竹内 雅耶

Abstract We aimed to improve the detection sensitivity for liquid measurement by developing an ultrathin photoelectron transmission window (SiNx membrane) for liquid cells via X-ray photoelectron spectroscopy or X-ray photoelectron emission microscopy at an ultrahigh vacuum. The membrane using gas-cluster ion beams (GCIB) was thinned, and its burst pressure was compared with those of membranes thinned with atomic 400 eV Ar⁺ ions. The SiNx membranes thinned by GCIB had approximately 2.5 times higher burst pressure than Ar⁺ ions. In addition, the improved sensitivity of the characteristic X-ray from liquid water induced by low-energy electrons was investigated. With the use of the 4.5 nm-thick SiNx membrane etched by GCIB, the X-ray intensity became 1.6 times higher than those of the 11 nm-thick pristine membrane at the electron beam (EB) energy of 1.5 keV. This result showed a good agreement with Monte Carlo simulation results of the EB-induced X-ray emission from liquid water beneath the SiNx membrane.

Abstract The atomic layer etching (ALE) of silicon nitride (SiN _x ) film was demonstrated using an oxygen gas cluster ion beam (O₂-GCIB) with acetylacetone (Hacac) as the adsorption gas. A GCIB is a beam of aggregates of several thousand atoms, and it enables high energy density irradiation with little damage. In this study, we characterized the ALE to reveal the etching mechanism. The XPS results indicated the following etching process: (i) O₂-GCIB irradiation oxidizes the surface of SiN _x film; (ii) the oxynitride layer reacts with Hacac vapor; (iii) the reaction layer is removed by the GCIB. The ALE can be executed by the sequential repetition of the processes (i) to (iii). This technique enables highly accurate control of thickness of SiN _x film with little irradiation damage.

Abstract Surface-activated bonding (SAB) of Cu by gas cluster ion beam (GCIB) irradiation with acetic acid vapor was studied. GCIB irradiation realizes surface smoothing and surface reaction enhancement without severe damage. Therefore, it is promising for SAB. In this study, acetic acid vapor was introduced during Ar-GCIB irradiation to assist the removal of surface oxides on the Cu surface. XPS results showed that Cu(OH)₂ was effectively removed by reaction with adsorbed acetic acid, and there was no residue by acetic acid adsorption. In addition, surface roughness decreased by Ar-GCIB irradiation with acetic acid because of the preferential removal of protrusion. Preliminary bonding experiments showed an increase of Cu–Cu bond strength by Ar-GCIB irradiation with acetic acid vapor.

Anisotropic pyrochemical micro-etching induced by synchrotron x-ray irradiation is developed as a microfabrication process for fluorinated ethylene propylene (FEP). X-ray irradiation is performed at room temperature, and the irradiation area is etched by heating in an oven. By measuring the irradiation area using Raman spectroscopy, the peak of the Raman spectrum is shown to decrease with an increasing irradiation dose. It is also observed that the etching can be performed at a heating temperature of around 200 °C while maintaining the chemical composition of the surface. The etching mechanism is speculated to be as follows: x-ray irradiation causes chain scission, which decreases the number-average degree of polymerization. The melting temperature of irradiated FEP decreases as the polymer chain length is decreased so that the irradiated area can be evaporated at low temperatures of post-heating. In this way, we demonstrate that anisotropic pyrochemical micro-etching of FEP proceeds only in the depth direction where x rays are absorbed. It is possible to avoid deterioration of the shape accuracy arising from thermal expansion during the transfer process of the mask pattern by separating pre-irradiation from post-heating. Through this method, it becomes possible to realize a high precision microstructure of FEP in a large area.

Abstract We demonstrated the on‐chip synthesis of Au nanoparticles achieved by a microwave‐induced reaction in a microfluidic channel. The chip structure consists of a waveguide and a microchannel through the inside of the waveguide. A postwall waveguide, in which metallic posts are continuously arranged on the side wall, is utilized to confine microwave fields. This configuration allows a solution to be inserted inside the waveguide by the microchannel passing between the metallic posts. In order to realize the miniaturization of the chip, the 24.125 GHz industrial, scientific, and medical (ISM) band is utilized instead of the commonly used 2.45 GHz ISM band. When pure water is heated in the microchannel under microwave input power of 3.0 W, temperature increases to 70°C were confirmed. In this paper, this chip is adapted to synthesize Au nanoparticles via a microwave‐induced reaction. After irradiating at a microwave power of 3.0 W and an irradiation time of 5 min, we observed absorbance and dynamic light scattering of the reactant, and the results indicated the generation of Au nanoparticles. This microwave synthesis system allows us to achieve automatic and rapid selective synthesis of nanoparticles in a solution.

