Molecular dynamic‐secondary ion mass spectrometry (D‐SIMS) ionized by co‐sputtering with C 60 + and Ar

• Published in: Rapid communications in mass spectrometry 2011-10, Vol.25 (19), p.2897-2904
• Main Authors: You, Yun‐Wen, Chang, Hsun‐Yun, Lin, Wei‐Chun, Kuo, Che‐Hung, Lee, Szu‐Hsian, Kao, Wei‐Lun, Yen, Guo‐Ji, Chang, Chi‐Jen, Liu, Chi‐Ping, Huang, Chih‐Chieh, Liao, Hua‐Yang, Shyue, Jing‐Jong
• Format: Article
• Language: English
• ISSN: 0951-4198; 1097-0231
• DOI: 10.1002/rcm.5181

Dynamic secondary ion mass spectrometry (D‐SIMS) analysis of poly(ethylene terephthalate) (PET) and poly(methyl methacrylate) (PMMA) was conducted using a quadrupole mass analyzer with various combinations of continuous C 60 + and Ar + ion sputtering. Individually, the Ar + beam failed to generate fragments above m / z 200, and the C 60 + beam generated molecular fragments of m / z ~1000. By combining the two beams, the auxiliary Ar + beam, which is proposed to suppress carbon deposition due to C 60 + bombardment and/or remove graphitized polymer, the sputtering range of the C 60 + beam is extended. Another advantage of this technique is that the high sputtering rate and associated high molecular ion intensity of the C 60 + beam generate adequate high‐mass fragments that mask the damage from the Ar + beam. As a result, fragments at m / z ~900 can be clearly observed. As a depth‐profiling tool, the single C 60 + beam cannot reach a steady state for either PET or PMMA at high ion fluence, and the intensity of the molecular fragments produced by the beam decreases with increasing C 60 + fluence. As a result, the single C 60 + beam is suitable for profiling surface layers with limited thickness. With C 60 + ‐Ar + co‐sputtering, although the initial drop in intensity is more significant than with single C 60 + ionization because of the damage introduced by the auxiliary Ar + , the intensity levels indicate that a more steady‐state process can be achieved. In addition, the secondary ion intensity at high fluence is higher with co‐sputtering. As a result, the sputtered depth is enhanced with co‐sputtering and the technique is suitable for profiling thick layers. Furthermore, co‐sputtering yields a smoother surface than single C 60 + sputtering. Copyright © 2011 John Wiley & Sons, Ltd.