WEB Automated crystal orientation mapping in the TEM using a pixelated CMOS detector coupled with electron precession
Understanding the processing-structure-property relations in nanocrystalline materials has been the main interest of researchers because of their excellent mechanical properties linked with the microstructure . Transmission electron microscopy (TEM) is the most widely used technique because it has the necessary spatial resolution to resolve nanometer sized grains. In addition, precession electron diffraction (PED) assisted orientation mapping in the TEM enables an accurate and automated quantitative analysis of nanocrystalline materials . However, orientation and phase identification are often unreliable due to the low sensitivity and ambiguity of spot diffraction patterns, despite of the use of PED to minimize these disadvantages. Moreover, the acquisition of diffraction data by external charge coupled device (CCD) cameras introduces additional artifacts obstructing orientation and phase identification and requires redundant post image processing such as distortion and inclination corrections.
In this study, we optimized the process of data acquisition and analysis for PED assisted orientation mapping in TEM. A high-resolution complementary metal-oxide-semiconductor (CMOS) camera was used to acquire diffraction patterns during scanning nanobeam-diffraction. While the orientation map obtained by the conventional method shows numerous misindexed data points and scanning noise, the data acquisition with the high resolution CMOS detector is strongly suppressing these artifacts. The results show that the image quality of the diffraction patterns was improved through increasing the number of captured diffraction spots and their sharpness. This results in a significant reduction of false indexing, as well as an increased matching index leading to a higher reliability in orientation determination.