + Ar mixtures under the conditions of a high-frequency (13.56 MHz) induction discharge. Using diagnostic methods and plasma modeling, the general features and differences of the plasma’s electrophysical parameters in the studied systems are established together with the key bulk processes that determine the stationary concentrations of neutral particles. Тhe CHF3 + Ar system in the range 0–75% Ar is shown to be characterized by lower values of the flux densities of the fluorine atoms and polymer of the forming radicals. Model analysis of the kinetics of the heterogeneous processes (etching, polymerization, degradation of the polymer film) confirmed the advantage of the C4F8 + Ar system of silicon etching anisotropy and etching selectivity compared to the SiO2/Si system.

Latitude variability of acoustic-gravity waves in the upper atmosphere based on satellite data

Based on satellite measurements, we investigated the properties of acoustic-gravity waves in different geographical areas of the Earth’s upper atmosphere. To study wave activity at high latitudes, we used the concentration of neutral particles measured by the low-altitude polar satellite Dynamic Explorer 2 and measurements from the equatorial satellite Atmosphere Explorer-E for analysis of waves at low latitudes. In the range of heights 250–400 km, there are observed latitudinal variations of amplitudes, together with variations in the morphological and spectral properties of acoustic-gravity waves. In the polar regions of thermosphere, the wave amplitudes amount to 3–10% in terms of relative variations of density and do not exceed 3% at low and middle latitudes. At low latitudes, regular fluctuations induced by the solar terminator are clearly seen with a predominant wave mode moving synchronously with terminator. Moreover, at low and middle latitudes, there are observed sporadic local wave packets of small amplitudes (1–2%) that can have origins of various natures. We also investigated the relation between some of the observed wave trains and the earthquakes.

Temporal evolution of charged and neutral nanoparticle concentrations during atmospheric new particle formation events and its implications for ion-induced nucleation

Time series of nanoparticle number concentration during new particle formation (NPF) events in the urban environment of Brisbane, Australia, showed that the formation of charged particles often occurred before that of neutral particles. We monitored 241 days during the calendar year 2012 over which NPF events were observed on 108 days. We studied the times at which the charged and neutral particle concentrations in the size range 1.8–3.2 nm reached their peak values and found that they were clearly different in 50 events with the peak neutral particle concentration lagging behind the charged particle concentration during 42 of these events with a mean time lag of 24±12 min. While the charged particles were more likely to form before the neutral particles, once formed, the growth rate of the particles did not depend on their charge. While ion-induced nucleation is not the dominant mechanism of NPF in the atmosphere, our observations suggest that the presence of ions in the atmosphere plays a role that cannot be ignored.

СПУТНИКОВЫЕ ИССЛЕДОВАНИЯ ИОНОСФЕРНЫХ ПРОЯВЛЕНИЙ РАСПРОСТРАНЕНИЯ АКУСТИКО-ГРАВИТАЦИОННЫХ ВОЛН

The response of the ionospheric plasma on the propagation of acoustic-gravity waves (AGW) studied at altitudes of 250 − 350 km using the satellite Dynamics Explorer 2 measurements. Wave perturbations are analyzed according to simultaneously measured data of temperature, concentration and velocity of neutral particles and ions at high and middle latitudes. The following features of ionospheric manifestations of acoustic-gravity waves have been established: 1) relative variations of temperature of neutral particles and ions are roughly the same for these latitudes, except for the regions of auroral ovals; 2) variations in total plasma concentration are antiphase to those in concentration of neutral particles, their relative amplitude being severatimes larger than the amplitude of neutral particles; 3) concentration of molecular ions is in phase with neutral particles;4) vertical velocity of the ions at high latitudes is consistent with that of neutral particles, thus showing their mutual movement along the magnetic field lines. In the high-latitude ionosphere, toseparate the ionospheric manifestations of acoustic-gravity waves from other types of disturbances, the simultaneous analysis of different parameters should be used. Key words: acoustic-gravity waves, moving ionospheric disturbances, auroral zone, ionosphere, atmosphere Manuscript submitted 13.05.2014 Radio phys. radio astron. 2014, 19(3): 206-216 REFERENCES 1. BURMAKA, V.P., TARAN, V. I., andCHERNOGOR, L. F., 2005. Results of the study of wave disturbances in the ionosphere by incoherent scattering. Uspehi sovremennoi radioelectroniki . no. 3, pp. 4–35 (in Russian). 2. LIZUNOV, G. V. and FEDORENKO, A. K., 2006. Atmospheric Gravity Waves Generation by Solar Terminator According to "Atmosphere Explorer-E" Satellite Data. Radio Phys. Radio Astron. , vol. 11, no. 1, pp. 49–62 (in Russian). 3. FEDORENKO, A. K., 2009. Determination Characteristics of Atmospheric Gravity Waves in the Polar Regions Using Mass-Spectrometer Satellite Measurements. Radio Phys. Radio Astron ., vol. 14, no. 3, pp. 254–265 (in Russian). 4. CARIGNAN, G. R., BLOCK, B. P., MAURER, J. C, HEDIN, A. E., REBER, C. A., and SPENCER, N. W., 1981.The neutral mass Spectrometron Dynamics Explorer. Space Sci. Instrum . vol. 5, pp. 429–441. 5. SPENCER, N. W., WHARTON, L. E., NIEMANN, H. B., HEDIN, A. E., CARIGNAN, G. R., and MAURER, J. C., 1981.The Dynamics Explorer wind and temperature spectrometer. Space Sci. Instrum. , vol. 5, pp. 417–428. 6. DUDIS, J. J. and REBER, C. A., 1976. Composition effects in thermospheric gravity waves. Geophys. Res. Lett ., vol. 3, No. 12, pp. 727–730. DOI: https://doi.org/10.1029/GL003i012p00727 7. RATCLIFFE, J. A., 1975. An Introduction to the Ionosphere and Magnetosphere . Moscow: Mir Publ. (in Russian). 8. BRYUNELLI, B. E. and NAMGALADZE, A. A., 1988. Physics of the Ionosphere . Moscow: Nauka Publ. (in Russian). 9. LYATSKY,W. B. and MALTSEV, Y. P., 1983. Magnetosphere-Ionosphere Interaction . Moscow: Nauka Publ. (in Russian).

