SIMS2015 Session MPS-MoM: Plenary Session

The demands for chemical imaging in industry and academia are growing at an unprecedented pace and so too are the challenges. These include imaging from the nanoscale to the macroscale, from graphene to rats, from atoms to proteins and in ambient conditions and in real-time. To date, there is no instrument that can do all of this! Instead, these requirements have driven innovation and revolution in techniques, with each bringing an important analytical perspective. Consequently, in a challenge-driven environment, a multi-technique approach is needed. For this to be successful, it is essential that the measurement information from each technique is well understood (for example SIMS has an information depth of a few nanometres, whereas optical techniques are many hundreds of nanometres) it is also imperative to be able to rationalise, computationally, all of the data so that it can be de-constructed into answers.

Recent progress in key chemical imaging techniques will be reviewed and a revolutionary 3D nanoSIMS instrument introduced. This instrument incorporates the powerful Thermo Scientific™ Orbitrap™ mass analyzer for high-performance identification of molecules. SIMS is, of course, excellent. However, a critical limitation, particularly in the important life-sciences is the sample vacuum environment. Raman is another powerful label-free technique but the application to imaging has been hampered by poor sensitivity. The use of stimulated Raman spectroscopy (SRS) by the Xie group for label-free biomedical imaging has overcome this barrier allowing video rate imaging. This is a tremendous complement to mass spectrometry imaging and the benefits of a combined approach of will be illustrated.

Raman is especially powerful for the analysis of graphene owing to the high scattering cross-section and the ability to clearly identify defects from the ratio of the D- and G-peak intensities. The ultimate in chemical resolution (<20 nm) is achieved with tip enhanced Raman spectroscopy, allowing defects in single layer graphene at the nanoscale to be measured. SIMS provides a detailed chemical characterisation of surface contamination and processing residues, which are increasingly of concern for device performance. A multi-technique approach for the study of graphene will be highlighted.

More techniques, more power, more speed also brings more data. The relentless power-law increase in data size (for example 4D ion mobility, mass spectrometry image exceeds 100 Gbytes) is now one of the major bottlenecks for analysis. Potential routes forward will be discussed.