Yuji Horino

Au + -Ion-Implanted Silica Glass with Non-Linear Optical Property

Au+ ions have been implanted in silica glass at an acceleration energy of 1.5 MeV and a fluence level of 1017 ions/cm2. The Au ions form colloid particles with the radius of 2.9 nm after heat treatment. The glass with Au colloid particles shows the large third order non-linear susceptibility; χ(3)=1.2×10-7 esu. The large χ(3) value of the glass is attributed to the high concentration of Au colloid particles in the narrow region.

Carbonization of polyimide film “Kapton”

Abstract Polyimide film “Kapton” C22H10O5N2 has been known to give well-oriented graphite film by high temperature heat treatment. Its carbonization behavior was followed as a function of carbonization temperature up to 1000°C. Carbon films without any appreciable deformation and cracks were obtained by carbonization up to 1000°C in between two alumina plates, though it showed large weight loss up to 40 wt% and also large shrinkage up to 23%. Carbonization proceeded in two steps; in the first step, an abrupt release of oxygen associated with remarkable weight loss and shrinkage occurred over a rather narrow temperature range of 550–650°C and in the second, nitrogen and the remaining oxygen were released gradually above 700°C. In the second carbonization step, a rapid increase of electrical conductivity, reaching about 65 S/cm after 1000°C and growth of carbon layers were observed.

High-Dose Implantation of MeV Carbon Ion into Silicon

The formation of SiC in silicon wafer by 1.5 MeV C+ implantation to doses of 1.5×1018 ions/cm2 followed by annealing is demonstrated using infrared absorption spectra and Rutherford backscattering (RBS). From the results of He+ backscattering under the channeling condition, the surface layer of Si is observed to remain crystalline even before annealing.

A new PBIID processing system supplying RF and HV pulses through a single feed-through

A new type of plasma based ion implantation and deposition system (PBIID) was developed. In this system, an RF pulse for plasma generation and a high-voltage pulse for ion implantation were supplied to a target through a single feed-through. Temporal and spatial evolutions of RF plasma around a spherical RF antenna were measured with a Langmuir probe. The plasma density had the largest value close to the RF antenna, while the electron temperature was almost constant in space. The plasma density after the RF pulse decreased almost exponentially in time and reduced more quickly in the region near the antenna. Using hydrocarbon gases in the PBIID system, the DLC film was prepared on an Si wafer substrate on each surface of the hexagonal sample holder. The thickness of each film was significantly uniform (93% in uniformity). The average thickness was 3.8±0.24 μm for a deposition time of 4 h, showing a deposition rate of 0.95 μm/h.

Formation of Crystalline SiC Buried Layer by High-Dose Implantation of MeV Carbon Ions at High Temperature

A buried layer of crystalline SiC in silicon wafer is synthesized by 1.5 MeV C+ implantation at a dose of 1.5×1018 ions/cm2 at a high temperature of 880°C. The infrared absorption spectrum and the X-ray diffraction pattern of this sample show formation of 3C-type SiC crystal. The pole figures of X-ray diffraction show that crystallographic orientation of the SiC buried layer is aligned along the lattice of the Si substrate, that is, topotaxial internal growth of crystalline SiC occurs in a single crystal of Si during the high-temperature ion implantation.

Macroparticle-Free Ti–Al Films by Newly Developed Coaxial Vacuum Arc Deposition

Titanium aluminide thin films are deposited on glassy carbon substrates by the coaxial vacuum arc deposition process. A rod-shaped Ti–Al alloy is employed as the evaporation source. In our vacuum arc system, because the spatial position of plasma on the surface of the evaporation source can be controlled by pulsed arc discharge, the thickness of the Ti–Al film can be controlled at nanometer scale. Amorphous stoichiometric Ti–Al films are synthesized from one Ti–Al alloy target at room temperature by changing the number of pulses of the arc discharge. Multilayered Ti and Al films could also be fabricated by changing the target and the number of pulsed arc discharges.

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.

Preferentially Oriented Crystal Growth in Dynamic Mixing Process–An Approach by Monte Carlo Simulation–

Titanium nitride films produced by a dynamic mixing method have a preferential crystallographic orientation, and the orientation varies with the arrival ratio of the depositing elements. For this study, we performed a Monte Carlo simulation of the damaging process caused by nitrogen ion irradiation onto (111) and (100) planes of a TiN single crystal. The simulation predicts that in (100)TiN, N+ penetrates through the open channel, losing its kinetic energy mainly by electronic stopping, while N+ loses its kinetic energy mainly by nuclear stopping in (111)TiN, leading the crystal to be amorphous. The contribution of this dynamic mixing process to the development of preferred orientation is discussed.

Optical properties of carbon and carbon nitride films prepared by mass-separated energetic negative carbon and carbon nitrogen ions

Carbon and carbon nitride (CN) films were prepared under ultrahigh vacuum condition by ion beam deposition using isotopically mass-separated, energetic (50–400 eV) negative 12C2− and 12C14N− ions, respectively. The optical properties as well as structures and chemical composition of the films have been characterized and discussed as a function of the kinetic energy of C2− and CN− ions. The structures of carbon and CN films in this study were hydrogen-free amorphous carbon (a-C) like. The N/C composition ratio of the CN films was N/C∼0.4, although the arrival ratio of N/C was N/C=1. The CN film properties depended weakly on kinetic energy of CN− ions, while on a-C films there were kinetic energy dependence of C2− ions of optical constant observed.

Titanium nitride prepared by plasma-based titanium-ion implantation

By using a titanium dc arc of 70 A with a pulse modulator with specifications of 60 kV/2.5 A/30 μs, titanium nitride (TiN) films were prepared on a silicon substrate (n-n+, [111],  400 μm in thickness) and titanium ions were simultaneously implanted by applying voltages of 20–50 kV of negative polarity to the substrate. The crystal orientation of the film produced by pulsed voltage application in plasma-based ion implantation (PBII) is different from that prepared by applying dc bias of −500 V. It is strongly (200) preferred orientation for PBII, while it is (111) and (220) preferred orientations for the dc bias. The film hardness increases with increasing pulse voltage, and the hardness for the application of −40 kV pulse is almost equal to that for the dc bias. Thus, the hardness maintains the same value while the crystal orientation differs from that for the dc bias.