Pub Date : 2024-08-14DOI: 10.1088/1361-6595/ad6b44
Hui Wen, Julian Schulze, Quan-Zhi Zhang
Capacitively coupled plasmas operated in CF4 at low pressure are frequently used for dielectric plasma etching. For such applications the generation of different ion and neutral radical species by energy dependent electron impact ionization and dissociation of the neutral background gas is important. These processes are largely determined by the space and time dependent electron energy distribution function and, thus, by the electron power absorption dynamics. In this work and based on a particle-in-cell/Monte Carlo collision model, we show that the electron heating mode in such plasmas is sensitive to changes of the gap at a constant pressure of 3 Pa. At a gap of 1.5 cm, the dominant mode is found to be a hybrid combination of the Drift-Ambipolar (DA) and the α-mode. As the gap is increased to 2 cm and 2.5 cm, the bulk power absorption and ambipolar power absorption decreases, and the DA mode decays. When the gap reaches 3 cm, the α-mode becomes more prominent, and at a gap of 3.75 cm the α-mode is dominant. These mode transitions are caused by a change of the electronegativity and are found to affect the discharge characteristics. The presence of the DA-mode leads to significant positive electron power absorption inside the bulk region and negative power absorption within the sheaths on time average, as electrons are accelerated from the bulk towards the collapsed sheath. The heating mode transitions result in a change from negative to positive total electron power absorption within the sheaths as the gap increases. When accounting for secondary electron emission, the transition of the heating mode can occur at shorter gaps due to the enhanced plasma density and decreased electronegativity.
{"title":"Heating mode transitions in capacitively coupled CF4 plasmas at low pressure","authors":"Hui Wen, Julian Schulze, Quan-Zhi Zhang","doi":"10.1088/1361-6595/ad6b44","DOIUrl":"https://doi.org/10.1088/1361-6595/ad6b44","url":null,"abstract":"Capacitively coupled plasmas operated in CF<sub>4</sub> at low pressure are frequently used for dielectric plasma etching. For such applications the generation of different ion and neutral radical species by energy dependent electron impact ionization and dissociation of the neutral background gas is important. These processes are largely determined by the space and time dependent electron energy distribution function and, thus, by the electron power absorption dynamics. In this work and based on a particle-in-cell/Monte Carlo collision model, we show that the electron heating mode in such plasmas is sensitive to changes of the gap at a constant pressure of 3 Pa. At a gap of 1.5 cm, the dominant mode is found to be a hybrid combination of the Drift-Ambipolar (DA) and the <italic toggle=\"yes\">α</italic>-mode. As the gap is increased to 2 cm and 2.5 cm, the bulk power absorption and ambipolar power absorption decreases, and the DA mode decays. When the gap reaches 3 cm, the <italic toggle=\"yes\">α</italic>-mode becomes more prominent, and at a gap of 3.75 cm the <italic toggle=\"yes\">α</italic>-mode is dominant. These mode transitions are caused by a change of the electronegativity and are found to affect the discharge characteristics. The presence of the DA-mode leads to significant positive electron power absorption inside the bulk region and negative power absorption within the sheaths on time average, as electrons are accelerated from the bulk towards the collapsed sheath. The heating mode transitions result in a change from negative to positive total electron power absorption within the sheaths as the gap increases. When accounting for secondary electron emission, the transition of the heating mode can occur at shorter gaps due to the enhanced plasma density and decreased electronegativity.","PeriodicalId":20192,"journal":{"name":"Plasma Sources Science and Technology","volume":"12 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142210081","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-14DOI: 10.1088/1361-6595/ad69c0
Xiao-Kun Wang, Ranna Masheyeva, Yong-Xin Liu, Yuan-Hong Song, Peter Hartmann, Zoltán Donkó, Julian Schulze
Neutral radicals generated by electron impact dissociation of the background gas play important roles in etching and deposition processes in low pressure capacitively coupled plasmas (CCPs). The rate and energy efficiency of producing a given radical depend on the space- and time-dependent electron energy distribution function (EEDF) in the plasma, as well as the electron energy dependent cross sections of the electron-neutral collisions that result in the generation of the radical. For the case of a CCP operated in CF4 gas, we computationally demonstrate that the energy efficiency of generating neutral radicals, such as F atoms can be improved by controlling the EEDF by using tailored voltage waveforms (TVW) instead of single-frequency driving voltage waveforms and that separate control of the radical density and the ion energy can be realized by adjusting the waveform shape at constant peak-to-peak voltage. Such discharges are often used for industrial etching processes, in which the F atom density plays a crucial role for the etch rate. Different voltage waveform shapes, i.e. sinusoidal waveforms at low (13.56 MHz) and high (67.8 MHz) frequencies, peaks- and sawtooth-up TVWs, are used to study their effects on the energy cost / energy efficiency of F atom generation by PIC/MCC simulations combined with a stationary diffusion model. The F atom density is enhanced by increasing the voltage amplitude in the single frequency cases, while the energy cost per F atom generation increases, i.e. the energy efficiency decreases, because more power is dissipated to the ions, as the sheath voltages and the ion energy increase simultaneously. In contrast, using TVWs can result in a lower energy cost and provide separate control of the F atom density and the ion energy. This is explained by the fact that tailoring the waveform shape in this way allows to enhance the high-energy tail of the EEDF during the sheath expansion phase by inducing a non-sinusoidal sheath motion, which results in acceleration of more electrons to high enough energies to generate F atoms via electron-neutral collisions compared to the single frequency cases. Similar effects of TVWs are expected for the generation of other neutral radicals depending on the electron energy threshold and the specific consequences of TVWs on the EEDF under the discharge conditions of interest.
