Cluster ions have become the ion beam of choice for the analysis of organics in ToF-SIMS, owing to the large enhancement of the molecular ion yield [1] and the ability to depth profile through certain organic materials [2,3]. However, there is currently a lack of practical reference data on the sputtering yield volumes and damage cross-sections for commonly encountered materials in industry. Aside from having fundamental importance, these data can aid analysis by informing optimal analysis parameters, such as the useful lateral resolution achievable [4]. In this work, a systematic study using Bi+, Bi3+, Bi5+ and C60+ ions is conducted for industrially relevant organics (PMMA, PVP, hydroxypropyl cellulose, phenylalanine, cholesterol, rhodamine and Irganox 1010). We provide general recommendations to help analysts.

 

For some organic materials thicker than a monolayer, the traditional static SIMS limit may be exceeded since the secondary ion intensity is retained as the material is consumed. The useful lateral resolution may therefore be improved by integrating intensity. However, the ultimate lateral resolution is also limited by the ion source brightness. The reference data here and ion source design constraints define the present frontier of SIMS in terms of spatial resolution and molecular information. We show how this frontier has moved forward dramatically over the last 10 years and what barriers need to be overcome to allow nanoscale molecular imaging in SIMS.

 

[1] M P Seah, Surf. Interface Anal. 2007; 39: 890.

[2] J Cheng, A Wucher, N Winograd, J. Phys. Chem. B 2006; 110: 8329.

[3] A G Shard, F M Green, P J Brewer, M P Seah and I S Gilmore, J. Phys. Chem. B 2008; 112: 2596.

[4] D Touboul, F Kollmer, E Niehuis, A Brunelle, O Laprevote, J. Am. Soc. Mass Spectrom. 2005; 16: 1608.