J. A. Meyer, S. J. Stranick, J. B. Wang, and P. S. Weiss
Ultramicroscopy 42-44, 1538 (1992).
The current-voltage (I-V) characteristics of a low temperature ultrahigh vacuum scanning tunneling microscope (STM) tip positioned >100 Å from a planar surface have been recorded. We find curvature in the Fowler-Nordheim plots due to the tip-plane geometry as has been predicted theoretically. Additionally, oscillations and sharp breaks in these I-V curves are observed over a wide voltage range, 50-1000 V. These I-V curves are used to characterize the STM tips prior to tunneling.