Laser-induced buried microstructure in bulk materials under intense excitation

While a Conventional Transmission Electron Microscope (CTEM) is based on a DC electron cathode at an acceleration voltage of a few hundreds of kV, RUEDI is equipped with a pulsed MeV electron beam in order to image transient microstructures at a time resolution less than a nanosecond.

For imaging, an objective lens of RUEDI consists of a wide gap pole piece that allows the observations of dynamics of buried microstructures in bulk under intense excitations.

In the process of silicon wafer dicing, for example, micrometer size voids are formed in the bulk via a laser-induced modified volume (LIMV) process. As the laser enter and exit the wafer, it heats up a microscopically local region in the bulk that causes defects, voids and crystallites. These phenomena occur in specimens with thicknesses of 100 micrometer. In order to investigate the buried transient structure, the wafer needs be thinned down to the thickness of more than a few micrometers, which are too thick for CTEM. Such dynamics are also not accessible using (Ultrafast) Scanning Electron Microscopy which is only sensitive to surface structures but not those in bulk.

Reference: D Kawaguchi, H Iwata & H Saka, Phil. Mag. (2019). DOI:10.1080/14786435.2019.1605216.

CTEM of an array of LIMVs just beneath an exit-surface

^{Image: CTEM of an array of LIMVs just beneath an exit-surface.}