Nanoscale Chemical Analysis in Various Interfaces with Energy Dispersive X-Ray Spectroscopy and Transmission Electron Microscopy

The properties of materials strongly depend on their microstructure such factors as lattice defect type and density, size, distribution of phases present. During last half century, the development of transmission electron microscopy (TEM) has provided an advance in our understanding of the details of not only the microstructure but also the crystallographic feature of materials on a sub-micrometer scale (Edington, 1974; Fultz & Howe, 2002; Wiliams and Carter, 1996). On the other hand, many of materials generally consist of more than two elements and include impurities and those are applied to the industrial field. Abovementioned lattice defects in those alloys are one of preferential site of segregation of alloying elements and impurities. In order to clarify the mechanical and functional behaviors of the alloys, we should investigate not only the microstructure but also the elemental distribution of alloying elements and impurities. For latter purpose, TEM equipped with a spectroscope is considered to be one of powerful tool. Typical spectroscopes installed to TEM are energy dispersive X-ray spectroscopy (EDS), wavelength dispersive X-ray spectroscopy (WDS) and electron energy loss spectroscopy (EELS). These spectroscopes are utilized some signals resulting from an interaction between electron and specimen as shown in Fig. 1. For EDS, characteristic X-ray shown as red colored characters in Fig. 1 is analyzed. In this chapter, the EDS is focused. EELS is also one of important spectroscopy in TEM as well as EDS. The EELS is detected and analyzed an inelastic electron interacted with the specimen. EELS has an advantage for analysis of light elements such as B, C, N and O. Additionally, obtained EEL spectrum provides the chemical bonding information of the specimen. Details can be referred to some references (Brydson, 2001; Egerton, 1996). EDS combined with TEM is one of useful spectroscopy in the materials science and widely used for chemical analysis such as identification and composition of the elements in desirable region on a submicrometer scale. Especially, the field emission (FE) type electron source in the electron gun of TEM has been developed recently, and it has been enabled to analyze the chemical composition on a nanoscale, since the electron probe size with the FE type electron gun can be easily converged to less than 1nm compared with conventional thermal filament type electron gun such as tungsten (W) and lanthanum hexaboride (LaB6). So far, we had investigated the chemical analysis around the interface