Post-thinning using Ar ion-milling system for transmission electron microscopy specimens prepared by focused ion beam system

Summary We investigate Ar ion‐milling rates and Ga‐ion induced damage on sample surfaces of Si and GaAs single crystals prepared by focused ion beam (FIB) method for transmission electron microscopy observation. The convergent beam electron diffraction technique with Bloch simulation is used to measure the thickness of the Ar‐ion milled samples to calculate the milling rates of Si and GaAs single crystals. The measurement shows that an amorphous layer is formed on the sample surface and can be removed by further Ar‐ion milling. In addition, the local symmetry breaking induced by FIB is investigated using quantitative symmetry measurement. The FIBed‐GaAs sample shows local symmetry breaking after FIB milling, although the FIBed‐Si sample has no considerable symmetry breaking.