Problems of Forensic Sciences 2001 Vol. 47 (XLVII) 110-121
SEMs AND FORENSIC SCIENCE
Hans KRÜSEMANN
Philips Electron Optics, Eindhoven, the Netherlands
Streszczenie
One of the latest developments in microscopy is the Environmental Scanning Electron Microscope (ESEM). TheESEMtechnology allows the microscope to operate in three modes: high vacuum typically at 10–4 mbar, low vacuum typically at 0.1 to 1.0 Tr and ESEM vacuum typically between 1 and 10 mbar. ESEM technology combines three microscopy modes in one instrument and therefore allows the widest range of samples to be investigated. ESEM allows imaging and analysis of uncoated, otherwise vacuum unstable, specimens. The ESEM microscope offers the possibility to image the specimen surface in a gaseous environment (using water vapor). Imaging is done by employing backscatter detection, for atomic number contrast, or the dedicated GSED (Gaseous Secondary Electron Detector) for secondary electron imaging giving topographic information. Backscatter imaging (BSI) will show elemental contrast, therefore showing difference between materials. Both detectors are commonly used in forensic investigations and can be run simultaneously. The SEM is very suitable for imaging non-conducting materials at high kV. For many materials such as plastics, polymers, glass, wood, paints, fibers, hairs, fingerprints, insects, etc., theESEMallows these types of specimen to be viewed in the natural uncoated state. The ESEM can also be used as traditional high vacuum SEM without changing any mechanical set-up. The software automatically controls the transition from low vacuum to high vacuum mode of operation. The third mode of operation in the range 1 to 10 mbar is very useful for delicate samples such as pollen and fungi, wet samples, dirty and oily samples and strongly outgassing materials such as shoes.
Słowa kluczowe
ESEM; Specimen analysis.