Influence Of Secondary Electron Emission Research Articles

The Influence of Secondary Electron Emission on Surface Charging on a Mask Trench in Plasma Etching

The Influence of Secondary Electron Emission on Surface Charging on a Mask Trench in Plasma Etching

Influence of secondary electron emission on plasma-surface interactions in the low earth orbit environment

The low earth orbit plasma experienced by exposed interconnect-dielectric junctions commonly found on spacecraft solar panel surfaces was modeled using a fully kinetic particle-in-cell (PIC) simulation of both ambient ions and electrons. From time-accurate simulations we observed that the plasma sheath had a formation time somewhere between the ion and electron time scales of 17 μs and 30 ps, respectively and electron and ion velocity distribution functions were observed to be highly non-Maxwellian. Comparison of the electron plasma sheath thickness with analytic cylindrical sheath models gave reasonable agreement if the embedded biased interconnect voltage was sufficiently high to cause the dielectric surface to act as a free electron flowing medium. Finally, it was found from the fully kinetic PIC simulations that the fundamental mechanism behind parasitic current is closely related to electron avalanche and the fraction of SEE emitted from different avalanche levels as well as the current collected at the interconnect could be modeled by a power law series for avalanche levels greater than two.

Gas Breakdown and Discharge Formation in High-Power Impulse Magnetron Sputtering

Discharge behaviors of high-power impulse magnetron sputtering with different targets have been investigated. Distinct current–voltage curves and target current waveforms are observed. Breakdown voltage and the maximum target current show a periodic drop with the increase of atomic number in subgroups and periods. The target current density is found to be mainly affected by the secondary electron emission yield. Thus, its magnitude is unable to directly evaluate the ionization degree of sputtered atoms in high-power impulse magnetron sputtering (HiPIMS) process. In this paper, the interactive influence of secondary electron emission, sputter yield, and ionization energy on the ionization degree of sputtered atoms is discussed based on the analysis of the voltage and current characteristics. As a result, targets can be categorized into three sorts according to the ionization degree: 1) low ionization degree targets, such as Ag and C less than 10%; 2) intermediate ionization degree targets like Cr and Cu with 55% and 35%; 3) Ti, Zr, and Mo targets with the second ionization processes. These results provide institutive operation ranges for the state-of-the-art HiPIMS applications.

Performance of the Secondary Townsend Emission through the Electric Discharge Characteristics in Coaxial Vircator

THE INFLUENCE of secondary electron emission on self sustaining and maintaining discharge current is studied using a new type of DC glow discharge operated on virtual cathode theory through argon gas. The radial electron beam is generated outside the diode in coaxial Vircator. The transported electric discharge, from non-self sustaining to self sustaining discharge, occurs in the Townsend region and strongly depends on the secondary electron emission. The first ionization acts as a breakdown starter, then the second emission completes the electric discharge without consumed energy. The present work aims to study the effect of some physical parameters on the secondary electron emission to reduce the applied breakdown voltage and improve the ionization process, as well as to reduce the consumed electric energy. During the study, it was found that the self discharge started due to the second electron emission (γ) from the cathode which increased by increasing the ionization potential and decreasing the electric field. There was a balance between the first ionization coefficient and the electron attachment which confirms that the ( γ ) is the main element in the glow discharge. The minimum breakdown voltage for argon gas is 219 volts at Pd= 8 x 10-2 Torr.cm.

The influence of secondary electron emission on the floating potential of tokamak-born dust

Dust production and its transport into the core plasma is an important issue for magnetic confinement fusion. Dust grains are charged by various processes, such as the collection of plasma particles and electron emissions, and their charge influences the dynamics of the dust. This paper presents the results of calculations of the surface potential of dust grains in a Maxwellian plasma. Our calculations include the charging balance of a secondary electron emission (SEE) from the dust. The numerical model that we have used accounts for the influence of backscattered electrons and takes into account the effects of grain size, material, and it is also able to handle both spherical and non-spherical grains. We discuss the role of the SEE under tokamak conditions and show that the SEE is a leading process for the grains crossing the scrape-off layer from the edge to core plasma. The results of our calculations are relevant for materials related to fusion experiments in ITER.

