Yoshitaka Kasukabe

Cubic Crystals in Ti Films Evaporated on NaCl Substrates

The growth and structure of Ti films evaporated on NaCl substrates have been studied by electron microscopy. The film showed cubic or fcc-like diffraction spots of three types in the early growth stage, depending on the preparation method and temperature of the substrate and film thickness. The lattice parameters corresponding to those spots taken from 2 nm-thick films formed on the substrate at 260°C were a=0.441 nm, 0.418 nm and 0.426 nm, which were determined to be those of CaF2-type TiH1.5, NaCl-type TiO1.0 and some titanium compound, respectively. The former two grew on the substrate cleaved in vacuum while the last one grew on that cleaved in air, only. When the film was thicker than 3 nm, hcp diffraction spots also appeared. The formation mechanism of the cubic and hcp crystallites is discussed.

Nitriding of Evaporated-Ti Thin Films by Ion Implantation

Nitrogen ions ( N2+) with 62 keV have been implanted into 100-nm-thick Ti films evaporated on thermally cleaned NaCl substrates. Unimplanted and N-implanted Ti films have been examined by transmission electron microscopy, Rutherford backscattering spectrometry and elastic recoil detection analysis. The analysis has provided evidence that N-implantation results in the epitaxial formation of NaCl-type TiNy and simultaneously induces the release of H from evaporated-Ti films containing TiHx. The nitriding of evaporated-Ti films is mainly divided into two elemental processes. One is accompanied by the hcp-fcc transformation and the other is not. The formation mechanism for TiNy is discussed.

Early nitriding stage of evaporated-Ti thin films by N-ion implantation

The early growth stage of epitaxial titanium nitride (TiN) films, formed by implanting nitrogen ions (N2+) with 62 keV into 100-nm-thick evaporated-Ti films, was studied by transmission electron microscopy, Rutherford backscattering spectrometry and elastic recoil detection analysis. Evaporated-Ti films spontaneously absorb hydrogen (H) from the interior of the NaCl substrate, and then TiHx partially grows in addition to the hcp-Ti. The implantation of N into evaporated-Ti films expands the hcp-Ti lattice and reduces the H concentration in the evaporated-Ti film. The former induces the hcp–fcc transformation and then leads to the growth of (001)-oriented TiNy by the occupation of N in octahedral (O) sites in the fcc-Ti sublattice. The latter induces contraction of the fcc-Ti sublattice by the escape of H from (110)-oriented TiHx and then leads to the growth of (110)-oriented TiNy by the occupation in O sites of the H-escaped metastable fcc-Ti lattice by N. The nitriding mechanism of epitaxial Ti thin film...

Epitaxial growth of TiN films by N-implantation into evaporated Ti films

Nitrogen ions (N2+) with 62 keV have been implanted into 100-nm-thick Ti films prepared by the evaporation on thermally cleaned NaCl substrates held at room temperature. The epitaxial growth process of resultant TiN films has been studied by transmission electron microscopy, Rutherford backscattering spectrometry, and elastic recoil detection analysis. It has been revealed that the (110)-oriented TiNy is formed by nitriding the (110)-oriented TiHx in the as-deposited Ti film without change of the orientation of the fcc-Ti sublattice, and that the (001)-oriented TiNy and the “rotated” (110)-oriented TiNy rotated by ∼9° with respect to the (110)-oriented TiNy, respectively, are epitaxially formed by the transformation of (03⋅5)-oriented hcp-Ti to (001)-oriented fcc-Ti and by the transformation of (21⋅0)-oriented hcp-Ti to rotated (110)-oriented fcc-Ti. Then, the inheritance of the square atomic arrangement and parallelogram atomic arrangement of hcp-Ti plays a very prominent role in the epitaxy of the (001...

Spontaneous Hydrogenation of Ti Films Evaporated on NaCl Substrates II

The growth and structure of Ti films evaporated on ultra-high-vacuum- and air-cleaved NaCl substrates at room temperature have been studied by reflection high-energy electron diffraction. The 2 nm-thick film on the former showed bcc- and CaF2-type (TiH1.5) reflections while that on the latter showed TiH1.5 ones immediately after the evaporation. Judging from the lattice parameter (0.33 nm), the bcc crystallite was analyzed to be β-Ti. This is the first observation of β-Ti grown in evaporated Ti films. The β-Ti changed into TiH1.5 with time. This spontaneous hydrogenation mechanism of the evaporated Ti films is discussed.

