Investigation of Raman depolarization ratio in topological insulator Bi2Se3 epitaxial films. (1st May 2023)

• Record Type: Journal Article
• Authors: Kondo, Tomohiro; Nozaki, Takamu; Kotabe, Ryuya; Terai, Yoshikazu
• