Scanning Tunneling Microscope (STM)
A tunnel current flowing between probe and sample is detected (controlled so that the tunnel current is fixed and sample surface is scanned) by applying a bias voltage between a metallic probe and conductive or semiconductive sample as the distance between them approaches less than several nm. Sample topography as well as its electronic state are observed.
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![Image of graphite atoms](/global/en/media/stm_02_jpg_tcm27-23282.jpg)