Dynamic electrochemical-etching technique for tungsten tips suitable for multi-tip scanning tunneling microscopes

Abstract

We present a method to prepare tungsten tips for use in multi-tip scanning tunneling microscopes. The motivation behind the development comes from a requirement to make very long and conical-shape tips with controlling the cone angle. The method is based on a combination of a "drop-off" method and dynamic electrochemical etching, in which the tip is continuously and slowly drawn up from the electrolyte during etching. Its reproducibility was confirmed by scanning electron microscopy. Comparison in tip shape between the dynamic and static methods was shown.

Macroscopic Single‐Walled‐Carbon‐Nanotube Fiber Self‐Assembled by Dip‐Coating Method

“…On the other hand, a tungsten wire was etched by an electrochemical process using a KOH solution as an electrolyte. [15] The etched part of the wire has a sharp conical shape with a tip radius with curvature of about 250 nm.…”

Two-step controllable electrochemical etching of tungsten scanning probe microscopy tips

“…40 However, tips remained very long and spindly. 41 Extremely sharp tips with low aspect ratio are vital for scanning tunnelling microscopy, and eventually atomically precise manufacturing.…”

“…Other reported techniques include cutting, 23,24 grinding, [1][2][3][4][5][6]25 pulling, 19,[26][27][28][29][30] beam deposition, [31][32][33][34] ion milling, [35][36][37][38][39] and others. For electrochemical etching, recent advances in tip fabrication came in the form of reverse biasing after "drop-off," 21 in 2002 and "dynamic electrochemical etching" 40 in 2007. Guise et al optimized etching conditions to produce probes with 5 nm radius of curvature reproducibly.…”

Independently driven four-probe method for local electrical characteristics in organic thin-film transistors under controlled channel potential

“…36 Etched gold tips have a long conical shape with a sharp apex suitable for multi-probe systems without the special treatment needed for tungsten tips. 37,38 Each of the probes is connected to a homebuilt variable gain preamplifier with internal semiconductor switches for multi-probe apparatus. 20 These preamplifiers are integrated into the probe control system for a controlled probe approach.…”