Organic Depth Profiling by Cluster Ion Sputter

Abstract

  Depth profiling of model organic thin films composed of Alq₃ and α-NPD on ITO-covered glass has been performed by Ar⁺ or C₆₀⁺⁺ ion sputter. In the case of conventional 2keV-Ar⁺ ion sputter, as a result of the severe damage there are no peaks characteristic of their molecular structure, and a specific elemental ion of Al⁺ is the only sign of Alq₃. Al⁺ profiles of Alq₃ with different thickness show a constant sputtering yield. On the other hand, we can observe the survival of C₁₈H₁₂N₂O₂Al⁺ (Alq₂⁺) by use of 20 keV-C₆₀⁺⁺ cluster ion sputter. However, Alq₃ films show the quite dose-dependent sputtering yields. The dose dependency is caused by the accumulation of the sample damage, which is represented by the increase of C⁺ and C₂⁺. The intensities of low mass fragment ions can be available as an index of the accumulating sample damage.