Satoru Iwamori

Characterization of silicon oxynitride gas barrier films

Abstract New transparent gas barrier materials made of thin silicon oxynitride films deposited on polyethylene terephthalate substrates via reactive sputtering in nitrogen plasma have been developed and characterized. The gas barrier properties of these materials have been evaluated and compared with silicon oxide thin films. The oxygen transmission rates of the silicon oxynitride (SiON) films were lower than those of the SiO x films. The SiON films are amorphous and contain no pinholes or cracks. The OTR decreases when relative nitrogen content in the SiON films increases. The increase in nitrogen content causes an increase in film density.

Silicon oxide gas barrier films deposited by reactive sputtering

Abstract Transparent silicon oxide thin films were deposited on polyethylene terephthalate substrates by means of reactive sputtering in oxygen and their gas barrier properties were evaluated. The SiO x film sputtered in 10% oxygen/90% argon mixture of inlet gases showed the lowest oxygen transmission rate, and this rate increased with an increase of inlet oxygen concentration. In addition, the oxygen contents of SiO x films increases rapidly within the range of small value of the inlet oxygen gas concentration (0–10%), and gently for oxygen gas concentration larger than 10%. The SiO x films sputtered at high oxygen concentration had more micro-defects than the films prepared at low oxygen concentration. The annealing at 120 °C in vacuum improved the gas barrier properties of the SiO x films sputtered at high oxygen concentration.

Effect of a metallic interfacial layer on peel strength deterioration between a Cu thin film and a polyimide substrate

The peel strength of a copper (Cu) thin film deposited on a polyimide (PI) substrate deteriorates after heat treatment at 150 °C in air. The deterioration involves Cu2O microparticles (10–100 nm) penetrating the PI substrate, both the substrate and film being oxidized. To prevent this penetration and oxidation, we introduced an interfacial layer (vanadium, titanium, or cobalt) at the interface between the Cu thin film and PI substrate. Both titanium and cobalt interfacial layers were effective as barriers against the penetration of Cu2O particles. The quality of the interfacial layers (e.g., quantity of dislocations) influenced their effectiveness. By annealing the cobalt interfacial layers at 280 °C for 1 h in a vacuum before sputter deposition of a Cu thin film, we succeeded in keeping the peel strength between the Cu thin film and the PI substrate above 0.1 N/m even after heat treatment of the laminate at 150 °C for three days.

Changes in the adhesion strength between copper thin films and polyimide substrates after heat treatment

The adhesion strength between a copper (Cu) thin film and a polyimide [pyromellitic dianhydride-oxydianiline (PMDA-ODA)] substrate is reduced by heat treatment at 150°C in air. In this work, we determined the changes in adhesion strength between Cu films and polyimide substrates using Auger electron spectroscopy (AES), attenuated total reflection Fourier-transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). The analysis showed that the weak boundary layer (WBL) shifted towards the Cu interface as the heat treatment time was increased. To confirm this shift, we looked at two other polyimide substrates: biphenyl dianhydride-p-phenylene diamine (BPDA-PDA) and biphenyl dianhydride-oxydianiline (BPDA-ODA). Comparing the adhesion strength for the Cu thin film, the adhesion strength was high for the Cu/PMDA-ODA and Cu/BPDA-ODA laminates, but very low for the Cu/BPDA-PDA laminate. One of the possible reasons for this behavior could be that the ether moiety between the two benzene rin...

Room temperature ethanol sensor based on ZnO prepared via laser ablation in water

The present work reports on room-temperature ethanol sensing performance of ZnO nanospheres and nanorods prepared using pulsed laser ablation in water. Nanosecond and millisecond lasers were used to prepare ZnO nanomaterials with hexagonal wurtzite crystal structure. The two contrasting nanostructures were tested as gas sensors towards volatile compounds such as ethanol, ammonia, and acetone. At room temperature, devices based on both ZnO nanomaterials demonstrated selectivity for ethanol vapor. The sensitivity of nanospheres was somewhat higher compared to that of nanorods, with response values of ~19 and ~14, respectively, towards 250 ppm. Concentrations as low as 50 ppm could be easily detected.

Changes in the Peeled Surfaces of Copper Thin Films Deposited on Polyimide Substrates After Heat Treatment

Abstract Peel strength between a copper (Cu) thin film and a polyimide (pyromellitic dianhydride-oxydianiline, or PMDA-ODA) substrate is reduced by heat treatment at 150°C in air. In this work, we investigated the peel strength, the morphology of the interface between Cu films and polyimide substrates using optical microscopy and electron microscopy, and chemical change of the interface using Auger electron spectroscopy (AES) and micro X-ray photoelectron spectroscopy (XPS). The analysis showed that CuO “lumps” were present on the peeled surface of PMDA-ODA after heat treatment at 150°C in air. The peeled surfaces of other polyimide substrates were also analyzed: biphenyl dianhydride-para phenylene diamine (BPDA-PDA) and biphenyl dianhydride-oxydianiline (BPDA-ODA). CuO lumps were present on the peeled surface of BPDA-ODA after the heat treatment, but not that of BPDA-PDA. Compared with the adhesion strength for the Cu thin film, the adhesion strength was high for the Cu/PMDA-ODA and Cu/BPDA-ODA laminates...

