F. Fujimoto

Variation of crystallization with arrival ratio in titanium nitride films formed by dynamic mixing method

Abstract The preferred orientation of titanium nitride films with cubic structure produced at about 400 °C by the dynamic mixing method is studied in the range of the arrival ratio Ti/N from 1.0 to 2.6 and in the case of normal incidence of nitrogen ion beam to the substrate surface. The accelerating voltage of nitrogen ions is 30 kV. The current density of nitrogen ions, in which the numerical ratio of atomic to molecular ions is about unity, is kept at a constant, 0.18 mA/cm2, and the deposition rate of titanium is changed. The composition ratio of titanium to nitrogen in the prepared films are roughly unity, in spite of the large difference of the arrival ratio. The preferred orientation varies from the 〈111〉 axis normal to the surface to the 〈100〉 axis normal as decreasing the arrival ratio, though the film prepared with Ti/N = 1.0 includes a small amount of crystals with the 〈111〉 and 〈110〉 axes as the surface normal and amorphous part. Such a variation of the crystallization is considered to arise by the difference in the energy deposition per a titanium atom.

Kα X-ray emission from resonant coherently excited F8+ ions channeled along a Au 〈110〉 axis and their exit charge-state distribution

Abstract Resonant coherent excitation and subsequent radiative de-excitation have been investigated for hydrogen-like heavy ions axially channeled in a gold single crystal. The intensity of the F8+ Kα X-ray has shown a clear increase at the third-order resonance for F8+ ions channeled along the 〈110〉 axis at an incident energy of 37.6 MeV. However, the energy dependence of the exit charge state distribution of hyperchanneled ions did not show a resonant behavior. In the case of hydrogen-like C ions penetrating the same crystal along the 〈111〉 axis, the fourth-order resonance was clearly observed in the exit charge-state distribution at the incident energy of 15.3 MeV. These results are explained by comparing the crystal channel size with the orbital radius of the excited electron.

Film formation of dititanium nitride by the dynamic mixing method

Abstract Coating film formation of titanium nitride is studied by means of the dynamic mixing method, where the deposition rate of titanium and the current density of nitrogen ions are widely changed and, for the first time, films of the pure Ti 2 N phase are prepared in a narrow range of the ratio of the deposition rate of the titanium and the current density of the nitrogen ions, Ti/N. Under the condition that the ratio Ti/N is larger than for Ti 2 N formation, a film consists of three phases: α-Ti, Ti 2 N and TiN. For lower Ti/N, the prepared films are a mixture of two phases: Ti 2 N and TiN. In the case of a much lower Ti/N only TiN films are prepared.

Focused High-Energy Heavy Ion Beams

A focused ion beam line of MeV heavy ions has been developed by combining a focusing system consisting of objective slits and a magnetic quadrupole doublet to the beam line of a tandem-type accelerator. The demagnification factors of this system were determined to be 1/3.4 for the horizontal direction and 1/14 for the vertical direction, and a minimum beam spot size of 5.6 µm×8.0 µm was achieved. This system allows us ion beam processes such as maskless MeV ion implantation and ion beam microanalysis using heavy ions.

Determination of the infrared proportionality coefficient of the CHn stretching mode for a-C:H and a-SiC:H films using ERD methods

Abstract The proportionality coefficient between hydrogen concentration and the integrated intensities of the infrared reflection-absorption spectrum (IRAS) for CH n bonds was determined in hydrogenated amorphous carbon films (a-C:H) and hydrogenated silicon carbide films (a-SiC: H). The hydrogen concentration in the films was measured by using elastic recoil detection (ERD) analysis. Since the absorption strength of the CH n band strongly depends on the chemical structure of the films, the proportionality coefficients were obtained by the band separation of the IR spectrum as A (CH) = 3.85 × 10 21 atoms/cm 2 , A (CH 2 ) = 3.85 × 10 20 atoms/cm 2 and A (CH 3 ) = 3.65 × 10 20 atoms/cm 2 . These values can be applicable universally to a-C:H and a-SiC:H films.

