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

Abstract

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.