Fluorine Impurities Research Articles

Boron- and Fluorine-Ion-Implantation into ZnSe Single Crystals

The photoelectric properties of boron- and fluorine-ion-implanted ZnSe have been investigated by means of photoconductivity and cathodoluminescence measurements. The photoconductivity spectra have shown the existence of shallow levels 0.12 and 0.10 eV originating from boron and fluorine impurities, respectively. The quenching effect on a copper green photoconduction band has been found in the fluorine-ion-implanted ZnSe. It is suggested that the quenching behaviour arises from the Coulombic interaction between the copper acceptors and the fluorine donors. The cathodoluminescence spectra have shown the formation of the self-activated luminescence (SAL) bands and the marked decrease of the copper green emission bands by the boron- and fluorine-ion-implantations.

Neutron production from (α, n) reactions in 241AmO2

The neutron yield from (α, n) reactions in a sample of 241AmO2 has been measured to be (2.78 ± 0.41) × 103 neutrons/sec/g 241Am. The presence of a small fluorine impurity in the sample is demonstrated to be of major importance.

Radiolysis of alkaline-earth fluorides

Alkaline-earth fluorides have been irradiated at temperatures between 4 and 300 K using electrons of energy 70 keV, 300 keV and 1 MeV. The coloration produced has been investigated by both EPR and optical methods. At 77 K and lower temperatures, a rapid first-stage coloration occurs which saturates and is followed by a slower second-stage coloration. The first stage is characterized by perturbed F centres and compensating VK centres. It seems that the perturbed F centres are associated with nearby interstitial fluorine ions but impurities may also be directly involved. The second stage is characterized by the production of isolated F centres and compensating H centres and appears to be the result of intrinsic radiolysis. Thermally induced annealing of the first- and second-stage coloration is investigated. The first stage coloration of BaF2 is described in some detail in an Appendix.

A MO‐SCF study of hydroxyl binding and hydroxyl diffusion in pure and fluorine‐containing hydroxyapatite

AbstractHydroxyl diffusion and interhydroxyl binding in hydroxyapatite has been studied. LCGO‐MO‐SCF calculations have been carried out on groups of hydroxyl ions in a perfect and a vacancy‐containing crystal.Electrostatic crystal effects were accounted for by including the crystal potential field in the SCF calculations. Nearest‐neighbour interactions were calculated to first order. Effects exerted by fluorine impurities were considered for the vacancy‐containing crystal.The calculations indicate that narrow bandwidths obtained in nmr experiments on biological hydroxyapatite may be caused by a hydroxyl displacement mechanism and that no interhydroxyl hydrogen bonds exist in hydroxyapatite. The suggestion that the caries‐inhibiting properties of fluorine impurities in human dental enamel is caused by a diffusion‐binding mechanism is supported by the results.

Infrared Absorption by Impurity-Pair Resonant Modes in NaCl: F

New resonant-mode infrared absorption lines have been observed in NaCl with high concentrations of fluorine impurities. The quadratic concentration dependence of the strength of these lines indicates that they are due to pairs of fluorine impurities. At the resonant frequencies, the motion of some host ions appears to be as important as the motion of the impurities themselves.

Electron-Paramagnetic-Resonance Studies of the Fluorine Donor in Beryllum Oxide

A prominent point imperfection observed by electron paramagnetic resonance in x-irradiated single-crystalline BeO containing fluorine has been studied under varying conditions of temperature and uniaxial stress. This point imperfection in its neutral, paramagnetic charge state consists of one electron in excess of saturated bonds and closed shells, trapped near the fluorine impurity. The fluorine impurity substitutes for oxygen in the BeO lattice and, isolated from other defects, is a deep donor. The extra electron occupies an orbital localized primarily on two of the three basal beryllium ions nearest the fluorine. The observed temperature dependence of the ${\mathrm{Be}}^{9}$ hyperfine structure is analyzed by using a classical model of random hopping among the three two-beryllium states of the donor. The resulting slight dependence of the hopping rate on temperature is discussed in terms of a quantum-statistical picture. The three states are coupled through nonzero matrix elements of the vibrational energy but are partially decoupled as a result of large static random strains in the crystals.