Irradiation effects of photoemission-assisted direct current discharge plasma on metal surfaces

2"-size Al and Si substrates were treated by photoemission-assisted DC discharge Ar plasma, in which photoelectrons emitting from the negatively biased substrate surface under UV light irradiation are utilized as a trigger of discharge and therefore the substrate surface can be exposed to accelerated Ar⁺ ions. The surface morphology of Al surfaces, prepared by mechanical grinding, showed a significant decrease of arithmetical average roughness (Ra) from 341.9 nm to 260.2 nm due to Ar⁺ ion sputtering for an irradiation time of 100 min. The Si surface was also etched with maintaining surface flatness at Ra= 1-2 nm, while protrusions grew, perhaps resulting from agglomeration of sputtered Si atoms and/or masking effects of dusts. These resulsts suggest that the photoemission-assisted DC discharge plasma is applicable as an ion source for improving surface roughness of substrates.