 |
||
 |
 |
 |
|
Volume projection using IMDS models is an important tool in researching block copolymer grain boundaries. It can be used to simulate TEM images of thin slices of block copolymer, as with the TEMsim package, and can even be finessed to simulate AFM images of the surfaces of such structures.
The usefulness of volume projection as a tool for simulating TEM images is based on the fact that the different phases (blocks) have different opacity to electrons. TEM Images of thin slices of block copolymer exhibit patterns of light and dark since electrons with different trajectories encounter different proportions of the different phases. Volume projection simulates this process by constructing a ray for each pixel, and assigning a color to the pixel based on the lengths of different volumes traversed by the ray as it passes through the IMDS model.
The task of matching simulated volume projections to actual TEM images is is simplified using symmetries. Parameters in sample preparation and TEM operation are typically adjusted until patterns exhibiting certain symmetries, such as periodicity and two-fold, 3-fold, 4-fold, and 6-fold symmetries, are found. These patterns can then be compared to standard projections with the same symmetries for possible matches.
The sample preparation and TEM parameters include net tilt angles and slice thickness. The net tilt angles are a result of the interaction of the tilts of the microtome plane (the plane along which the sample is sliced) and the tilts of the microscope sample platform.