We have developed a growth system for carbon nanotubes (CNTs) based on an alcohol thermal chemical vapor deposition (A-CVD). This system, which is similar to a cold wall-type CVD system, has an additional tubular electric furnace. The additional furnace is installed at a gas inlet in order to heat the carbon source gas. In this study, we have investigated the effect of the gas inlet heating to the grown CNTs by Raman spectroscopy and scanning electron microscopy (SEM). It was found that the smaller diameter single-walled CNTs (SWCNTs) could be grown with a gas inlet heating at 800°C compared to the grown SWCNTs obtained without gas inlet heating. The two-furnace A-CVD system can provide a new method of a diameter-controlled growth of SWCNTs.
Quartz sensor (Q-sensor) measurement, which can detect the change in gas composition in plasmas, was investigated with varying bias voltage near the sensor. It was found that the change in the Q-sensor output by hydrogen (H2) plasmas depends on bias voltages. In addition, their bias voltage dependences were similar to those by Langmuir probe measurement. Judging from the comparison to the results by Langmuir probe measurement, the Q-sensor output change measured at positive and negative bias voltages correlated to current to the Q-sensor bias electrode and positive ion density in H2 plasmas, respectively. Above results indicated that Q-sensor measurement can obtain information on ion and electrons in H2 plasmas with varying bias voltages near the Q-sensor.
In order to examine the deuterium retention properties of SiC/SiC compositess, the deuterium ion irradiation was conducted followed by a thermal desorption spectroscopymeasurement. The deuterium retained was desorbed in forms of HD, D2, HDO, CD4 and C2D4. The ratio of the amount of desorbed hydrocarbons to the total amount of retained deuterium was approximately 6%, which is much smaller, compared with the case of carbon material. Namely, we confirmed that the chemical erosion of SiC/SiC composites isquite small. In the D2 desorption spectra, two desorption peaks appeared. The lower and higher temperatures peaks were regarded to be due to detrappings of Si-D and C-D bonds, respectively. The ratio of deuterium amount desorbed at highertemperature decreased with increase of the deuterium fluence.This behavior could be explained that the carbon content at thesurface is reduced by the selective sputtering due to deuteriumions.
Performance of a compact cell stack of thin film solid oxide fuel cell (SOFC) using yttria-stabilized zirconia (YSZ) electrolyte films between 7 μm and 9 μm thick grown by RF magnetron sputtering was studied to power generation property at intermediate temperatures from 700 to 900°C. The series connected SOFC using YSZ film of 7 to 9 μm thick showed a stable generation property at intermediated temperature of 700°C. Moreover, the V-I property of series connected SOFC using YSZ film of 9 μm thick obtained higher than that of the cell prepared with YSZ film of 7 μm thick. As the result, it was found that series connection of two cells could improve the cell performance, and a compact cell stack of thin film SOFC could be operable at intermediate temperatures.
Radiation shields are required in beamlines (BL) that transport synchrotron radiation (SR) to stop high energy radiation that is scattered by instruments upstream of a BL. Radiation shields guarantee radiation safety in the downstream of the BL and need to be installed in the vacuum system of the BL. In order to limit the opening against unnecessary scattered radiation and to keep the effective aperture for SR as large as possible, a new type of radiation shield, which utilizes tungsten alloy with an opening as an ultra-high vacuum chamber, has been developed.
A lot of aluminum (A2219-T852) flanges with a knife-edge seal have been used at the SPring-8 storage ring. We investigated an Electron Beam Modified (EBM) knife-edge seal for the flange to confirm seal compatibility with the original A2219-T852 flange. We already confirmed that mechanical properties of EBM are equal to those of the original flange. In comparison with the original flange, we found that an ability of anti-scratch is almost equal, but corrosion resistance is inferior to that of the original flange.
Rather large errors occur when measuring pressures of around 5×103-104 Pa with a Pirani vacuum gauge in constant current mode, as the change in output voltage is very small. Thus, an attempt was made to achieve more accurate pressure measurement in this range by modifying the thermal conductivity arising from the natural convection flow of gas with the shape of the envelope. The experimental results showed that the pressure range with a large change in output per relative change in pressure expanded to lower pressures when the inner diameter of the envelope increased. For envelopes with an inner diameter of 72 mm, the change |pd V/dp| was greater than 50 mV at pressures from 1.5×103 Pa to atmospheric pressure, while the change |pd V/dp| was less than 20 mV at pressures of less than 2×104 Pa for envelopes with an inner diameter of 34 mm. Thus, more accurate pressure measurement near 104 Pa was achieved with this large envelope.
