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Plasma-sputtered amorphous films for all-solid-state Li+-ion batteries are investigated. In LiPON electrolyte films, the amount of N incorporated into LiPO films is controlled by the sputtering discharge gas. Ionic conductivity increases with increasing N2 gas proportion in Ar/N2 discharge, reaching a maximum of 2.7 × 10−6 S/cm at Li2.39PO3.71N0.13. In amorphous LiAlGePO electrolyte films, the amounts of Al and Ge incorporated into LiPO films are controlled in a combinatorial approach using two-source co-sputtering. The P/Ge ratio varies over a wide range from 23.3 to 1.61 at the radial substrate positions, and the highest ionic conductivity of 4.32 × 10−5 S/cm is achieved at Li4.80Al0.80Ge1.16P3O13.1. We evaluate all-solid-state Li+-ion batteries fabricated using the developed amorphous LiPON electrolyte and GeSn anode films, where GeSn films with about 50 nm nanograins are fabricated by high-gas-pressure sputtering at 500 mTorr. A maximum capacity of 2.86 µAh/cm2 is attained for all-solid state Li+-ion battery.

The homogeneous formation of high-mobility oxide semiconductor thin films over large areas at low temperatures was accomplished by optimizing both the film formation process and the low-temperature post-processing via plasma annealing. Increasing the substrate-to-target distance (D ST) and the applied target voltage was found to produce more uniform deposition. The results of the field-effect mobility distributions of IGZO TFTs processed using plasma annealing were founded that plasma annealing generated essentially uniform distributions with μ FE values in the range of 32–35 cm2 V−1 s−1.

We fabricated nanostructured Ge and GeSn films in He radio-frequency magnetron plasma sputtering deposition. Monodisperse amorphous Ge and GeSn nanoparticles of 30-40 nm in size were orderly arranged without aggregation by off-axis sputtering deposition in high He-gas-pressure range of 0.1 Torr. The Ge film porosity was over 30%. We tested the charge/discharge cycle performance of Li-ion batteries with nanostructured Ge and GeSn anodes. The Ge anode with an ordered arrangement of nanoparticles showed Li-storage capacity of 565 mAh/g after the 60th. The capacity retention was markedly improved by the addition of 3at% Sn in Ge anode. GeSn anode (3at% Sn) achieved a higher capacity of 1,128 mAh/g after 60th cycles with 92% capacity retention. Precise control of the nano-morphology and electrical characteristics by a single step procedure using low temperature plasma is effective for stable cycling of high-capacity Ge anodes.

Functional thin films on organic materials are important in flexible electronics including next-generation flexible displays and photovoltaic cells. Herein, we describe the formation of SiNx films by plasma-assisted reactive sputtering deposition at low temperature, and detail the properties of the formed films. The effect of plasma assistance on the deposition rate and the properties of the SiNx films deposited by this system are reported as functions of relative N2 partial pressure. Plasma assistance led to a deposition rate as high as 1.63 nm/s. The thin film formed at a relative nitrogen partial pressure of 21.4% exhibited a density of 2.73 g/cm3 and was more than 95% transparent over the entire visible region of the spectrum. The properties of SiNx films formed by plasma-assisted reactive sputtering deposition demonstrate the feasibility of forming SiNx films that are suitable for passivation applications in devices such as organic light-emitting diodes (OLEDs) and solar cells.

The effects of sputtered atom flux on the electrical properties of a-IGZO films before and after thermal annealing were examined by varying the fluxes of sputtered atoms at the substrate holder. The electrical proprieties of IGZO TFTs fabricated from a-IGZO films were found to vary widely depending on the sputtered atom flux. Specifically, the electrical properties of a-IGZO films after thermal annealing improved considerably with increasing sputtered atom flux, such that a field effect mobility as high as 23.6 cm2V−1s−1 was achieved following annealing. These results suggest that the electrical characteristics of IGZO TFTs after annealing are affected by the film structure, including the density and quality of the as-deposited a-IGZO films.

We present a study on morphological control of nanostructured Ge films by the Ar gas pressure in plasma sputtering deposition. In the low Ar-gas-pressure range, aggregated islands of amorphous grains are formed on the film surface, while in the high-pressure range of 500 mTorr monodisperse nano-grains of about 30 nm in size are orderly arranged without aggregation. The film porosity shows a high value of over 10%. We tested the charge/discharge cycle performance of Li-ion batteries with nanostructured Ge films as anodes. The battery cell with an ordered arrangement structure maintained a high capacity of 434 mAh g−1 after 40 charge/discharge cycles, while that with an aggregated structure exhibited a rapid degradation of capacity to 5.08–183 mAh g−1. An ordered arrangement of Ge nano-grains with a high porosity, which is realized in a simple one-step procedure using high Ar-gas-pressure plasma sputtering, is effective for the stable cycling of high-capacity metal anodes.