Kinetic Analysis of Electron Transport in a Cylindrical Hall Thruster

Transport of electrons across magnetic field lines in a Hall thruster is driven by factors such as collisions with background heavy particles, plasma turbulence, and wall effects. In this paper, we analyze the influence of secondary electron emission and electron scattering with thruster walls on cross-field diffusion in cylindrical Hall thrusters.

Experimental study and modeling of the electron-attracting sheath: The influence of secondary electron emission

A copper sample facing an energy-resolved mass spectrometer is biased positively beyond plasma potential in low-pressure argon plasma. Some ions are created in the sheath by electrons extracted from plasma and accelerated toward the mass spectrometer where they are detected according to their energy. Ion energy is related to local electrical sheath potential at which the ion has been created. Therefore, the Ion Distribution Function (IDF) allows us to probe in a nonperturbative way electron-attracting sheath potential. We observe a strong decrease of ion signal a few volts before sample bias. We attribute this effect to the presence of secondary electrons shielding positive sample potential. Potential profile and IDFs are computed using a model including secondary emission. The fit of IDFs provides an estimation of secondary emission yield and secondary electron temperature.

Influence of secondary electron emission on breakdown voltage in a plasma display panel

A measurement of the secondary electron-emission coefficient γ from MgO film in a plasma display panel is carried out. The influence of the secondary electron emission on the breakdown voltage in microdischarges on the plasma display panel is investigated by making use of the Townsend sparking criterion. Experimental data agree well with theoretical results, verifying the previous theoretical model.

Influence of Secondary Electron Emission on the Characteristics of Langmuir Probes

The characteristics of Langmuir probes have been calculated for such electron temperatures (≥15 eV) where the probe surface emits secondary electrons. Under these conditions, the floating potential of the probe shifts towards the plasma potential. The calculations provide a guideline by which to determine the plasma potential near the edge of fusion plasmas more accurately.

Measurements of the influence of secondary electron emission on the currents and voltages between different wall probes facing a plasma

The current-voltage characteristics of wall probes, made from materials of different secondary electron emission, have been measured on the endplates of a small magnetic mirror and in the scrape-off layer of the TEXTOR tokamak. The probes were operated like double Langmuir probes. It is found that for electron temperatures significantly exceeding 10 eV the characteristics become non symmetric with respect to the ordinate. The results are compared to a theoretical model.

The influence of secondary electron emission on the energy transport to the limiter of a tokamak

The influence of secondary electron emission on the energy transport to the limiter of a tokamak

Influence of secondary-electron emission from MgO surfaces on voltage-breakdown curves in Penning mixtures for insulated-electrode discharges

Influence of secondary-electron emission from MgO surfaces on voltage-breakdown curves in Penning mixtures for insulated-electrode discharges

Influence of secondary-electron emission from MgO surfaces on voltage-breakdown curves in Penning mixtures for insulated-electrode discharges

Voltage-breakdown curves in a Ne+0.1% Ar Penning mixture for insulated-electrode discharges are strongly influenced by changes in the surface properties of a deposited MgO cathode. A model has been developed to calculate an effective secondary-electron-emission coefficient γ in Penning mixtures as a function of the insulator-energy-band parameters. Incorporation of the calculated γ into the breakdown criterion results in good agreement between calculated and measured voltage-breakdown curves for differently prepared MgO cathode surfaces. The calculated results show that the value of γ for argon ions depends on the state of the MgO surface, and this occurs through a change in the width of the band gap of MgO. The results also show that a nonzero value of γ (Ar+) significantly lowers the breakdown voltages and changes the shape of the breakdown curves at higher values of P0d.

Electrostatic probe measurements of low-density medium-pressure magneto-plasmas

The influence of secondary electron emission from a probe surface on the probe diagnostics are studied in a medium-pressure low-density plasma with a weak magnetic field. Both electron and ion saturation currents are used to obtain Ne, and the results are compared with microwave measurements. The increase of Ii due to electron emission occurs; this prevents the accurate determination of Ne in the same manner as that reported in a plasma without a magnetic field. Even though the uncertainty in determining Ne due to the effect of emission decreases with increasing B, Iis is not always suitable for Ne determination. On the other hand, Ne determined from Ies corrected for magnetic field effects agrees with microwave measurements within 50%.