Elektronenmikroskopie einmal anders : Mikroskopie mit ballistischen Elektronen

Seit ihren Anfängen vor 350 Jahren öffnet die Mikroskopie mit ihren Entwicklungen den Naturwissenschaften immer wieder neue Türen. Die aktuellste Entwicklung – ergänzend zur Rastertunnelmikroskopie – ist die Mikroskopie mit ballistischen Elektronen, die so genannte Ballistische Elektronen Emissions Mikroskopie, die einen Einblick in die elektronischen Umlaufbahnen einzelner Moleküle erlaubt.
The development of microscopy has played and still plays a key role for science. The discovery of bacteria and viruses is one example. The various forms of electron microscopy enable to go far beyond the resolution of optical microscopy. With the invention of scanning probe microscopy about 25 years ago it became possible to image surfaces with atomic resolution. These techniques are based on the interaction of a local probe which is brought very close to the surface. In scanning tunneling microscopy the current of electrons between a very sharp metallic tip and the conducting surface provides a measure of the distance between tip and sample. For the standard applications only the total current matters. However, in a special configuration one can distinguish between those electrons which are scattered and loose energy, and those who traverse the configuration without significant energy loss, the latter are called “ballistic”. If this current of ballistic electrons is measured while imaging the surface, the ballistic transmission through individual objects may be analyzed. This new kind of transmission electron microscopy may become especially important for the development of future molecular based electronic devices with minimal energy dissipation.
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