Orientation imaging using wide angle convergent beam diffraction in transmission electron microscopy
View Patent ↗Methods of orientation imaging microscopy (OIM) techniques generally performed using transmission electron microscopy (TEM) for nanomaterials using dynamical theory is presented. Methods disclosed may use a wide angle convergent beam electron diffraction for performing OIM by generating a diffraction pattern having at least three diffraction discs that may provide additional information that is not available otherwise.
1. A method for orientation imaging microscopy, the method comprising:
obtaining a sample material to be imaged;
determining an optimized acquisition angle for a convergence electron beam;
applying the convergence electron beam to the sample, wherein convergence beam electron diffraction patters result in at least three diffraction discs, one or more of the diffraction discs having an intensity variation within the disc;
measuring diffraction patters of the sample at a plurality of points on said sample using the convergence beam electron diffraction patterns; and
processing the diffraction patterns by assigning reciprocal lattice points based on the intensity variation within the disc to determine a crystal orientation at each one of the plurality of points on the sample by comparison of diffraction disc distances or angles with distances or angles of the assigned reciprocal lattice points.
2. The method of claim 1 , wherein the sample has a thickness of about 200 nm or less.
3. The method of claim 2 , wherein the sample has a thickness of about 60 nm or less.
4. The method of claim 1 , wherein the orientation imaging microscopy is performed using one of conventional transmission electron microscopy or scanning transmission electron microscopy.
5. The method of claim 1 , wherein the convergence beam electron diffraction patterns result in between 6 and 20 diffraction discs.
6. The method of claim 1 , wherein the optimized acquisition angle is between about 0 and 50 milliradians.
7. The method of claim 1 , further comprising: generating a grain orientation map, wherein the orientation of each grain of the sample is indicated by color.
8. The method of claim 1 further comprising subtracting thermal diffusive intensity from the diffraction patterns.