ABSTRACT
We have successfully developed a spherical aberration (Cs)-corrected electron microscope for probe- and image-forming systems using hexapole correctors. The performance of the microscope has been evaluated experimentally. The point resolution attained using the image-forming Cs-corrector is better than 0.12 nm. For scanning transmission electron microscopy, the Ronchigram flat area was >40 mrad in half-angle using the probe-forming Cs-corrector.
ABSTRACT
An energy-filtering transmission electron microscope with 300 kV acceleration voltage was developed and the spatial resolution of elemental distribution images was improved. Observing oxygen monolayers in Al(11)O(3)N(9), it was shown that the actual resolution attained is up to 0.5 nm. Surface plasmon loss images of silver particles were taken with a resolution of better than 0.4 nm. Furthermore, the sensitivity is sufficiently high to distinguish indium content differences of 2.5 atomic percent in In(x)Al(1-x)As. This performance is good enough to analyze elemental distribution with atomic-level resolution. Furthermore, since analysis with the energy-filtering microscope is easy and practical, nanoanalysis may come into wide use not only in academic fields but also in industry.
ABSTRACT
A spherical aberration (Cs)-corrected 200 kV TEM was newly developed. The column of the microscope was extended by 25 cm and the inner yoke of the objective lens was modified to insert some parts of the corrector elements. The corrector has two hexapole elements that play a main role in Cs correction and they are placed at a position equivalent to the coma-free point of the objective lens by using two transfer doublet lenses. The Cs correction was successfully carried out by means of the third-order aberration that was generated in the two extended hexapoles. The Cs can be corrected to the desired value and also can be overcompensated in order to produce a negative Cs, as with the corrected Cs of -23 microm shown in this work. The optical system of the corrector does not produce second- and fourth-order aberrations, and can correct residual aberrations up to the third order. All of the corrector elements are computer-controlled and the third-order aberrations are quite stable after they are properly corrected. The resolution of 0.135 nm was experimentally confirmed by the Young's fringe method. Image simulations of a silicon [110] single crystal were made with various Cs and defocus values to demonstrate the effectiveness of arbitral control of Cs.
