In-situ TEM and EELS observations have elucidated that the release of H atoms in TiHx proceeds preferentially in the early N-implantation stage, and that in the subsequent N-implantation stage the number of N atoms bonding to Ti atoms increases gradually with increasing N-concentration. It is concluded that the shift of the atoms on the closed-packed plane induced by the change of bonding interaction of Ti sublattices with ligand N atoms plays an important role in the epitaxial transformation between fcc- and hcp-Ti sublattices due to the occupation by implanted N atoms, and that the invasion of an implanted N atom to the N-unoccupied octahedral site in the neighboring unit cell next to the N-occupied one in hcp-Ti occurs preferentially above the N/Ti＝0.25, and induces the growth of nucleus of the hcp-fcc transformation.

In order to clarify atomistic growth processes of TiN_y films due to the implantation of nitrogen ions (N_2^+) with 62keV into Ti films, changes of the concentration of H and/or N atoms in Ti films, and of the crystallographic and electronic structures of the films by heating and by nitriding have been investigated by in-situ transmission electron microscope (TEM) equipped with electron energy loss spectroscopy (EELS), with the aid of molecular orbital calculations. By taking into account the bonding interaction of Ti sublattices with ligand N atoms, it is clarified that the TiN_y is epitaxially formed by the N-implantation into the hcp-Ti, through the epitaxial transformation of the hcp-Ti to fcc-Ti sublattice, partially inheriting the atomic arrangement of the hcp-Ti, and accompanying the occupation of O-sites of the transformed fcc-Ti by N atoms.

Recently, it has been reported that properties of non-stoichiometric titanium nitride compounds (TiN_y), such as electrical conductivity, diffusion barrier, wear resistance, etc. depend not only on chemical composition, but also on orientation relationships between TiN_y films and substrates. Therefore, much interest has been focused on atomistic growth processes of TiN_y films.In order to clarify the atomistic growth processes due to ion implantation and to control the orientation, in-situ observations by using transmission electron microscope and electron energy loss spectroscope have been carried out, along with composition analysis and with the characterization of electronic structure. TiN_y has epitaxially grown in N-implanted Ti films by nitriding both hcp-Ti and TiH_x., or only hcp-Ti with epitaxial orientations in as-deposited Ti films on NaC1 (001) substrates at room temperature or 250 ℃. The characterizations of electronic structure of Ti films before and after implantation indicate that octahedral sites of hcp-Ti with larger space have higher electron density, which leads to the invasion of implanted ions into the octahedral sites, and that the hcp-fcc transformation accompanied with the partial inheritance of atomic arrangement of hcp-Ti is induced by the shear in <01・0> direction on (00・1) plane promoted by the forming of strong covalent bonds mainly consisted of hybridized orbitals due to combination of Ti3d and N2p, and by the weakening of Ti-Ti bonds. In conclusion, atomistic epitaxial growth processes of Ti compound films by ion implantation have been clarified by the approach of the detailed analysis of experimental results, combined with the characterization of electronic structure, which gives rise to a possibility to develop new functionalized Ti compound films with controlled orientations, for example, TiN_y diffusion barriers in Au/α-Sn systems, band-gap-controlled functionalized SiTi_xN_y systems.

The property of titanium nitride, TiN_y, gradually changes from metallic to covalent and then to ionic with increasing the ratio of N to Ti, which makes TiN_y fascinating for both points of view of technological applications such as diffusion barriers in microcircuits and fundamental research. In order to elucidate the interesting physical properties of TiN_y films, investigation of bonding properties between Ti and N atoms by in-situ observations during the growth of TiN_y films is necessary. However, knowledge of changes in the crystallographic and electronic structures during nitriding of Ti films, is not complete yet. Thus, to obtain the knowledge, in the 400 kV analytical and high resolution transmission electron microscope (TEM) combined with ion accelerators, nitrogen ions (N_2^+) with 62 keV were implanted into 100 nm-thick Ti films, which were grown in ultra-high vacuum with evaluation of the crystallinity by reflection high energy electron diffraction (RHEED). Observations by in-situ TEM equipped with electron energy loss spectrometer and by RHEED and Auger electron spectroscopy, along with the results of the discrete variational Xα molecular orbital calculations, revealed changes in the crystallographic and electronic structures of evaporated-Ti films due to N-implantation. As-grown Ti films consist of (110)-oriented TiH_x and (03・5)-oriented hcp-Ti. Heating of evaporated Ti films up to 350℃ gives rise to release of H from TiH_x and transformation or TiH_x to hcp-Ti. A (001)-oriented NaC1-type TiN_y is epitaxially formed by the transformation of (03・5)-oriented hcp-Ti to (001)-oriented fcc-Ti and by the occupation of N in the octahedral (O-) sites, whereas a (110)-oriented TiN_y is formed by nitriding a (110)-oriented TiH_x. The release of H from the TiH_x precedes the occupation of N in the O-sites of fcc-Ti sublattice. The energy loss peak due to plasmon excitation of the areas where TiH_x has grown in the as-grown films shifts to lower loss energy in the early N-implanting stage, while that of the areas, where hcp-Ti has grown, gradually shifts to higher loss energies with increasing N-dose. Analysis of Mulliken bond overlap populations revealed that occupation of N in the O-sites gives rise to weakening of Ti-Ti bonds and forming of Ti-N covalent bonds.

Interaction of energetic ion beams with solids and materials property change induced under ion-beam irradiatin have long been attracting attention from both points of view of its basic understanding and application. In order to understand the phenomena, a large number of works have already been performed both theoretically and experimentally. However, the process of the interaction and material property change induced under ion-beam irradiation have not yet been fully understood and still remain as a field of fundamental scientific problems, although material modification by ion-beam irradiation has widely been applied in various engineering fields. In this study, Rutherford backscattering and channeling measurements have been applied to investigate both deep radiation damage and depth profile of implanted Au atoms in pure Cu and Cu-1at.% Ni alloy single-crystal specimens, which were irradiated off axis at room temperature by 300 keV Au+ ions to a dose of 2x10^<16> ions/cm^2. The damage range and depth range of the implanted Au atoms in the specimens of pure Cu were strikingly deeper than those in the specimens of Cu-1at.% Ni alloys, respectively. An atom movement mechanism in solids under ion beam irradiation is proposed as the origin of the observed results.