We measured the sputtering yield, surface roughness and surface damage of thin leucine films bombarded with Ar cluster ions and examined the usefulness of large gas cluster ions for the depth pro. ling of organic compounds. Ar cluster ion beams with a mean size of 2000 atoms/cluster and energies from 5 to 30 keV were used. Sputtering yields increased linearly with incident ion energy and were extremely high compared to inorganic materials. Surface damage was investigated by measuring positive secondary ions emitted from the leucine film before and after cluster ion irradiation. After irradiation the leucine surface became smoother. The yield ratio of protonated leucine ions to other fragment ions kept constant before and after Ar cluster ion irradiation. These results indicate that large gas cluster ions are useful for depth pro. ling of organic compounds. (c) 2008 Published by Elsevier B.V.