NEW ETCHING PROCEDURE FOR SILVER SCANNING-TUNNELING-MICROSCOPY TIPS

Due to its physical and chemical features silver is a promising materi al for scanning tunneling microscopy (STM) tips in the field of nanost ructuring 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 util ized tip. State of the art procedures of processing silver tips cannot be applied to this application due to insufficient quality and reprod ucibility, respectively. We have developed a new simple single-step et ching procedure for silver tips with a high reproducibility and a tip radius of less than 100 nm. This was realized by electrochemical etchi ng in an ammonia solution and subsequent electronic controlled movemen t of the tip out of the electrolyte. (C) 1996 American Institute of Ph ysics.