ABSTRACT
A Fischione model 1020 Plasma cleaner was used for thinning the C replicas to reduce and in some cases eliminate the a-C background. The plasma cleaner was operated in the inductively coupled mode using a gas mixture of 75% argon and 25% oxygen as recommended for preventing hydrocarbon contamination in the TEM (Isabell et al 1999). The replicas were plasma cleaned to a point where the films began to break up as shown in figure 3. The film in central portions of the grid squares has been lost. The remaining film is full of voids and cracks and precipitates can be found overhanging the edges as in figure 4. PEELS spectra may then be obtained with a minimal a-C contribution. Figure 5 shows a spectrum from such a precipitate. The C Kedge differs in shape and is much smaller than that in figure 1 .
