Evaluation of Transmission-EBSD Method and Its Application to Observation of Microstructures of Metals

Transmission-EBSD (t-EBSD) method is proposed as a new method for nano-scale microstructures analysis of materials. t-EBSD uses TEM thin foil specimen. Electrons transmitted through the specimen form EBSD patterns. A EBSD detector used for standard EBSD (s-EBSD) is used to acquire these t-EBSD patterns. The patterns are indexed in the same manner as s-EBSD to get crystal orientation. The conditions to get good t-EBSD patterns, formation of t-EBSD patterns and spatial resolution of this method are studied in this paper. Specimen thickness affects seriously to the results of orientation mapping by t-EBSD. It is confirmed that t-EBSD patterns are formed at the bottom layer of the specimen. If the specimen is very thin, the patterns become very weak and noisy. If the specimen becomes thicker, t-EBSD patterns lose its contrast and sometimes patterns become weak with reverse contrast bands. This means that total thickness of the specimen is important for t-EBSD method, but overlapped grains look not so big problem to get t-EBSD patterns. Electron beam spread in the specimen is reduced due to thin foil specimen, and it improves spatial resolution of EBSD orientation map. It is confirmed that it can achieve about 10 nm spatial resolution and about 30 nm size grains can be detected with reasonable thickness specimen.