Plasma sheath material induced dependence due to secondary electron emission

Abstract : Plasma sheaths in front of six different materials samples (BN, BNSiO 2 , Al 2 O 3 , SiO 2 , stainless steel and silicon) used in various experiments and devices (Hall thrusters, plasma discharge, microelectronics) are studied using the Laser Induced Fluorescence diagnostic. The specific Secondary Electron Emission (SEE) yield of each material is expected to induce differences in the sheath structure from one sample to another. The experiments are carried out in two different plasma discharges (multipolar device and ECR device), exhibiting distinct electron distribution functions: bi-maxwellian and maxwellian. The agreement between the two experiments is good and allow to classify the materials in a consistent way regarding their SEE yields. The multipolar experiments results are compared to a 1D kinetic sheath model and a 1D-1V kinetic sheath simulation code. The predictions of the model are discussed and are in good agreement with previous theory. The influence of the low energy impinging electrons on the SEE yield and emissive sheaths is investigated with the code.