Noriaki Ikenaga

Surface modification of PET film by plasma-based ion implantation

Abstract It has been reported that thin diamond like carbon (DLC) coating is very effective for enhancing the barrier characteristics of polyethylene terephthalate (PET) against CO 2 and O 2 gases. However, coating technique has a problem of DLC-deposit peeling. In this research, we develop a new technique to change the PET surface into DLC by ion implantation instead of coating the surface with the DLC deposit. The surface of PET film is modified by plasma-based ion implantation using pulse voltages of 10 kV in height and 5 μs in width. Attenuated total reflection FT-IR spectroscopy shows that the specific absorption peaks for PET decrease with dose, that is, the molecules of ethylene terephthalate are destroyed by ion bombardment. Then, laser Raman spectroscopy shows that thin DLC layer is formed in the PET surface area.

Structural evaluation of defects in β-Ga2O3 single crystals grown by edge-defined film-fed growth process

We have structurally evaluated β-Ga2O3 crystals grown by edge-defined film-fed growth process using etch pitting, focused ion beam scanning ion microscopy, transmission electron microscopy, and related techniques. We found three types of defects: arrays of edge dislocations corresponding to etch pit arrays on -oriented wafers, platelike nanopipes corresponding to etch pits revealed on the (010)-oriented wafers, and twins including twin lamellae.

Simultaneous Sterilization With Surface Modification Of Plastic Bottle By Plasma-Based Ion Implantation

Dry sterilization of polymeric material is developed. The technique utilizes the plasma‐based ion implantation which is same as for surface modification of polymers. Experimental data for sterilization are obtained by using spores of Bacillus subtilis as samples. On the other hand we previously showed that the surface modification enhanced the gas barrier characteristics of plastic bottles. Comparing the implantation conditions for the sterilization experiment with those for the surface modification, we find that both sterilization and surface modification are simultaneously performed in a certain range of implantation conditions. This implies that the present bottling system for plastic vessels will be simplified and streamlined by excluding the toxic peroxide water that has been used in the traditional sterilization processes.

Effects of additional vapors on sterilization of microorganism spores with plasma-excited neutral gas

Some fundamental experiments are carried out in order to develop a plasma process that will uniformly sterilize both the space and inner wall of the reactor chamber at atmospheric pressure. Air, oxygen, argon, and nitrogen are each used as the plasma source gas to which mixed vapors of water and ethanol at different ratios are added. The reactor chamber is remotely located from the plasma area and a metal mesh for eliminating charged particles is installed between them. Thus, only reactive neutral particles such as plasma-excited gas molecules and radicals are utilized. As a result, adding vapors to the source gas markedly enhances the sterilization effect. In particular, air with water and/or ethanol vapor and oxygen with ethanol vapor show more than 6-log reduction for Geobacillus stearothermophilus spores.

Influence of Substrate Temperature on Texture for Deposited TiNi Films

In order to fabricate two-dimensional micro actuators with shape memory alloy films, it is especially important to evaluate the anisotropy of transformation strain that is caused by texture. In this paper, microstructures of sputter-deposited TiNi films are examined. The films of 1 μm in thickness are sputter-deposited on Si(001) substrates by RF magnetron multi-sputtering system equipped with four separate confocal sources as well as with substrate heating. Pure Ti and Ni targets of 50 mm in diameter are used for the sources. The films deposited at ambient temperature have been generally amorphous. However, we find that some films which are deposited at 773K of substrate temperature are crystalline, when we appropriately choose sputtering parameters such as source voltage and the distance between a target and the substrate. X-ray powder diffraction and pole figure measurements reveal that these films are oriented with {110}B2 parallel or inclined at 45 degree to the substrate. Furthermore, we also find that crystallized film is deposited even at 673K of substrate temperature by applying pulse bias voltage to the substrate.

