Chemical erosion and sputtering of solid surfaces with liquid cluster ions

The sputtering phenomena of solid surfaces such as Si(111) and SiO2 surfaces were investigated using ethanol and water cluster ion beams. To be compared with Ar monomer ion irradiation, the sputtering yield of Si surfaces was approximately 100 times higher for ethanol cluster ion irradiation and approximately 10 times higher for water cluster ion irradiation. Furthermore, for the ethanol cluster ion irradiation, chemical erosion such as silicon hydride and hydro-carbide reaction occurred on the Si surface, which resulted in the high-rate sputtering of the surface. On the other hand, for the water cluster ion irradiation, oxidation occurred on the Si surface, and physical sputtering was performed on the surface. Based on these results, chemical reaction at a nano-scale area on the Si(111) surfaces was discussed from the thermodynamic approach, and the impact of cluster ions on the surface exhibited high temperature such as a few tens of thousands degrees, which resulted in the enhancement of the chemical reaction. Thus, liquid cluster ion irradiation exhibited unique erosion and sputtering even at room temperature, which were not obtained by a conventional wet process.