Electrochemically etched Ni tips in a constant-current mode for spin-polarized scanning tunneling microscopy

The authors present an efficient method to fabricate Ni tips for spin-polarized scanning tunneling microscopy (SP-STM) via electrochemical etching of Ni wires in a constant-current mode. Instead of applying constant voltages to trigger the electrochemical etching of Ni wires in previous reports, here a constant current is applied, which ensures a stable etching process and favors a high yield of Ni tips with good quality. The prepared Ni tips have been applied to obtain atomic resolution images on various surfaces in conventional STM measurements and to resolve magnetic-state-dependent contrast of Co islands grown on a Cu(111) surface in SP-STM experiments. (C) 2014 American Vacuum Society.