New etching procedure for silver scanning tunneling microscopy tips

Due to its physical and chemical features silver is a promising material for scanning tunneling microscopy (STM) tips in the field of nanostructuring by a laser/STM combination. This nanostructuring is archived by field enhancement of optical radiation by a factor of up to 10(3) in the near field between a STM tip and a substrate. The magnitude of the field enchantment depends on the geometry and material of the utilized tip. State of the art procedures of processing silver tips cannot be applied to this application due to insufficient quality and reproducibility, respectively. We have developed a new simple single-step etching procedure for silver tips with a high reproducibility and a tip radius of less than 100 nm. This was realized by electrochemical etching in an ammonia solution and subsequent electronic controlled movement of the tip out of the electrolyte. (C) 1996 American Institute of Physics.