Structural and stoichiometry change in NiO with a Thin IrO₂ layer

An IrO₂ layer has been proposed as the material for minimizing dispersion of several memory switching parameters of resistance-change random access memory devices using NiO. We present Raman scattering and ellipsometry measurements on NiO films with and without an IrO₂ layer. Our Raman measurements on the NiO films show that the addition of an IrO₂ layer enhances the local crystalline quality, which is completely consistent with previous results. Moreover, we found an IrO₂ layer to be associated with the changing stoichiometry in the NiO film. This can also be related to an abrupt change in the optical transition near 2.7 eV with IrO₂, which is known to reflect the NiO stoichiometry.