Temperature-dependent optical properties of CuFeO(2) through the structural phase transition

Delafossite CuFeO(2) has recently attracted considerable attention because of its complex phase transitions and practical applications. A thorough understanding of the optical properties of CuFeO(2) is essential for its further exploration. In this paper, we investigated the temperature-dependent optical properties of CuFeO(2) single crystals through Raman scattering spectroscopy and spectroscopic ellipsometry. The room temperature Raman scattering spectrum exhibited six phonon modes at approximately 352, 509, 692, 1000, 1052, and 1171 cm(−1). Upon cooling across 11 K, which is the rhombohedral to monoclinic structural phase transition temperature, a softening of the E(g)-symmetry 352 cm(−1) mode and a hardening of the A(1g)-symmetry 692 cm(−1) mode were observed. Moreover, analysis of the temperature-dependent real part of the dielectric function and direct band gap revealed anomalies at 11 K. These results demonstrate a profound connection between the structural phase transition, lattice dynamics, and electronic structure of CuFeO(2) and provide key information for CuFeO(2)-based device design and fabrication.