Graphene was synthesized by radio-frequency magnetron-plasma-enhanced chemical vapor deposition on Si and SiO2 substrates along with on Cu substrate. Although the incubation period was longer and the nucleation density was smaller than the growth on Cu substrate, graphene was grown on Si and SiO2 substrates. It was speculated that the incubation period and nucleation density depend on the density of carbon precursor on substrate that is affected by the desorption speed of carbon or hydrocarbon.
Ion implantation into microspheres and wires may open a new application field. Therefore, we extended the TRIM (Transport of Ions in Matter) code that simulates ion distributions for substrates to be applicable to spherical and cylindrical targets. Next, we fitted simulated profiles calculated by the TRIM code to the experimental ones to determine adequate parameters of electronic stopping powers. And, we simulated about various combinations to use the extended TRIM code which used parameters. Calculated projected ranges and implantation energies are reduced to modified reduced projected ranges and average reduced energy. Also, we derive the relations between the average reduced energy and the modified reduced projected ranges for spherical and cylindrical targets.
We developed a low-energy (≤100 eV) electron gun that uses the photoelectric effect, and demonstrated its capability for the study of electronic excitation processes at the surfaces of solids. A LaB6(100) single crystal was used as a photocathode and a laser diode (Ephoton=2.62 eV) was used as a light source. The electron gun was compatible with ultra-high vacuum (UHV) conditions due to its low outgassing. An energy width of 0.11 eV was obtained without an energy selector, and the maximum current was 38 nA. The energy width of the emitted electrons and the work function of the photocathode were estimated from the relation between the photoelectron energy distribution and the cathode temperature. Using the electron gun, we successfully observed the electron-stimulated desorption of metastable Ne atoms from a solid Ne surface.
In conventional studies on the Crookes radiometer, vane temperature was presumed to be higher at the black side than at the shiny side. In this study, a new hypothesis - vane is isothermal but accommodation coefficients are different at the black side and at the shiny side - has been proposed and examined using heat transfer and Direct Simulation Monte Carlo (DSMC) simulations. The results prove that the vane is indeed isothermal under the sunlight and that gas temperature and pressure at the black side with the perfect accommodation coefficient become higher than those at the shiny side with a small accommodation coefficient. The pressure gradient across the vane acts as an area force to push the vane from the black side. It is also found the glass bulb temperature strongly affects the revolution of the vanes.
The flow rate of a rarefied gas through a long rectangular channel with a very small height (a) to width (b) ratio (a/b) was experimentally investigated using N2 and Ar for a wide range of the Knudsen number (Kn). Kn is defined as the ratio of the height (a) to the mean free path. The dimensions of the rectangular channel are as follows: a=0.1 mm, b=50 mm, and the length (ℓ)=100 mm. As the inlet gas pressure increases, the conductance decreases from the value in the free molecule regime and reaches the Knudsen minimum at Kn≈1.2, which is approximately 0.46 times the value in the free molecule regime. The reduced flow rate (G) has been derived from the experimental data as a function of the local rarefaction parameter δ≡(π1/2/2)×(1/Kn), assuming fully developed gas flow. The rate (G) is defined by the following equation: G=Qm/(a2b/v0)/(dp/dx); where Qm, v0, and (dp/dx) are the mass flow rate, most probable molecular velocity, and local pressure gradient at a longitudinal coordinate x, respectively. For the above rectangular channel, the value of G is minimum when the value of δ is 0.9. Finally, the pressure distribution along the channel has been calculated taking into consideration the value of G.
A stackable Knudsen pump consisting of multistage pump units driven by temperature difference between hot and cold water is fabricated. Each unit has a porous membrane of 64 cm2 area, through which thermal transpiration flow, the driving force of the Knudsen pump, is induced at atmospheric ambient pressure. This study demonstrates the present device facilitates the cascade or parallel connection of multiple pump units to improve performance. For example, a Knudsen pump consisting of 6-cascaded units provides a shut-off pressure of 9.2 kPa and a 300 sccm maximum flow rate at the temperature difference of 45 K. The feasibility of the pumping system driven by low-grade waste heats is also demonstrated.
