Swift heavy ion
Encyclopedia
Swift heavy ions are a special form of particle radiation
for which electronic stopping
dominates over nuclear stopping
.
They are accelerated in particle accelerator
s to very high energies, typically in the MeV
or GeV
range and have sufficient energy and mass to penetrate solids on a straight line. In many solids swift heavy ions release sufficient energy to induce permanently modified cylindrical zones, so-called ion tracks. If the irradiation is carried out in an initially crystalline material, ion tracks consist of an amorphous cylinder. Ion tracks can be produced in many amorphizing materials, but not in pure metals, where the high electronic heat conductivity dissipates away the electronic heating before the ion track has time to form.
some debate. They can in some sense considered to produce thermal spikes
in the sense that they lead to strong lattice heating and a transient
disordered atom zone. However, at least the initial stage of the damage might be
better understood in terms of a Coulomb explosion
mechanism
. Regardless of what the heating mechanism is, it is well established that
swift heavy ions typically produce a long cylindrical track of damage in insulators
, which
has been shown to be underdense in the middle at least in SiO2
.
Ion tracks in polymers can be etched to form a nanometer-thin channel through
a polymer foil, so called track etch membranes. These are in
industrial use .
Irradiation of polyimide resists have potential to be used as templates
for nanowire growth
Tracks can also be used to sputter materials
.
They can also be used to elongate nanocrystals
embedded in materials
.
Particle radiation
Particle radiation is the radiation of energy by means of fast-moving subatomic particles. Particle radiation is referred to as a particle beam if the particles are all moving in the same direction, similar to a light beam....
for which electronic stopping
Stopping power (particle radiation)
In passing through matter, fast charged particles ionize the atoms or molecules which they encounter. Thus, the fast particles gradually lose energy in many small steps. Stopping power is defined as the average energy loss of the particle per unit path length, measured for example in MeV/cm...
dominates over nuclear stopping
Stopping power (particle radiation)
In passing through matter, fast charged particles ionize the atoms or molecules which they encounter. Thus, the fast particles gradually lose energy in many small steps. Stopping power is defined as the average energy loss of the particle per unit path length, measured for example in MeV/cm...
.
They are accelerated in particle accelerator
Particle accelerator
A particle accelerator is a device that uses electromagnetic fields to propel charged particles to high speeds and to contain them in well-defined beams. An ordinary CRT television set is a simple form of accelerator. There are two basic types: electrostatic and oscillating field accelerators.In...
s to very high energies, typically in the MeV
MEV
MeV and meV are multiples and submultiples of the electron volt unit referring to 1,000,000 eV and 0.001 eV, respectively.Mev or MEV may refer to:In entertainment:* Musica Elettronica Viva, an Italian musical group...
or GeV
GEV
GEV or GeV may stand for:*GeV or gigaelectronvolt, a unit of energy equal to billion electron volts*GEV or Grid Enabled Vehicle that is fully or partially powered by the electric grid, see plug-in electric vehicle...
range and have sufficient energy and mass to penetrate solids on a straight line. In many solids swift heavy ions release sufficient energy to induce permanently modified cylindrical zones, so-called ion tracks. If the irradiation is carried out in an initially crystalline material, ion tracks consist of an amorphous cylinder. Ion tracks can be produced in many amorphizing materials, but not in pure metals, where the high electronic heat conductivity dissipates away the electronic heating before the ion track has time to form.
Mechanisms
The mechanisms by which ion tracks are produced are subject tosome debate. They can in some sense considered to produce thermal spikes
in the sense that they lead to strong lattice heating and a transient
disordered atom zone. However, at least the initial stage of the damage might be
better understood in terms of a Coulomb explosion
Coulomb explosion
A Coulomb explosion is a mechanism for coupling electronic excitation energy from intense electromagnetic fields into atomic motion. The atomic motion can break the bonds that hold solids together...
mechanism
. Regardless of what the heating mechanism is, it is well established that
swift heavy ions typically produce a long cylindrical track of damage in insulators
, which
has been shown to be underdense in the middle at least in SiO2
.
Applications
Swift heavy ion tracks have several established and potential practical applications.Ion tracks in polymers can be etched to form a nanometer-thin channel through
a polymer foil, so called track etch membranes. These are in
industrial use .
Irradiation of polyimide resists have potential to be used as templates
for nanowire growth
Tracks can also be used to sputter materials
.
They can also be used to elongate nanocrystals
embedded in materials
.