Ion track etching requires at least one energetic heavy ion or fission fragment to supply the energy necessary for rendering a cylindrical volume around the ion path developable. It opens a new route to micro technology decisively different from conventional lithography.
It enables narrow, high aspect ratio structures with defined cutting angle whereby each structure is exactly due to one penetrating ion. Various other shapes are possible, such as narrow and wide cones, spherical troughs, barrels, and bottle necked structures. Etched ion track shapes depend on the presence or absence of surfactants during etching.
The influence of a surfactant (Dowfax 2A1) on ion track etching at low etch rate (5 M NaOH at 41.5±2°C) is studied using electro conductivity measurements.
(1) Above surfactant concentrations of 10-4 vol.-% the surfactant improves the access of the etchant (5 M NaOH) to the hydrophobic polymer film (30 µm polycarbonate) associated with reproducibly short break-through times of (315± 96) s.
(2) With increasing surfactant concentration, (10-3 to 1) vol.-%, a steady-state of radial etching is reached at increasingly reduced time.
(3) At high concentration of the surfactant (0.1 vol.-%) the radial etch rate becomes constant above a radius of 100 nm. This favours the formation of a cylindrical channel, in particular at large radius (r > 0.9 µm).
SEM observations of etched channel replicas confirm the electro conductivity measurements for channel radii of between 0.9 and 1.8 µm.
(4) A technique for localizing and manipulating individual micro wires by their end bud is described.
(5) Depending on the limiting current during electro replication compact or hollow cylinders are formed.
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