Fast ions create linear trails of intense atomic disorder in many solids. The particle tracks are in themselves scientifically interesting because they consist of unique, localized radiation damage. They also are noteworthy for their diverse practical uses, which range from improved high field superconductors to mineral exploration and bird altimetry. The two areas—what tracks are and what they do practically—are the subjects of this introduction and the following three articles. Although the mechanism for producing tracks in insulators is semi-quantitatively well-established, there is a distinct mystery as to the formation mechanism in superconductors, inter-metallics, and metals. This mystery is the subject of the next two articles written by discoverers of tracks in these materials.

We will not discuss in detail the multitude of scientific uses for these tracks as particle-track detectors. Uses range from nuclear, elementary-particle, and cosmic-ray physics to geochronology, geochemistry, and geophysics; chemistry; and radiobiology. The interested reader can learn more on the subject through a book, part of which surveys scientific applications of particle tracks in solids. The key to these uses—and most of the practical uses—is that, in materials where tracks can be observed, either directly or by a widely applicable trick to be described, each detector sample is a nuclear particle-track chamber—the solid-state equivalent of the well-known gaseous and liquid detectors (i.e., cloud chambers and bubble chambers). The major distinction is that tracks in solids are long-lasting rather than transient features.

Transition metal oxides belong to the class of iono-covalent materials in which electrons are, to first order, localized in tight metal-oxygen bonds. They appear to be quite different from classical metals in which electrons are assumed to be delocalized in a free electron gas. Nevertheless, due to exchange interactions and hybridization of atomic orbitals, oxides exhibit many interesting physical properties like magnetic ordering and various electron transport properties that extend from wide gap insulators to narrow band conductors and high-temperature superconducting (HTS) superconductors. This class of materials appears well-suited to the study of the damage induced by heavy ion irradiation and its consequence on physical properties like electrical resistivity.

In this article, we will describe the results of heavy ion irradiations in magnetic oxides, exhibiting a wide palette of electron transport properties from insulators to metals through hopping semiconductors and in HTS copper oxides that are narrow-band metals above Tc. We will show that heavy ion irradiation, in addition to disordering matter, can induce changes in some physical properties like magnetic ordering and orientation of magnetic fields, and can produce large increases of the critical current. To account for these results, the thermal spike model will be considered as a possible way to understand the damage creation in iono-covalent compounds.

When an energetic ion penetrates a target, it loses its energy via two nearly independent processes: (1) elastic collisions with the nuclei (nuclear-energy loss (dE/dx)n), which dominate the ion slowing down in the low energy range (i.e., in the stopping region); (2) electronic excitation and ionization (electronic-energy loss (dE/dx)e), which strongly overwhelm (dE/dx)n in the high energy range (typically above 1 MeV/nucleon). Until the 1980s, researchers considered that electronic-energy deposition could participate in damaging creation in many insulators, but the effects observed in bulk metals were solely ascribed to elastic nuclear collisions. This widely held opinion was due to the fact that in metallic systems the numerous very mobile conduction electrons allow a fast spreading of the deposited energy and an efficient screening of the space charge created in the projectile wake so that it seemed unreasonable to hope for damage creation or track formation in metallic targets following high levels of electronic-energy deposition.

A particular case is the observation more than 30 years ago of damage in thin or discontinuous. metallic films after fission fragment irradiation or MeV heavy ion bombardment. The spreading of the deposited energy is then strongly limited by the close vicinity of surfaces and interfaces.

Natural nuclear tracks in solids have existed since close to the beginning of the solar system, billions of years ago. Only during the last few decades have we learned how to employ tracks practically. Uses now range from radiation dosimetry to microchemical analysis, virus counting, oil and uranium exploration, and aiding earthquake prediction. The key to these applications is track etching, which in insulators allows tracks to be revealed simply and then enlarged. Etching also makes it possible to produce minute holes with clean, geometric shapes.

The pervasive impetus of modern semiconductor technology has become an accepted fact. Scientific mastering of materials and processes has increased tremendously within a short time frame. Technological control has been derived from this scientific base. An industry with more than $100 billion worth of silicon devices per annum in 1994 as well as incredibly high growth rates of production and applications is an economic reality in addition to being a matter of international industrial policy. The materials aspect of using perfected single crystals and applying local doping control provides the basis of this unusual success. Earlier usage of materials differed remarkably. Bronze and steel are used for their specific bulk properties. Shaping and connecting pieces is at the heart of iron-age or bronze-age technologies. Integration inside a regular spatial array of a host crystal is the semiconductor principle. The “Royal Road” to modern microelectronics consists of initially procuring a perfected single-crystal host, then locally establishing electrical and optical properties inside the host by specific replacements of host atoms by foreign “dopants.” The somewhat disparaging expression of defect as a generic term for all deviations from the host perfection does not really convey the power of this “doping doctrine” for semiconducting materials. The early pioneers of germanium and silicon however, placed great emphasis on the experimental verification that n-type and p-type doping by elements of the adjacent columns in the periodic table were accompanied by changes in the lattice parameter with atomic substitution of the host atoms as the guiding principle.