Yasunori Andoh

Crystallization of carbon films by ion beam assist technology

Abstract Carbon films were prepared by evaporation of carbon and simultaneous bombardment with argon and neon ions in the low energy region (IVD method) on substrates of silicon crystal wafers. Infrared absorption spectra showed two peaks due to the TYPE-1 and TYPE-2 diamond structures. In addition, Raman-scattering patterns indicated a clear peak which agreed with the diamond structure, together with a broad peak corresponding to graphite and/or the amorphous phase. The spectra depend on the ion species, energy and composition ratio. The results show that the crystal growth of carbon films can be induced by optimizing the preparation conditions.

Coating Films of Titanium Nitride Prepared by Ion and Vapor Deposition Method

Titanium nitride coating films were prepared on polished stainless steel and graphite plates by vacuum evaporation of titanium with simultaneous bombardment by nitrogen ions with an energy of 10 to 30 keV (IVD method). The compositional variations of each element with depth and the crystal structure were analysed by means of XPS, RBS and X-ray diffraction. It was confirmed that a significant intermixed layer exists at the interface. The thickness of this layer was about 440 A for a film prepared on a stainless-steel plate at about 300°C by a 30 keV nitrogen ion beam, and decreased with decrease of the ion energy. Films were mainly composed of TiN crystallites with [100] axes preferentially oriented normal to the film surfaces. Some titanium was bound to oxygen and carbon atoms, but there were no metallic-state titanium atoms.

A new machine for film formation by ion and vapour deposition

Abstract A new machine for film coating with ion beam and vapour deposition (IVD) has been designed in order to realize practical applications of IVD. The machine consists of a rectangular bucket type multi-aperture ion source, evaporator with electron gun, rotary specimen holder and film thickness monitor. The ion energy is variable in the region 2–40 keV and the current for nitrogen ions is 100 mA. The area of the ion beam is 4 × 10 cm 2 . The beam uniformity is ± 10% and in the central region within a length of 6 cm it is ± 5%. The temperature of a specimen is controlled by water cooling. The technology was applied to a process of aluminum coating on low carbon steel. After coating with a 300 A layer of aluminum, an implantation process using 1 × 10 17 /cm 2 argon ions with 30 keV energy was performed. Then the aluminum deposition was continued by electron beam evaporation to a thickness of 1 μm. The resulting aluminum coating is maintained during a peel-off test up to 300 kg/cm 2 . Results related to the bending and corrosion properties of aluminum layers formed with ion beam assisted techniques are reported.

Properties of boron nitride coating films prepared by the ion beam and vapor deposition method (IVD)

The authors have studied coating films of boron nitride prepared by the ion implantation and vapor deposition method (IVD method) and it was found that the films consisted of the cubic, wurzite and hexagonal boron nitride. These films were manufactured by bombardment of nitrogen molecular ion with energy 25–40 keV. In the present work, we prepared films by the nitrogen molecular ions with much lower energy than the previous case. Boron was evaporated by electron beam bombardment on substrates of silicon crystal wafers and nitrogen molecular ions with energy 2–25 keV were simultaneously irradiated. Infrared absorption spectra showed a clear and strong peak due to the boron nitride of cubic structures together with a broad peak of hexagonal one. The hardness of the films was tested. The result showed that the films had 3000–5000 Hv which is much harder than titanium carbide.

Crystalline orientation control by the IVD method

Abstract Titanium nitride films were prepared by nitrogen ion irradiation with 100 to 1000 eV during titanium vapor deposition (IVD method) at room temperature, and the relation between the crystalline orientation, the direction of ion incidence and the energies of nitrogen ions were studied. The direction of ion incidence was varied from 0 to 45° from the normal to the substrate surface. X-ray diffraction spectra indicated that every film had Bl structure, and that the direction of the 〈100〉 axis of titanium nitride agreed with one of the incident ion directions when ions with about 200 to 1000 eV were used. On the other hand, when ions with the energies less than about 200 eV were used, the 〈111〉 axis was grown, and this was independent of the direction of irradiation. These results were independent of the kinds of substrates (Si〈100〉, 〈111〉, fused silica and sapphire) used.

