Plasma polymerization of cyclopropylamine in a low-pressure cylindrical magnetron reactor: A PIC-MC study of the roles of ions and radicals

A study of plasma polymerization of cyclopropylamine in a low-pressure cylindrical magnetron reactor is presented. Both experimental and numerical approaches are used to investigate thin film growth mechanisms and polymer film properties depending on the magnetic field strength. Combining both approaches enables the consistency of the numerical model to be checked while acquiring data for understanding the observed phenomena. Samples are first analyzed by x-ray photoelectron spectroscopy, time of flight secondary ion mass spectrometry, and ion beam analysis to illustrate the differences in degrees of chemical functionalization and cross-linking between the regions of high and low magnetic fields. 3D particle-in-cell Monte Carlo collision simulations are then performed to shed light on experimental results, after implementing a set of electron-cyclopropylamine collision cross sections computed using the R-matrix method. The simulations enable the main radicals produced in the discharge to be tracked by determining their production rates, how they diffuse in the plasma, and how they absorb on the reactor walls. Additionally, the cyclopropylamine ion (C₃H₇N⁺) behavior is followed to bring insights into the respective roles of ions and radicals during the plasma polymerization process.