Development of Atomic-Resolution Low-Voltage TEM and Observation of Low-Dimensional Materials

Shigeyuki Morishita, Masaki Mukai, Hidetaka Sawada, Yung-Chang Lin, Ryosuke Senga and Kazu Suenaga

Abstract: Low-voltage TEM is used for analyzing low-dimensional materials which are damaged by high energy electrons. However, spatial resolution at low voltages is severely degraded by geometric and chromatic aberrations. Here we developed low-voltage TEM equipped with delta-type aberration correctors and a monochromator to suppress the effect of these aberrations. By using the TEM, an atomic distance of 0.142 nm in monolayer graphene was resolved at 15–60 kV. In addition, Fourier transform of monolayer WS₂ image at 15 kV shows spots corresponding to less than 10 times the electron wavelength. Observation of carbon atomic chains indicated that dynamic observation with large field of view is available with atomic resolution. Various kinds of low-dimensional materials will be analyzed by using this atomic-resolution low-voltage TEM.

Key words: low-voltage transmission electron microscope, atomic resolution, aberration correction, monochromator, graphene