In general, various improvements have been made to SEM vacuum systems, and clean high vacuum specimen chambers are now routinely available. However, in the ultra high resolution scanning electron microscope, the prevention or reduction of contamination on the specimen surface has recently become an important subject when SEM imaging is done at higher than 200,000x magnification using a very fine electron probe. Typically, the specimen carries hydrocarbon gas molecules which are the source of the contamination, into the SEM. They adhere not only to the specimen surface but may also incorporated in the specimen, most typically in biological specimens, and cannot be reduced by the anti-contamination device of the SEM. Recently, a specimen heating holder was used in a JSM-890 ultra high resolution SEM, to reduce the contamination deposition on the specimen surface during SEM imaging. Using this holder, the specimen can be heated up to 300°C inside the SEM. Images 1 to 4 in Fig. 1 are the secondary electron images showing the cone-shaped deposition of contamination on a platinum-coated carbon film at different heating temperatures. This platinum-coated film, which had been kept in wet and oily atmosphere for several weeks to insure it was well covered with hydro carbon gas molecules, was irradiated by an electron probe in a spot mode for 30sec. with 1×10−11 Amp. of probe current at 20kV. After the electron probe irradiation, the platinum-coated carbon film was tilted 45° for imaging. Image 1 in Fig. 1 shows the cone-shaped deposition of contamination when the specimen was not heated. Image 2 was at 35°C, Image 3 was at 55°C, and Image 4 in Fig. 1 was at 115°C. At higher than 120°C specimen heating temperature, the cone-shaped deposition of contamination could not be observed any more. On the other hand, we can heat up the specimen outside the SEM before we put the specimen into the SEM. Image 5 in Fig. 1 shows the results of specimen heating by a hair dryer. The same platinum- coated carbon film was heated by a hair dryer for 1 minute before it was intro- duced into the SEM, and was irradiated by the electron probe for 15, 30, and 45sec. in a spot mode. This 1 min. heating by a hair dryer shows almost same result as 55°C specimen heating in the SEM.
Scanning electron microscope (SEM) imaging and analysis of magnetic minerals of lake Diatas peatland section DD REP B 693
