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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.

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.

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 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.

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 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.

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.

Si clusters formed in silane discharge plasmas are mainly responsible for light induced degradation of hydrogenated amorphous Si (a-Si:H) thin films deposited by the plasmas. Here we have investigated effects of grid DC bias on incorporation amount of Si clusters into a-Si:H films in multi-hollow discharge plasma CVD reactor using quartz crystal microbalances, by which volume fraction of Si clusters in deposited films is quantitatively measured. When the grid potential is lower than plasma potential, the negatively charged clusters are repelled away from the grid by electrostatic force, resulting in lower volume fraction.

ZnO-based TCO has attracted much attention because it has potential to replace Sndoped In2O3 (ITO) due to its low toxicity and abundance in nature. We have demonstrated a novel method to fabricate high quality ZnO films via nitrogen mediated crystallization (NMC) method [1]. Utilizing the NMC ZnO as buffer layers, ZnO:Al films with low resistivity have been obtained. Here we have studied the growth mechanism of the NMC ZnO at the early stages of growth by means of height-height correlation function analysis of the surface morphology that derives lateral correlation length ξ. NMC-ZnO films were fabricated on quartz glass substrates by RF magnetron sputtering using Ar-N2 gas at the substrate temperature of 300°C. Figure 1 shows ξ of NMC ZnO as a function of the deposition time (t). At the early stage of crystal growth until t= 12 sec, the nuclei are sparsely distributed, being indicated by the decrease in ξ. At t= 15 sec, ξ reaches the minimum where the nuclei are uniformly distributed over the surface and the crystallite nuclei start to grow, which can be seen from the increase in ξ. The value of ξ at NMC-ZnO thickness of 10 nm was found to be 0.42 μm that is significantly longer than that for a conventional ZnO fabricated without nitrogen (0.2 μm), indicating that nitrogen has obvious effects on the nucleation and growth of ZnO. The detail will be discussed at the conference. *, K. Oshikawa, H. Seo, D. Yamashi ta, K. Kamataki, G. Uchida, K. Koga, M. Shiratani, N. Itagaki Graduate School of Information Science and Electrical Engineering, Kyushu University, Fukuoka 819-0395, Japan PRESTO, Japan Science and Technology Agency, Tokyo 102-0075, Japan

Graduate School of Information Science and Electrical Engineering, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan Joining and Welding Research Institute, Osaka University, 11-1 Mihogaoka, Ibaraki, Osaka 567-0047, Japan Department of Electrical Engineering and Computer Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan Japan Science and Technology Agency (JST), Core Research for Evolutional Science and Technology (CREST), Saitama 332-0012, Japan

Here are presented experiments on fine particles levitating in low-pressure weakly ionized plasmas under a vertical magnetic field. The magnetic field is useful to provide a vertically long cylindrical column of fine-particle clouds, yielding even string-shaped vertically aligned fine particles, under the double-plasma configuration. Measurements show that fine-particle clouds rotate in the azimuthal direction on the horizontal plane even in such a weak magnetic field that positive ions are slightly magnetized. With an increase of the magnetic field, the rotation speed increases, being followed by subsequent saturation. The rotation speed and direction can be controlled by varying radial plasma potential and/or density profiles. The rotation is induced under the condition that the interparticle distance is small enough for the strong Coulomb coupling among fine particles. A mechanism of the rotation could be explained by effects of ion motions on fine particles, which are modified in the presence of the vertical magnetic field.

The spatial shape of fine-particle clouds in a strongly coupled state is controlled by varying a radial potential profile provided by radially segmented electrode for particle levitation and confinement under a completely DC configuration. Fine-particle clouds change their shapes from a usual two-dimensional disk to a three-dimensional cone, and finally concave cone with an increase in the radial potential slope. These profiles are closely related to an axial variation of the radial potential profile in the ion sheath above the segmented electrode. When we apply to the segmented electrode a potential profile with peaks between the radial center and edge, fine particles are rearranged to form azimuthal rings on the horizontal plane. The radial width of the rings is controlled by changing the peak width of the radial potential profile.

Cyclic transport of dust particles (dust hour glass) in a capacitively coupled radio frequency discharge with horizon- tal electrodes is demonstrated. Dust transport toward the upper electrode is initiated by varying the electrical asymmetry of the discharge. A shaped upper electrode guides dust particles to move toward the center of the discharge. Subsequently, the dust drops through the plasma bulk spontaneously, this way returning to the starting location.

A chemical interaction between an atmospheric pressure plasma jet and liquid media is of great interest for biomedical applications. In this paper, the visualization method and typical results of the 2-D distribution of oxidizing substances generated by the plasma jet were reported using the gel visualization reagent. The plasma jet generator consists of a glass tube and two electrodes. As a result, the distribution of oxidizing substances was able to be visualized around the contact point between the plasma jet and the reagent in atmospheric air. The interesting distribution patterns depending on the supplied gas were visually obtained by the reagent. In addition, its relative concentration distribution was also obtained by an absorbance measurement.

We present here analysis of electron energy of a micro dielectric barrier discharge (micro-DBD) for alternating-current plasma display panel (ac-PDP) with Ne/Xe gas mixture by using the optical emission spectroscopy (OES). The OES method is quite useful to evaluate a variety of electron energy in a high pressure DBD ignited in a PDP small cell. Experiment shows that the ratio of Ne emission intensity (I-Ne) relative to Xe emission intensity (I-Xe) drastically decreases with time. This temporal profile is well consistent with dynamic behavior of electron temperature in a micro-DBD, calculated in one-dimensional fluid model. I-Ne/I-Xe also decreases with an increase in Xe gas pressure and a decrease in applied voltage especially in the initial stage of discharge, and these reflect the basic features of electron temperature in a micro-DBD. The influences of plasma parameters such as electron temperature on luminous efficacy are also theoretically analyzed using one-dimensional fluid model. The low electron temperature, which is attained at high Xe gas pressure, realizes the efficient Xe excitation for vacuum ultraviolet radiation. The high Xe-pressure condition also induces the rapid growth of discharge and consequent high plasma density, resulting in high electron heating efficiency.

