Structural, optical, and electronic properties of cubic TiNx compounds

Abstract

Structural, optical, and electronic properties of cubic TiNx compounds were investigated by x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), spectroscopic ellipsometry (SE), and dc resistivity measurements. The samples were thin films prepared by dc reactive magnetron sputtering of a Ti target at various nitrogen partial pressures in an argon–nitrogen gas mixture. XRD and XPS analyses on the samples indicated a linear increase of the lattice parameter of the compounds with the nitride composition in the 0.7<x<1.2 range. The measured dielectric functions of the compounds by SE show significant low-energy shift of the screened plasma frequency as the nitride composition increases while the interband-transition structures above 3 eV remain at about the same energy. The dielectric functions of the compounds in the intraband-transition region are well described by the Drude model with constant plasma frequency and relaxation time. The estimated dc resistivity using the Drude parameters is minimized near x=1 and its variation with the nitride composition is in good agreement with the result of dc resistivity measurements on the compounds.