Diagnostics Of Low-temperature Plasma Research Articles

Brewster angle-cavity ringdown spectroscopy for low temperature plasma measurements in multiphases

We report on the development of a Brewster angle-cavity ringdown spectroscopy (BA-CRDS) system for low temperature plasma diagnostics. The system can measure gas species in solutions, with a detection limit (minimum detectable absorbance) of 9.1 × 10−5, which is equivalent to a detection limit of 0.04 parts per billion for measuring OH radicals in water at 308 nm. With higher reflectivity ringdown mirrors and improved design of a Brewster angle cell, the detection limit can potentially be up to 10−6 or lower. In this exploratory study, the absorption cross sections of HgBr2 and H2O2 in the aqueous phase at 256 nm are measured to be (1.8 ± 0.1) × 10−18 cm2 and (5.2 ± 0.5) × 10−20 cm2, respectively. Furthermore, temporal profiles of absorbance from distilled water, HgBr2, and H2O2 solutions when interacting with a helium atmospheric plasma jet are individually characterized at different plasma powers, gas flow rates, and/or solute concentrations. The observed linear temporal profiles of absorbance from the plasma-interacted water suggest formation of H2O2 from plasma-generated OH radicals, while the nonlinear temporal profiles from the plasma-treated HgBr2 solutions reveal possible removal of HgBr2 by OH radicals. Our results demonstrate that the new BA-CRDS system is a powerful tool for quantification of reactive plasma species in multiphases or other complex settings.

XIII Scientific Technical Conference on Low Temperature Plasma During the Deposition of Functional Coatings

In the city of Kazan from November 2 to November 4, 2021 on the basis of the Kazan Federal University hosted the XIII Scientific Technical Conference on Low Temperature Plasma during the Deposition of Functional Coatings.One of the main tasks of the conference is to discuss and develop the fundamental principles of plasma deposition of functional coatings. Conference papers were presented in the following areas:- Physics of gas discharge;- Physical processes in low-temperature plasma when applying functional coatings;- Thermodynamic, portable and optical properties of low-temperature plasma in coating processes;- Interaction of plasma and high-energy ion beams with a solid;- Combustion processes and heat and mass transfer in multiphase media;- Dusty plasma;- Plasma chemistry. Electrochemistry;- Diagnostics of low-temperature plasma;- Characteristics of coatings obtained using low-temperature plasma;- Application of ion-plasma coatings.Within the framework of the conference, a school for young scientists is held, lectures by leading scientists and specialists in the field of low-temperature plasma application are held.Gas-discharge plasma is widely used in various fields of science and technology. Plasma is used in industry, medicine, ecology and is the basis of various devices and technologies, for example, it is used in the technology of applying functional coatings.The friendly atmosphere at the XIII Scientific Technical Conference on Low Temperature Plasma during the Deposition of Functional Coatings allowed it to become an excellent platform for the exchange of experience and generation of new ideas in the field of physics and the use of low-temperature plasma.This year, studies of gas-discharge phenomena in electrolytes, studies on the use of ultrasound to obtain metal powder in a plasma discharge electrolyte, calculations of electro-contact firing of steel powders were presented. A series of works is devoted to heat and mass transfer in multiphase media and the study of materials and coatings obtained using low-temperature plasma.List of Organizing Committee, Scientific Committee are available in this Pdf.

Low-Temperature Plasma Diagnostics to Investigate the Process Window Shift in Plasma Etching of SiO2.

As low-temperature plasma plays an important role in semiconductor manufacturing, plasma diagnostics have been widely employed to understand changes in plasma according to external control parameters, which has led to the achievement of appropriate plasma conditions normally termed the process window. During plasma etching, shifts in the plasma conditions both within and outside the process window can be observed; in this work, we utilized various plasma diagnostic tools to investigate the causes of these shifts. Cutoff and emissive probes were used to measure the electron density and plasma potential as indicators of the ion density and energy, respectively, that represent the ion energy flux. Quadrupole mass spectrometry was also used to show real-time changes in plasma chemistry during the etching process, which were in good agreement with the etching trend monitored via in situ ellipsometry. The results show that an increase in the ion energy flux and a decrease in the fluorocarbon radical flux alongside an increase in the input power result in the breaking of the process window, findings that are supported by the reported SiO2 etch model. By extending the SiO2 etch model with rigorous diagnostic measurements (or numerous diagnostic methods), more intricate plasma processing conditions can be characterized, which will be beneficial in applications and industries where different input powers and gas flows can make notable differences to the results.

