Time-of-flight secondary ion mass spectroscopy for surface analysis of insulators using a cluster ion beam

An effect of the impact of cluster ions into insulating materials on charged secondary emission [K. Hirata, Y. Saitoh, K. Narumi, and Y. Kobayashi, Appl. Phys. Lett. 81, 3669 (2002)] was applied to secondary ion mass spectroscopy. Positive secondary ion time-of-flight (TOF) measurements of polycarbonate films using 0.5 MeV/atom C1+ monoatomic and 0.5 MeV/atom C8+ cluster ions as primary ions were performed as a function of atomic dose without charge compensation. The use of C8+ instead of C1+ eliminated dose-dependent peak shifts and overall spectrum compression due to charging observed with C1+ bombardment. Furthermore, the C8+ bombardment was found to provide better spectrum resolution than the C1+ bombardment. The superior stability of the TOF spectra against charging makes mass spectrometry with cluster ion ionization a promising tool for the chemical analysis of insulating materials.