Novel Hybrid Sample Preparation Method for In Situ Liquid Cell TEM Analysis

In situ environmental transmission electron microscopy (TEM) research has increased dramatically in recent years [1-3]. However, due to the difficulty in sample preparation, liquid environmental TEM studies have been limited to materials such as nanoparticles or nanowires [3-5]. To date, no work has been reported on conventional metals/alloys in liquid environment. This is due to the significant difficulty in preparation of suitable “bulk” metal specimens that are compatible with the requirements of the liquid cell in situ specimen holders. We demonstrate a new sample preparation method for the in situ liquid cell TEM study of cold-rolled Type 304 austenitic stainless steel. The proposed new procedure takes advantage of electropolishing and focused ion beam (FIB) sample preparation techniques to extract large electron-transparent site-specific areas with minimum contamination. The liquid cell TEM holder used in these experiments was a Protochips Poseidon 200 liquid cell system, but this novel method can be extended as a general procedure applicable to other types of in situ environmental (E)-TEM studies.