Dielectric and Lattice Vibrational Spectra of Cu₂O Hollow Spheres in the Range of 1–10 THz

The transmitted spectra of Cu 2 O hollow spheres have been measured in the range of 1–10 THz and analyzed by the classical dispersion theory and group theoretical analysis. Two strong phonon resonances are observed at v 1 = 4.54 THz (148.3 cm –1 ) and v 2 = 4.91 THz (163.5 cm –1 ), corresponding to the transverse optical (TO) phonon and longitudinal optical (LO) phonon modes, respectively. In addition, we have identified a possible surface optical (SO) phonon mode located between the TO and LO phonon frequencies and have observed that a forbidden phonon mode at 9.36 THz (312 cm –1 ) is activated due to the imperfect lattice of the Cu 2 O hollow spheres. The optical and dielectric parameters are also derived and discussed based on the Lorentz model of dielectric response.