X-RAY PHOTOEMISSION SPECTRA OF REACTIVELY SPUTTERED TIN

X-ray photoemission spectra of reactively sputtered TiN1.0 films are recorded without interference from adsorbed contaminants or ion sputter cleaning damage. In this way, the transition from hcp TiN0.3 to fcc TiN1.0 is characterized by a discontinuity in film stoichiometry, Ti 2p splitting energy, and Ti 2p3/2 binding energy as a function of the Ar/N2 ratio during sputtering. The line shapes of the N 1s and 2s transitions experience only an asymmetric broadening on forming fcc TiN. The core-level N Is transition of fcc TiN is modeled as two components peaks with binding energies at 396.8 and 396.0 eV. Similarly, the valence band N 2s transition has corresponding component peaks at 16.8 and 16.2 eV. These high and low binding energy pairs are interpreted as on-site N(s) and interstitial site N(i) populations of nitrogen in a fcc TiN lattice, respectively. The ratio of N/Ti is 1.0 and the N(s)/N(i) ratio is approximately 6. Both ratios are independent of the composition of the sputtering gas mixture and the substrate temperature once fcc TiN is formed. The core level Ti 2p transition in fcc TiN is characteristic of a single Ti3+ oxidation state with a line shape that is also insensitive to the gas composition and the substrate temperature during sputtering.