Progress in High-resolution Scanning Probe Microscopy

In scanning probe microscopy, a probe is raster-scanned across an object. The first high-resolution scanning probe microscope has been developed by Crewe in the late sixties, and his group built a scanning transmission electron microscope (STEM), which attained atomic scale resolution [1]. This was achieved by using a cold field-emitter based on an etched single crystal tungsten wire that produced electrons emerging from a 100 A spot. A single lens demagnifying this spot 50x and double deflection scan coils produced exciting images of biological macromolecules that fostered the development of multiple STEMs around the world. This type of instrument allows the mass of single macromolecules to be determined and images of unprecedented clarity to be acquired [2] — possibilities of great potential for biological studies. However, only few STEMs are currently operated for biological applications.