电子撞击背景气体解离产生的中性自由基在低压电容耦合等离子体（CCP）的蚀刻和沉积过程中发挥着重要作用。产生特定自由基的速率和能效取决于等离子体中与空间和时间相关的电子能量分布函数（EEDF），以及导致产生自由基的电子-中性碰撞的电子能量相关截面。对于在 CF4 气体中运行的 CCP，我们通过计算证明，通过使用定制电压波形（TVW）而不是单频驱动电压波形来控制 EEDF，可以提高产生中性自由基（如 F 原子）的能量效率；通过调整恒定峰-峰电压下的波形形状，可以实现自由基密度和离子能量的单独控制。这种放电通常用于工业蚀刻工艺，其中 F 原子密度对蚀刻速率起着至关重要的作用。我们使用不同的电压波形，即低频（13.56 MHz）和高频（67.8 MHz）的正弦波形、峰值和锯齿形的 TVW，通过 PIC/MCC 模拟结合静态扩散模型，研究它们对 F 原子生成的能源成本/能源效率的影响。在单频情况下，通过增加电压振幅可以提高 F 原子密度，但由于鞘电压和离子能量同时增加，更多的功率会耗散到离子上，因此产生每个 F 原子的能量成本会增加，即能量效率会降低。相比之下，使用 TVW 可以降低能量成本，并对 F 原子密度和离子能量进行单独控制。这是因为以这种方式定制波形可以在鞘膨胀阶段通过诱导非正弦鞘运动来增强 EEDF 的高能尾部，从而使更多电子加速到足够高的能量，从而通过电子-中性碰撞产生 F 原子。根据电子能量阈值以及 TVW 在相关放电条件下对 EEDF 的具体影响，预计 TVW 对其他中性自由基的生成也会产生类似的影响。
{"title":"Energy efficient F atom generation and control in CF4 capacitively coupled plasmas driven by tailored voltage waveforms","authors":"Xiao-Kun Wang, Ranna Masheyeva, Yong-Xin Liu, Yuan-Hong Song, Peter Hartmann, Zoltán Donkó, Julian Schulze","doi":"10.1088/1361-6595/ad69c0","DOIUrl":"https://doi.org/10.1088/1361-6595/ad69c0","url":null,"abstract":"Neutral radicals generated by electron impact dissociation of the background gas play important roles in etching and deposition processes in low pressure capacitively coupled plasmas (CCPs). The rate and energy efficiency of producing a given radical depend on the space- and time-dependent electron energy distribution function (EEDF) in the plasma, as well as the electron energy dependent cross sections of the electron-neutral collisions that result in the generation of the radical. For the case of a CCP operated in CF<sub>4</sub> gas, we computationally demonstrate that the energy efficiency of generating neutral radicals, such as F atoms can be improved by controlling the EEDF by using tailored voltage waveforms (TVW) instead of single-frequency driving voltage waveforms and that separate control of the radical density and the ion energy can be realized by adjusting the waveform shape at constant peak-to-peak voltage. Such discharges are often used for industrial etching processes, in which the F atom density plays a crucial role for the etch rate. Different voltage waveform shapes, i.e. sinusoidal waveforms at low (13.56 MHz) and high (67.8 MHz) frequencies, peaks- and sawtooth-up TVWs, are used to study their effects on the energy cost / energy efficiency of F atom generation by PIC/MCC simulations combined with a stationary diffusion model. The F atom density is enhanced by increasing the voltage amplitude in the single frequency cases, while the energy cost per F atom generation increases, i.e. the energy efficiency decreases, because more power is dissipated to the ions, as the sheath voltages and the ion energy increase simultaneously. In contrast, using TVWs can result in a lower energy cost and provide separate control of the F atom density and the ion energy. This is explained by the fact that tailoring the waveform shape in this way allows to enhance the high-energy tail of the EEDF during the sheath expansion phase by inducing a non-sinusoidal sheath motion, which results in acceleration of more electrons to high enough energies to generate F atoms via electron-neutral collisions compared to the single frequency cases. Similar effects of TVWs are expected for the generation of other neutral radicals depending on the electron energy threshold and the specific consequences of TVWs on the EEDF under the discharge conditions of interest.","PeriodicalId":20192,"journal":{"name":"Plasma Sources Science and Technology","volume":"7 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142226690","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-13DOI: 10.1088/1361-6595/ad69bf
Kyungtae Kim, Kil-Byoung Chai, Gunsu S Yun
