Optical, microstructural, vibrational and theoretical studies of p-type SrCu₂O₂ and BaCu₂O₂ transparent conductive oxides

Transparent conducting metal oxides (TCO) are unusual semiconducting materials displaying transparency to visible light. TCO materials are used for electrostatic shielding, antistatic screens, transparent heating devices, solar cells and even organic light emitting diodes. However, most TCOs are n-type, while p-type TCOs are scarce. SrCu₂O₂ is a leading candidate as a p-type transparent conductive oxide. In this paper, we report theoretical calculations and experimental studies on the vibrational, optical and microstructural properties of both bulk and thin films of polycrystalline undoped SrCu₂O₂ obtained by pulsed laser deposition (PLD). Barium doping of the SrCu₂O₂ by substitution of Sr atoms is also reported. The simulated crystal structures of both SrCu ₂O₂ and BaCu₂O₂ materials, obtained through a state-of-the-art implementation of the Density functional theory, are compared with experimental X-ray diffraction data of undoped and Ba-doped SrCu₂O₂ bulk materials. Raman spectra of both SCO and BCO materials are simulated from the derivatives of the dielectric susceptibility and a symmetry analysis of the optical phonon eigenvectors at the Brillouin zone center is proposed. Good agreement with Raman scattering experimental results is demonstrated.