Bulk polytetrafluoroethylene (PTFE) can be modified via X-ray irradiation. The X-rays, which have a continuous spectrum from 3 to 8 keV, penetrate deep into the PTFE substrate and induce a scission in the polymer main chain,-C-C-. In previous research, the optical properties of a PTFE sample were successfully modified; UV and visible transmittance drastically increased in the irradiated area of the substrates. In this study, the characterization of the chemical structure of the samples was carried out using Raman and FTIR spectroscopies. The results suggest the formation of CF3 branches, which are not intrinsic to PTFE. In previous works, it has been reported that a similar modification was achieved using electron beam irradiation of several-MeV in molten PTFE, or by α-irradiation onto a PTFE substrate, where the modification depth was of tens of micrometers. On the contrary, we have succeeded the similar modification by using the X-rays.

<p>We demonstrate the modification of transmittance of bulk polytetrafluoroethylene (PTFE) via synchrotron X-ray irradiation. X-ray irradiation of the PTFE substrate is conducted to mechanically suppress the photoevaporation of PTFE molecules. This method drastically increases the ultraviolet and visible transmittance of the irradiated areas of the substrates, with greater than 80% transmittance observed at the 350-nm wavelength. We observed the irradiated area via scanning electron microscopy and determined that this optical property modification is due to the homogenization of the bulk PTFE texture with nanometer to micron-sized pores. We expect that this modified PTFE will be employed as a construction material for various micro system devices such as Lab-on-a-chip and micro total analysis systems.</p>

<p>A novel process was developed for fabricating a polytetrafluoroethylene (PTFE) thin film using synchrotron radiation (SR). First, a PTFE substrate was exposed to high-energy X-rays (2–8 keV) at room temperature. Afterwards, the PTFE substrate (target) was heated under atmospheric pressure and fragments desorbed from the surface deposited on a glass substrate to produce a film with a thickness of above 10 µm. The characterization of the chemical structure of the deposited film was carried out using X-ray diffraction (XRD). The results indicated that the crystalline structure of the film became closer to those of the PTFE substrate upon an increase in the X-ray irradiation of the sample. The fabrication process of this PTFE thin film could be applied to various fields because surface modification of the substrate can be easily carried out.</p>

A new lithography system to fabricate high-aspect-ratio 3D microstructures was developed at the NewSUBARU synchrotron radiation facility (University of Hyogo, Japan). The X-ray beam generated by this system has high parallelism (horizontal and vertical divergence angles of 278 µrad and 14 µrad, respectively) and high photon flux (31 mW mm⁻² at a beam current of 300 mA). The high photon flux and exposure area of the system were validated and a beam-scan method for a large exposure area with a uniform dose distribution has been proposed. In addition, the deep X-ray lithography performance was characterized using a conventional photosensitive material and the synchrotron-radiation-induced direct etching of polytetrafluoroethylene (PTFE) was demonstrated. An enlargement of the microfabrication area up to 100 mm × 100 mm while contemporarily ensuring high uniformity was achieved.

<p>In the present paper, the mixing performance of a 3D lab-on-a-chip device, which is used for small immunoassay systems for medical diagnosis and environmental analysis such as enzyme-linked immunosorbent assay (ELISA), was investigated by using 3D fluid dynamics simulation and design of experiment (DOE) to optimize the micro channel structure. The degree of mixing was calculated by a three-dimensional finite element analysis code "Fluent" applying k-ε model, which is a typical turbulence model, changing design parameters (temperature, angle, flow rate, viscosity, length, hole diameter, degree of overlap). 18 sets of conditions determined by DOE were conducted. As a result, it was found that the effective parameters for promoting the mixing were half-cross structure, smaller tilt angle and higher viscosity, probably due to enhancement of shear stress in the fluid. Furthermore, in the newly suggested structures "half-cross" and "improved halfcross", the degrees of mixing were improved to 40% and 60% respectively, in comparison to the conventional mixing structures of "straight" and "full cross" which showed the degrees of mixing of 10% and 25% respectively.</p>

<p>We demonstrated microfabrication of polytetrafluoethylene (PTFE) using X-ray-induced pyrochemical anisotropic etching process. We found the scission of PTFE main polymer chain was induced by X-ray irradiation. The decrease of fragment length enabled pyrochemical etching because of decreasing the desorption temperature of scission fragment. Here, we can diminish the distortion of fabricated PTFE fine pattern in a large area using the pyrochemical anisotropic etching process. We also found the thermal exchange process and vapor pressure through a He gas can provide a clue to achieve the higher precision fabrication of PTFE.</p>