Layered Synthetic Microstructures in Sequential and Simultaneous X-Ray Spectrometry

Abstract

SummaryFor many years Layered Synthetic Microstructures (LSM's) have been used successfully as dispersive devices. The commercial variety introduced in 1984 offered significantly greater stability and diffracted intensity characteristics over Thallium Acid Phthalate (TAP) crystals. These devices offer superior sensitivity for fluorine, sodium and magnesium in all but a few applications where resolution is very critical. Subsequently, a variety of these devices have been optimised for analysis of the lower atomic number elements.Recently, several industrial applications have required the development of LSM's with 2d spacings optimised to enable quantitative analysis of oxygen, nitrogen, carbon and even boron. In these applications, the large incremental difference in characteristic wavelength per atomic number step limits the dynamic range of elements over which the LSM can be optimised. These considerations are discussed as they relate to routine analyses of very low atomic number elements by sequential Wavelength Dispersive Spectrometry (WDS).Newly developed fabrication techniques are used to produce curved LSM's for use with the focusing optics of simultaneous WDS. Application of these curved devices for the analysis of Mg in steel, Na in slags and F in glass will be discussed.Finally, an application which requires the analysis of thin films on semiconductor devices will be described. In this method, characteristic K-spectra and L-spectra of low and high atomic number elements, respectively, are selected for optimum sensitivity to the surface composition.