Charging effects and ultraviolet irradiation for carbon films prepared by ion beam bombardment

Abstract Carbon films were prepared by evaporation of carbon during neon ion bombardment (IVD method) in the low-energy region and the films were exposed to charged particles induced by rf plasma and irradiated by ultraviolet rays simultaneously for enhancing the crystalline growth. Charging effects were studied by the measurement of surface potential, and the crystalline state for carbon films was evaluated by Raman scattering spectroscopy and SEM images. The spectra of the film prepared under optimum conditions indicated a clear peak which agreed with the diamond structure. The status of crystallization of carbon films depended on the rf power of discharge, and the growth of diamond crystals was enhanced by ultraviolet irradiation at the same time.

Crystalline orientation control for aluminum nitride films prepared by ion-beam-assisted technology

Abstract Aluminum nitride films were prepared by evaporation of aluminum and simultaneous bombardment of nitrogen ions in the low-energy region 200–1000 eV (IVD method) on substrates of fused silica and on Si (100), (111) wafers. The ion incident angle was changed from 0° to 45° from the normal to the substrate surface, and the relation between the direction of ion incidence, ion beam energies, and crystalline orientation of A1N films was studied. X-ray diffraction patterns indicated that each film had a hexagonal structure and the direction of the (002) axis was parallel to the ion beam direction. Every film showed the same tendency irrespective of the substrate used. In addition, the dielectric constants of the A1N films were measured by means of an impedance analyzer and ellipsometry. The relation between the direction of crystalline orientation and the dielectric constant was also studied.

A study of hydrogen atoms on solid surfaces by utilizing the doppler broadening of the 1H(15N, αγ)12C nuclear reaction

Abstract The Doppler broadening of the very narrow 6.4 MeV 1 H( 15 N, αγ) 12 C resonant nuclear reaction is discussed and surveyed with respect to the behavior of hydrogen atoms adsorbed on tungsten crystal surfaces. For the (001) surface, the thermal vibration energy of the hydrogen atoms is definitely obtained. However, for the (110) surface, the resonance line shape is much wider than would be expected by the Doppler broadening contribution alone. This result may suggest that the stable site of the adsorbed hydrogen is not only on the surface but also inside the crystal.

Resonant coherent excitation of channeled heavy ions and photon emission due to its deexcitation

Abstract Resonant coherent excitation of channeled ions and the possibility of its radiative deexcitation are discussed and an experiment on the photon emission due to the deexcitation of the ions is reported. The experiment is performed on the 6th order resonance for the 1s to 2p transition of hydrogen-like 20 Ne 9+ ions channeled along the 〈111〉 axis of a gold crystal. The intensity of the Ne 9+ K α X-rays (1.02 keV) normalized to the Au M X-rays is measured for the 〈111〉 channeling and the random directions as a function of the incident energy and an enhancement in the normalized intensity of the Ne 9+ K X-rays in the vicinity of the calculated resonance energy. 87.3 MeV, is observed.

Formation of indium-tin oxide (ITO) films by the dynamic mixing method

Abstract Indium-tin oxide (ITO) films are prepared on silica glass substrates by the dynamic mixing method, that is, indium and tin are simultaneously evaporated on the substrates and the oxygen ions with energies of 10, 2 and 0.6 keV are also simultaneously bombarded normal to the substrate surface. The film thickness is about 500 A and the substrate temperature is lower than 50° C. Films formed with 10 keV ions have a preferred orientation of the [111] axes of In2O3 crystals which are normal to the film surface and the film with the deposition rates O/In = 3.2, and Sn/In = 0.19 has a transmittance of 96% and an electric resistivity of 7 × 10−3 Ω cm. Films prepared with 0.6 keV ions and O/In = 2.1, Sn/In = 0.2 have a transmittance of 92% and a resistivity of 2.5 × 10−4 Ω cm. The film has a preferred orientation of the [110] axes which are normal to the film surface. Films produced with 2 keV have no definite preferred orientation and have worse quality than those prepared with 10 and 0.6 keV.