The effects of working pressure on the physical properties of amorphous InGaZnO x (a-IGZO) films fabricated using inductively coupled plasma-enhanced reactive sputtering deposition were studied, while also assessing the plasma employed during film deposition. With decreasing working pressure, the ion saturation current corresponding to the plasma density increased along with the film deposition rate, because of the greater number of ions incident on the IGZO target. The physical properties of the resulting a-IGZO films were examined to determine the effect of ion energy while varying the working pressure. With decreasing working pressure, the film densities estimated from X-ray reflection data were found to increase. In addition, the concentrations of excess oxygen and hydrogen species incorporated into the a-IGZO films, which can potentially lead to structural and electrical instability, decreased. These results indicate the feasibility of enhancing the electrical properties of a-IGZO films.

We present evidence for the decomposition and oxidation of amino acids in aqueous solution following irradiation with a nonequilibrium plasma jet. Of 15 amino acids tested in cell culture medium, plasma irradiation induced a marked chemical change in methionine and tryptophan due to the effective production of reactive oxygen species by plasma-water interaction. We also report that plasma-treated methionine and tryptophan aqueous solutions can kill cancer cells, greatly decreasing the viability of human endometrial carcinoma (HEC-1) cancer cells due to the presence of decomposition or oxidation products generated from the amino acid. Plasma-treated methionine and tryptophan aqueous solutions also induced an anti-cancer effect on cancer-initiating cells.

We present evidence for the decomposition and oxidation of amino acids in aqueous solution following irradiation with a nonequilibrium plasma jet. Of 15 amino acids tested in cell culture medium, plasma irradiation induced a marked chemical change in methionine and tryptophan due to the effective production of reactive oxygen species by plasma-water interaction. We also report that plasma-treated methionine and tryptophan aqueous solutions can kill cancer cells, greatly decreasing the viability of human endometrial carcinoma (HEC-1) cancer cells due to the presence of decomposition or oxidation products generated from the amino acid. Plasma-treated methionine and tryptophan aqueous solutions also induced an anti-cancer effect on cancer-initiating cells.

We present here an analysis of the discharge characteristics near the liquid surface in the plasma jet operated at a He gas flow rate of 1.5–10 slm. The plasma diameter on the liquid surface increases with an increase in He gas flow rate, which results in an increase in the total amount of charge particles transferred from the plasma to the liquid. We also analyzed the gas flow patterns using a Schlieren gas flow imaging system. The diameter of the laminar flow and the gas flow distance along the liquid surface increase with an increase in He gas flow rate, which well explains the increase in the plasma diameter on the liquid surface. Our experiments clearly demonstrate that high gas flow rate realizes the large reaction area between the water molecule and the plasma in the plasma jet system.

In this study, an inductively coupled plasma (ICP)-enhanced reactive sputter deposition system with a rectangular target was developed as a linear plasma source for roll-to-roll deposition processes. The longitudinal distribution of the film thickness indicated the feasibility of uniformity control via the control of the power deposition profile of the assisted ICPs. The characteristics of Si films were investigated in terms of the film thickness uniformity and film crystallinity. The results of Raman and X-ray diffraction measurements indicated the crystallization of the Si film with a crystallinity as high as 73%–78% in all the samples of the longitudinal position.

We present He atmospheric-pressure gas-breakdown phenomena with radio frequency (RF) voltages in the frequency region from a few tens MHz to 100 MHz. The gas-breakdown voltage for RF and very high frequency (VHF) discharges is considerably lower than that for the DC discharge, and the gas-breakdown voltage is effectively reduced to be as low as 160 V in VHF region. The discharge characteristics drastically change with increasing discharge-voltage frequency, and strong emisson is highly loclized in front of the power- and ground-electrode in the VHF discharges. The lowering gas-brakdown voltage and the localized emission-profile are well explained by the effect of the charged-particle confinement in a micro dishcarge-space.

Investigation of plasma-organic materials interaction in aqueous solution with atmospheric pressure plasmas have been carried out. Degradation of methylene blue (MB) in aqueous solution via atmospheric pressure He plasma exposure through gas/liquid interface have been investigated. The optical emission spectrum shows considerable emissions of He lines and the emission of O, OH and N radicals attributed to dissociation of water (H2O) and air has been confirmed. Structure variation of MB in solution treated with the atmospheric-pressure He plasma has been measured by Fourier transform infrared spectroscopy (FT-IR). The results obtained from FT-IR analysis show degradation of MB in solution treated with the atmospheric-pressure He plasma. The pH effect of MB degradation was investigated using controlled pH solutions by an ultraviolet-visible (UV-Vis) spectroscopy and FT-IR. The results show no effect of MB degradation on pH. The results exhibit that the atmospheric pressure plasmas exposure has made it possible to degrade organic materials in solution due to irradiated radicals from plasma through plasma/liquid interface.