We present here measurements of plasma display panel (PDP) ignited by SrO and SrCaO cold cathodes with high yield of ion-induced secondary electron emission (high gamma(1)). SrO- and SrCaO-cathode PDPs attain high luminous efficacy at low applied voltage, where the breakdown voltage is 304000wer than that of ordinary MgO-cathode PDP. Current and emission measurement clearly demonstrates that SrO- and SrCaO-cathode PDPs operated at low voltage realize a discharge with smaller current flow and lower electron energy, which are considerably appropriate for high luminous efficacy of PDP. Simulation analysis shows the effect of the high-gamma(1), cathode on the luminous efficacy of PDP. A discharge ignited by the high-gamma(1), cathode realizes high electron heating efficiency due to the abundant seed electrons from the high-gamma(1). cathode, resulting in high luminous efficacy of PDP. (C) 2009 American Institute of Physics. [doi: 10.1063/1.3253723]

We report here deposition of crystalline Ge nanoparticle films using a radio frequency magnetron sputtering method in argon and hydrogen gas mixture under a high pressure condition. The size of Ge nanoparticles is deduced to be 6.3-6.4 nm from the peak frequency shift of Raman spectra. Raman and X-ray diffraction spectra show that the films are crystalline. The film crystallinity strongly depends on substrate temperature (Ts). Highly crystalline Ge nanoparticle films are successfully fabricated at Ts = 180?C.

We compare growth enhancement effects due to atmospheric air dielectric barrier discharge plasma irradiation and heat shock to seeds of radish sprouts (Raphanus sativus L.). Interactions between radicals and seeds in a short duration of 3 min. lead to the growth enhancement of radish sprouts in a long term of 7 days and the maximum average length is 3.7 times as long as that of control. The growth enhancement effects become gradually weak with time, and hence the ratio of the average length for plasma irradiation to that for control decreases from 3.7 for the first day to 1.3 for 7 day. The average length for heat shock of 60°C for 10 min. and 100°C for 3 min. is longer than that for control, and the maximum average length is 1.3 times as long as that of control. Heat shock has little contribution to the growth enhancement due to plasma irradiation, because the maximum temperature due to plasma irradiation is less than 60°C.

The sterilization effect has been investigated using the sheet-type plasma jet, which was generated between asymmetric electrodes with dielectric plates in gas flow released into the atmospheric air. In this paper, it is indicated there is a possibility that the plasma jet irradiation area can be controlled only by supplied gases without changing a generator structure. The irradiation area control was evaluated from both the sterilization area size and the oxidizing substances distribution. The oxidizing substance distribution was obtained using the chemical reagent prepared in our laboratory. The width of the sheet-type plasma jet was able to be controlled by N2 addition into He gas. As a result, the width of the sterilization area was able to be controlled within the range of 2 to 12 mm at a constant height without changing the generator structure. On the other hand, the evaluation from the oxidizing substances distribution indicated that the irradiation area cannot be controlled in one direction.

Physical and chemical interactions between plasmas and nano-featured surfaces are one important issue in the plasma processing. Here we optically trap single fine particle levitated at plasma/sheath boundary with an infrared laser to realize in-situ analysis of such interactions. We have measured time evolution of the diameter of the single fine particle in Ar plasma. The trapped particle was etched at an etching rate of 1 nm/min in Ar plasma. We also obtained a Raman peak at around 2950 cm−1 corresponding to C-H bonds in the single fine particle in Ar plasma. The results open a new possibility to observe directly interactions between plasma and single fine particle.

ZnO has attracted much interesting as one of unique materials. Especially, it is suitable for the easy fabrication of nano-structures such as rod, wire and tube as well as particles. ZnO nano-rod is one of good sensitized electrodes because it has good electron transfer and is easily fabricated. In the chemical bath deposition process, seed layer plays an important role in the growth of nano-rod. This work investigated and analyzed the effect of seed layer on the growth of ZnO nano-rod. Fabricated nano-rods were applied to dye-sensitized solar cell. For better performance, ZnO was surface-modified by TiO2. Surface-modified ZnO had improved electron transfer and wider surface area. Consequently, the current and fill factor were much improved and overall performance was also enhanced with them.

We have investigated the effects of plasma fluctuation on the growth of nanoparticles in capacitively-coupled rf discharges with amplitude modulation (AM). Nanoparticles grow more slowly for higher AM levels, which causes the density of nanoparticles to increase by 100% and their size to decrease by 23%. The increase in the number of radicals for nucleation and nanoparticles by AM is thought to cause a decrease in the radical flux for a nanoparticle because the rate of increase in the number of radicals is smaller than that of nanoparticles. Therefore, this causes the generation of a large amount of nanoparticles with small sizes.

We propose a novel method of oxide crystal growth via atomic-additive mediated amorphization. By utilizing this method, solid-phase crystallization (SPC) of ZnO from amorphous phase has been successfully demonstrated via nitrogen atom mediation. The resultant SPC-ZnO films are highly orientated and the crystallinity is higher than that of the films prepared by conventional sputtering. By using the SPC-ZnO as a buffer layer, the resistivity of ZnO:Al (AZO) films is drastically decreased. 20-nm-thick AZO films with a resistivity of 5 × 10^ Ω cm and an optical transmittance higher than 80% in a wide wavelength range of 400-2500 nm have been obtained.