Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Shimoyama, Iwao; Baba, Yuji; Hirao, Norie*
Applied Surface Science, 405, p.255 - 266, 2017/05
Times Cited Count：1 Percentile：5.94(Chemistry, Physical)NEXAFS spectroscopy is applied to study orientation structures of polydimethylsilane (PDMS) films deposited on heteroatom-doped graphite substrates prepared by ion beam doping. The Si 
-edge NEXAFS spectra of PDMS show opposite trends of polarization dependence for non irradiated and N
-irradiated substrates, and show no polarization dependence for an Ar-irradiated substrate. Based on a theoretical interpretation of the NEXAFS spectra via first-principles calculations, we clarify that PDMS films have lying, standing, and random orientations on the non irradiated, N-irradiated, and Ar-irradiated substrates, respectively. Furthermore, photoemission electron microscopy indicates that the orientation of a PDMS film can be controlled with microstructures on the order of 
m by separating irradiated and non irradiated areas on the graphite surface. These results suggest that surface modification of graphite using ion beam doping is useful for micro-orientation control of organic thin films.
Shimoyama, Iwao; Baba, Yuji
Carbon, 98, p.115 - 125, 2016/03
Times Cited Count：34 Percentile：72.68(Chemistry, Physical)The amounts of adsorbed thiophene were compared among phosphorus- and nitrogen-doped graphite and graphite damaged by Ar irradiation to clarify the influence of heteroatom doping on the adsorptive desulfurization properties of 
-conjugated carbon materials. On the basis of thiophene coverages estimated from X-ray photoelectron spectroscopy, Phosphorus-doped graphite had an adsorption ability that was 10-20 times larger than that of Nitrogen-doped graphite, indicating that the adsorptive desulfurization property of carbon largely depends on dopant atoms. Polarization dependent analysis using near-edge X-ray absorption fine structure spectroscopy was used to distinguish the configurations at dopant sites, indicating that the curved structures of phosphorus sites exhibited approximately 10 times greater adsorption abilities when compared with the planar structures. Theoretical simulation using molecular orbital calculations indicated different dopant effects between phosphorus and nitrogen along with different thiophene adsorption behaviors between planar and curved structures. Finally, experimental thiophene desorption results obtained at different temperatures revealed an advantage of phosphorus doping for reactivation.
Shimoyama, Iwao; Baba, Yuji; Hakoda, Teruyuki; Hirao, Norie; Shimada, Akihiko
no journal, ,
no abstracts in English
Shimoyama, Iwao; Baba, Yuji
no journal, ,
Carbon alloy is a series of materials prepared by heteroatom doping in -conjugated carbon materials and recently attracts much attention due to some functionalities such as catalytic activity. We study the changes of two functionalities, catalytic activity on oxygen reduction reaction and adsorptive desulfurization property for thiophene, induced by phosphorus doping in graphite. The configurations at phosphorus sites were investigated by near-edge X-ray absorption fine structure spectroscopy and molecular orbital (MO) calculations, and we clarified that phosphorus sites formed planar and curved configurations depending on substrate temperature during ion doping. We also found that curved phosphorus-doped graphite had better catalytic activity and desulfurization property when curved configuration was preferentially formed. Comparison between phosphorus and nitrogen dopings suggests that phosphorus is superior to nitrogen with regard to adsorptive desulfurization. We interpreted these experimental results based on MO calculations and clarified the role of phosphorus as a dopant.