We present here the analysis of the characteristics of a dielectric-barrier-discharge (DBD) plasma jet in open air using the optical emission spectroscopy (OES). The OES on oxygen emission is useful to estimate the presence of reactive excited O atoms. The O emission intensity is much higher near the quartz-tube outlet and abruptly decreases with distance from the quartz tube. Our experiments also show that the DBD plasma jet is quite sensitive to He gas flow rate ( $R_{{\rm He\mbox{-}gas~flow}})$ : increasing $R_{{\rm He\mbox{-}gas~flow}}$ induces weak pulse discharge, resulting in decreasing O emission intensity.

Molecular-structure variation of organic materials irradiated with atmospheric pressure He plasma jet have been investigated. Optical emission spectrum in the atmospheric-pressure He plasma jet has been measured. The spectrum shows considerable emissions of He lines, and the emission of O and N radicals attributed to air. Variation in molecular structure of Polyethylene terephthalate (PET) film surface irradiated with the atmospheric-pressure He plasma jet has been observed via X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR). These results via XPS and FT-IR indicate that the PET surface irradiated with the atmospheric-pressure He plasma jet was oxidized by chemical and/or physical effect due to irradiation of active species.

We report characteristics of quantum dot (QD) sensitized solar cells using Si nanoparticles and Ge nanoparticles. Si nanoparticles were synthesized by multi-hollow discharge plasma chemical vapor deposition, whereas Ge nanoparticles were done by a radio frequency magnetron sputtering using Ar+H2 under high pressure conditions. The electrical power generation from Si QDs and Ge QDs was confirmed. Si QD sensitized solar cells show an efficiency of 0.024%, fill factor of 0.32, short-circuit current of 0.75 mA/cm2 and open-circuit voltage of 0.10 V, while Ge QD sensitized solar cells show an efficiency of 0.036%, fill factor of 0.38, short-circuit current of 0.64 mA/cm2 and open-circuit voltage of 0.15 V.

A dye-sensitized solar cell is one of the representative photochemical solar cells. It has been actively studied and its performance has been much enhanced so far. For better performance, various additional layers such as compact, barrier, and light scattering layers have been applied. Compact and barrier layers suppress the charge recombination with redox electrolyte and light scattering layer improves the light harvesting. Although it was confirmed that these layers were clearly effective for the performance enhancement, there is still a variety of opinions concerning their electrochemical impedance analyses. Therefore, this work tried to analyze their effect on the internal impedance using electrochemical impedance spectroscopy. The most widely used materials were employed for the fabrication of additional layers. TiCl 4 and Zn(NO 3 ) 2 ∙6H 2 O aqueous solutions, and a 400 nm sized TiO 2 were used for compact, barrier, and light scattering layers, respectively. The photovoltaic characteristics confirmed their effect on the performance and their impedance spectra were analyzed according to high, middle, and low frequency bands. As a result, these layers mainly affected the impedance in the middle frequency range because the change of TiO 2 /dye/electrolyte interface was significantly associated with this impedance. Finally, all three layers were applied to a single cell and the performance was considerably increased with reduced charge recombination and improved light harvesting.

This work first introduced Si quantum dots (QDs) for QD-sensitized solar cells (QDSCs). However, the particle size of Si QDs, which had visible light absorption, was relatively large. The paint-type Si QDSC was proposed in this work because Si QDs could not penetrate into nano-porous TiO2 network. Si QDs were synthesized by multi-hollow plasma discharge CVD and mixed with TiO2 paste. For better performance, thickness of Si-TiO2 layer was varied by coating times and Si-TiO2 films were optically and electrically analyzed. As a result, 6 times screen printed Si-TiO2 film had the best performance with the smallest internal impedance and the highest photon to current efficiency.

This work demonstrated the low-temperature fabrication of high-mobility a-InGaZnOx (a-IGZO) films using plasma-enhanced reactive processing. The effect of the post-processing temperature on the performance of IGZO thin-film transistors (TFTs) using these a-IGZO films as a channel layer was also investigated. IGZO TFTs incorporating a-IGZO films plasma-treated at temperatures as low as 200 °C exhibited the expected TFT transfer characteristics, with field effect mobility values as high as 40 cm2 V−1 s−1. The fabrication of IGZO TFTs that exhibited homogeneous characteristics over large substrate areas was attempted, by assessing the effects of the plasma treatment on a-IGZO films deposited at various oxygen flow rate ratios. The electrical properties of IGZO TFTs using plasma-treated films were found to be dramatically improved, irrespective of the film deposition conditions prior to the plasma treatment. These results confirm the feasibility of producing IGZO TFTs with uniform characteristics over large substrates areas.

