High Resolution TEM Imaging with Hollow-cone illumination presented at MSA'97 Meeting, Cleveland, OH August 13, 1997 [Abstract is here]

Imaging with tilted illumination: how does it work?

For axial illumination (above, left) the incident beam is in the center (in reciprocal space) and directly interpretable information transferred through the microscope is limited either by the objective aperture or by point-to-pint resolution of the microscope (if no objective aperture is used). In the case shown above, information up to 2 gets transferred. Now, if one tilts the beam as shown above (right), 1 information gets transferred. In the case of fixed tilt, this resolution enhancement will be highly directional and, in fact, in the perpendicular direction one would lose resolution. Hollow cone illumination takes care of this directionality as can be seen in the picture below where 2-dimensional contrast transfer functions corresponding to axial, fixed tilt, and hollow cone are shown.

Experimental Images

Gold particles on amorphous carbon axial and hollow-cone (for two different tilt angles) images Note: reduced contrast from amorphous carbon axial (left)and hollow-cone (right) images Note: nicely resolved Au lattice and reduced contrast from amorphous carbon

Si/SiO2 interface axial (bottom) and hollow-cone (top) images Note: nicely resolved Si lattice and reduced contrast from amorphous SiO2 hollow-cone image of Si (right) Note: Si dumbbells are clearly resolved! Left: Fourier transform of the image Note: presence of the 422 peak of Si indicates information transfer up to (down to?) 1.095

CdTe axial image of CdTe and its Fourier transform hollow-cone image of CdTe and its Fourier transform High-pass filtered hollow-cone image of CdTe Note CdTe dumbbells in the inset

Last updated: April 28, 2017