We have studied the thermoelectric properties of InSb thin films. They were prepared by metalorganic vapor phase epitaxy on sapphire substrate using sputtered InAs buffer layer. Substrate temperature during the deposition of InAs buffer layer was changed between 65°C and 250°C. Electrical properties, thermoelectric properties, and crystalline properties of InSb thin films with a InAs buffer were assessed using Hall measurement, Power factor and X-ray diffraction. The power factor of InSb was as high as 2.1×10−4 W/mK2 at a deposition temperature of 150°C of InAs.
Vanadium sesquioxide (V2O3) is known as a crystalline phase of vanadium oxide with metal-insulator transition (MIT). This V2O3 has hexagonal corundum crystalline structure same as sapphire. In this study, highly c-axis textured V2O3 crystalline growth on c-plane sapphire substrate was realized even at film thickness around 15 nm under carefully-controlled small oxygen flow conditions in reactive magnetron sputtering. In-plane compressive strain state was found for the thin V2O3 films, while lattice relaxation was observed with increase of film thickness. Under higher growth temperature, abrupt MIT of the films with resistance change over several decades was achieved at temperature around 160 K.
Two methods of copper (Cu) filling into through-holes and trenches with various barrier metals were investigated: high-vacuum magnetron sputtering and the supercritical carbon dioxide method. In spite of good Cu-filling by using the supercritical carbon dioxide method, adhesion of the Cu films to the barrier metals worsened with relative resistivity. Examples of Cu-filling by both high-vacuum magnetron sputtering and the supercritical carbon dioxide method for obtaining good adhesion to the barrier metals are shown.
Highly efficient micro-sized force sensor by using chromium silicon carbide (Cr-Si-C) composite thin film has been developed. The characteristic of the tension measurement system by using this force sensor for tension control as “Sensor roll”, for roll-to-roll sputtering system is also described. Sensor roll can speed up the response to tension changes for 0.5 seconds than that of electromagnetic transformer type tension sensor. Sensor roll has been installed in roll-to-roll sputtering system and the behavior of the film has been observed, Sensor roll has enabled measuring in real time transient changes in tension. The tension measurement system with high-efficiency and high-stability has been prepared in a vacuum environment by using the highly efficient micro-sized force sensor.
We have newly devised a magnetic field distribution variable-type facing target sputtering system. The magnetic field distribution between facing targets can be easily changed by moving a magnet without breaking the vacuum. This function can realize with one cathode about both low-damage-sputtering and high-rate-sputtering, and offer a newly thin film fabrication method. By changing the magnetic field distribution between facing targets, Niobium deposition rate has changed three or more times with the same sputtering conditions, such as RF applied electric power and Argon pressure.
Various metal films were deposited by magnetron sputtering, and their thickness distributions were measured. The distributions are considered to depend on the angular distribution of the atoms ejected from a target. Some metals showed a thickness distribution with its maximum at the anode center while the others showed a thickness distribution with its maximum at a position slightly inside the target erosion. According to a theory and computer simulation, as the binding energy (i.e. cohesive energy) of a target decreases and the mass of the target atoms increases, the atoms tend to be ejected normally with their angular distribution being apt to be over-cosine. Thus, the thickness distributions were discussed in relation to the binding energy of the metals and the mass of the target atoms. The thickness distributions were also investigated for different discharge voltages.
The generation of radial gas flow by rotating a combination of parallel disks and screens has been investigated by Monte Carlo simulation. This time, the authors studied radial gas flow from a rotor with two different structures. The inner part of the rotor consisted of parallel disks, while the outer part was made up of parallel disks with screens. The rotor, which had an outer part with special off-center screens, was found to have both a pumping efficiency greater than 0.5 and a compression ratio greater than 104 with a velocity ratio rω/<v> of 2, where <v> was the mean velocity of gas molecules and rω was the additional circumferential velocity due to rotation.
We have analyzed an optical system for a spin-polarized atomic hydrogen beam. By calculating the model emittance of atomic hydrogen beams, we simulated the beam profile. We predicted that a hexapole magnet with a length of 75 mm and magnetic flux density of 0.65 T results in a spin polarization of 95% and a beam separation of 9 mm, which is sufficient for our purpose. We also found that the longer hexapole manget results in a higher spin polarization and smaller beam separation.
