Type: Article
Publication Date: 2007-11-30
Citations: 74
DOI: https://doi.org/10.1103/physrevb.76.195127
The electronic structure of nanolaminate ${\mathrm{Ti}}_{2}\mathrm{Al}\mathrm{N}$ and TiN thin films has been investigated by bulk-sensitive soft x-ray emission spectroscopy. The measured Ti ${L}_{2,3}$, N $K$, Al ${L}_{1}$, and Al ${L}_{2,3}$ emission spectra are compared with calculated spectra using ab initio density-functional theory including dipole transition-matrix elements. Three different types of bond regions are identified; a relatively weak $\mathrm{Ti}\phantom{\rule{0.2em}{0ex}}3d\text{\ensuremath{-}}\mathrm{Al}\phantom{\rule{0.2em}{0ex}}3p$ bonding between $\ensuremath{-}1$ and $\ensuremath{-}2\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ below the Fermi level, and $\mathrm{Ti}\phantom{\rule{0.2em}{0ex}}3d\text{\ensuremath{-}}\mathrm{N}\phantom{\rule{0.2em}{0ex}}2p$ and $\mathrm{Ti}\phantom{\rule{0.2em}{0ex}}3d\text{\ensuremath{-}}\mathrm{N}\phantom{\rule{0.2em}{0ex}}2s$ bondings which are deeper in energy observed at $\ensuremath{-}4.8\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ and $\ensuremath{-}15\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ below the Fermi level, respectively. A strongly modified spectral shape of $3s$ states of Al ${L}_{2,3}$ emission from ${\mathrm{Ti}}_{2}\mathrm{Al}\mathrm{N}$ in comparison with pure Al metal is found, which reflects the $\mathrm{Ti}\phantom{\rule{0.2em}{0ex}}3d\text{\ensuremath{-}}\mathrm{Al}\phantom{\rule{0.2em}{0ex}}3p$ hybridization observed in the Al ${L}_{1}$ emission. The differences between the electronic and crystal structures of ${\mathrm{Ti}}_{2}\mathrm{Al}\mathrm{N}$ and TiN are discussed in relation to the intercalated Al layers of the former compound and the change of the materials properties in comparison with the isostructural carbides.