CdF2-CaF2 superlattices on Si(111): MBE growth, structural and luminescence studies

New pseudomorphic superlattices (SLs) based on calcium and cadmium fluoride s have been grown from molecular beams and structurally characterized by hi gh-resolution X-ray diffractometry. It was found that positions of the CdF2 and CaF2 emission bands in the SLs with the shortest periods shifted to th e blue and red parts of the optical spectra, respectively. It was revealed that the Eu2+ luminescence intensity under continuous optical excitation dr astically decreases in a few seconds after the beginning of the excitation. This effect was accounted for by the photoionization of Eu2+ ions with cha rge transfer from their 4f(6)5d excited state to the neighbouring CdF2 laye rs. (C) 1999 Elsevier Science B.V. All rights reserved.