Plasma cleaning of carbonaceous samples using a shield

Plasma cleaning is a useful technique to clean transmission electron microscopy (TEM) sample surfaces from carbon hydroxide. However, selective material removal rates can be hard to establish. As a result, carbonaceous samples are significantly impacted by the plasma process since by the very nature of an oxygen plasma it chemically reacts with carbon structures. We propose the use of a shield, provided by Fischione Instruments, to see whether this reduces significantly the plasma cleaning speed without reducing its effectiveness and without the need for a delicate tuning of the gas mixture or instrumentation parameters. Plasma cleaning could then be applied to carbonaceous samples such as graphite, diamond, amorphous carbon films as well as to any sort of powder deposited on holey carbon films. Tests were performed by electron energy-loss spectroscopy (EELS) using a post-column GIF attached to a Philips CM 30-UT and by high resolution imaging (HREM) with a top-entry JEOL 4000 EX.