Principles and Applications of Zone Plate X-Ray Microscopes

In this chapter, we outline some of the properties of X-ray microscope systems in operation today, and highlight some of their present applications. We will not discuss the history of X-ray microscopes prior to about 1975 but instead refer the reader to a series of conference proceedings known as “X-ray Optics and X-ray Microanalysis,” which began in 1956. Originally these had valuable material on X-ray microscopy but this diminished after about 1970. The first five were at Cambridge (1956) (Cosslett et al., 1957), Stockholm (1959) (Engström et al., 1960), Stanford (1962) (Pattee et al., 1963), Orsay (1965) (Castaing et al., 1966) and Tubingen (1968) (Molenstedt et al., 1969). We also recommend the historical perspectives by A. Baez (Baez, 1989, 1997) and the book by Cosslet and Nixon (1960). There is a recognisable thread of continuity between today’s status of the field and efforts that began slowly around 1975 (Niemann et al., 1976; Parsons, 1978; Kirz and Sayre, 1980c; Parsons, 1980) and blossomed with the availability of synchrotron light sources and nanofabrication technologies; this thread can be traced in part via the proceedings of another conference series that began in 1984 (Schmahl and Rudolph, 1984a) and has continued until today (Sayre et al., 1988; Michette et al., 1992; Aristov and Erko, 1994; Thieme et al., 1998b; Meyer-Ilse et al., 2000b; Susini et al., 2003). Zone-plate X-ray microscopes now exist at roughly two dozen international synchrotron radiation research centers (see Table 13–3), and commercial lab-based instruments are also available. Three types are in especially widespread use. Transmission X-ray microscopes (TXMs) specialize in the rapid acquisition of 2D images using high flux sources, and in the collection of tilt sequences of projection images for 3D imaging by tomography. Scanning transmission X-ray microscopes (STXMs) specialize in the acquisition of reduced dose images and point spectra with high energy resolution for elemental and chemical state mapping, and require high source brightness. Scanning fluorescence X-ray microprobes (SFXMs) are similar to STXMs except that fluorescence X-rays are collected by energy-resolving detectors for trace element mapping. All three approaches are now working below 100 nm resolution, to the point of reaching 15 nm resolution in some demonstrations (Chao et al., 2005). While many of the new technical developments continue to be pursued by specialists in X-ray optics and microscopy, much of presentday activity comes from scientists in other fields of research who are using X-ray microscopes to address their particular questions. This chapter is mainly aimed at scientists from the latter group as well as those from the other communities represented in the content of this series of books.