In-situ transmission electron microscope observation of nitriding processes of titanium thin films by nitrogen-implantation

摘要

To clarify the "epitaxial" formation process of TiN films due to nitrogen-implantation, changes of crystallographic structures of as-deposited Ti films during N-implantation were studied by using a transmission electron microscope (TEM). Analysis of the results of TEM observations indicated that H atoms which constituted TiH_x were completely released from as-deposited Ti films when the films were heated up to 350℃, and that the H-released unstable fcc-Ti sublattice was transformed into hep-structure. Ions of N_2~+ with 62 keV were implanted into the hcp-Ti films held at 350℃. In the N-implanted Ti film (N/Ti = 0.954), there coexisted NaCl-type TiN_y and a small amount of hcp-Ti. The (001)- and (110)-oriented TiN_y were "epitaxially" formed by the transformation of (03·5)- and (21·0)-oriented hcp-Ti, respectively. The lattice of N-implanted hcp-Ti was expanded by the occupation of octahedral sites by N atoms. Strain due to the lattice expansion was considered as a driving force for the hcp-fcc transformation of Ti sublattice.