Smoothing of an atomically rough vicinal surface – STM observation and MC simulation

Irisawa, Toshiharu; Matsumoto, Kiiko; Sudoh, Koichi; Iwasaki, Hiroshi; Uwaha, Makio

doi:10.1016/j.susc.2008.07.018

Cited by 6 publications

(1 citation statement)

References 16 publications

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“…Crystal surfaces of sapphire transform at around 473 K. 33 This is probably due to the surface diffusion. 34 With an annealing temperature of 973 K, the surfaces of the diamond-polished and H-ion irradiated crystals are flattened by the surface diffusion and transform thereby affecting light scattering and improving the optical transmittances.…”

Section: -6mentioning

confidence: 99%

Optical transmittance investigation of 1-keV ion-irradiated sapphire crystals as potential VUV to NIR window materials of fusion reactors

et al. 2016

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We investigate the optical transmittances of ion-irradiated sapphire crystals as potential vacuum ultraviolet (VUV) to near-infrared (NIR) window materials of fusion reactors. Under potential conditions in fusion reactors, sapphire crystals are irradiated with hydrogen (H), deuterium (D), and helium (He) ions with 1-keV energy and ∼ 1020-m-2 s-1 flux. Ion irradiation decreases the transmittances from 140 to 260 nm but hardly affects the transmittances from 300 to 1500 nm. H-ion and D-ion irradiation causes optical absorptions near 210 and 260 nm associated with an F-center and an F+-center, respectively. These F-type centers are classified as Schottky defects that can be removed through annealing above 1000 K. In contrast, He-ion irradiation does not cause optical absorptions above 200 nm because He-ions cannot be incorporated in the crystal lattice due to the large ionic radius of He-ions. Moreover, the significant decrease in transmittance of the ion-irradiated sapphire crystals from 140 to 180 nm is related to the light scattering on the crystal surface. Similar to diamond polishing, ion irradiation modifies the crystal surface thereby affecting the optical properties especially at shorter wavelengths. Although the transmittances in the VUV wavelengths decrease after ion irradiation, the transmittances can be improved through annealing above 1000 K. With an optical transmittance in the VUV region that can recover through simple annealing and with a high transparency from the ultraviolet (UV) to the NIR region, sapphire crystals can therefore be used as good optical windows inside modern fusion power reactors in terms of light particle loadings of hydrogen isotopes and helium.

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Section: -6mentioning

confidence: 99%