EBSD Analysis Of Long Period Structures Based On Dynamical Electron Diffraction Theory

The long-period structure has attracted extensive attention due to its special microstructure and excellent performance.The complex stacking sequence of the long-period makes its structure special.It was found that EBSD pattern was different with the change of electron beam incident depth during the analysis the long-period structural materials.This may be contributed to the different structural symmetry of the long-period structure with different thickness.However,it is difficult to profoundly understand the relationship between the crystal structure and EBSD pattern of the long-period structure at different thickness through EBSD experiments.The influence of the depth change along the thickness direction of the long-period structure on the EBSD pattern can be revealed by using the dynamic electron diffraction theory.In this paper,a representative long-period structure Si C was selected for research.The main research contents and results are as follows.(1)The EBSD pattern of the long-period structural Si C at the different depth of the electron beam incident was simulated based on the unit cell as a whole.The formula of EBSD patterns simulated by dynamical electron diffraction theory in the non-orthorhombic system was derived.The conversion relationship of the convertor aperture between non-orthorhombic system and orthogonal system was obtained.The drawing method of EBSD pattern in the non-orthorhombic system was summarized.By comparing the experimental EBSD pattern with the simulated EBSD pattern and the projection diagram of the atomic model with the simulated potential function,it was verified that our simulation method was correct.The real-space method based on the dynamical electron diffraction theory in non-orthogonal system was used to simulate the EBSD patterns of 2H-Si C,3C-Si C,4H-Si C and 6H-Si C at different depths of the incident electron beam.The results indicated that EBSD pattern was different at the different depth of the electron beam incident due to the different structure symmetry.(2)EBSD pattern was simulated for the different stacking sequences of Si C based on the stacking structure.The real space method based on the stacking structure was established and EBSD patterns of several different stacking sequences in long-period structural Si C were simulated.The simulation results based on the stacking algorithm were compared with those based on the unit cell algorithm.The results revealed that EBSD pattern was different due to the different symmetry of stacking sequences.Moreover,the period of the unit cell was destroyed since the calculation process of EBSD pattern based on the stacking unit cell was not performed in a complete unit cell,resulting in no high-order Laue band effect in the simulated EBSD pattern.