Twin-probe scanning tunneling microscope

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Abstract
Probes having two mechanically fixed, electrically independent tips were proposed (‘‘twin probes’’). A control system and mechanism for STM with a twin probe has been designed and fabricated. Two types of twin probes are fabricated. The first had Pt‐Ir tips with 1.5 mm distance between the tips. The other had tungsten tips with 0.1 μm distance. Since the lengths of the two tips are not equal, the system controls not only the distance between the probe and the sample surface but also the angle between the probes and the sample to allow detection of tunneling currents with both tips of the probe at the same time. The sum of the tunneling currents is used to control the height of the probe and the difference between currents is used to control the angle of the sample. Using this system with the Pt‐Ir probe, two independent images of graphite atoms from one sample were simultaneously obtained.