EPITAXIAL GROWTH OF (001)-ORIENTED TITANIUM NITRIDE THIN FILMS BY N IMPLANTATION

The epitaxial growth process of titanium nitride (TiN) films, formed by implanting nitrogen ions (N2+) with 62 keV into 100-nm-thick Ti films grown on NaCl substrates held at 250 °C, has been studied by transmission electron microscopy, Rutherford backscattering spectrometry, and elastic recoil detection analysis. It has been revealed that the (001)-oriented TiNy is epitaxially grown by N implantation into the as-grown (03⋅5)-oriented hcp Ti. The TiNy is formed by the transformation of the hcp Ti to (001)-oriented fcc Ti during the N implantation, partially inheriting the atomic arrangement of the square and/or the octahedron of the hcp Ti, as well as the occupation of N in octahedral sites of the fcc Ti. Strain due to the expansion of the lattice and/or the volume of hcp Ti by N implantation can be considered as one of the driving forces for the hcp–fcc transformation of the Ti lattice. The nitriding mechanism of epitaxial Ti thin films is discussed.

Initial stage of SiC film growth on Si(111)7×7 and Si(100)2×1 surfaces using C 60 as a precursor studied by STM and HRTEM

We have investigated the structure and the growth mechanism of cubic silicon carbide (3C–SiC) films formed by thermal reaction of Si(111) and Si(100) substrates with C60 molecules, using scanning tunneling microscopy (STM) and high-resolution transmission electron microscopy (HRTEM). The cross-sectional HRTEM images show the good epitaxial growth of SiC films on the Si(111) surface and the 3×3 surface reconstruction is observed by STM. In contrast, many dislocations are formed in the SiC films grown on the Si(100) surface and no surface structure is observed by STM. We find that the amorphous buffer layers, which have relevance to release the strain due to the lattice mismatching, are formed at the interface between SiC films and the Si(111) substrate.

Control of epitaxial orientation of TiN thin films grown by N-implantation

Nitrogen ions (N 2 + ) with 62 keV have been implanted into 100-nm thick films prepared by evaporation of Ti on thermally cleaned NaCI substrates held at room temperature (RT) and 250°C. Unimplanted and N-implanted Ti films have been examined mainly by transmission electron microscopy. The evaporated films grown at RT consisted of (03 5)- and (21 . 0)-oriented hcp-Ti, and (110)-oriented CaF 2 -type TiH x , The N-implantation into the (03.5)-oriented hcp-Ti and (110)-oriented TiH x , results in the epitaxial growth of the (001)- and (110)-oriented TiN y , respectively, whereas nitriding of the (21 . 0)-oriented hcp-Ti gives rise to the growth of (110)-oriented TiN y rotated by ∼ 9° with respect to that grown from the (110)-oriented TiH x , On the other hand, the Ti films grown at 250°C consisted of only the (03 5)-oriented hcp-Ti. It has been clearly shown that only the (001)-oriented TiN y film is epitaxially grown by N-implantation into the as-grown (03 . 5)-oriented hcp-Ti. The control of epitaxial orientation of the TiN y films grown by N-implantation and nitriding mechanism of epitaxial Ti thin films are discussed.

Titanium Nitride Thin Films Epitaxially Grown by N-Implantation

The epitaxial growth of titanium nitride (TiN) films, formed by implanting nitrogen ions (N2+) with 62 keV into 100-nm-thick Ti films grown on NaCl substrates held at 250°C, has been studied mainly by transmission electron microscopy. It has been revealed that (001)-oriented TiNy is epitaxially grown by N-implantation into the as-grown (035)-oriented hcp-Ti. The nitriding mechanism of epitaxial Ti thin films is discussed.

The Dynamical Observation of α-Sn (111) This Films Grown on InSb (1̄1̄1̄) by RHEED

The α-Sn (111) films of 150 monolayers (ML) will grow at room temperature on thermally cleaned InSb () substrates having a 2×2 reconstructed surface. The α-Sn (111) surfaces are observed to most clearly exhibit a 3×3 reconstruction at a film thickness of 30 ML by reflection high energy electron diffraction (RHEED). When the 30 ML films are heated at 170°C, the liquid phase begins to appear without the transition to the β-phase. From these result, effects of the InSb () substrate on the thermal stability of the α-Sn (111) film are discussed.