Optical Measurements on ZnS:Cu Produced by Neutron Irradiation of ZnS

Abstract

AcknowledgmentsThe a u t h o r s wish to t h a n k M. tI. W h i t e h i l l for t a n t a l u m s p u t t e r i n g , K. L. B r o w n and E. E. P a c h e r for e l e c t r i c a l m e a s u r e m e n t s , and D. P. C a m e r o n for the e l e c t r o n m i c r o g r a p h s .ABSTRACT ZnS powder, irradiated in a high density thermal neutron flux, was p a r t l y converted to radioactive Zn-65, Zn-69, and S-35. These radioisotopes decay to Cu-65, Ga-69, and C1-35, respectively. One week after removal from the nuclear reactor the sample was fired at 900~ to anneal out radiation damage occurring in the reactor. The brightness and spectral distribution under 3650A excitation and the diffuse reflectance spectra of the annealed sample were monitored during a period of 600 days. The principal results are interpreted in terms of an increasing concentration of uncompensated copper centers produced by the decay of Zn-65.) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 138.251.14.35 Downloaded on 2015-03-10 to IP

Donor—acceptor pairs in semiconductors

“…The Fermi level does indeed drop during the transmutation, however, a detailed analysis of the kinetics of the luminescence revealed that a difference in state of ionization of substitutional copper does not by itself explain the experimental results [45]. The experimental studies with zinc sulfide doped with copper by radioactive decay of Zn66 have been confirmed and extended by Aven, Kastner, and Potter [46] and by Broser and Franke [47]. Hoogenstraaten [21] made a detailed critical analysis of the possible contributions of donor-acceptor pairs to the luminescence of zinc sulfide, including probably the earliest derivation of equation (20) as applied to the excitation of a pair.…”

Recombination emission in inorganic solids

“…Association of pairs of impurities, particularly donor-acceptor pairs, can produce sets of electronic states within the forbidden energy gap of a solid. Prener and Williams (1956 a, b) and later Apple and Williams (1959) suggested that emission bands in ZnS might be due to electronic transitions in associated donor-acceptor pairs. Williams (1960) treated the problem by a Heitler-London approach giving a two-particle wave function as a product of donor and acceptor wave functions with no exchange interactions.…”

“…This would seem to indicate little close association between the halogen and the zinc-ion vacancy but a little more between the trivalent impurities and the vacancy. However, Prener and Williams (1956 a, b) suggested a nearest-neighbour pairing of co-activator and vacancy. Koda and Shionoya (1964) adopt this model since their studies of polarization show an axial symmetry for the centre rather than tetrahedral symmetry (see figure 32).…”

Radiative Recombination in Cadmium Sulfide

“…Radioisotope or tracer techniques have been employed widely in diffusion studies. But the method of introducing impurity atoms into a crystal through the decay of radio-active host atoms for luminescence studies has been used only sparingly (Prener and Williams 1956;Potter, Aven and Kastner 1962;Broser and Franke 1965;Blount, Phipps and Bube 1967). All these investigations were made in ZnS.…”