Dependence of Plasma Density on Air Gap Length of Resonant Cavity with Bottom Plate Replaced by High-Density Plasma

Abstract

To excite selectively transverse magnetic (TM) waves and to maximize E-field of a microwave oriented parallel to the plasma density gradient at a plasma surface, a resonant cavity was formed using an air gap between an upper conduction plate with a slot antenna (part of a waveguide) and a dielectric window of a microwave plasma source, in which a high-density plasma has been shown to act as the bottom plate of the cavity. The local maxima of plasma density have been observed experimentally when changing the air gap length. Finite-difference time-domain (FDTD) simulations and analytical studies show that two of these maxima may be due to the formation of TM111 and TM112 wave resonant cavities.