Characterization and tribological properties of two polyimide thin films sputtered onto a copper substrate

Two kinds of polyimide (PI), pyromellitic dianhydride-oxydianiline (PMDA-ODA) and biphenyl dianhydride-p-phenylene diamine (BPDA-PDA), thin films were sputtered onto a copper substrate by conventional RF sputtering with argon. These PI thin films were characterized, and their adhesion and tribological properties were evaluated. Elemental compositions and chemical bonding states of these thin films were analyzed with X-ray photoelectron spectroscopy (XPS). Oxygen and nitrogen concentrations in these thin films were less than those in bulk PIs. In addition, the amounts of C—O and C—N moieties in these PI thin films decreased as compared to the bulk PIs. Contact angles of water and methylene iodide on these PI thin films were higher than those on the bulk PIs. Surface energies of these PI thin films were calculated by measuring contact angles of water and methylene iodide. Surface energies of these PI thin films were lower than those of the bulk PIs and the polar components of these PI thin films were one-third of those of the bulk PIs. Friction coefficients of these thin films were almost the same as those of the bulk PIs. The abrasion durability of PMDA-ODA thin film was higher than that of BPDA-PDA thin film. The adhesion strength between the PMDA-ODA thin film and copper substrate was also higher than that between BPDA-PDA thin film and copper substrate.

Characterization of Polymer Thin Films Sputtered onto a Copper Substrate with Two Kinds of Polyimide Targets

Polymer thin films were sputtered with two kinds of polyimide (PI) targets, pyromellitic dianhydride-oxydianiline (PMDA-ODA) and biphenyl dianhydride-p-phenylene diamine (BPDA-PDA), onto a copper substrate by a conventional RF sputtering with argon (Ar) and nitrogen (N2). These polymer thin films were characterized, and their adhesion and tribological properties were evaluated. Sputtering rate of the polymer thin film with PMDA-ODA target (sputtered PMDA-ODA thin film) with Ar was higher than that with BPDA-PDA target. Although the sputtering rate of the polymer thin film with the BPDA-PDA target (sputtered BPDA-PDA thin film) with Ar showed highest value at a pressure of 5 mTorr, that with N2 showed highest value at a pressure of 60 mTorr. Nitrogen content in the sputtered BPDA-PDA thin film with N2 increased compared to that of the sputtered BPDA-PDA thin film with Ar and target material (pristine). Although friction coefficients of these sputtered BPDA-PDA thin films with Ar were almost the same as those of the pristine PIs, that of the sputtered BPDA-PDA thin film with N2 was much higher than that of the pristine BPDA-PDA. The wear durability of the sputtered PMDA-ODA thin film with Ar was slightly higher than that of sputtered BPDA-PDA thin film. The wear durability of the sputtered BPDA-PDA thin film with N2 was much higher than that of the polymer thin film sputtered with Ar. The adhesion strength between the sputtered BPDA-PDA thin film with N2 and copper substrate was higher than that between the thin film sputtered with Ar and copper substrate. In addition, the sputtered BPDA-PDA thin film with N2 was introduced between the copper substrate and the sputtered BPDA-PDA thin film with Ar (Ar/N2 laminate). The adhesion strength of this laminate was higher value than that between the sputtered BPDA-PDA thin film with Ar and copper substrate.

Adhesion and Friction Properties of Fluorocarbon Polymer Thin Films Coated onto Metal Substrates

Poly(tetrafluoroethylene)(PTFE) thin films were coated onto metal substrates by a spin coat apparatus, vacuum evaporator and RF sputtering, and their adhesion and friction properties evaluated. PTFE thin film coated onto nickel-titanium (Ni-Ti) substrate by spin coating showed a low friction coefficient, however pull strength between the thin film and Ni-Ti substrate was low. In order to increase the pull strength, PTFE and poly(vinyl alcohol) (PVA) composite thin films were introduced between the PTFE thin film and Ni-Ti substrate by spin coating. PTFE thin film was also coated onto SUS302 substrate by a vacuum evaporator. This PTFE thin film showed poor adhesion to the SUS302 substrate. The adhesion was enhanced by heating of the substrate during the evaporation. In addition, a PTFE and ethylene vinyl alcohol (EVOH) composite thin film showed higher adhesion strength than that of the PTFE thin film. Poly(fluorocarbon) thin films were prepared by a conventional RF sputtering with PTFE target. These thin films showed a higher friction coefficient than that of the pristine PTFE. Molecular structures of the poly(fluorocarbon) thin films prepared by RF sputtering were different from the pristine PTFE. This difference may have influenced the friction coefficient. The pull strength of metal thin films such as gold, copper, nickel and aluminum deposited on the sputtered PTFE thin films by vacuum evaporation was measured. The nickel thin film adhered to the PTFE thin film most strongly of all the thin films.

Investigation of a sterilization system using active oxygen species generated by ultraviolet irradiation.

We have been investigating an advanced sterilization system that employs active oxygen species (AOS). We designed the sterilization equipment, including an evacuation system, which generates AOS from pure oxygen gas using ultraviolet irradiation, in order to study the conditions necessary for sterilization in the systems chamber. Using Geobachillus stearothermophilus spores (10(6) CFU) in a sterile bag as a biological indicator (BI) in the chamber of the AOS sterilization apparatus, we examined the viability of the BI as a function of exposure time, assessing the role of the decompression level in the sterilization performance. We found that the survival curves showed exponential reduction, and that the decompression level did not exert a significant influence on the survival curve. Subsequently, we investigated the sterilization effect as influenced by the spatial and environmental temperature variation throughout the chamber, and found that the sterilization effect varied with position, due to the varying environmental temperature in the respective areas. We confirmed that temperature is one of the most important factors influencing sterilization in the chamber, and estimated the temperature effect on the distribution of atomic oxygen concentration, using the quartz crystal microbalance (QCM) method with fluorocarbon thin film prepared by radio frequency sputtering.