Mokuyoshi Kishimoto

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...

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.

Effect of silicon preimplantation on carbon nitride formation by nitrogen implantation into glassy carbon

Abstract We have studied the effects of Si-preimplantation on the formation of carbon nitride by N implantation into glassy carbon (GC). Structure, composition and chemical bonding of the Si-implanted carbon nitride layers are examined by using Backscattering spectroscopy (BS), X-ray diffraction (XRD), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). Raman spectroscopy reveals that the carbon nitride layer containing up to 8 at.% Si is amorphous and has an sp2 bonded structure with a small amount of CN bonds. XPS analysis suggests that local CN–Si(CnN3−n) arrangements exist in the nitride layer. It was revealed from backscattering measurements that the Si-preimplantation increases the saturation concentration of the implanted N atoms; it increases from 26 at.% N for the nitride layer without Si-preimplantation to 35 at.% for the Si-preimplanted nitride. In addition, Si atoms in the nitride layer suppress oxygen incorporation during N implantation.

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.

Epitaxy of titanium nitride thin films grown by nitrogen implantation

Abstract Nitrogen ions (N 2 + ) with energy 62 keV were implanted into 100 nm thick Ti films evaporated onto thermally cleaned NaCl substrates. Unimplanted and N-implanted Ti films were examined by transmission electron microscopy, Rutherford backscattering spectrometry and elastic recoil detection analysis. It was revealed that N-implantation expands the h.c.p. Ti lattice and reduces the hydrogen concentration in the evaporated Ti film. The former induces the h.c.p.-f.c.c. transformation and then leads to the growth of (001) oriented TiN y by occupation of the octahedral sites in the f.c.c. Ti sublattice by N. The latter indicates the escape of H from TiH x , and leads to the growth of (110) oriented TiN y , by the similar occupation by N.

Deceleration of ion beams for film deposition by an electrostatic field

Abstract For the practical use of ion beam deposition (IBD), the deceleration characteristics of Ar+ ion beams of the order of mA and of 10 kV were investigated by using an electrostatic field of a flat deposition electrode. The experiments were carried out by means of measurement of the electrode currents of a deceleration unit settled in an electromagnetic isotope separator and by photographic observation of the ion beams. A preliminary Si deposition was attempted and a metallic film appearance was obtained on an Al2O3 substrate.

A Study of the Production of Transuranium Elements and its Application to the Solution Chemistry in Tohoku University

About 2.8 g of UO2 were irradiated with neutrons(about 1.6 × 1020 nvt) at the Japan Material Testing Reactor(JMTR). After 140 days cooling, the irradiated sample was processed chemically. The isotopic ratios of U and Pu were determined by a-ray spectrometry and mass spectrometry. A small amount of 242Am(<100 μg) was also irradiated in JMTR. Am and Cm were purified mainly by ion-exchange chromatography. We have tried to estimate the irradiation conditions in JMTR. The thermal neutron flux(Ф) and the epithermal ratio (the ratio of the epithermal to the pure thermal neutron density)(f) were chosen as adjustable variables for the calculation of the isotopic ratios of U, Pu, Am, and Cm. Then, the most reasonable values of Ф and f were obtained which explained the values of the isotopie ratios obtained experimentally. Short-lived Bk tracers, 243–246Bk were produced by the 241Am + α and 243Am + α reactions using the A.V.F. cyclotron at the Cyclotron and Radioisotope Center, Tohoku University. A compressed aluminium powder disk, in which Am was suspended, was used as the target. Bk tracers were isolated from Am and fission products by HDEHP or TTA extraction of Bk(IV). Stability constants(β1 and β2) of the chloro and bromo complexes of trivalent Sm, Eu, Gd, Tb, Ac, Am, Cm, Bk, and Cf were determined by a solvent extraction method using HDEHP with an ionic strength and acidity of 3.0 M and 0.15 M, respectively. Stability constants could be roughly estimated by assuming inner sphere complex formation.