Realistic Treatment of Plasma-Surface Interactions in Simulations of Low Temperature Plasmas: From a New Diagnostic to Optimization of Process Control

West Virginia University Research Corporation, Morgantown WV

Investigators

Abstract

This project will develop a new experimental diagnostic and an improved computational model to characterize interactions between a material surface and a low temperature plasma, a weakly ionized gas composed of electrons, ions, and neutral atoms and molecules. Low temperature plasmas are essential for modern life as they form the basis for manufacturing a variety of high-technology products ranging from laptops and smartphones to displays and solar cells. They are also relevant for a variety of medical applications such as sterilization of medical equipment and wound healing. All these applications are based on the ability of the plasma to induce distinct surface reactions in a controlled way. In order to optimize these applications, plasma simulations, including a realistic implementation of plasma-surface interactions, are crucial. In this project, a new diagnostic to measure key aspects of the plasma-surface interaction physics will be developed, and results will be implemented into a computational model. Results obtained from this research will also be incorporated into graduate level lectures on low temperature plasma science. Most simulations of capacitive radio frequency plasmas (CCP) only include constant ion induced electron emission and electron reflection at guessed probabilities. Any dependencies on the incident particle energy, angle, and surface material as well as other effects are neglected. This leads to an incorrect description of the particle heating dynamic and flux-energy distribution functions (FEDF). For many surface materials and gases secondary electron emission coefficients induced by electron, ion, and neutral impact as well as particle reflection and sputter rates are unknown in the presence of plasmas that alter the surface conditions. In this project, a novel simulation based diagnostic to measure effective gamma-coefficient by Optical Emission Spectroscopy in the plasma will be developed. Realistic energy and surface dependent electron emission and reflection coefficients for different incident particle species will then be implemented into PIC simulations of CCPs. The simulation code will be benchmarked against experiments and the effects of realistic surface coefficients on the electron heating dynamics and the control of FEDFs of different particle species will be studied. All investigations will combine state-of-the-art simulations with experiments.