Nitride film formation by ion and vapour deposition

Abstract Boron nitride coating films were produced using ion beams of nitrogen molecules with energies 25–40 keV and simultaneous evaporation of boron (IVD method) and were analysed by infrared absorption spectra. X-ray diffraction and electron microscopy. Films with the composition ratio B N larger than about 0.9 have structures of cubic BN or close to this. Those with smaller B N than about 0.9 consist of hexagonal (layered) boron nitride or close to this. On some films, well oriented wurtzite type crystal was observed. A depth analysis for a titanium nitride film deposited on stainless steel prepared by IVD indicates the presence of a thick mixed layer of film and substrate.

Properties of aluminum nitride films by an ion beam and vapor deposition method

Abstract Aluminum nitride (AlN) films were prepared by evaporation of aluminum and simultaneous irradiation with nitrogen ions in the low energy regions, 200–1000 eV. These films were formed on substrates of fused silicas at room temperature. XPS analysis revealed that the AlN bonding state varied with the composition ratio of aluminum and nitrogen. In films with Al/N > 1, these spectra showed clear peaks and humps due to AlN chemical bonding and metallic aluminum atoms. Properties of the optical transmittance and electrical resistivity depended on the ratio of Al/N. The films prepared with Al/N = 1 indicated that the transmittance was approximately 98% and the resistivity 10 14 Ω cm .

On the formation of BN films by ion beam and vapor deposition

Abstract Boron nitride films were prepared by using a low energy nitrogen ion beam and simultaneous vapor deposition of boron at room temperature. Films were analyzed by X-ray diffraction. Diffraction patterns show sharp peaks due to crystalline of the cubic boron nitride phase for every film formed with ion energies of 200–1000 eV. It is concluded that an ion beam in the low energy region is effective for forming the metastable cubic phase, c-BN.

Formation of molybdenum nitride films by ion beam and vapor deposition method

Molybdenum nitride films were prepared using nitrogen ions with energies of 5 and 20 keV and simultaneous evaporation of molybdenum either at room temperature or at 400–500°C. In almost all the cases, the films had a cubic structure of NaCl type and their lattice constant was 4.19–4.24 A. Films produced at room temperature had a preferential orientation of [110] axes normal to the substrate surface and those at high temperature grew epitaxially. XPS analysis revealed that all molybdenum atoms made Mo-N bonding and nitrogen atoms made one kind of Mo-N bonding in films with the composition ratio N/Mo = 1.0. In films with N/Mo > 1.0, the excess nitrogen atoms made a different bonding. The superconducting transition temperature was measured and it ranged from 4.5 to 5.8 K. These values are much lower than the expected ones from theoretical and empirical considerations. Crystal imperfection is considered as the most probable reason for the low transition temperature.

Activation behavior of boron and phosphorus atoms implanted in polycrystalline silicon films by heat treatment at 250°C

The activation behavior of boron and phosphorus implanted into laser-crystallized silicon films were investigated. The ratio of recrystallization of an ion-doping-induced amorphous region by heat treatment at 250°C was 0.35 for a boron concentration lower than 6.4×1019 cm-3 and 0.5 for a phosphorus concentration lower than 2.5×1019 cm-3. This ratio decreased as dopant concentration increased. High electrical conductivities of 1.1×102 S/cm and 7.3 S/cm were achieved by oxygen plasma treatment at 250°C for 1 h in the cases of 3.2×1020-cm-3 boron and 5.0×1019-cm-3-phosphorus doping, respectively. Numerical analysis of the electrical conductivity revealed that the electrical conductivity was governed by recrystallization ratio and the density of the intrinsic defects of polycrystalline films.