Resolution Enhancement at Low-Accelerating-Voltage by Improvements of Diffraction Limit and Chromatic Aberration

H. Sawada, T. Sasaki, F. Hosokawa, K. Suenaga
2014 Microscopy and Microanalysis  
An atomic-resolution microscope operating at a lower voltage is increasingly requested because the lower accelerating voltage provides less specimen damage and larger scattering cross-section that results in a high signal for analysis [1] [2] [3] . However, a resolution reduction by a diffraction limit becomes severe with an increase in the wavelength of an electron as an accelerating voltage decreases. Another resolution reduction is caused by a chromatic aberration due to an energy spread of
more » ... he electron source. For maintaining atomic resolution at low accelerating voltage, a larger convergence angle realized with an aberration corrector and a narrower energy spread of the source are required. The developed microscope by us achieved atomic resolution at the accelerating voltage lower than 60 kV, using a higher-order aberration corrector [4] . The atomic-resolution imaging showing 136 pm resolution using a Si [110] has been demonstrated at 30 and 60 kV [5] . This paper reports the realization of sub-angstrom imaging at 60 kV using a Ge [112] specimen which shows 82-pm dumbbells [6] . 380
doi:10.1017/s1431927614003626 fatcat:x7tzuja535ae3cj4zk5gqwbzqi