The impact of hydrogen plasma on the structure and morphology of tin and lead micrometer sized particles

The stability of micrometer sized particles in hydrogen plasma is essential for extreme ultraviolet lithography, the ITER fusion program and the application of hydrogen plasma etching. We experimentally investigated the morphological evolution of tin (Sn), lead (Pb), and lead (II) oxide (PbO) micrometer sized particles on a surface that is exposed to a low pressure hydrogen plasma. Post exposure particle cross sections obtained by a scanning electron microscope accompanied by a focused ion beam demonstrated a significant influence of hydrogen plasma exposure on both the surface and the bulk material of the particles. Chemical sputtering at the surface and accumulation of pressurized hydrogen bubbles in cavities in the bulk material are the main drivers of the morphological changes. These mechanisms may influence the adhesion of particles to the surface through the introduction of asperities, increase of contact spot area, or fragmentation after the accumulation of mechanical stress.