RHENIUM TIPS FOR SCANNING-TUNNELING-MICROSCOPY IN AIR

The performance of rhenium (Re) tips has been investigated for scanning tunneling microscopy in air. Both tips machined mechanically and tips etched electrochemically from poly-crystalline wires were examined and the tip apexes were observed with a transmission electron microscope. Stable atomic images of graphite surfaces were almost always obtained using the Re tips sharpened mechanically, whose apexes were jagged and had thin oxide layers. Atomic images were not obtained, however, with the electrochemically etched Re tips, whose contamination layers were field-evaporated and the apexes of which were controlled so that a single atom was on the apex of the (11 (2) over bar 0) surface, although atomic images were always observed stably in UHV with these lips.