Cluster secondary ion mass spectrometry: an insight into “super-efficient” collision cascades

• Published in: Applied surface science Vol. 231; pp. 54 - 58
• Main Authors: Rickman, Richard D., Verkhoturov, Stanislav V., Schweikert, Emile A.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.06.2004
• Subjects: Cluster SIMS; Coincidental ion mass spectrometry (CIMS); Nanoanalysis; Polyatomic projectiles; Cluster SIMS; Nanoanalysis; Polyatomic projectiles; Coincidental ion mass spectrometry (CIMS)
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2004.03.026

Some collision cascades, induced by keV polyatomic projectiles, result in the emission of multiple secondary ions. Such coincidental ion emission implies that the ejecta originate from molecules co-located within a nano-volume perturbed by a single projectile impact, thus providing an approach for the chemical analysis of nano-domains. The relevance for the chemical analysis of nano-structures depends on the effectiveness of the projectile to cause co-emission of two or more analytically significant secondary ions. The experiments involved Au n m+ projectiles (1≤ n≤4; m=1, 2) on phenylalanine targets. We have measured the yields for events in which multiple ions were detected as a function of projectile characteristics. The data show that some collision cascades are “super-efficient”. For example, in a four-ion detection event, the yield for the phenylalanine molecular ion is two orders of magnitude larger from Au 4 impacts than from equal velocity Au + projectiles.