Influence of a neutral component on the liquid–vapor coexistence and the surface tension of an ionic fluid

We investigate the effect that a neutral component has on the liquid–vapor coexistence curve and the surface tension of an ionic fluid. Molecular dynamics simulations of a ternary mixture containing ions and neutral particles are performed. We found that the vapor branch is dominated by neutral particles and the liquid phase by ions. A comparison of our results and those of the soft primitive model (SPM) of a pure ionic fluid is made. For a fraction of neutral particles x0=0.2, the density of the liquid phase is the same as that of the SPM, except for temperatures close to the critical point. As compared to the SPM, the surface tension takes the same values for low temperatures. For high temperatures, deviations of about 30% are observed. The estimated critical temperature and density of this ternary mixture are higher than those of the pure ionic fluid. In a preliminary study our results indicate that as x0 increases the vapor density shifts to higher values, basically due to the concentration of neutral particles in that region. The liquid branch changes slowly until x0=0.5, from that concentration of neutral particles, the liquid density decreases considerably. For high concentrations of the neutral component, the repulsive interactions dominate the system and the coexistence region in strongly reduced. Concerning the surface tension, we observed an increase with the fraction of neutral particles until x0=0.5, from that value it reduces significantly, also as an indication of the strong repulsion in the system.

Physics of a fusion plasma boundary layer

A theoretical and computational study has been made of plasma phenomena occurring when a hot, dense plasma containing a transverse magnetic field is brought into sudden contact with a cold metal wall; thermal and magnetic boundary layers develop. The time evolution of the plasma temperature, pressure, the charged and neutral particle concentration, magnetic and electric field strengths, and the plasma current density in the neighborhood of the solid surface are investigated. The rate of energy transfer from the plasma to the wall is calculated, and the conditions under which wall surface melting occurs are estimated. The physical conditions previously studied experimentally by Feinberg, are calculated, and the predicted rate of energy transfer from the plasma to the wall is found to be in good agreement.

EFFECTS PRODUCED BY AN ARTIFICIAL SATELLITE RAPIDLY MOVING IN THE IONOSPHERE OR IN AN INTERPLANETARY MEDIUM

I. Introduction 13 1. Formulation of Problem, Initial Data 13 2. Brief Summary of the Literature 16 II. Structure of Disturbed Region in the Vicinity of a Body Moving Rapidly in a Plasma 17 3. Initial Equations 17 4. Disturbances of Neutral-particle Concentration 18 5. Influence of Magnetic Field on the Ion-concentration Disturbance 21 6. Electric Field Around a Body 25 III. Scattering of Radiowaves by the of a Body Moving Rapidly in a Plasma 29 7. Formulation of the Problem 29 8. Calculation of the Fourier Components of the Electron-concentration Disturbance 30 9. Effective Cross Section for the Scattering by the Trail of the Body 34 10. Character of the Field of the Scattered Wave at the Point of Observation 38 11. Effective Scattering Cross Section in the Absence of an External Magnetic Field 40 12. Disturbances Brought About by a Point-like Body 41 IV. Particle Flux in the Vicinity of the Body 42 13. General Remarks 42 14. Flux of Neutral Particles in the Vicinity of a Rapidly Moving Body 43 V. Conclusion 45 Cited Literature 45

Perturbations in the Ionosphere Caused by a Moving Body

Abstract : Calculation of the magnitude of perturbations is accomplished. The changes in concentrations of neutral particles in the vicinity of a moving body are calculated. A problem is solved for the concentration of electrons and ions; also the magnitude of the electric field was determined. An analysis is made of the problem concerning the possibility of exciting longitudinal waves in plasma by a stream of ions reflected from the body. (Author)

The collision frequency of electrons in the ionosphere

Theoretical analysis shows that the electron collision frequency in the ionosphere depends on the neutral particle concentration in Regions D and E and on the electron concentration in Region F. Any atmospheric model above the E layer cannot, therefore, be based on the electron collision frequency with neutral particles.