EPR OF [F-A](0) CENTERS IN ZINC CHALCOGENIDES

[F-A](0) centres in ZnO and ZnS single crystals have been detected by electron paramagnetic resonance. The [F-A](0) centre consists of an an ion vacancy with a localized electron and a monovalent substitutional impurity replacing an adjacent Zn2+ ion. This impurity is probably a L i+ ion in the case of ZnO and a Cu+ ion in the case of ZnS. The values obtained for the spin Hamiltonian parameters of the [F-A](0) centre i n ZnO at 60 K are: g(parallel to) = 1.9951, g(perpendicular to) = 1.99 56, A(parallel to) = 2.36 MHz and A(perpendicular to) = 2.75 MHz. In Z nS at 30 K the corresponding values are g(parallel to) = g(perpendicul ar to) = 2.0017, A(parallel to) = 4.06 MHz and A(perpendicular to) = 3 .67 MHz. A thermally-stimulated ionic process occurs in ZnO at 530-650 K and in ZnS at 720-820 K. In the first stage of this process the ani on vacancies of the regular lattice detected as F+ centres disappear a nd, in the second stage the destruction of [F-A](0) centres occurs.