Surface reactivity imaging, scanning

Over the past decade or so, our understanding of oxide surfaces has markedly improved, especially in the case of the model oxide surface-Ti02(l 10). In particular, the influence of defects such as oxygen vacancies on the surface reactivity has been demonstrated in exquisite detail and it is clear that they play a crucial role in many surface reactions. As we have shown in this chapter, scanning probes have been instrumental in evaluating the surface reactivity as they allow individual defects, reactants, and products to be imaged on relatively short timescales (seconds or minutes). 

The capabilities of SECCM are demonstrated most powerfully when it is used in the imaging mode, where a surface of interest is scanned with the SECCM probe meniscus to produce x-y maps of surface reactivity, simultaneously with topography and ion conductance (between the two QRCEs). SECCM images can be complemented with a variety of structural characterization techniques, applied to the same region of the surface, such as FE-SEM, micro-Raman, AFM, and electron backscatter diffraction (EBSD). This type of multimicroscopy approach provides a rich and powerful platform for elucidating how local reactivity is influenced by the properties of the surface under investigation. 

G. Wittstock, Imaging localized reactivities of surfaces by scanning... 

When the tip is scanned laterally above the substrate, the obtained image reflects both the surface topography and the distribution of its chemical reactivity. This makes the data interpretation difficult if no a priori information... 

In 1967 Liebl reported the development of the first imaging SIMS instrument based on the principle of focused ion beam scanning [24]. This instrument, the ion microprobe mass analyzer, was produced by Applied Research Laboratories (Fig. 4.5). It used an improved hollow cathode duoplasmatron [25] ion source that eliminated filaments used in earlier sources and allowed stable operation with reactive gases. The primary ion beam was mass analyzed for beam purity and focused in a two-lens column to a spot as small as 2 pm. The secondary ions were accelerated from the sample surface into a double focusing mass spectrometer of Mattauch-Herzog geometry. Both positive and negative secondary ions were de-... 

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