Particle bombardment radiation damage

Radiation Damage. It has been known for many years that bombardment of a crystal with energetic (keV to MeV) heavy ions produces regions of lattice disorder. An implanted ion entering a soHd with an initial kinetic energy of 100 keV comes to rest in the time scale of about 10 due to both electronic and nuclear coUisions. As an ion slows down and comes to rest in a crystal, it makes a number of coUisions with the lattice atoms. In these coUisions, sufficient energy may be transferred from the ion to displace an atom from its lattice site. Lattice atoms which are displaced by an incident ion are caUed primary knock-on atoms (PKA). A PKA can in turn displace other atoms, secondary knock-ons, etc. This process creates a cascade of atomic coUisions and is coUectively referred to as the coUision, or displacement, cascade. The disorder can be directiy observed by techniques sensitive to lattice stmcture, such as electron-transmission microscopy, MeV-particle channeling, and electron diffraction. 

Re-emission rate data are needed during bombardment, as a function of time. Fluxes should be of the order 1020 particles m-2s 1, and target temperatures should range up to 800 °C. Targets should include samples that have undergone radiation damage by hydrogen and helium ions and by neutral atoms. 

The formation of radiation defects under irradiation of the fullerene films by the bombarding particles leads to the essential modification of electronic subsystem, which determines their optical and electrophysical properties. However, the mechanisms of radiation defect formation with the use of different types of irradiation and dose load, and also the nature of a change in the electronic properties in this case are studied insufficiently. It is necessary to note that in the case of the condensed state of fullerenes not only the radiation damages of the molecular polyhedrons, which by themselves influence the redistribution of... 

The classical methods for the analysis of the chemical state of an atom are the spectroscopic ones. Therefore, it is natural to consider them for studies of the chemical state of implanted ions as well. But in contrast to the investigation of radiation damage caused by the bombarding particles, one has the additional factor of intensity in the detection of the implanted ions themselves. 

Neutron radiation occurs only on fission (fission is the splitting of a nucleus) or by the bombardment (irradiation) of atomic nuclei with charged particles. Neutrons have mass but no charge, and like gamma radiation penetrate and damage many materials. 

Damage threshold (bombardment) The energy at which radiation or bombarding particles introduce damage to the atomic structure of a material, thus changing its properties. 

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