The vibrating quartz oscillator in the viscous-flow gas was observed to compare the pressure (P) dependence between the impedance change (ΔZ) and the frequency change (ΔF). We obtained the ΔZ and the ΔF for Ar, O2, and Ne gases. Among Ar and O2 both the ΔZs and the ΔFs had no intersection with each other. However, Ne gas had the intersections with Ar gas with the ΔZ(P) and with O2 for the ΔF(P). The phenomenon was caused by the Ne property which Ne has smaller mass but larger viscosity compared with Ar and O2. The ΔZ-ΔF property showed that the property of each gas lied in the viscosity descending order, i.e., Ne, Ar, O2. The measurement of (ΔZ, ΔF) property could give the viscosity related information.
We have deposited Cu thin films on a water-resistant paper substrate using magnetron sputtering with multipolar magnetic plasma confinement assisted by inductively coupled plasma and investigated the effects of the substrate negative pulse voltage (Vs) and pulse frequency on the properties of the films. The X-ray diffraction results showed that the intensities of the Cu(111) and Cu(200) peaks depended strongly on both Vs and the pulse frequency. In addition, atomic force microscopy of the surface morphology revealed that increasing Vs in the range from 0 to −120 V resulted in a decrease in the root-mean-square roughness from 13.7 to 9.48 nm.
We have investigated structural and magnetic properties of Ni and Ni75Fe25 thin films evaporated on polyethylene naphtalate (PEN) organic substrates, which can be expected as electrodes of our proposed nanoscale junctions utilizing thin-film edges. As a result, there is no diffusion of Ni and Fe atoms into PEN substrates, resulting in clear and smooth formation of the interface. The surface roughness is also as small as 0.28-0.37 nm in the same scanning scale as the film thickness. As for the magnetic properties, the squareness of the hysteresis loop is as small as 0.24 for Ni/PEN, where there is no observation of the anisotropy magnetoresistance (AMR) effect. In contrast, the squareness of the hysteresis loop is as large as 0.95 for Ni75Fe25/PEN, where the AMR effect has been successfully obtained. These experimental results indicate that Ni75Fe25/PEN is a promising material for use in electrodes of nanoscale junctions from the viewpoint of structural and magnetic properties.
The nitrogen addition to argon gas during the Ag deposition was investigated to lower the deposition rate. As a result, it was found that the deposition rate systematically decreased with the increase of nitrogen gas concentration; furthermore, the Ag thin films deposited with nitrogen gas exhibited sufficient optical reflectance. It can be considered that the nitrogen gas addition leads to the decrease of sputtering yield and positive ions accelerated to the target, hence, the deposition rate of the Ag thin films decreases.
It is the purpose of this report to fabricate transparent conducting multilayered films with anti-heat properties using ZnO as the chief ingredient. The multilayered films are composed of ATO (1.0 wt.% Sb2O3 doped tin oxide)/AZO (1.5 wt.% Al2O3 doped zinc oxide) structure. After the fabrication process, a test of anti-heat properties was carried out at 500°C for 24 hours. Electrical and optical properties were compared before or after the test of anti-heat properties. In this report, favorable experimental results are described.
Ge embedded SiO2 films are expected as hopeful blue-ultraviolet light source. We research for low voltage electroluminescence (EL) from Ge implanted SiO2 thin film. We have obtained EL emission by using SiO2 thin film with thickness of 50 nm by applying DC 15 V. In order to realize low-voltage EL at less than 10 V, to control optical emission site is very important. In this work, we implanted Ge− at multi-energy of 50 keV, 20 keV, 10 keV into 50 nm SiO2 thin layer at the angle of 30°, 45°, 60°. Then the samples were annealed at two stages each for 1 hour: the first stage was in N2 flow at temperature of 700°C, and the second was in air flow at 600°C. X-ray photoelectron spectroscopy (XPS) was used to analyze Ge profile of the 60° implantation sample, and photoluminescence (PL) was studied. As a result, XPS showed Ge distribution peak at shallow region of 8 nm and it corresponded to the simulation by TRIM-DYN. PL spectra at 290 and 390 nm were obtained. PL intensity from 60° and 45° tilt type sample were stronger than that from 30° tilt type, therefore we investigated that light emission center would be created in the shallow depth less than 25 nm.