Multi-turn H− beam injection method is used in the J-PARC 3 GeV synchrotron to match the incident beam and the circulating beam. In this method, two electrons of the H− beam from the Linac are stripped by passing through the carbon thin film at the beam injection point. The remaining protons are made to go around and combined with the next injection beam bunch to increase the beam intensity. During the beam injection, the charge stripping thin film is heated due to the beam energy deposition in the film and the outgassing is released. Therefore, investigating of the outgassing characteristics of the charge stripping thin films is essential for maintaining the beam line at ultra-high vacuum. Released outgassing from heated thin films was measured by thermal desorption spectroscopy. Several types of thin films, which are used or candidate for the injection beam charge stripping films, were prepared as samples. Each type of film showed different outgassing characteristics during the heating. It was found that the heat treatment at high temperature effectively reduced the outgassing even after the films were taken out to the atmosphere. For the thin film formed by the vacuum evaporation method, the bake-out at 100℃ was effective to reduce the outgassing other than hydrogen. The results of this survey gave the guide to not only the outgassing reduction process but also the improvement of the making process of the thin films.
Secondary standard ionization gauges (VS-1) had been calibrated by using the primary standard McLeod gauge at former Electrotechnical Laboratory for about twenty years around 1980's. VS-1 is a triode gauge. Sensitivity coefficient of VS-1 was measured experimentally and reported by Hirata et. al. Simulation of the electrical potential profile of the gauge, electron trajectory emitted from a hot filament, and ion current produced by electron impact ionization of gas assuming a simple electrode geometry was done. The space charge is also taken into consideration in the simulation. In the simulation results in the pressure range above 10−2 Pa the relative sensitivity coefficient of Ar increased with pressure and that of He decreased with pressure. In the pressure range between 10−3 Pa and 10−2 Pa the relative sensitivity coefficient of Ar and He were constant respectively. These features are similar to the experimental results. Taking the characteristics of the relative sensitivity coefficient into account, it is recommendable to use this gauge in the pressure range between 10−3 Pa and 10−2 Pa.
Nano-scale structures of a single graphene oxide (GO) layer deposited on Au(111) covered with the octanethiolate self-assembled monolayer (C8S-SAM) have been investigated by scanning tunneling microscopy (STM). Using a spin-coating method, we found that GO flakes are isolated and are dispersed on the C8S-SAM/Au(111) surface whereas these are likely to pile up on the bare Au(111) surface. Furthermore, the C8S-SAM formed on Au(111) enables us to deposit GO keeping the surface clean even if we prepared the sample in the atmosphere. By using the C8S-SAM/Au(111) substrate, we succeeded in observing an STM image of the unreduced GO. The STM image of a single GO layer exhibits the grain-like structure having the range in height from 0.6 to 1.1 nm. The bias-dependent STM study indicated that the STM image of GO is stably and reproducibly obtained at the voltage where the density of states of GO exists.
Stability improvement of the output of a quartz-oscillator-based pressure sensor for outdoor use was attempted by maintaining a constant temperature of the preamp connected to the quartz oscillator; this is because the preamp output is affected by temperature, which results in fluctuation of the pressure sensor output. The preamp was located at a place where the temperature is constant, while the quartz oscillator was fixed outdoor where temperature fluctuates. However, the stability of the pressure sensor output was not significantly improved by this method as compared to the other previous procedures to reduce influences of preamp temperature on pressure sensor output, although the fluctuation of preamp temperature was drastically and sufficiently reduced. The results obtained in the present study depict that the fluctuations in pressure sensor output in outdoor use may be attributed to other reasons than the fluctuation of preamp temperature.
Gas permeation test equipment was developed to measure the gas permeability through O-ring shape elastomers under actual condition of semiconductor manufacturing such as high vacuum and high temperature. The temperature dependencies of gas permeability on three kinds of elastomers, silicone (VMQ), fluoroelastomer (FKM) and perfluoroelastomer (FFKM), were investigated. Permeation rate for all materials increased as temperature increased. O2 and N2 gas permeation rate through VMQ was much higher than that through the other materials, especially in lower temperature. Moreover, the temperature dependencies of gas permeability with VMQ were completely different from those of FKM and FFKM. This was coming from different polymer structure which caused difference of solubility and diffusivity between silicon and fluoroelastomers.