Population Kinetics Modeling of Low-Temperature Argon Plasma

Optical emission spectroscopy has been widely used in low-temperature argon plasma diagnostics. A coronal model is usually used to analyze the measured line ratios for diagnostics with a single temperature and density. However, many plasma processing conditions deviate from single temperature and density, optically thin conditions, or even coronal plasma conditions due to cascades from high-lying states. In this paper, we present a collisional-radiative model to investigate the validity of coronal approximations over a range of plasma conditions of Te = 1–4 eV and Ne = 108–1013 cm−3. The commonly used line ratios are found to change from a coronal limit where they are independent of Ne to a collisional-radiative regime where they are not. The effects of multiple-temperature plasma, radiation trapping, wall neutralization, and quenching on the line ratios are investigated to identify the plasma conditions under which these effects are significant. This study demonstrates the importance of the completeness of atomic datasets in applying a collisional-radiative model to low-temperature plasma diagnostics.

Probes to measure kinetic and magnetic phenomena in plasmas.

Diagnostic tools are of fundamental importance in experimental research. In plasma physics, probes are usually used to obtain the plasma parameters, such as density, temperature, electromagnetic fields, and waves. This Review focuses on low-temperature plasma diagnostics where in situ probes can be used. Examples of in situ and remote diagnostics will be shown, proven by many experimental verifications. This Review starts with Langmuir probes and then continues with other diagnostics such as waves, beams, and particle collectors, which can provide high accuracy. A basic energy analyzer has been advanced to measure distribution functions with three-dimensional velocity resolution, three directions in real space and time resolution. The measurement of the seven-dimensional distribution function is the basis for understanding kinetic phenomena in plasma physics. Non-Maxwellian distributions have been measured in magnetic reconnection experiments, scattering of beams, wakes of ion beams, etc. The next advance deals with the diagnostics of electromagnetic effects. It requires magnetic probes that simultaneously resolve three field components, measured in three spatial directions and with time resolution. Such multi-variable data unambiguously yield field topologies and related derivatives. Examples will be shown for low frequency whistler modes, which are force-free vortices, flux ropes, and helical phase rotations. Thus, with advanced probes, large data acquisition and fast processing further advance in the fields of kinetic plasma physics and electromagnetic phenomena can be expected. The transition from probes to antennas will also be stimulated. Basic research with new tools will also lead to new applications.

XII Scientific Technical Conference On Low Temperature Plasma During The Deposition Of Functional Coatings

In the city of Kazan from November 10 to November 12, 2020 on the basis of the Kazan Federal University hosted the XII Scientific Technical Conference on Low Temperature Plasma during the Deposition of Functional Coatings.One of the main tasks of the conference is to discuss and develop the fundamental principles of plasma deposition of functional coatings. Conference papers were presented in the following areas:– Physics of gas discharge;– Physical processes in low-temperature plasma when applying functional coatings;– Thermodynamic, portable and optical properties of low-temperature plasma in coating processes;– Interaction of plasma and high-energy ion beams with a solid;– Combustion processes and heat and mass transfer in multiphase media;– Dusty plasma;– Plasma chemistry. Electrochemistry;– Diagnostics of low-temperature plasma;– Characteristics of coatings obtained using low-temperature plasma;– Application of ion-plasma coatings.Within the framework of the conference, a school for young scientists is held, lectures by leading scientists and specialists in the field of low-temperature plasma application are held.Gas-discharge plasma is widely used in various fields of science and technology. Plasma is used in industry, medicine, ecology and is the basis of various devices and technologies, for example, it is used in the technology of applying functional coatings.The friendly atmosphere at the XII Scientific Technical Conference on Low Temperature Plasma during the Deposition of Functional Coatings allowed it to become an excellent platform for the exchange of experience and generation of new ideas in the field of physics and the use of low-temperature plasma.List of Organizing Committee are available in this pdf.

