Ultrathin specimen preparation by a low energy Ar ion milling method

An ultra low energy ion milling method was used to prepare ultrathin specimen for transmission electron microscope observation. The samples were thinned initially by a usual focused ion beam technique or a usual ion milling with higher energy of 2-10 keV, and were thinned additionally by Ar+ ion beam with energy lower than 1 keV, typically 500-900 eV. The ultra low energy ion beam was scanned on the specimen and secondary electrons induced by the ion beam can be detected to form secondary electron images with resolution of a few μm. Because a desired area can be selected and thinned by the ultra low energy ion beam, redeposition or cross contamination with irradiating a metal mesh that supports the sample can be prevented. Final thickness of the specimen was typically 10 nm with a damage