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Laser-induced structural disordering and optical phase change in semimetal bismuth observed by Raman microscopy

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Title: Laser-induced structural disordering and optical phase change in semimetal bismuth observed by Raman microscopy
Authors: Handegard, Orjan S. Browse this author
Kitajima, Masahiro Browse this author
Nagao, Tadaaki Browse this author →KAKEN DB
Keywords: Bismuth
Raman scattering
Laser heating
Optical phonon
Dielectric response
Issue Date: 15-Oct-2019
Publisher: Elsevier
Journal Title: Applied surface science
Volume: 491
Start Page: 675
End Page: 681
Publisher DOI: 10.1016/j.apsusc.2019.05.013
Abstract: We observed strong enhancement of the Raman signal from a silicon (Si) substrate hidden beneath nano/microdroplets of bismuth (Bi) after exposing them to a high-power laser beam (785 nm). Confocal Raman microscopy indicated that the as-fabricated Bi droplets inhibit the Raman signal from the underlying Si substrate. After the laser flash heating step, the intensity of Si optical phonons was strongly enhanced at the positions of Bi droplets, becoming even more intense than that of the bare Si substrate. Analyses of the Bi optical phonon modes, E-g and A(1g), confirmed a loss of long-range ordered crystallinity in the laser exposed droplets. Such lattice disordering can increase the available free carrier density in semimetal Bi, as occurs in the case of its amorphous and liquid states. And this can induce an optical phase change, which causes a marked enhancement of Si Raman signals through an effect similar to surface-enhanced Raman scattering (SERS).
Rights: © 2019. This manuscript version is made available under the CC-BY-NC-ND 4.0 license
Type: article (author version)
Appears in Collections:理学院・理学研究院 (Graduate School of Science / Faculty of Science) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

Submitter: 長尾 忠昭

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