The application of the environmental scanning electron microscope in biological and materials sciences

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• 作者：Gilpin ; Christopher J.
• 刊名：Biology of the Cell
• 出版年：1998
• 出版时间：June, 1998
• 年：1998
• 卷：90
• 期：3
• 页码：249
• 全文大小：55.7 K

文摘

The environmental scanning electron microscope (ESEM) utilises a secondary electron detector capable of operating at pressures in the range of 1 20 Torr (130 2700 Pascals). By use of differential pumping apertures the electron gun and column can be maintained at “normal” vacuum levels of 10-5 Torr. A pressure of 10-2 Torr exists within the secondary electron detector separated from the specimen chamber by another differential pumping aperture. The specimen chamber pressure is produced by admitting a gas to the chamber under operator control. The gas can be any ionisable gas. When the electron beam strikes the sample secondary electrons are produced. These secondary electrons travel towards the positively biased detector and are amplified in a cascade by gas ionisation. Positively charged gas ions eliminate any surface negative charge on the sample. Water vapour is a commonly used chamber gas. By controlling chamber gas pressure and sample temperature, by means of a Peltier effect stage, condensation and evaporation can be produced. The ability to maintain samples in a fully hydrated state singles out the Philips Electroscan ESEM as a unique instrument. Specific applications for the ESEM will be presented.