Electrical Study of Pr3+ Ion Environment in Ca1?xPrxF2+x Thin Films

Abstract

The environment of Pr 3 ions and their spatial distribution in Ca 1Àx Pr x F 2x thin films epitaxially grown on silicon substrates were studied by means of complex admittance spectroscopy (CAS) and thermally stimulated depolarization (TSD) studies. Contrary to the case of bulk single crystals, these techniques reveal only one type of praseodymium-fluoride compensating ion centers in the layers, whatever x varying from 0.001 to 0.10. These centers correspond to isolated substituted Pr 3 ions compensated by interstitial F À i ions in nearest-neighbor (nn) sites of C 4v symmetry. Moreover, it is demonstrated that for these praseodymium concentrations, the F À i ions can be transferred between two neighboring centers. The corresponding dipolar characteristics show that the nn pairs are homogeneously distributed into the bulk of the layers. These results are of great interest. They indicate that energy transfers between excited rare-earth ions, which arise in bulk single crystals for high concentrations, must be considerably reduced in thin films. Consequently the selfquenching phenomena, which rapidly annihilate the luminescence, must be minimized.

Ca1-x-yYbxPryF2+x+y solid solution powders as a promising materials for crystalline silicon solar energetics

“…Effective up-and down-conversion luminescence is carried out through the interaction of the cations introduced in the matrix. Calcium fluoride matrix possesses certain technological advantages, for it has crystal lattice parameters close to that of silicon, so CaF 2 -based films can easier be attached to silicon substrates by epitaxy [11][12][13].…”