Study on monatomic fraction improvement with alumina layer on metal electrode in hydrogen plasma ion source

Abstract

A high monatomic beam fraction is an important factor in a hydrogen ion source to increase the application efficiency. The monatomic fraction of hydrogen plasmas with different plasma electrode materials is measured in a helicon plasma ion source, and aluminum shows the highest value compared to that with the other metals such as copper and molybdenum. Formation of an aluminum oxide layer on the aluminum electrode is determined by XPS analysis, and the alumina layer is verified as the high monatomic fraction. Both experiments and numerical simulations conclude that a low surface recombination coefficient of the alumina layer on the plasma electrode is one of the most important parameters for increasing the monatomic fraction in hydrogen plasma ion sources.

Surface enhancement of molecular ion ${{\rm{H}}}_{2}^{+}$ yield in a 2.45-GHz electron–cyclotron resonance ion source

“…[12] Furthermore, alumina also had a high secondary electron emission ability which was advantageous for the dissociation of H + 2 and formation of proton. [9] This may explain why the current of H + 2 was the lowest with Al liner in experimental materials.…”

“…Jung et al also investigated the suitable material of the plasma electrode for proton generation in a helicon ion source, and alumina that had a very low recombination possibility was concluded to be very effective. [9] However, there is no particular investigation concerning the dependence of hydrogen molecular ion on the plasma chamber surface. Here, SS, Ta, quartz, and Al are selected in our study.…”