There are many reasons for NOT using grease-base polishes for cleaning parts to be inserted into the interior of high vacuum systems, as is so commonly done in electron microscopy laboratories. This matter is discussed in some detail in my book Vacuum Methods in Electron Microscopy. (Portland Press, Ashgate Publishers, 800-535-9544), pp. 69-74.

Basically, one principal reason for cleaning most parts in the first place is to remove hydrocarbon materials from their surfaces, and so it makes no sense at all to use a greasy material to do the job.This is the equivalent of taking a bath in a mud puddle. Then, it becomes necessary to use ‘toxic’ organic solvents to remove the grease-base compounds, which in turn generates expensive and annoying procedures for the use and disposal of the solvents. In addition, the grease and abrasive materials are likely to get embedded in cracks and crevices of the parts on which they are used, and since they often are not readily soluble they may not be completely removed, whereupon they will subsequently act as a persistent source of contamination inside the vacuum system.

There is a considerable body of information of a technical and review nature on negative staining elsewhere in the literature (Bremner et al., 1992; Harris and Home, 1991, 1994; Hayatand Miller, 1990; Holzenburg, 1988; Home, 1991; Nermut, 1991; Spiess et al., 1987; Valentine and Home, 1962); therefore, I shall attempt to avoid undue repetition and present the current laboratory approaches with which I am personally familiar and have achieved some technical success. After considering the range of procedures necessary for the production of carbon and carbon-plastic support films (sometimes termed substrates) emphasis will be placed upon the droplet negative staining technique (Harris and Agutter, 1970; Harris and Horne, 1991). I was introduced to this approach by Ennio Lucio Benedetti in his laboratory, at the start of my doctoral studies in 1966 (Anderson, 1966; Benedetti and Emmelot, 1965,1968) and with minor variations it is still useful for many biological applications.

The following is a technique for analyzing the area underneath a GaAs integrated circuit or discrete device which may aid in failure analysis. This procedure has been used in the past by the microelectronics community, and it is reviewed here for GaAs monolithic microwave integrated circuits (MMICs) and discrete devices. Because it is a destructive method, we use it in our lab after all other testing is completed. The substrate thickness of the GaAs is ∼4 mils (25 μm).

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