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A fully automated, ‘thimble‐size’ scanning tunnelling microscope

A novel, fully automated high‐stability, high‐eigenfrequency scanning tunnelling microscope (STM) has been developed. Its key design feature is the application of two piezoelectric ceramic tubes, one for the x‐y‐z motion of the tip and one for a linear motor (‘nano‐worm’) used for the coarse positioning of the tip relative to the specimen. By means of the nano‐worm, the tip can be advanced in steps between 16 and 0·2 nm. The walking distance is >2 mm, with a maximum speed of 2000 steps/s. The nano‐worm positioning implies that this STM is fully controlled by electronic means, and that no mechanical coupling is needed, which makes operation of the STM extremely convenient. The axial‐symmetry construction is rigid, small and temperature‐compensated, yielding reduced sensitivity to mechanical and acoustic vibrations and temperature variations. The sample is simply placed on a piece of invar which surrounds the scanner tube and the nano‐worm and is held by gravity alone. This allows for easy sample mounting. The performance of the microscope has been tested in air by imaging a variety of surfaces, including graphite and biological samples.