First-principles calculations of hydrogen trapping energy on incoherent interfaces of aluminum alloys

Yamaguchi, Masatake; Ebihara, Kenichi; Tsuru, Tomohito; Itakura, Mitsuhiro

Materials Transactions, 64(11), p.2553 - 2559, 2023/11

https://doi.org/10.2320/matertrans.MT-M2023106

We attempted to calculate the hydrogen trapping energies on the incoherent interfaces of MgZn precipitates and MgSi crystallites in aluminum alloys from first-principles calculations. Since the unit cell containing the incoherent interface does not satisfy the periodic boundary condition, resulting in a discontinuity of crystal blocks, the hydrogen trapping energy was calculated in a region far from the discontinuity (vacuum) region. We found considerable trapping energies for hydrogen atoms at the incoherent interfaces consisting of assumed atomistic arrangement. We also conducted preliminary calculations of the reduction in the cohesive energy by hydrogen trapping on the incoherent interfaces of MgSi in the aluminum matrix.

Automation of precise gas control for material-process researches; Application to synchrotron radiation real-time observation of surface reactions

Nakamura, Takafumi*; Yamamoto, Yukio*; Arakawa, Masakazu*; Maruyama, Akio*; Yoshigoe, Akitaka

Sangyo Oyo Kogakukai Rombunshi, 11(2), p.109 - 114, 2023/09

https://doi.org/10.12792/jjiiae.11.2.109

Surface chemistry experimental end-station at BL23SU in SPring-8 is widely used to study various surfaces and interfaces of functional materials by means of soft X-rays synchrotron radiation. To analyze surface chemical reactions between gas and solid surfaces, an accurate control of flow-rates of gases is essential. This paper describes a computerized automatic gas flow control system to improve the accuracy and reproducibility of gas-surface reaction experiments in the pressure range of ultra-high vacuum (molecular flow) conditions. The system uses feedback control to operate the slow-leak valve to control the gas-pressure. As a result, the system achieved results equivalent to those of a skilled experimenter.

Formation of high-quality SiO/GaN interfaces with suppressed Ga-oxide interlayer via sputter deposition of SiO

Onishi, Kentaro*; Kobayashi, Takuma*; Mizobata, Hidetoshi*; Nozaki, Mikito*; Yoshigoe, Akitaka; Shimura, Takayoshi*; Watanabe, Heiji*

Japanese Journal of Applied Physics, 62(5), p.050903_1 - 050903_4, 2023/05

https://doi.org/10.35848/1347-4065/acd1ca

While the formation of an GaO interlayer is key to achieving SiO/GaN interfaces with low defect density, it can affect the reliability and stability of metal-oxide-semiconductor (MOS) devices if the annealing conditions are not properly designed. In the present study, we aimed to minimize the growth of the GaO layer on the basis of the sputter deposition of SiO on GaN. Synchrotron radiation X-ray photoelectron spectrometry measurements confirmed the suppressed growth of the GaO layer compared with a SiO/GaN structure formed by plasma-enhanced chemical vapor deposition. Negligible GaO growth was also observed when subsequent oxygen annealing up to 600C was performed. A MOS device with negligible capacitance-voltage hysteresis, nearly ideal flat-band voltage, and low leakage current was demonstrated by performing oxygen and forming gas annealing at temperatures of 600C and 400C, respectively.

Structural Approach to Understanding the Formation of Amorphous Metal Hydroxides

Kobayashi, Taishi*; Fushimi, Tomokazu*; Mizukoshi, Hirofumi*; Motokawa, Ryuhei; Sasaki, Takayuki*

Langmuir, 38(48), p.14656 - 14665, 2022/12

https://doi.org/10.1021/acs.langmuir.2c02081

no abstracts in English

Structure analysis of a buried interface between organic and porous inorganic layers using spin-contrast-variation neutron reflectivity

Kumada, Takayuki; Miura, Daisuke*; Akutsu, Kazuhiro*; Oishi, Kazuki*; Morikawa, Toshiaki*; Kawamura, Yukihiko*; Suzuki, Junichi*; Oku, Takayuki; Torikai, Naoya*; Niizeki, Tomotake*

Journal of Applied Crystallography, 55(5), p.1147 - 1153, 2022/10

AA2021-0903.pdf:1.06MB

https://doi.org/10.1107/S1600576722007506

Spin-contrast-variation neutron reflectivity obtains multiple reflectivity curves from a single sample and a single beam source. We used the strong point of the technique to reveal that, although methylated-perhydropolysilazane-derived silica layer has a higher porosity near the interface with acrylic urethane resin, the resin did not permeate the pore network.

