User:Reimarspohr/sandbox

Ion tracks are created by swift heavy ions penetrating through solids. (Young) They correspond to activated zones which can be selectively etched in many insulating solids (FleischerPriceWalker). The resulting structures can be used in microtechnology and nanotechnology.

In minerals, the ion tracks remain unaltered for millions of years. Their gradual fading tells about the time when the mineral has solidified from its melt and is used as a geological clock (fission track dating).

Properties


 * Due to the high energy density, radiation resistant materials can be used. (SchweizerAutor)
 * Each latent track leads exactly to one etched track.
 * Object dimensions down to 10 nm are possible. (ref)
 * The track length is given by the range of the ion in the solid. (Stopping and Range of Ions in Matter)
 * The variation of parameters leads to a number of different shapes such as cones, rounded cones, diabolos, and cylinders. (ref)
 * Due to the high aspect ratio (seePhotolithography) of etched ion tracks, tilted structures are possible (crisscross).

Other techniques

Structure definition does not require a mask.

Photolithography and electron beam lithography require a mask for structure generation. Masking techniques can be applied to create multi-track pattern.

Historic note

A precursor of ion track etching is the selective etching of dislocations (Baumhauer, FleischerPrice)

=Irradiation=

Irradiation techniques for generating ion tracks

Linear accelerator for wide beam irradiation of samples

Ion accelerators
Heavy ion accelerators provide parallel beams with high flux density. The total number of ions available each second ranges from one individual ion up to billions of ions per square meter. The diameter of the modified zone ranges between micrometers and meters. The distance traveled by the ion in the solid, the ion range, varies between micrometers and millimeters. Scribing with individual ions is possible with an aiming precision of one micrometer at present. A refinement of the aiming precision down to the nanometer scale is possible. Ion track channels down to less than 10 nanometer diameter (about 100 atomic diameters) can be fabricated. The unique combination of materials, range, and precision provides a basis for fascinating innovations based on ion track technology. Applications range from single bio sensors to water repellent surfaces.

Ion accelerators provide an immense technological potential for applications. They are the driving force behind ion track technology.

Scribing with single particles

 * Single-ion fabrication techniques are possible (FischerSpohr Figure).

=Formation=

Energy transfer occurs via binary collisions between the heavy ion and the target electrons.

The energy transfer process is known as electronic stopping. (stopping power)

Due to the high mass ratio between ion and electron this process, electronic stopping is smooth over most of the ion range.

Toward the end of the track, the energy transfer occurs in binary collisions between the heavy ion and the target atoms. This process is known as nuclear stopping.

Due to the comparable mass ratio this process is unpredictably bumpy.

Nuclear stopping can only be predicted as an average value for a large ensemble of ions.

In contrast to other types of radiation, such as photons or electrons, each track corresponds to the passage of exactly one ion through the solid.

=thermal spike=

The track diameter corresponds to the diameter of the

collision cascade

thermal spike.

=Etching=

The shape of an etched track is defined by the etching process.

=Replication=

Etched ion tracks can be filled and replicated.

=Applications=

Among the first applications was filtration (Fleischer). Etched tracks can be used as Coulter counter,(ref) modified with monolayers, (ref), and filled by electroplating (ref, ref).