AVS 51st International Symposium
    Applied Surface Science Wednesday Sessions
       Session AS+BI-WeA

Paper AS+BI-WeA1
G-SIMS-MS: Towards Molecular Structure at Surfaces

Wednesday, November 17, 2004, 2:00 pm, Room 210A

Session: Biological Applications of Surface Analysis
Presenter: I. Gilmore, National Physical Laboratory, UK
Authors: I. Gilmore, National Physical Laboratory, UK
F. Green, National Physical Laboratory, UK
M. Seah, National Physical Laboratory, UK
Correspondent: Click to Email
SSIMS is a powerful technique for the analysis of complex surfaces. However, many view SSIMS as an excellent research tool but unreliable as an analytical method. This is changing. Modern instruments have superb repeatability and reliability. In the VAMAS 2002 SSIMS inter-laboratory study, the average repeatability of 27 instruments was already 2%. Accessibility to SSIMS measurements is increasing rapidly. However, the complexity of mass spectra makes identification and quantification far from straightforward, even for the experts! This is a major barrier to the wider take-up of SSIMS, especially in new fields. One way around this problem is G-SIMS. G-SIMS or gentle SIMS is a library independent method providing a straightforward way to simplify SSIMS spectra@footnote 1 @@footnote 2 @@footnote 3 @. SSIMS spectra are composed of parent fragment ions amongst a large number of high intensity degradation products. In G-SIMS, this fragmentation may be quantified in terms of the partition functions of the fragments emitted from a surface plasma with effective temperature, T@sub p@. By extrapolation of the data to low T@sub p@, the intensity of the degradation products rapidly reduces, revealing the parent fragments. The latter peaks are directly characteristic of the material without rearrangement and can enable direct interpretation and identification. This is fine for smaller molecules but, within the plethora of possible larger molecules for which a total mass is insufficient to provide adequate characterisation, an extension of G-SIMS has exciting prospects to elucidate the required structure. Here we use, G-SIMS-MS, to explore the re-building of parent molecules using the fragmentation pathways that are mapped out as T@sub p@ is varied. @FootnoteText@ @footnote 1@ I S Gilmore and M P Seah, Appl. Surf. Sci., 161 (2000) 465. @footnote 2@ I S Gilmore and M P Seah, Appl. Surf. Sci., 187 (2002) 89. @footnote 3@ I S Gilmore and M P Seah, Appl. Surf. Sci., 203-204 (2003) 551.