Formation of Cs3Cu2I5 microcrystals in CsI crystals through the aggregation of Cu+ ions

Abstract

We have investigated X-ray diffraction (XRD) patterns of CsI bulk crystals highly doped with Cu+ ions (1 and 10 mol%) and a Cs3Cu2I5 bulk crystal in order to clarify the formation of microcrystals of Cu-based compounds through the aggregation of Cu+ ions in CsI host crystals. We have also measured photoluminescence (PL) and photoluminescence excitation (PLE) spectra of the above three crystals and a CsI bulk crystal lowly doped with Cu+ ions (0.001 mol%) at 10 K. The XRD patterns, PL, and PLE spectra show that the CsI bulk crystals doped with Cu+ ions (1 and 10 mol%) comprise Cs3Cu2I5 microcrystals formed in CsI crystals. On the basis of those results, we discuss the formation of microcrystals of Cu-based compounds through the aggregation of Cu+ ions in CsI bulk crystals with CsCl-type structure.