| Pacific Rim Symposium on Surfaces, Coatings and Interfaces (PacSurf 2016) | |
| Thin Films | Monday Sessions |
| Session TF-MoM |
| Session: | Advances/Innovation in Synthesis & Characterization |
| Presenter: | John Newman, Physical Electronics, USA |
| Authors: | J.G. Newman, Physical Electronics, USA S.R. Bryan, Physical Electronics, USA G.L. Fisher, Physical Electronics, USA P.E. Larson, Physical Electronics, USA J.S. Hammond, Physical Electronics, USA R.M.A. Heeren, Maastricht University S. Iida, Ulvac-PHI H. Chang, Ulvac-PHI T. Miyayama, Ulvac-PHI |
| Correspondent: | Click to Email |
Over the last quarter century Time-of-Flight Secondary Ion Mass Spectrometry (TOF-SIMS) has been successfully used to characterize the molecular composition of the outermost layers of solid surfaces. However, even with mass resolutions greater than 15,000 m/Δm and mass accuracies better than 10 ppm, making definitive chemical assignments of higher mass peaks above ~200 m/z has continued to be a challenge. This problem has become even more pronounced with the advent of cluster beams (e.g. Au3, Bi3, C60 and Ar gas cluster) which provide substantially improved yields for higher mass fragment ions. To overcome this shortcoming, Physical Electronics has developed a revolutionary TOF-SIMS tandem mass spec method specifically designed to unambiguously identify the composition of higher mass secondary ions [1]. The method allows for MS/MS spectra (MS2) of select secondary ions of interest (precursor ions) to be acquired in parallel with conventional TOF-SIMS spectra (MS1); both being simultaneously generated from the same analytical volume. The precursor ion, defined by a 1 Da selection window, is deflected from the MS1 secondary ion stream into an argon filled high energy (1.5 keV) collision-induced-dissociation (CID) cell. In the CID cell, the precursor ions collide with argon atoms which results in partial fragmentation of the precursor ions. The precursor and its fragment ions are then accelerated into a linear TOF analyzer and recorded by a pulse-counting detector. In both the MS1 and MS2 data, a full mass spectrum is collected for each image pixel, with spatial resolutions in the tenths of a micrometer. As the MS2 spectra are predominantly generated from single molecular ions, they are much cleaner and simpler than conventional MS1 spectra which usually contain secondary ions from multiple chemical species. The MS/MS fragmentation spectrum (MS2) is used to identify the composition of the precursor ion by either identification of the fragmented ions and/or comparison to spectra contained in on-line databases. Applications of this new method will be shown for a variety of materials including polymers, pharmaceuticals, tissue cross sections, and other organics.
References
[1] P.E. Larson, J.S. Hammond, R.M.A. Heeren and G.L. Fisher, Method and Apparatus to Provide Parallel Acquisition of MS/MS Data, U.S. Patent 20150090874, April 2015