Sample preparation for analytical scanning electron microscopy using initial notch sectioning.

A novel method for broad ion beam based sample sectioning using the concept of initial notches is presented. An adapted sample geometry is utilized in order to create terraces with a well-define d step in erosion depth from the surface. The method consists of milling a notch into the surface, followed by glancing-angle ion beam erosion, which leads to preferential erosion at the notch due to increased local surface elevation. The process of terrace formation can be utilized in sample preparation for analytical scanning electron microscopy in order to get efficient access to the depth-dependent microstructure of a material. It is demonstrated that the method can be applied to both conducting and non-conducting specimens. Furthermore, experimental parameters influencing the preparation success are determined. Finally, as a proof-of-concept, an electron backscatter diffraction study on a surface crystallized diopside glass ceramic is performed, where the method is used to analyze orientation dependent crystal growth phenomena occurring during growth of surface crystals into the bulk.

Rapid and localized ion-beam etching of surfaces using initial notches.

Glancing-angle Ar+ broad ion beam erosion is widely used for the preparation of high-quality transmission electron microscopy (TEM) samples. However, low erosion rates and lack of site specificity are major drawbacks of the method. Being inexpensive and easy to use - in particular when compared to widely used focused ion beam preparation methods - overcoming these drawbacks would significantly improve many existing preparation workflows. We present a novel method for rapid and localized surface erosion which combines laser-machining preprocessing with broad ion beam etching. In this article, preliminary studies of the method on bulk samples are reported. Furthermore, an electron-transparent lamella has been prepared as proof of concept. Using an ultrashort-pulsed solid-state laser, notches were created on (100)-Si substrates. Due to the local change in surface inclination, preferential erosion took place behind the notches upon subsequent ion beam etching at glancing angles. As a consequence, a terrace structure possessing a well-defined jump in surface height was formed. The surface topography and its evolution dynamics were characterized and the findings compared to numerical simulations based on a deterministic, two-dimensional model. On this basis, a workflow utilizing these initial notches (iNotches™) for the preparation of an electron transparent lamella was realized and TEM micrographs of the prepared sample were taken.