Kazuhiro Kanda

Abstract Positron annihilation spectroscopy was used to investigate vacancy-type defects in diamond-like carbon (DLC) films. From Doppler broadening measurements of the γ-rays produced by annihilation and positron annihilation lifetime (PAL) using a slow positron beam on DLC films deposited by various deposition methods and conditions, it was found that there is a good correlation between the S parameter obtained by Doppler broadening and PAL. The result of PAL correlates well with film density and hardness, indicating that PAL measurements can be used as an indicator of these film properties. The hydrogen content in the DLC film was roughly proportional to the PAL. However, there were also cases in which PAL differed greatly even with almost the same hydrogen content, and the sp²/(sp²+sp³) ratio of carbon in DLC films has no direct relationship with PAL.

<jats:title>Abstract</jats:title> <jats:p>The effects of soft X-ray irradiation and atomic hydrogen annealing (AHA) on the reduction of graphene oxide (GO) to obtain graphene were investigated. To clarify the interaction between soft X-rays and GO, soft X-rays of 300 eV and 550 eV were used for C 1s and O 1s inner-shell electron excitation, respectively at the NewSUBARU synchrotron radiation facility. Low-temperature reduction of the GO film was achieved by using soft X-ray at temperatures below 150 °C at 300 eV, and 60 °C at 550 eV. O-related peaks in X-ray photoelectron spectroscopy, such as the C–O–C peak, were smaller at 550 eV than those at 300 eV. This result indicates that excitation of the core–shell electrons of O enhances the reduction of GO. Soft X-rays preferentially break C–C and C–O bonds at 300 and 550 eV, respectively.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The reduction of graphene oxide (GO) through atomic hydrogen annealing (AHA) and soft X-ray irradiation is investigated using microwell substrates with μm-sized holes with and without Ni underlayers. The GO film is reduced through AHA at 170 °C and soft X-ray irradiation at 150 °C. In contrast, some GO films are not only reduced but also amorphized through soft X-ray irradiation. The effect of the Ni underlayer on GO reduction differs between AHA and soft X-ray irradiation. In AHA, the difference in GO reduction between SiO<jats:sub>2</jats:sub> and Ni underlayer was originated from the atomic hydrogen density on sample surface. On the other hand, in soft X-ray irradiation, the difference in GO reduction between SiO<jats:sub>2</jats:sub> and the Ni underlayer originates from the excited electrons generated by soft X-ray irradiation. Reduction without damage is more likely to occur in the suspended GO than in the supported GO.</jats:p>