By thermal desorption spectroscopy (TDS), we evaluated the hydrogen storage properties of carbon fine particles including single-wall carbon nanotubes (SWNTs) synthesized by plasma-assisted hot filament chemical vapor deposition, along with commercialized single-wall carbon nanotubes. Two hydrogen desorption peaks, one between 100 and 200°C and the other between 500 and 600°C, were observed for the carbon fine particles as well as for SWNTs in the spectra of TDS. Activation energy determined by varying raising temperature revealed that the lower-temperature peak is derived from physisorbed hydrogen. Peaks of CO desorption from the carbon fine particles, which appeared by the oxidation of carbon, were also observed around the higher-peak temperature. The result suggests that synthesized carbon fine particles contain a lot of defects and bents with large specific surface areas, which have the potential of larger amount of hydrogen adsorption.
Adsorption and desorption processes of potassium on a Si(001) surface were investigated by means of Reflectance Difference Spectroscopy (RDS). When potassium was evaporated at a constant current, we could observe monotonous increase in RD intensity towards saturation both at room temperature and 673 K. No indication of desorption of potassium after evaporation was observed at room temperature. At high temperature of 673 K, almost all the potassium atoms were desorbed after evaporation was stopped. Two step desorption processes occurred corresponding to two different adsorption sites.
2″-size Al and Si substrates were treated by photoemission-assisted DC discharge Ar plasma, in which photoelectrons emitting from the negatively biased substrate surface under UV light irradiation are utilized as a trigger of discharge and therefore the substrate surface can be exposed to accelerated Ar+ ions. The surface morphology of Al surfaces, prepared by mechanical grinding, showed a significant decrease of arithmetical average roughness (Ra) from 341.9 nm to 260.2 nm due to Ar+ ion sputtering for an irradiation time of 100 min. The Si surface was also etched with maintaining surface flatness at Ra=1-2 nm, while protrusions grew, perhaps resulting from agglomeration of sputtered Si atoms and/or masking effects of dusts. These resulsts suggest that the photoemission-assisted DC discharge plasma is applicable as an ion source for improving surface roughness of substrates.
Recently, the idea that the resistance change phenomenon is caused by oxidation/reduction of the filament formed in the transition metal oxide has been widely accepted. However, it is difficult to cause the forming equally for every cell in a high-density memory cell array. Therefore, the existence of the forming is high barrier for resistive random access memory (ReRAM) to be put into practical use. In this paper, the initial resistance dependence of the reset current and the distribution of the forming and set voltages were investigated for the forming-free ReRAM cells, which start with the reset process. As a result, it was clarified that the reset current is proportional to the reciprocal of initial resistance independently of the film thickness and the film formation temperature. In addition, it was suggested that there are two kinds of filaments in the forming-free ReRAM. One is the filament which is completely restored by the first reset process. The other continues to operate even after the first reset.
In order to reduce amount of electrolyte solvent desorbed from anode material in lithium ion battery, hydrogen plasma irradiation for the anode material was conducted. During the irradiation, the sample was negatively biased. Natural graphite sample after the hydrogen plasma irradiation was soaked in propylene carbonate (PC) used as electrolyte solvent. Then, the gas desorption behavior was investigated by using a technique of thermal desorption spectroscopy (TDS). The amount of gasses in the sample irradiated by hydrogen plasma due to the PC was reduced compared with case in the non-irradiated sample. The reduction by the irradiation became large with the increase of negative bias voltage. The reduction also increased with the fluence and became roughly constant in the higher fluence regime. In order to discuss this mechanism, the sample without the soaking in PC was heated up to 1173 K. H2 desorption at high temperature region, around 1173 K, increased for the irradiated sample, compared with non-irradiated sample. This result suggests that implanted hydrogen ions form C-H bond with carbon of active sites and then the C-H bond might prevent the PC from adsorbing during the subsequent soaking.
The outgassing rate of the clay-based gas barrier film “CLAIST” was measured by the throughput method. “CLAIST” would be usable under a vacuum condition, as the outgassing rate was lower than that of the conventional epoxy resin in vacuum. Diffusion coefficient DCLAIST∼10−16 m2•s driven by the time dependent outgassing rate was consistent with the water vapor transmission rate WVTRCLAIST∼10−3 g/(m2•day).