Theoretical level energies, radiative lifetimes and transitions in W IX

The atomic states of the W IX (W8+) tungsten ion lying below the W9+ ionisation threshold have been studied theoretically, employing the multiconfiguration Dirac–Hartree–Fock method with configuration interaction. The level electronic structures and their energies are presented. The electric dipole (E1), magnetic dipole (M1), electric quadrupole (E2), and magnetic quadrupole (M2) radiative transitions have been computed in order to calculate the radiative lifetimes of given states. Transition wavelengths, energies, and decay rates are also presented for selected high-intensity E1 transitions. The configuration interaction method was applied to estimate electron correlation effects. The aim of the present research was to fill a lack of atomic data for low-charged tungsten ions, which may be useful in low-temperature plasma diagnostics and may form the base for collisional–radiative modelling of spectra for low-charged tungsten ions.

An optical trapping system for particle probes in plasma diagnostics.

We present one of the first experiments for optically trapping of single microparticles as probes for low temperature plasma diagnostics. Based on the dual laser beam, counter-propagating technique, SiO2 microparticles are optically trapped at very large distances in low-temperature, low-pressure rf plasma. External forces on the particle are measured by means of the displacement of the probe particle in the trap. Measurements can be performed during plasma operation as well as without plasma. The paper focuses on the optical setup and the verification of the system and its principle. Three examples for the particle behavior in the trapping system are presented: First, we measured the neutral gas damping as a verification of the technique. Second, an experiment without a plasma studies the changing particle charge by UV light radiation, and third, by moving the probe particle in the vertical direction into the sheath or into the plasma bulk, respectively, the acting forces on the probe particle are measured.

VIII All-Russian (with international participation) Conference on Low Temperature Plasma in the Processes of Functional Coating Preparation

Under the chairmanship of a member-correspondent of the Academy of Sciences of RT, Doctor of Technical Sciences, Professor N F Kashapov, in 2016 from 6 to 9 November in the Academy of Sciences of the Republic of Tatarstan, Kazan Federal University held the scientific-technical conference “Low-temperature plasma in a functional coating process” (with international participation).The modern development of technology requires a broad introduction to the industry of new efficient processes based on innovative achievements in the field of science and technology. One of the areas, significantly expands technological possibilities of material processing process, is the use of concentrated energy flows, which are prepared using a low-temperature plasma generators. In order to create conditions for the unification of Russian and foreign scientists, engineers and technologists in the solution of fundamental and applied problems in the fields of research processes applying functional coatings, plasma dynamics, plasma modification of materials of low-temperature plasma flows.Topics of the conference were oriented in the following directions:1. Gas discharge physics.2. Physical processes in low-temperature plasma in the deposition of functional coatings.3. Thermodynamic, portable and optical properties of low-temperature plasma in the coating process.4. Plasma chemistry. Electrochemistry.5. Combustion and heat and mass transfer in multi-phase media.6. Diagnostics of low-temperature plasma.7. Dusty plasma.8. Interaction of plasma and high-energy ion beams with a solid state. Laser plasma.9. Characterization of coatings produced using low-temperature plasma.10. Use of ion-plasma coatings.Presented posts set high scientific level of the conference. The reports correspond to the world level of science in the field of plasma physics. The conference was productive for the participants both in terms of familiarization with the new results, often from related fields, and in terms of establishing and strengthening contacts between scientists from different research centers. A large number of young participants testifies to the continuity of scientific traditions represented at the conference of scientific schools, the present and the relevance of these research schools.

Diagnostics of Low Temperature Plasma by CO Laser Radiation (5.0-7.5 μm)

A review of the work conducted in Gas Lasers Laboratory of P.N. Lebedev Physical Institute of the Russian Academy of Sciences and devoted to a research of the diagnostic of dynamics of small-signal gain, temperature and population of vibrational levels in the CO-containing gas mixtures excited by pulsed electron-beam sustained discharge is presented. With the help of laser probing techniques the nonlinear Zeeman splitting of the NO lines in a strong magnetic field was also investigated. The studies of gain of the train of nanosecond pulses allowed us to estimate the intensity of the gain saturation of the active medium of the pulsed electron-beam sustained discharge CO laser.

Neutral lithium spectral line 460.28 nm with forbidden component for low temperature plasma diagnostics of laser-induced plasma

We present the results of theoretical and experimental line shape study of the Li I 460.28nm line with a forbidden component in a low temperature laser-induced plasma. For this purpose a computer simulation method is used to calculate the overall line profile in the electron number density range of (0.5–11.0)×1016cm-3 and the electron temperature 5800K. The same computer simulation method is used to evaluate asymmetric profiles of the isolated Li I 497.17nm line in the same electron density range and for several electron temperatures between 3500K and 10300K. The results for the Li I isolated line are used together with two other theoretical calculations for independent electron density measurements in laser induced plasma. The electron temperatures in the range of 4000–7000K were determined from relative Li I line intensities using Boltzmann plot technique. The comparison between calculated profiles and experimental data for the Li I 460.28nm line with a forbidden component indicates that theoretical results can be used for electron density diagnostics in the aforementioned density range with an accuracy of ±10–15%. To facilitate the application of theoretical line profiles simple expressions are supplied.