Quantum dots (QDs) have been attractive recently with their multiple exciton generation characteristics. QD solar cells can more effectively use the incident energy because one or more electrons are generated with the photon of high energy. They have less heat loss and higher theoretical efficiency (44%) than single exciton generation solar cells (33%). This work focused on Si as alternative to conventional QD materials. Si has QD's unique characteristics such as the quantum size effect and quantum confinement with non-toxicity and abundance. Si QDs were fabricated by the multi-hollow discharge plasma chemical vapor deposition and applied to QD-sensitized solar cells (QDSCs). Contrary to the good characteristics of Si QDs, Si QDSCs had poor performance as compared with conventional QDSCs because of the weak combination between Si QDs and TiO 2 . Small amounts of adsorbed Si QD on TiO 2 made low photocurrent and TiO 2 surface widely exposed to redox electrolyte caused charge recombination, the decrease of open-circuit voltage, and low fill factor. For improving their combination, Si QDs were functionalized. The electron transfer from Si to TiO 2 and the bonding with TiO 2 were improved and more Si QDs were adsorbed by the functionalization. In the functionalization process, the linking source is one of the key parameters. Therefore, 4-vinylbenzoic acid was controlled and its effect was analyzed. The change in the photovoltaic parameters according to the concentration of 4-vinylbenzoic acid and the performance dependence were investigated. In order to verify their characteristics, the effects in terms of the photovoltaic performance, electrochemical impedance, and optical properties were examined.

In order to obtain high density carbon films with keeping anisotropic deposition profile on trench substrates, we control mass density of carbon films deposited by a H-assisted plasma chemical vapor deposition (CVD) method by ion kinetic energy of ions irradiating on film surface during deposition. The highest mass density of 2.14 g/cm 3 is obtained for deposition under the ion energy of 75 eV and it is 1.4 times as high as that for the ion energy of 32 eV. We also have studied etching rate of these films using H 2 + N 2 discharge plasmas. The lowest etch rate of 1.8 nm/min is obtained for the ion energy of 75 eV and it is 2.8 times as low as that for the ion energy of 32 eV. Etching rate of carbon films decreases exponentially with increasing the mass density of carbon films. Control of ion energy is the key to obtain high mass density carbon films with keeping anisotropic deposition profile on trench substrates.

We investigated the effects of incorporation of crystalline nanoparticles on properties of microcrystalline Si films deposited using multi-hollow discharge plasma CVD. Both photo and dark conductivity of films with nanoparticles are lower than the films without nanoparticles. Films with nanoparticles have higher photosensitivity than those of films without nanoparticles in a low crystallinity region. Microcrystalline films of high crystallinity and high photosensitivity are obtained only in a range of small volume fraction of nanoparticles under low dilution ratio, R = ([SiH 4 ] + [H 2 ])/[SiH 4 ]. Incorporation of small amount of nanoparticles into films strongly affects photo and dark conductivity of films.

In fusion devices, dust particles are generated due to plasma–wall interactions and may cause safety or operational problems. Therefore it is necessary to clarify the generation and transport mechanisms of dust particles. Here we have measured energy influx from H 2 plasmas toward a graphite target using a calorimetric probe and compared the results with the dust flux toward a dust collecting substrate set on the reactor wall. The dust flux decreases with increasing the energy influx. For the higher discharge power, the more number of dust particles tend to redeposit onto the graphite target due to the higher ion drag force and hence the dust flux toward the reactor wall becomes smaller. The results show that dust inventory depends strongly on energy influx to graphite divertor plates in fusion devices.

We measured the dependence of the collected flux of dust particles on the bias potential Δ ϕ with respect to ground in the Large Helical Device at the National Institute of Fusion Science. This is a first step toward developing a novel method for removing dust for fusion reactors based on applying a local bias potential. The collected dust particles were classified into two kinds: spherical carbon particles smaller than 300 nm and stainless-steel flakes smaller than 1 μm. For Δ ϕ = −70 to +70 V, the flux of spherical particles increased exponentially with increasing Δ ϕ . The flux of flakes increased when Δ ϕ was increased from −70 V to +30 V and it decreased at higher Δ ϕ . These results suggest that this method is useful for removing carbon and metal dust particles from the shadow area of fusion devices using appropriate control of the local bias potential.

