System, apparatus, and method for determining elemental composition using 4D STEM
The present disclosure relates to transmission electron microscopy for evaluation of biological matter. According to an embodiment, the present disclosure further relates to an apparatus for determining the structure and/or elemental composition of a sample using 4D STEM, comprising a direct bombardment detector operating with global shutter readout, processing circuitry configured to acquire images of bright-field disks using either a contiguous array or non-contiguous array of detector pixel elements, correct distortions in the images, align each image of the images based on a centroid of the bright-field disk, calculate a radial profile of the images, normalize the radial profiles by a scaling factor, calculate the rotationally-averaged edge profile of the bright-field disk, and determine elemental composition within the specimen based on the characteristics of the edge profile of the bright-field disk corresponding to each specimen location.
1. A method for determining material properties of a sample using 4D STEM, comprising:
directing an electron beam from an electron source toward the sample;
detecting electrons of the electron beam interacting with the sample via an electron detector including an array of detector elements;
acquiring, from the electron detector, images of bright-field disks and surrounding dark-field diffraction based on the detected electrons; and
determining an elemental composition of the sample based on the acquired images of the bright-field disks and the surrounding dark-field diffractions,
wherein the detecting detects the electrons using the electron detector in a global shutter readout mode, and synchronizes each acquired image from the electron detector with a movement of a probe directing the electron beam.
2. The method according to claim 1 , further comprising:
correcting distortions in the acquired images.
3. The method according to claim 2 , wherein the determining of the elemental composition of the sample based on the acquired images of the bright-field disks and the surrounding dark-field diffractions further comprises:
calculating a radial profile of the distortion-corrected acquired images;
normalizing the radial profile by a scaling factor;
determining a shape of the radial profile at an edge of the bright-field disks; and
determining the elemental composition based on the shape of the radial profile at the edge of the bright-field disks.
4. The method according to claim 2 , wherein the distortions in the acquired images are geometric and the correcting of the geometric distortions includes fitting an ellipse to the bright-field disks.
5. The method according to claim 3 , wherein the radial profile is normalized based on an average intensity of the bright-field disks.
6. The method according to claim 1 , further comprising:
aligning each image of the images of the bright-field disks with one another based on a center of each of the bright-field disks.
7. The method according to claim 3 , where the shape of the radial profile corresponds to a slope of the radial profile for a transition between areas of the bright-field disks and the surrounding dark-field diffractions.