Artifacts in sample preparation of transmission electron microscopy

Two types of typical artifacts induced by ion milling, damage on the surface and temperature elevation, were investigated. The ion-induced damage layer on the surface reached as high as 3.46 nm when 5 keV argon ions were bombarded at 75 degrees of incidence from the surface normal of Si(001). Cleaning up the surface using 250 eV argon ions could minimize the surface damage close to the level of natural oxide thickness. The local temperature was measured from samples with thermocouples mounted in two different ways. The temperature reached 296degreesC when a single ion gun was used to mill the sample at 5 keV with 80 degrees of incidence angle, while the sample with thick substrate was heated up to 198degreesC. A gold thin film was investigated to confirm the ion beam-induced annealing as an artifact. Possible ways to reduce the thermal load in the sample are suggested.