Effects of humidity on sterilization of Geobacillus stearothermophilus spores with plasma-excited neutral gas

We investigate the effects of relative humidity on the sterilization process using a plasma-excited neutral gas that uniformly sterilizes both the space and inner wall of the reactor chamber at atmospheric pressure. Only reactive neutral species such as plasma-excited gas molecules and radicals were separated from the plasma and sent to the reactor chamber for chemical sterilization. The plasma source gas is nitrogen mixed with 0.1% oxygen, and the relative humidity in the source gas is controlled by changing the mixing ratio of water vapor. The relative humidity near the sample in the reactor chamber is controlled by changing the sample temperature. As a result, the relative humidity near the sample should be kept in the range from 60 to 90% for the sterilization of Geobacillus stearothermophilus spores. When the relative humidity in the source gas increases from 30 to 90%, the sterilization effect is enhanced by the same degree.

Crystallizing compound film on plastics by ion irradiation in plasma

Micro machines are expected in advanced medical instruments for micro surgery. Typical materials for the actuators are shape memory alloys such as TiNi(titanium nickel) and piezoelectric compounds such as PZT(lead zirconate titanate). For future medical application the materials will be required to be deposited directly on the surfaces of plastics in the form of crystalline thin film, since most medical instruments such as catheters for blood vessel surgery are made of polymeric plastics. Then the film will be finished into some micro actuators.

Low Temperature Crystallization of Sputter-Deposited TiNi Films

We have found that deposited film can be crystallized without the post-annealing treatment but with the simultaneous ion-irradiation during sputter-deposition at very low substrate temperature. The present paper reviews the low temperature crystallized TiNi films deposited by the above technique. An RF magnetron sputtering apparatus equipped with separate confocal sources as well as with a heating and ion-irradiating system for substrates was used to make the films crystalline. Without using the ion-irradiating system, the films deposited on ambient-temperature substrate have been amorphous. However, crystallized film is deposited even at 353 K of substrate temperature with using the system. Appropriate ion-irradiation is considered to be help to crystallize the film at low substrate temperature. Broad and doublet X-ray diffraction profile of the film, which was diffracted from B19’ and/or R phase, was recorded between 42 degree to 45 degree in 2 theta. The crystallized film deposited on a polyimide sheet was cut into the shape of a double-beam cantilever and the ends of the two beams were connected to an electrical power supply. The cantilever shows a repeatable two-way motion by electrical cycle of 0.1 Hz at room temperature.

Factors determining energy values of ion beams for ion-beam deposition

Abstract IBD (ion-beam deposition) is performed with a very low-energy ion beam, whose energy value is not simply determined. For the accurate evaluation an excess energy due to the source-plasma potential should be added to the energy value obtained simply from the source-bias voltage. However, the plasma potential is changing dependently on the secondary electrons from chamber wall as well as the plasma parameters. We studied theoretically how the plasma potential is affected by the chamber material as well as by the plasma parameters. Then, we measured floating potentials of several materials immersed in a microwave plasma for studying the influence of secondary electrons from the wall. The result suggests that the potential of a plasma surrounded by material of a high secondary-electron coefficient becomes low and consequently the excess energy decreases.

Measurement of excess energies of ion beams extracted from a microwave ion source

Abstract When an ion beam is used as a tool for analysis based on its energy value, the precision of the measurement depends on how accurately the ion energy is evaluated. However, as far as a plasma type ion source is concerned, the energy value of a very low-energy ion beam, lower than 100 eV specifically, should be carefully treated. Strictly speaking, the ion energy is equal to the ion charge multiplied by the sum of the source bias potential supplied to the chamber and the plasma potential with respect to the chamber. Of course, when the bias potential is sufficiently high, the plasma potential can be neglected. Theoretically, the plasma potential is determined by the electron temperature which is changeable depending on the source operating condition. Furthermore, the fact, that most plasmas of industrially used ion sources have plural electron temperatures and not a single one, makes the problem difficult to resolve. In this paper, we used the magnetic field of a mass separator to directly evaluate the plasma potential in a microwave ion source by utilizing the linear relationship between the squared magnetic flux of the mass separator and the ion acceleration voltage, i.e. the sum of the source bias potential and the plasma potential. The measurement showed that the excess energy of the ion beam due to the plasma potential rises above 100 eV at a microwave power of more than 500 W. Thus, when we handle a low energy ion beam of the order of 100 eV, the real ion energy may be more than twice the value given only by the source bias voltage at the chamber. The result is compared with the theoretical calculation for a plasma model of double electron temperatures.