STEM tomography in the scanning electron microscope
Matteo FERRONI
(Università degli Studi di Brescia)
In the 3D methods in the SEM presently implemented, the specimen is serially-sectioned by focused ion beam or microtome cutting and the reconstruction of relatively large volumes is obtained by reassembling the images obtained through this slice-and-view method. A complementary approach is hereby reported, were the three-dimensional reconstruction of a microscopic specimen is achieved from a set of images obtained in the SEM, followed by reconstruction of the mass distribution using the backprojection algorithm of tomography. Operating the microscope in the scanning-transmission imaging mode fulfills the projection requirement needed for the tomographic workflow. A Si-based electron detector has been specifically developed for the purpose, and the detection strategy has been tailored in order to maintain the projection requirement over the large tilt range. Compressed sensing was used to solve the undetermined problem of structure reconstruction from few projections and was proved capable to overcome the limitations arising from the sampling scheme. The proposed system exploits the flexibility of the SEM platform and the capability of the STEM imaging mode to be applied for both biological and physical science.
