  The Field Ion Microscope (FIM) can be used to characterize the atomic
configuration of the apex of sharp tips. These tips are well suited for
Scanning Probe Microscopy (SPM) since they predetermine SPM resolution and
electronic structure for spectroscopy. A protocol is proposed to preserve the
atomic structure of the tip apex from etching due to gas impurities during the
transfer period from FIM to SPM, and estimations are made regarding the time
limitations of such an experiment due to contamination by ultra-high vacuum
(UHV) rest gases. While avoiding any current setpoint overshoot to preserve the
tip integrity, we present results from approaches of atomically defined
tungsten tips to the tunneling regime with Au(111), HOPG, and Si(111) surfaces
at room temperature. We conclude from these experiments that adatom mobility
and physisorbed gas on the sample surface limit the choice of surfaces for
which the tip integrity is preserved in tunneling experiments at room
temperature. The atomic structure of FIM tip apices is unchanged only after
tunneling to the highly reactive Si(111) surface.