Microwave-driven Coaxial Transmission Line Resonator (µ-CTLR) produces a small-volume high density plasma plume. In the previous study, we discovered that the plasma generated by the µ-CTLR remains stable even at low pressure around tens of mTorr, while consuming minimal power below 10 W (Kim et al 2022 Plasma Sources Sci. Technol.31 105006). In this study, we have investigated the capability of the µ-CTLR plasma operating at 900 MHz for micro-propulsion applications. At the argon gas flow rate of 100 SCCM (3 mg s−1), and the power of 8 W, the plasma plume attains high gas temperature (>3000 K), high electron density (>1020m−3), and electron temperature of about 2 eV. The estimated thrust is about 3.4 mN, demonstrating that the µ-CTLR has high thrust desirable for space micro propulsion systems, together with the other merits of low power consumption and small size.
{"title":"Analysis in microwave-driven plasma for miniature space propulsion","authors":"Kyungtae Kim, Kil-Byoung Chai, Gunsu S Yun","doi":"10.1088/1361-6595/ad69bf","DOIUrl":"https://doi.org/10.1088/1361-6595/ad69bf","url":null,"abstract":"Microwave-driven Coaxial Transmission Line Resonator (<italic toggle=\"yes\">µ</italic>-CTLR) produces a small-volume high density plasma plume. In the previous study, we discovered that the plasma generated by the <italic toggle=\"yes\">µ</italic>-CTLR remains stable even at low pressure around tens of mTorr, while consuming minimal power below 10 W (Kim <italic toggle=\"yes\">et al</italic> 2022 <italic toggle=\"yes\">Plasma Sources Sci. Technol.</italic> <bold>31</bold> 105006). In this study, we have investigated the capability of the <italic toggle=\"yes\">µ</italic>-CTLR plasma operating at 900 MHz for micro-propulsion applications. At the argon gas flow rate of 100 SCCM (3 mg s<sup>−1</sup>), and the power of 8 W, the plasma plume attains high gas temperature (<inline-formula>\u0000<tex-math><?CDATA ${gt}$?></tex-math><mml:math overflow=\"scroll\"><mml:mrow><mml:mrow><mml:mo>></mml:mo></mml:mrow></mml:mrow></mml:math><inline-graphic xlink:href=\"psstad69bfieqn1.gif\"></inline-graphic></inline-formula>3000 K), high electron density (<inline-formula>\u0000<tex-math><?CDATA ${gt}10^{20} mathrm{m}^{-3}$?></tex-math><mml:math overflow=\"scroll\"><mml:mrow><mml:mrow><mml:mo>></mml:mo></mml:mrow><mml:msup><mml:mn>10</mml:mn><mml:mrow><mml:mn>20</mml:mn></mml:mrow></mml:msup><mml:mtext> </mml:mtext><mml:msup><mml:mrow><mml:mi mathvariant=\"normal\">m</mml:mi></mml:mrow><mml:mrow><mml:mo>−</mml:mo><mml:mn>3</mml:mn></mml:mrow></mml:msup></mml:mrow></mml:math><inline-graphic xlink:href=\"psstad69bfieqn2.gif\"></inline-graphic></inline-formula>), and electron temperature of about 2 eV. The estimated thrust is about 3.4 mN, demonstrating that the <italic toggle=\"yes\">µ</italic>-CTLR has high thrust desirable for space micro propulsion systems, together with the other merits of low power consumption and small size.","PeriodicalId":20192,"journal":{"name":"Plasma Sources Science and Technology","volume":"105 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142210080","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-08DOI: 10.1088/1361-6595/ad6cf1
Min-Seok Kim, Jiwon Jung, Junyoung Park, Chin-Wook Chung
The formation of the plasma potential and the generation mechanism of very low electron temperature plasma are investigated in an inductively coupled plasma (ICP) with a DC biased grid. The electron temperature is controlled from 2.4 eV to 0.2 eV according to the grid voltage (10 V to -40 V). Interestingly, when the grid voltage is negatively biased, the electron temperature decreases and the plasma potential decreases with the grid voltage, but then increases below -10 V which is abnormal. This behavior of the plasma potential is abnormal since the plasma potential is generally proportional to the electron temperature. The main reason for the abnormal increase of the plasma potential is the difference in the flux of electrons and ions below the grid. As the grid is negatively biased, the electron flux is greatly reduced compared to the ion flux, leading to an increase in plasma potential. After -20 V, the plasma potential saturates, because although the number of electrons entering the grid decreases, the electron flux is maintained by secondary electrons generated in the grid mesh. This abnormal increase in plasma potential decreases with pressure. An increase in plasma potential with gas species is also observed. The same behavior is observed for Ar, He, and N2 gases. The abnormal behavior of the plasma potential is explained with the current continuity.
