Influence of Partial Metal Ion Substitution on the Temperature Evolution of the Optical Absorption Edge in ((CH₃)₂CHNH₃)₄Cd₃Cl₁₉:Cu Crystals

Abstract

On the basis of absorption spectroscopy data the temperature evolution of the optical absorption edge in the region of phase transitions of [(CH3)2CHNH3]4Cd3Cl10 (IPACC) and the same crystal doped with Cu 2+ (IPACCC) was studied. Performed investigations ascertained a noticeable influence of the doping with Cu 2+ ions on the exciton-phonon interaction and respectively on the shape and temperature evolution of the optical absorption edge of IPACC crystals. It has been found that characteristic parameters of Urbach's rule show anomalous behaviour at the phase transition point T2 = 293 K. It was shown that the low energy tail of the charge transfer band in IPACCC is formed with participation of the internal vibrations of the metal-halogen complex. On the other hand, the low energy tail of the fundamental edge for both IPACC and IPACCC is formed with participation of the internal vibrations of the metal-halogen complex or skeletal (or translational) vibration of IPA cation.