Electron Beam Driven Plasmas in O$_{\mathrm{2}}$: Modeling and Diagnostics

Electron beam driven plasmas are well-known for their low electron temperature ($T_{e})$, which leads to low plasma potential. These plasmas have been demonstrated as ideal sources for high-precision plasma processing applications such as atomic layer etching and functionalization of 2-dimensional materials (e.g., Graphene). Several diagnostic techniques were used to characterize magnetized electron beam plasmas in O$_{\mathrm{2}}$. These diagnostics allowed measurements of spatially-resolved electron density, electron temperature and ion flux for a range of pressures, beam currents, magnetic fields and beam electron energies. As expected $T_{e}$ was low (\textless 0.3 eV) in these plasmas. There were however some surprises, such as a O$^{\mathrm{+}}$ flux being higher compared to O$_{\mathrm{2}}^{\mathrm{+}}$ flux. This paper focuses on 2-dimensional modeling of the O$_{\mathrm{2}}$ electron beam driven plasma with detailed comparison to experiments. The simulations utilized a hybrid plasma model with bulk electrons and ions treated as a fluid and a Monte Carlo model for the beam electrons. We will discuss the enhancements in the O$_{\mathrm{2}}$ plasma chemistry that allowed the model to capture most experimental observations. This work is partially supported by the Naval Research Laboratory base program.