在带有直流偏置栅的电感耦合等离子体（ICP）中，研究了等离子体电势的形成和极低电子温度等离子体的产生机制。电子温度根据栅极电压（10 V 至 -40 V）从 2.4 eV 控制到 0.2 eV。有趣的是，当栅极电压为负偏置时，电子温度降低，等离子体电位随栅极电压降低，但在低于-10 V时又会升高，这是不正常的。等离子体电位的这种行为是不正常的，因为等离子体电位通常与电子温度成正比。等离子体电位异常升高的主要原因是栅格下方电子和离子通量的差异。由于栅极处于负偏压状态，电子通量与离子通量相比大大减少，从而导致等离子体电位上升。在 -20 V 电压之后，等离子体电位达到饱和，这是因为虽然进入栅格的电子数量减少，但栅格网状结构中产生的次级电子维持了电子通量。等离子体电位的这种异常增加会随着压力的增加而减小。我们还观察到等离子体电位随气体种类的增加而增加。在 Ar、He 和 N2 气体中也观察到了同样的现象。等离子体电位的异常行为可以用电流连续性来解释。
{"title":"Abnormal behavior of the plasma potential in an inductively coupled plasma with a DC-biased grid","authors":"Min-Seok Kim, Jiwon Jung, Junyoung Park, Chin-Wook Chung","doi":"10.1088/1361-6595/ad6cf1","DOIUrl":"https://doi.org/10.1088/1361-6595/ad6cf1","url":null,"abstract":"\u0000 The formation of the plasma potential and the generation mechanism of very low electron temperature plasma are investigated in an inductively coupled plasma (ICP) with a DC biased grid. The electron temperature is controlled from 2.4 eV to 0.2 eV according to the grid voltage (10 V to -40 V). Interestingly, when the grid voltage is negatively biased, the electron temperature decreases and the plasma potential decreases with the grid voltage, but then increases below -10 V which is abnormal. This behavior of the plasma potential is abnormal since the plasma potential is generally proportional to the electron temperature. The main reason for the abnormal increase of the plasma potential is the difference in the flux of electrons and ions below the grid. As the grid is negatively biased, the electron flux is greatly reduced compared to the ion flux, leading to an increase in plasma potential. After -20 V, the plasma potential saturates, because although the number of electrons entering the grid decreases, the electron flux is maintained by secondary electrons generated in the grid mesh. This abnormal increase in plasma potential decreases with pressure. An increase in plasma potential with gas species is also observed. The same behavior is observed for Ar, He, and N2 gases. The abnormal behavior of the plasma potential is explained with the current continuity.","PeriodicalId":20192,"journal":{"name":"Plasma Sources Science and Technology","volume":"22 6","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141928727","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-29DOI: 10.1088/1361-6595/ad5d11
S Chouteau, A Durocher-Jean, A Granier, M Richard-Plouet, L Stafford
Misty plasmas have recently emerged as a promising tool for nanocomposite thin films deposition. However, aerosol-plasma interactions remain poorly documented, especially at low working pressure. In this work, optical emission spectroscopy is used to probe the temporal evolution of three fundamental plasma parameters during pulsed liquid injection in an inductively coupled argon plasma at low-pressure. Time-resolved values of metastable argon density, electron temperature, and electron density are determined from radiation trapping analysis and particle balance equations of selected argon 1s and 2p levels. Pulsed liquid injection is found to induce a sudden drop in metastable density and electron temperature, and an increase in electron density. These results are attributed to the lower ionization thresholds of the injected molecular species compared to the one of argon. In addition, upstream liquid temperature is found to affect the transitory kinetics for non-volatile solvents more than volatile ones, in accordance with a previously reported flash boiling atomization mechanism.
