We have simultaneously measured the surface topography and the tunneling current‐voltage (I‐V) characteristics of thin films of NbN as a function of lateral position using a low‐temperature scanning tunneling microscope. We have imaged the superconducting energy gap by fitting the I‐V’s with an energy gap for each spatial position. Such images showed significant variation of the gap, including areas with reduced gap when a magnetic field (up to 6 T) was applied. The features in the gap image were often correlated with features in the surface topographic images.
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© 1987 American Institute of Physics.
1987
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