Ion microscopy

While field ion microscopy has provided an effective means to visualize surface atoms and adsorbates, field emission is the preferred technique for measurement of the energetic properties of the surface. The effect of an applied field on the rate of electron emission was described by Fowler and Nordheim [65] and is shown schematically in Fig. Vlll 5. In the absence of a field, a barrier corresponding to the thermionic work function, prevents electrons from escaping from the Fermi level. An applied field, reduces this barrier to 4> - F, where the potential V decreases linearly with distance according to V = xF. Quantum-mechanical tunneling is now possible through this finite barrier, and the solufion for an electron in a finite potential box gives... 

Measuring the electron emission intensity from a particular atom as a function of V provides the work function for that atom its change in the presence of an adsorbate can also be measured. For example, the work function for the (100) plane of tungsten decreases from 4.71 to 4.21 V on adsorption of nitrogen. For more details, see Refs. 66 and 67 and Chapter XVII. Information about the surface tensions of various crystal planes can also be obtained by observing the development of facets in field ion microscopy [68]. 

FIM Field ion microscopy [63, 62, 103] He ions are formed in a high field at a metal tip Surface structure... 

E. W. Miiller and T. T. Tsong, Field Ion Microscopy, American Elsevier, New York, 1969. 

Mobility of this second kind is illustrated in Fig. XVIII-14, which shows NO molecules diffusing around on terraces with intervals of being trapped at steps. Surface diffusion can be seen in field emission microscopy (FEM) and can be measured by observing the growth rate of patches or fluctuations in emission from a small area [136,138] (see Section V111-2C), field ion microscopy [138], Auger and work function measurements, and laser-induced desorption... 

Figure Bl.24.17. An example of scanning transmission ion microscopy (STIM) measurements of a human oral cancer cell. The different images indicate different windows in the energy of transmitted helium ions as indicated in the figure. White indicate areas of high counts. The teclmique offers a thickness scan through the sample, and, in this case, the cell walls of one specific cell can be seen in the areas dominated by thicker structures (data from C A Pineda, National Accelerator Centre, Fame, South Africa).

L. E. Murr, Electron and Ion Microscopy and Microanalysis Principles and Applications, 2nd ed.. Optical Engineering Vol. 29, Dekker, New York, 1991. 

Muller, E.W. and Tsong, T.T. (1969) Eield-Ion Microscopy Principles and Applications (Elsevier, Amsterdam). 

The last twenty years have seen a rapid development of surface physics. In particular, the properties of clean perfect surfaces (with two-dimensional periodicity) are henceforth well known and understood. In recent years, the focus has been put onto surfaces with defects (adatoms, steps, vacancies, impurities...) which can now be investigated experimentally due either to the progress of old techniques (field ion microscopy or He diffraction, for instance) or to the rapid development of new methods (STM, AFM, SEXAFS...). 

Field ion microscopy, scanning tunnelling microscopy (morphology analysis, etc.) L.E.E.D. (structure)... 

Field-ion Microscopy , Defects In Crystalline Solids Series, 2, North Hoiland Pub Co. (1970) 43) J.A. Swift, Electron Microscopes , Barnes Noble Publ (1970) 44) W.E. Voreck,... 

Many years have passed since the early days of AFM, when adhesion was seen as a hindrance, and it is now regarded as a useful parameter for identification of material as well as a key to understanding many important processes in biological function. In this area, the ability of AFM to map spatial variations of adhesion has not yet been fully exploited but in future could prove to be particularly useful. At present, the chemical nature and interaction area of the AFM probe are still rarely characterized to a desirable level. This may be improved dramatically by the use of nanotubes, carbon or otherwise, with functionalized end groups. However, reliance on other measurement techniques, such as transmission electron microscopy and field ion microscopy, will probably be essential in order to fully evaluate the tip-sample systems under investigation. 

FIM Field ion microscopy GFAAS Graphite furnace atomic absorption... 

Miller, M.K., Cerezo, A., Fletherington, M.G. Smith, G.D.W. (1996) Atom Probe Field Ion Microscopy, Oxford University Press, Oxford, UK. 

A flat surface required for best depth resolution and for ion microscopy Destructive analysis. 

Fast Fourier Transform Flow Injection Analysis Field Ion Atom Probe Flame-Ionization Detector Field Ion Microscopy... 

---