{"title":"Time-resolved analysis of Ar metastable and electron populations in low-pressure misty plasma processes using optical emission spectroscopy","authors":"S Chouteau, A Durocher-Jean, A Granier, M Richard-Plouet, L Stafford","doi":"10.1088/1361-6595/ad5d11","DOIUrl":"https://doi.org/10.1088/1361-6595/ad5d11","url":null,"abstract":"Misty plasmas have recently emerged as a promising tool for nanocomposite thin films deposition. However, aerosol-plasma interactions remain poorly documented, especially at low working pressure. In this work, optical emission spectroscopy is used to probe the temporal evolution of three fundamental plasma parameters during pulsed liquid injection in an inductively coupled argon plasma at low-pressure. Time-resolved values of metastable argon density, electron temperature, and electron density are determined from radiation trapping analysis and particle balance equations of selected argon 1s and 2p levels. Pulsed liquid injection is found to induce a sudden drop in metastable density and electron temperature, and an increase in electron density. These results are attributed to the lower ionization thresholds of the injected molecular species compared to the one of argon. In addition, upstream liquid temperature is found to affect the transitory kinetics for non-volatile solvents more than volatile ones, in accordance with a previously reported flash boiling atomization mechanism.","PeriodicalId":20192,"journal":{"name":"Plasma Sources Science and Technology","volume":"19 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141869841","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-25DOI: 10.1088/1361-6595/ad6500
D Poli, P Fajardo and E Ahedo
A non-neutral model (NNM) of the axial plasma discharge in a Hall thruster, including full electron inertia, is presented. In the finite-volume formulation, two types of sheath boundary conditions previously used in the literature are tested and proven to behave practically identically in this model. Both normal and reversed (i.e. electron repelling and attracting, respectively) anode sheaths are admitted. This model is compared with the quasineutral model developed in a previous work, which includes only azimuthal electron inertia and normal anode sheaths. Both models agree excellently within the parametric region where steady-state solutions with a normal anode sheath exist. The NNM shows the absence of steady-state solutions with a reversed anode sheath. Nonetheless, a reversed sheath can appear during the transient to a steady-state solution with a normal sheath and the periodic transition from a normal to a reversed sheath can be observed in the presence of breathing-mode oscillations. In other cases, the reversed sheath leads to the discharge shut-off. Full electron inertia is always important in the presence of a reversed sheath. The parametric threshold of the wall accommodation parameter from a stationary solution to a breathing mode one differs slightly between the non-neutral and the quasi-neutral model.
