Introduction

This chapter is intended as a convenience to those readers actively engaged in the investigation of high Tc superconductors by transmission electron microscopy (TEM). A future possible application of the newly discovered high Tc superconductors is their use in electronic devices. The electrical properties of a device strongly depend on their microstructure, since grain boundaries in these materials can behave as weak links as reported by Dimos et al. [4.1]. Therefore, TEM is an important tool in the study of the relationship between the microstructure and the electrical properties.

To obtain a TEM sample representative of the as-received sample is not only a technical problem but also a problem of understanding the sample preparation process. Unfortunately, the solution is often strongly dependent on the materials being prepared. For instance, high Tc superconductors easily react with moisture and degrade during sample preparation. Moreover, they easily become amorphous during ion milling. For high Tc thin films, the films are usually softer than the substrate, thus have a much higher ion-milling rate. Taking precautions against these kinds of difficulties makes sample preparation for high Tc superconductors relatively difficult.

There have been a number of review articles on TEM sample preparation techniques [4.2–4.5]. TEM samples of high Tc superconductors are mostly prepared either by crushing, cleaving or ion milling. These methods will be dealt with in Sections 4.2 and 4.3. Minor details frequently determine the success of a technique. To illustrate this, we will describe the normal preparation procedure for both techniques while we will concentrate on some ‘tricks’ to obtain a good TEM sample reliably and fast. The method described here will mainly be focused on cross-section sample preparation.