Shadowgraph images of the WO4 2− layer at various stages in probe fabrication. The difference in light/dark areas indicate where WO4 2− is flowing as in the diagram on the left, such that the etching converges to a sharp point.
A cross section of a 3D model for the tungstate sharpening. The connection to the tungsten probe is electrically insulated from the KOH.
Automated current analysis of typical tungstate sharpening with various etching regimes.
Coulometric graph of tungsten removed for 2 different duty cycles showing repeatability.
The typical range of lengths for short and long probes, their overall profile and the respective cut-off currents.
SEM images for the apex profile and a 15 nm radius probe tip.
STM image of HOPG crystal lattice in air at room temperature. Voltage bias: 770 mV.
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