{"title":"A non-neutral 1D fluid model of hall thruster discharges: full electron inertia and anode sheath reversal","authors":"D Poli, P Fajardo and E Ahedo","doi":"10.1088/1361-6595/ad6500","DOIUrl":"https://doi.org/10.1088/1361-6595/ad6500","url":null,"abstract":"A non-neutral model (NNM) of the axial plasma discharge in a Hall thruster, including full electron inertia, is presented. In the finite-volume formulation, two types of sheath boundary conditions previously used in the literature are tested and proven to behave practically identically in this model. Both normal and reversed (i.e. electron repelling and attracting, respectively) anode sheaths are admitted. This model is compared with the quasineutral model developed in a previous work, which includes only azimuthal electron inertia and normal anode sheaths. Both models agree excellently within the parametric region where steady-state solutions with a normal anode sheath exist. The NNM shows the absence of steady-state solutions with a reversed anode sheath. Nonetheless, a reversed sheath can appear during the transient to a steady-state solution with a normal sheath and the periodic transition from a normal to a reversed sheath can be observed in the presence of breathing-mode oscillations. In other cases, the reversed sheath leads to the discharge shut-off. Full electron inertia is always important in the presence of a reversed sheath. The parametric threshold of the wall accommodation parameter from a stationary solution to a breathing mode one differs slightly between the non-neutral and the quasi-neutral model.","PeriodicalId":20192,"journal":{"name":"Plasma Sources Science and Technology","volume":"69 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141773826","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-25DOI: 10.1088/1361-6595/ad647c
Jiayun Qi, Zhongkai Zhang, Zun Zhang, Junxue Ren, Yibai Wang, Weizong Wang and Haibin Tang
Vacuum arc thruster (VAT) is a type of pulsed electric propulsion device that generates thrust based on vacuum arc discharges, it has great candidate for micro-newton force applications in orbit. To improve both the thrust and longevity of the VAT, a novel dual-anode structure, comprising a central anode and a ring anode, was developed. We conducted an investigation into the plasma discharge and acceleration process within the influence of a magnetic nozzle. The dual-anode architecture resulted in a reduction in the initial plasma impedance, thereby enhancing ion current and velocity. Analysis of surface parameters during discharge revealed a synergistic mechanism between the two insulator-conducting films, enabling a co-cyclic distribution of energy and resistance fluctuations within the discharge. Consequently, the dual-anode setup demonstrated a lifespan extension of at least twofold. Comparative analyses of arc energy, plasma velocity, ion current, and thrust variations with magnetic field strength were conducted between the dual-anode and single-anode configurations under magnetic nozzle influence. Results showed that the dual-anode structure increased ion current and velocity when subjected to magnetic nozzle influence, resulting in a thrust increase of up to 303%. Additionally, we developed a theoretical model for the diffusion coefficient to elucidate the adaptive splitting phenomenon of the arc within the dual-anode structure under magnetic field influence. This model suggests that the dual-anode structure can achieve a more significant enhancement in beam current from the magnetic nozzle compared to the single-anode configuration.
{"title":"Plasma plume enhancement of a dual-anode vacuum arc thruster with magnetic nozzle","authors":"Jiayun Qi, Zhongkai Zhang, Zun Zhang, Junxue Ren, Yibai Wang, Weizong Wang and Haibin Tang","doi":"10.1088/1361-6595/ad647c","DOIUrl":"https://doi.org/10.1088/1361-6595/ad647c","url":null,"abstract":"Vacuum arc thruster (VAT) is a type of pulsed electric propulsion device that generates thrust based on vacuum arc discharges, it has great candidate for micro-newton force applications in orbit. To improve both the thrust and longevity of the VAT, a novel dual-anode structure, comprising a central anode and a ring anode, was developed. We conducted an investigation into the plasma discharge and acceleration process within the influence of a magnetic nozzle. The dual-anode architecture resulted in a reduction in the initial plasma impedance, thereby enhancing ion current and velocity. Analysis of surface parameters during discharge revealed a synergistic mechanism between the two insulator-conducting films, enabling a co-cyclic distribution of energy and resistance fluctuations within the discharge. Consequently, the dual-anode setup demonstrated a lifespan extension of at least twofold. Comparative analyses of arc energy, plasma velocity, ion current, and thrust variations with magnetic field strength were conducted between the dual-anode and single-anode configurations under magnetic nozzle influence. Results showed that the dual-anode structure increased ion current and velocity when subjected to magnetic nozzle influence, resulting in a thrust increase of up to 303%. Additionally, we developed a theoretical model for the diffusion coefficient to elucidate the adaptive splitting phenomenon of the arc within the dual-anode structure under magnetic field influence. This model suggests that the dual-anode structure can achieve a more significant enhancement in beam current from the magnetic nozzle compared to the single-anode configuration.","PeriodicalId":20192,"journal":{"name":"Plasma Sources Science and Technology","volume":"14 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141773821","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-14DOI: 10.1088/1361-6595/ad5df4
Ibrahim Sadiek, Alexander Puth, Grzegorz Kowzan, Akiko Nishiyama, Sarah-Johanna Klose, Jürgen Röpcke, Norbert Lang, Piotr Masłowski and Jean-Pierre H van Helden
Non-thermal molecular plasmas play a crucial role in numerous industrial processes and hold significant potential for driving essential chemical transformations. Accurate information about the molecular composition of the plasmas and the distribution of populations among quantum states is essential for understanding and optimizing plasma processes. Here, we apply a mid-infrared frequency comb-based Fourier transform spectrometer to measure high-resolution spectra of plasmas containing hydrogen, nitrogen, and a carbon source in the 2800–3400 cm–1 range. The spectrally broadband and high-resolution capabilities of this technique enable quantum-state-resolved spectroscopy of multiple plasma-generated species simultaneously, including CH4, C2H2, C2H6, NH3, and HCN, providing detailed information beyond the limitations of current methods. Using a line-by-line fitting approach, we analyzed 548 resolved transitions across five vibrational bands of plasma-generated HCN. The results indicate a significant non-thermal distribution of the populations among the quantum states, with distinct temperatures observed for lower and higher rotational quantum numbers, with a temperature difference of about 62 K. Broadband state-resolved-spectroscopy via comb-based methods provides unprecedented fundamental insights into the non-thermal nature of molecular plasmas—a detailed picture that has never been accomplished before for such complex non-thermal environment.
