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Ultrafast phonon dynamics of epitaxial atomic layers of Bi on Si(111)
| Title: | Ultrafast phonon dynamics of epitaxial atomic layers of Bi on Si(111) |
| Authors: | Ishioka, Kunie Browse this author | | Kitajima, Masahiro Browse this author | | Misochko, Oleg V. Browse this author | | Nagao, Tadaaki Browse this author →KAKEN DB |
| Issue Date: | Mar-2015 |
| Journal Title: | Physical Review B |
| Volume: | 91 |
| Issue: | 12 |
| Start Page: | 125431 |
| Publisher DOI: | 10.1103/PhysRevB.91.125431 |
| Abstract: | Ultrathin bismuth (Bi) layers on Si(111)-7×7 undergo a structural phase transformation with reducing the number of atomic layers at 3 bilayers (BL). We investigate the phonon dynamics of the Bi films close to the phase transformation by pump-probe reflectivity measurements. Coherent A1g and Eg phonons at 3 and 2 THz are clearly observed for the Bi layers with thicknesses down to 3 BL, confirming their rhombohedral crystalline structure. The A1g frequency exhibits an abrupt redshift and splits into two components at 3 BL, which are attributed to the vertical motions of Bi atoms localized at the surface and subsurface bilayers. The Eg frequency, by contrast, shows a gradual blueshift with reducing the thickness, possibly due to the lateral compressive stress at the Bi/Si interface. Below 3 BL, no coherent phonon signal is detected, in agreement with the phase transformation to the black-phosphoruslike structure. Our observations indicate that the vertical vibrations are significantly softened at 3 BL, but become almost as hard as those in the bulk crystal by adding another bilayer. |
| Rights: | ©2015 American Physical Society |
| Type: | article |
| URI: | http://hdl.handle.net/2115/72128 |
| 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)
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Submitter: 長尾 忠昭
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