Jie Tang

This study employs 1D particle-in-cell/Monte Carlo collision simulations to systematically investigate the modulation of capacitively coupled plasma by a unidirectional electron beam under tunable magnetic field gradients. The results reveal a remarkable sensitivity of electron beam injection to both the orientation and intensity of the magnetic field gradient, enabling precise tailoring of plasma properties. Critically, the contribution of injected electrons to the discharge is maximized when their cyclotron radius matches the electrode gap, yielding peak plasma density. Furthermore, while ion bombardment energy remains stable under optimal beam injection, the ion flux exhibits significant modulation, demonstrating a decoupling between energy and flux control. These findings establish magnetic field gradients as a powerful tool for real-time plasma tuning in applications requiring dynamic control of density and ion flux.

In this study, a one-dimensional particle-in-cell/Monte Carlo collision model was employed to simulate capacitively coupled plasma discharges driven by tailored voltage waveforms and modulated with electron beam (EB) injection. The electrical asymmetry introduced by tailored voltage waveform leads to distinct plasma behaviors depending on the EB injection side. The effects of injection location, EB current, and electron energy on plasma characteristics were systematically investigated. Injection from the powered electrode significantly enhances plasma density and produces striped ionization structures in the sheath, resulting from the combined effects of the ionization energy threshold and sheath acceleration. As the electron energy increases, injection from the grounded side becomes more effective, eventually yielding higher densities due to longer electron trajectories and enhanced ionization. Increasing the EB current density from 0.5 to 2.0 A/m2 results in more uniform ionization in the bulk while maintaining an expanded but stable sheath. Moreover, the maximum ion energy at the grounded electrode decreases with increasing EB current, offering potential for ion energy control in plasma processing.

In this study, a one-dimensional particle-in-cell/Monte Carlo collision model is developed to investigate the effects of harmonic number and magnetic field variation on electron beam modulation discharges. The results show that increasing the harmonic number leads to greater voltage waveform asymmetry, which enhances sheath expansion on the powered electrode side. This enables more effective electron acceleration, resulting in higher plasma density, elevated electron temperature near the powered sheath, and the formation of a self-bias voltage. Additionally, under a fixed harmonic number, increasing the magnetic field strength initially increases the plasma density due to extended electron paths that enhance ionization. However, at stronger fields, the electron Larmor radius decreases, leading to more localized ionization near the injection side and reduced overall density. The ion energy distribution function at the powered electrode becomes narrower with decreasing peak energy, while that at the grounded electrode shows an increasing and broadened energy spectrum. These findings provide guidance for optimizing plasma density and ion energy control in plasma processing applications.

This study explores the combined effects of electron beam (EB) injection and magnetic field gradients on argon capacitively coupled plasma driven by tailored voltage waveforms, using a one-dimensional implicit particle-in-cell/Monte Carlo collision model. Simulation results show that applying a positive magnetic field gradient enhances plasma density and suppresses the asymmetry induced by EB injection and waveform excitation. As the gradient increases, electron confinement improves, leading to more localized ionization during the sheath expansion phase and a broader enhancement in plasma uniformity. In contrast, a negative magnetic field gradient intensifies density asymmetry by restricting the EB to the powered side, concentrating ionization near the injection region. Additionally, the ion energy distribution function (IEDF) becomes increasingly monoenergetic at the powered electrode, while the grounded electrode exhibits a multi-peaked profile due to sheath dynamics. These findings provide insights into magnetic-field-assisted control of plasma properties and offer promising strategies for tuning IEDF in plasma processing applications.