{"title":"Precision spectroscopy of non-thermal molecular plasmas using mid-infrared optical frequency comb Fourier transform spectroscopy","authors":"Ibrahim Sadiek, Alexander Puth, Grzegorz Kowzan, Akiko Nishiyama, Sarah-Johanna Klose, Jürgen Röpcke, Norbert Lang, Piotr Masłowski and Jean-Pierre H van Helden","doi":"10.1088/1361-6595/ad5df4","DOIUrl":"https://doi.org/10.1088/1361-6595/ad5df4","url":null,"abstract":"Non-thermal molecular plasmas play a crucial role in numerous industrial processes and hold significant potential for driving essential chemical transformations. Accurate information about the molecular composition of the plasmas and the distribution of populations among quantum states is essential for understanding and optimizing plasma processes. Here, we apply a mid-infrared frequency comb-based Fourier transform spectrometer to measure high-resolution spectra of plasmas containing hydrogen, nitrogen, and a carbon source in the 2800–3400 cm–1 range. The spectrally broadband and high-resolution capabilities of this technique enable quantum-state-resolved spectroscopy of multiple plasma-generated species simultaneously, including CH4, C2H2, C2H6, NH3, and HCN, providing detailed information beyond the limitations of current methods. Using a line-by-line fitting approach, we analyzed 548 resolved transitions across five vibrational bands of plasma-generated HCN. The results indicate a significant non-thermal distribution of the populations among the quantum states, with distinct temperatures observed for lower and higher rotational quantum numbers, with a temperature difference of about 62 K. Broadband state-resolved-spectroscopy via comb-based methods provides unprecedented fundamental insights into the non-thermal nature of molecular plasmas—a detailed picture that has never been accomplished before for such complex non-thermal environment.","PeriodicalId":20192,"journal":{"name":"Plasma Sources Science and Technology","volume":"53 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141720069","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-11DOI: 10.1088/1361-6595/ad5ebb
Seong-Cheol Huh, Jin Hee Bae, Hyungyu Lee, Jinwoo Kim, Wonho Choe and Sanghoo Park
Ozone (O3), nitrogen oxides (NOx), and reactive nitrogen species (RNS) play critical roles in atmospheric-pressure plasma applications. Although it is crucial to individually quantify these species to understand atmospheric-pressure plasmas and increase their effectiveness, the lack of reliable and cost-effective diagnostics makes this difficult for many researchers. To address this problem, we introduce a new deconvolution method of broadband ultraviolet–visible absorption spectra for the simultaneous measurement of eight species—O3, NO, NO2, NO3, N2O4, N2O5, HONO, and HNO3. Processing of broadband spectra enables deconvolution of similar cross-section profiles and measurement of high densities exceeding the instrumental limit. Novel correction processes enable accurate analysis despite incomplete cross-section data and utilize a priori chemical knowledge to ensure theoretically reasonable results. Two case studies test the efficacy of the method: NO2 and N2O4 equilibria, and reactive species produced by a surface dielectric barrier discharge. With an analysis time of 15–20 ms per spectrum, the measured densities agree well with other theoretical and experimental results, and detection limits on the order of ppmv were achieved with a short path length of 15 cm. This spectral analysis method will facilitate the real-time monitoring of O3, NOx, and RNS in many scientific research and industrial applications of atmospheric pressure plasmas.