Development of heavy element chemistry at interfaces; Observing actinide complexes at the oil/water interface in solvent extraction by nonlinear vibrational spectroscopy

Kusaka, Ryoji; Watanabe, Masayuki

Journal of Physical Chemistry Letters (Internet), 13(30), p.7065 - 7071, 2022/08

https://doi.org/10.1021/acs.jpclett.2c01550

Analysis of the electric double layer structure formed in an ionic liquid using neutron reflectivity

Tamura, Kazuhisa; Akutsu-Suyama, Kazuhiro*; Cagnes, M.*; Darwish, T. A.*

ECS Advances (Internet), 1(2), p.020503_1 - 020503_5, 2022/06

https://doi.org/10.1149/2754-2734/ac6963

The ionic liquid/Si electrode interface was investigated using neutron reflectivity. We precisely elucidated the structure of the electrical double layer formed at 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ([BMIM]TFSA)/Si(100) electrode interface with the orientation of the [BMIM]TFSA molecule using a partially deuterated [BMIM]TFSA. The results revealed that [BMIM]TFSA molecules form a layered structure. Cation and anion molecules are alternatingly stacked and molecules in the first three layers are horizontally oriented to the electrode surface at E = -1.2 V, i.e., on the negatively charged electrode surface. It was also revealed that the imidazole ring in [BMIM] cation is parallel to the electrode surface.

Impact of nitridation on the reliability of 4H-SiC(110) MOS devices

Nakanuma, Takato*; Kobayashi, Takuma*; Hosoi, Takuji*; Sometani, Mitsuru*; Okamoto, Mitsuo*; Yoshigoe, Akitaka; Shimura, Takayoshi*; Watanabe, Heiji*

Applied Physics Express, 15(4), p.041002_1 - 041002_4, 2022/04

https://doi.org/10.35848/1882-0786/ac5ace

The leakage current and flat-band voltage (VFB) instability of NO-nitrided SiC (110) (a-face) MOS devices were systematically investigated. Although NO nitridation is effective in improving the interface properties, we found that it reduces the onset field of Fowler-Nordheim (F-N) current by about 1 MVcm, leading to pronounced leakage current. Synchrotron X-ray photoelectron spectroscopy revealed that the nitridation reduces the conduction band offset at the SiO/SiC interface, corroborating the above finding. Furthermore, systematical positive and negative bias stress tests clearly indicated the VFB instability of nitrided a-face MOS devices against electron and hole injection.

Effect of oxygen concentration on corrosion rate of carbon steel in air/solution alternating condition

Otani, Kyohei; Ueno, Fumiyoshi; Kato, Chiaki

Zairyo To Kankyo, 71(2), p.40 - 45, 2022/02

https://doi.org/10.3323/jcorr.71.40

The purpose of this study is to investigate the effect of oxygen concentration in the air on the corrosion rate of carbon steel in an air/solution alternating environment in the low oxygen concentration range and to clarify the corrosion rate and corrosion mechanism of carbon steel depending on the oxygen concentration in air by the mass change of specimens before and after the corrosion test and observing the iron rust layer formed on the surface of carbon steel. The corrosion rate increases with increasing oxygen concentration in the air, and the gradient of the corrosion rate decreases gradually. The maximum erosion depth increased with increasing oxygen concentration except for the case of 1% oxygen concentration, however, the maximum erosion depth for 1% oxygen concentration was larger than that for 5% air oxygen concentration.

Electrochemically driven specific alkaline metal cation adsorption on a graphene interface

Yasuda, Satoshi; Tamura, Kazuhisa; Kato, Masaru*; Asaoka, Hidehito; Yagi, Ichizo*

Journal of Physical Chemistry C, 125(40), p.22154 - 22162, 2021/10

https://doi.org/10.1021/acs.jpcc.1c03322

Understanding electrochemical behavior of the alkaline metal cation-graphene interface in electrolyte is essential for understanding the fundamental electrochemical interface and development of graphene-based technologies. We report comprehensive analysis of the electrochemical behavior of both alkaline metal cations and graphene using electrochemical surface X-ray diffraction (EC-SXRD) and Raman (EC-Raman) spectroscopic techniques in which the interfacial structure of cations and the charging state and mechanical strain of the graphene can be elucidated. EC-SXRD and cyclic voltammetry demonstrated electrochemically driven specific adsorption and desorption of cations on the graphene surface involved in the dehydration and hydration process. This study provides new insight for understanding fundamental electrochemical behavior of the alkaline metal cation-graphene interface and contributes to the development of carbon-based novel applications.