Diagnostics of Low Temperature Plasmas by Optical Means

AbstractIn this paper a short overview of the diagnostics of low temperature plasmas by optical means is presented. It is described how the results of the optical measurements, namely the intensities and profiles of the spectral lines can be used for measuring the low temperature plasma parameters ‐ temperatures, electron density, plasma velocity, magnetic and electric field in the plasma etc. Discussed are the strengths and limitations of these methods (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Measurements of transition probabilities for two N I infrared transitions and their application for diagnostics of low temperature plasmas

Spectra emitted from a wall-stabilized arc, running in a gas mixture of helium, argon, nitrogen, oxygen and traces of hydrogen have been studied. Intensities of selected spectral transitions of neutral nitrogen and oxygen have been measured. Applying the Boltzmann plot method and using a reliable set of O I transition probabilities of spectral lines, originating from levels considerably spread in excitation energies, the temperatures of arc plasmas have been determined. Line intensities of two N I infrared transitions, originating from doubly excited terms 3p′ 2F o and 3p′ 2G have been measured. In order to obtain the corresponding transition probabilities ( A ki ) for these lines, intensities of other N I infrared lines, with well known transition probabilities (taken from recently published data by Wiese and Fuhr [W.L. Wiese and J.R. Fuhr, Improved critical compilations of selected atomic transition probabilities for neutral and singly ionized carbon and nitrogen, J. Phys. Chem. Ref. Data 36 (2007) 1287–1345] from National Institute of Standards and Technology — NIST) have been measured. For evaluation of the transition probabilities the temperatures obtained from the above mentioned O I Boltzmann plots have been used. The results agree satisfactorily with older data found in literature. The new A ki values for transitions involving the doubly excited levels, together with A ki values taken from the above mentioned NIST source (used for determination of the new A ki values), are proposed as a convenient set for determining temperatures of plasmas containing nitrogen atoms.

Transition probabilities for some infrared O I spectral lines—Application for determining excitation temperatures in low temperature plasmas

Intensities of selected spectral transitions of neutral oxygen emitted from a wall-stabilized arc have been measured. Applying reliable transition probability data taken from literature, Boltzmann plots have been constructed and the temperatures of the plasma have been obtained. At arc plasma conditions ensuring partial local thermal equilibrium, transition probabilities for 4 O I spectral lines from the near infrared spectral range have been obtained. These new results, together with data for two other studied O I spectral lines taken from the National Institute of Standards and Technology data base, are proposed as a suitable set of transition probabilities applicable for diagnostics of low temperature plasmas.

Extreme ultraviolet spectroscopy diagnostics of low-temperature plasmas based on a sliced multilayer grating and glass capillary optics

New extreme ultraviolet (EUV) spectroscopic diagnostics of relatively low-temperature plasmas based on the application of an EUV spectrometer and fast EUV diodes combined with glass capillary optics is described. An advanced high resolution dispersive element sliced multilayer grating was used in the compact EUV spectrometer. For monitoring of the time history of radiation, filtered fast EUV diodes were used in the same spectral region (>13 nm) as the EUV spectrometer. The radiation from the plasma was captured by using a single inexpensive glass capillary that was transported onto the spectrometer entrance slit and EUV diode. The use of glass capillary optics allowed placement of the spectrometer and diodes behind the thick radiation shield outside the direction of a possible hard x-ray radiation beam and debris from the plasma source. The results of the testing and application of this diagnostic for a compact laser plasma source are presented. Examples of modeling with parameters of plasmas are discussed.