Quantum dot-sensitized solar cell (QDSC) based on multiple exciton generation of QD has been expected to realize high efficiency. This work focused on Si QD instead of conventional QD materials because of their toxicity and scarcity. Si QDs were fabricated by multi-hollow discharge plasma chemical vapor deposition. General QDSCs use polysulfide electrolyte because it is suitable for stabilizing QDs and its redox reaction is the best as compared with other redox systems. The improvement of redox reaction which is one of the slowest reactions in the kinetic analysis is closely connected with the enhancement of performance. For the enhancement on the overall performance of Si QDSC, the performance dependence on electrolyte composition was investigated. The concentrations of Na2S and S were varied for the activation of redox reaction and KCl concentration was optimized for the improvement of electrolyte characteristics. Consequently, the best performance of Si QDSC was obtained with 1 M Na2S, 2 M S, and 0.4 M KCl polysulfide electrolyte.

The collection of dust particles using divertor simulation helicon plasmas has been carried out to examine dust formation due to the interaction between a graphite target and deuterium plasmas, which are planned to operate in the large helical device (LHD) at the Japanese National Institute for Fusion Science (NIFS). The collected dust particles are classified into three types: (i) small spherical particles below 400 nm in size, (ii) agglomerates whose primary particles have a size of about 10 nm, and (iii) large flakes above 1 μm in size. These features are quite similar to those obtained through hydrogen plasma operation, indicating that the dust formation mechanisms due to the interaction between a carbon wall and a plasma of deuterium, which is the isotope of hydrogen, is probably similar to those of hydrogen.

Multiple exciton generation solar cell based on quantum dots has higher theoretical efficiency than single exciton generation solar cell. In this work, Si quantum dots with the diameter of 10 nm were fabricated by the multi-hollow discharge plasma chemical vapor deposition and applied to the quantum dot-sensitized solar cell. In this cell, there was considerable electron recombination with redox electrolyte in the Si–TiO 2 network because of large Si particle size. For the reduction of recombination and the enhancement of performance, a barrier layer was introduced. Zinc nitrate hexahydrate (Zn(NO 3 ) 2 ·6H 2 O) and zinc acetate dihydrate (Zn(CH 3 COO) 2 ·H 2 O) were employed as precursors for surface modification. Consequently, short circuit current and open circuit voltage of the cells were increased by the surface modification with both precursors. The improvement was ascribed to the inhibition of electrons back transfer from TiO 2 to the electrolyte by the barrier layer. This result clearly demonstrated that the surface modification with ZnO was advantageous for the performance enhancement.

We investigate uniformity of radial density profile of nano-particles in capacitively-coupled radio frequency discharge with an amplitude modulation (AM) of rf discharge voltage, by a two-dimensional laser light scattering method. Their densities at the center and that at the edge of the electrode increase by 3 and 24 times when the amplitude modulation level increases from 0 (without AM) to 30%. The uniformity of radial density profile of nano-particles is significantly improved by using the AM method.

We investigated effects of incorporation of Si crystalline nanoparticles into microcrystalline Si films during their deposition on their growth, structure and properties using multi-hollow discharge plasma chemical vapor deposition. The films with nanoparticles show a lower (220) orientation ratio than those without nanoparticles, whereas both the films have nearly the same film thickness and crystallinity. The films with nanoparticles have inverted conical growth, while the films without nanoparticles have columnar growth. Nucleation density of the films with nanoparticles is higher than that of the films without nanoparticles. Both photo and dark conductivities of the films with nanoparticles tend to be lower than those without nanoparticles. Thus, incorporation of small amount of nanoparticles into microcrystalline Si film affects growth, structure and properties of the films.

High quality epitaxial ZnO films on sapphire (110) plane have been fabricated on ZnO homo-buffer layers crystallized via solid-phase epitaxially (SPE). The SPE-ZnO films are fabricated by annealing of amorphous ZnON (a-ZnON) films deposited by RF magnetron sputtering. During annealing, the a-ZnON films are oxidized and converted to ZnO crystal. X-ray diffraction (XRD) analysis shows that the resultant films are epitaxially grown on the sapphire substrates. By using the SPE-ZnO films as homo-buffer layers, the ZnO films with high crystallinity, which are deposited by RF magnetron sputtering, are fabricated. The full width at half-maximum of XRD patterns for 2θ-ω and ω scan of (002) plane are 0.094° and 0.12°, respectively, being significantly small compared with 0.24° and 0.55° for the films without buffer layers. Thus utilizing SPE buffer layers is very promising to obtain epitaxial ZnO films with high crystallinity.