ESR study of Ce3+ ions doped in the CdIn2S4 lattice Original Research Article

Rare earth elements doped IIa–III2–VI4 compounds are expected as host materials for fluorescent devices. In particular, since blue emission was observed in alkaline earth thiogallates doped with Ce3+ ions, much attention has been paid to develop full color displays made of thin films of the compounds above. Especially Ce3+ ions are thought as promising candidates for dopants realizing blue light emission. Normally doped Ce3+ ions are considered to substitute the sites which are occupied with divalent elements such as Ca or Cd. However, the substituting mechanism is not fully understood, since in view of the number of valence, it is natural for a Ce atom to substitute a trivalent one. In this report, we have grown single crystals of CdIn2S4 as host materials for Ce doping and investigated the site substitution of the Ce atom in this crystal lattice by means of ESR. Two types of ESR centers are found. One consists of a Ce3+ ion substituting a Cd site and a sulfur vacancy, and the other consists of a similar Ce3+ ion with 4 tetrahedrally surrounding sulfur atoms.