Relative and absolute intensity calibrations of a modern broadband echelle spectrometer

We report on relative and absolute intensity calibrations of a modern broadband echelle spectrometer (type ESA 3000® trademark of LLA Instruments GmbH, Berlin) for use in the diagnostics of low-temperature plasma. This type of device measures simultaneously complete emission spectra in the spectral range from 200 to 800 nm with a spectral resolution of several picometres by using more than 90 spectral orders, causing a strongly structured efficiency function. The assumptions and approximations entering the calibration procedure under these conditions are discussed in section 3. For coping with the strongly structured efficiency function a continuum light source is needed, which covers the entire spectral range. Furthermore, the variation of its intensity must be low enough to ensure that neither statistical errors perturb the calibration in regions with low photon flux and/or low efficiency, nor local memory overflow in regions with high photon flux or high efficiency. In our case this requires that during calibration over the whole spectral range of the spectrometer the counts per pixel in one measurement vary at highest by a factor 10 to 12. Usual broadband light sources do not meet this latter requirement. We, therefore, use an uncalibrated ‘composite’ source, an adjustable combination of a standard tungsten strip lamp and a deuterium lamp, and calibrate the spectrometer in a two-step process against the tungsten strip lamp and well-known rovibrational intensity distributions in the emission spectra of NO and N2. We adjust the composite source in a way to produce a perturbation-free first approximation of an (uncalibrated) efficiency function, which is then corrected and thus calibrated by comparison with the (secondary) standards mentioned above. For absolute calibration we use the tungsten strip lamp. The uncertainty attained in this way for the relative calibration depends on the wavelength and varies between 5% and 10%. For the absolute calibration we obtained an uncertainty of 12%. We further discuss problems caused by the non-uniform spectral efficiency and dispersion of the spectrometer, which complicate the calibration procedure.

On Stark broadening as a tool for diagnostics of high density plasmas

We present the current status-of-the-art in Stark broadening theory as a theoretical basis for diagnostics of low temperature plasmas in gas discharges, and of high temperature laser produced or z-pinch dense plasmas. The diagnostics abilities vary depending on the parameters of the gas discharges, or on the range of intensity, and duration of the laser or z-pinch pulses. In the case of high temperature plasmas, besides the conventional diagnostics based on the Stark broadening, the contemporary possibilities of UV and XUV interferometry for plasma density measurements and of tomography reconstruction of the macroscopic gradients of temperature and densities in laser produced plasmas are discussed.

Plasma diagnostics by laser spectroscopic electric field measurement

Abstract Laser spectroscopic electric field measurements have the potential to become a versatile tool for the diagnostics of low-temperature plasmas. From the spatially and temporally resolved field distribution in the sheath close to electrodes or surfaces in general, a broad range of important plasma parameters can be inferred directly: electron temperature; ion density distribution; displacement-, ion-, electron-diffusion current density; and the sheath potential. Indirectly, the electron and ion energy distribution functions and information on the ion dynamics in the sheath can also be obtained. Finally, measurements in the quasi-neutral bulk can also reveal even the plasma density distribution with high spatial and temporal resolution. The basic concepts for analysis of the field data are introduced and demonstrated by examples in hydrogen discharges.

Microwave Diagnostics of Fluctuating Low-Temperature Plasma with the Help of an Open Slowing Structure

A modified method of microwave diagnostics of low-temperature plasma is described. The method utilizes the filtering properties that an open slowing structure shows in the presence of plasma. The edge of the filtering band depends on the medium's permittivity. This simplifies the determination of the plasma electron density, because the spatial resolution is substantially higher than in conventional diagnostic techniques based on the free propagation of a microwave beam. A prototype of the plasma density sensor operating in the 3-cm wave band has a sensitivity to the electron density of ∼108cm–3; the resolved volume is ∼1 cm in diameter and 4 cm in length. A procedure is developed that enables the recording of the fluctuations of the plasma density near the sensor.

Efficient multichannel Thomson scattering measurement system for diagnostics of low-temperature plasmas

An efficient multichannel Thomson scattering measurement system for measuring the electron energy distribution function in low-temperature processing plasmas was constructed. It consists of a specially designed triple-grating spectrometer, equipped with a spatial filter for eliminating the interference due to Rayleigh scattering, and an image-intensified charge-coupled-device (ICCD) camera working in the photon counting mode. The spectrometer produces a dispersed Thomson spectrum with the Rayleigh interference highly suppressed, thereby enabling us to operate the ICCD camera in the photon-counting mode giving a high signal-to-noise ratio; the measured Rayleigh light suppression ratio was ∼10−6 at the center wavelength. Proper operation of the system was demonstrated in the measurements for a low-pressure (20–100 mTorr) inductively coupled Ar plasma.