Preliminary first principles study of Hf and Zr aluminates as replacement high-k dielectrics

摘要

Bulk Density Functional Theory calculations were performed on Hf and Zr substitutions for Al in kappa-alumina.The lowest energy configuration found was an octahedrally coordinated Zr site.Zr dissolution was favorable with an enthalpy of -2eV/unit cell for forming Al_(1.875)Zr_(0.125)O_3 from pure Zr and kappa-alumina.Hf and Zr substitution for Al atoms introduced empty d-states below the conduction band edge reducing the E_g of pure kappa-alumina (7.5eV) to 6.4-5.9eV.The edge of the valence band however remained fixed by the O p-state character.The substitution of Hf and Zr into the alumina structure may lead to a higher dielectric constant,but will also reduce E_g and result in a trade off in tunneling currents in devices.