Characterization of Deposited and Nitrogen-implanted Titanium Films

Abstract

Deposited Ti films and TiN films formed by nitrogen-implantation were investigated by transmission electron microscope (TEM) observation and electron energy loss spectroscopy (EELS). Titanium films in the thickness of 100 nm were deposited by an electron beam heating method onto thermally cleaned NaCl(001) surfaces held at room temperature under ultra-high vacuum. In the deposited Ti films, there coexist mainly (03 · 5)-oriented hcp-Ti and (110)-oriented TiH_x crystallites: the hydrogen atoms are originally contained in NaCl substrates. The (03 · 5)-oriented hcp-Ti grows inheriting the fourfold symmetry of the square atomic arrangement of TiH_x grown in the early deposition stage. On the other hand, the (110)-oriented TiH_x nucleates and grows naturally inheriting the rectangle atomic arrangement of the (03 · 5)-oriented hcp-Ti to form the band-like region. The deposited Ti films were implanted by N₂⁺ ions with 62 keV in the 400 kV analytical high resolution TEM combined with ion accelerators. In the N-implanted Ti film, the (001)-oriented TiN_y and (110)-oriented TiN_y crystallites are formed outside and inside the band-like regions, respectively. The (110)-oriented TiN_y is formed by nitriding the (110)-oriented TiH_x in the as-deposited Ti film, whereas the (001)-oriented TiN_y is epitaxially formed by the transformation of the (03 · 5)-oriented hcp-Ti to (001)-oriented fcc-Ti, partially inheriting the atomic arrangement of the square and/or the octahedron of the hcp-Ti, accompanied by the occupation of O-sites of the fcc-Ti sublattice by N atoms. In these transformations, the inheritances of the local atomic arrangement of Ti sublattices play a prominent role in the epitaxial fcc-hcp and hcp-fcc formations of the Ti sublattices. The epitaxial formation mechanisms of deposited Ti films and N-implanted Ti films are discussed. [DOI: 10.1380/ejssnt.2005.476]