FIB and Wedge Polishing Sample Preparation for TEM Analysis of Sol-Gel Derived Perovskite Thin Films

Abstract

In ceramic thin films, choosing an appropriate sample preparation method for transmission electron microscopy (TEM) analyses is of paramount importance to avoid preparation-induced damage and retain nanoscale features that require investigation. Here we compare two methods of TEM thin film sample preparation, namely conventional wedge polishing and focused ion beam (FIB) based lift out preparation applied to ferroelectric barium titanate (BaTiO3, BT) thin films made by chemical solution deposition (CSD). The aim of the work is to determine the pros and cons of each method considering not only the quality of the TEM specimen, but also aspects such as availability, ease of use, and affordability. Besides some limitations on the selection of visualized area due to thickness constraints on the FIB-made sample, both methods offer the capability to prepare samples with very comparable quality, as indicated by achieving the same thickness, a largely agreeing microstructure, no secondary phases on the diffraction pattern, and good atomic resolution. This last observation is especially important in the current context of material science, where more nanoscale phenomena are becoming the subject of study. The wedge polishing method, however, is deemed more affordable in terms of instrumentation, as it only requires a tripod polisher, a polishing wheel, and a precision ion polishing system, whereas the lift out method requires a scanning electron microscope (SEM) equipped with an FIB system. We believe that this work serves groups working on ferroelectric thin films in preparing TEM samples in a more effective and uncomplicated manner, facilitating progress in understanding this fascinating class of materials.