{"title":"Individual quantification of ozone and reactive nitrogen species in mixtures by broadband UV–visible absorption spectra deconvolution","authors":"Seong-Cheol Huh, Jin Hee Bae, Hyungyu Lee, Jinwoo Kim, Wonho Choe and Sanghoo Park","doi":"10.1088/1361-6595/ad5ebb","DOIUrl":"https://doi.org/10.1088/1361-6595/ad5ebb","url":null,"abstract":"Ozone (O3), nitrogen oxides (NOx), and reactive nitrogen species (RNS) play critical roles in atmospheric-pressure plasma applications. Although it is crucial to individually quantify these species to understand atmospheric-pressure plasmas and increase their effectiveness, the lack of reliable and cost-effective diagnostics makes this difficult for many researchers. To address this problem, we introduce a new deconvolution method of broadband ultraviolet–visible absorption spectra for the simultaneous measurement of eight species—O3, NO, NO2, NO3, N2O4, N2O5, HONO, and HNO3. Processing of broadband spectra enables deconvolution of similar cross-section profiles and measurement of high densities exceeding the instrumental limit. Novel correction processes enable accurate analysis despite incomplete cross-section data and utilize a priori chemical knowledge to ensure theoretically reasonable results. Two case studies test the efficacy of the method: NO2 and N2O4 equilibria, and reactive species produced by a surface dielectric barrier discharge. With an analysis time of 15–20 ms per spectrum, the measured densities agree well with other theoretical and experimental results, and detection limits on the order of ppmv were achieved with a short path length of 15 cm. This spectral analysis method will facilitate the real-time monitoring of O3, NOx, and RNS in many scientific research and industrial applications of atmospheric pressure plasmas.","PeriodicalId":20192,"journal":{"name":"Plasma Sources Science and Technology","volume":"25 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141612167","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-10DOI: 10.1088/1361-6595/ad5d12
Joseph R Vella, Qinzhen Hao, Mahmoud A I Elgarhy, Vincent M Donnelly and David B Graves
We present a transient site balance model of plasma-assisted atomic layer etching of silicon (Si) with alternating exposure to chlorine gas (Cl2) and argon ions (Ar+). Molecular dynamics (MD) simulation results are used to provide parameters for the model. The model couples the dynamics of a top monolayer surface region (‘top layer’) and a perfectly mixed subsurface region (‘mixed layer’). The differential equations describing the rates of change of the Cl coverage in the two layers are transient mass balances. Model predictions include Cl coverages and rates of etching of various species from the surface as a function of Cl2 or Ar+ fluence. The simplified phenomenological model reproduces the MD simulation results well over a range of conditions. Comparing model predictions directly to experimental optical emission spectroscopy data, as reported in a previous paper (Vella et al 2023 J. Vac. Sci. Technol. A 41, 062602), provides further evidence of the accuracy of the model.
{"title":"A transient site balance model for atomic layer etching","authors":"Joseph R Vella, Qinzhen Hao, Mahmoud A I Elgarhy, Vincent M Donnelly and David B Graves","doi":"10.1088/1361-6595/ad5d12","DOIUrl":"https://doi.org/10.1088/1361-6595/ad5d12","url":null,"abstract":"We present a transient site balance model of plasma-assisted atomic layer etching of silicon (Si) with alternating exposure to chlorine gas (Cl2) and argon ions (Ar+). Molecular dynamics (MD) simulation results are used to provide parameters for the model. The model couples the dynamics of a top monolayer surface region (‘top layer’) and a perfectly mixed subsurface region (‘mixed layer’). The differential equations describing the rates of change of the Cl coverage in the two layers are transient mass balances. Model predictions include Cl coverages and rates of etching of various species from the surface as a function of Cl2 or Ar+ fluence. The simplified phenomenological model reproduces the MD simulation results well over a range of conditions. Comparing model predictions directly to experimental optical emission spectroscopy data, as reported in a previous paper (Vella et al 2023 J. Vac. Sci. Technol. A 41, 062602), provides further evidence of the accuracy of the model.","PeriodicalId":20192,"journal":{"name":"Plasma Sources Science and Technology","volume":"29 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141587257","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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