Tungstate sharpening: A versatile method for extending the profile of ultra sharp tungsten probes

Abstract

The benefits of a new electrochemical etching method for the controlled sharpening of sub-micron tungsten probes are demonstrated. The proposed technique only utilizes the insulating effect of the WO₄(2-) by-product which offers more practical ways of controlling the process parameters. The electrosharpening method was fully automated through the analysis of the process current, bulk coulometry, shadowgraphs, and time lapse microscopy. Tip radii smaller than 15 nm were maintained over a wide range of controlled lengths up to 4.5 mm with conic angles of less than 1°.

Simulation-guided nanofabrication of high-quality practical tungsten probes

“…For comparison, Fig. 5(c) and (d) show the STM images of highly oriented pyrolytic graphite (HOPG) in other works also by their electrochemically fabricated tungsten probes, 27,45 demonstrating an imaging resolution of 0.95 A and 2.1 A, respectively. Therefore, it is clearly indicated that the STM images in this work are with higher quality and ner resolution.…”

“…[9][10][11][12][13] Compared to mechanical methods, [14][15][16][17] ame etching 18 and others, 19,20 electrochemical etching of tungsten wire has been extensively adopted due to its convenience, reliability and easy operation. [21][22][23][24] A number of etching strategies and methods, including the drop-off method, 23 liquid membrane etching, 25 two-step etching, 26 inversing etching 27 and post-annealing, 28 have been developed for the fabrication of various probes. Among them, the drop-off method is the most popular one due to its convenient operability and high controllability.…”

Note: Advancement in tip etching for preparation of tunable size scanning tunneling microscopy tips

“…In the experiment, a 200 ml, 2M NaOH solution is used to electrochemically etch a 3N8 purity, 0.020 ′′ diameter, W wire under a 4.0 V AC potential applied between the W wire (primary electrode) and a carbon counter-electrode. 5,6 A specially designed C-flex bobber sheaths the wire, providing insulation from the solution and restricting the reaction to occur at the air-solution-electrode (ASE) interface [see Figs. 1(a) and 1(b)].…”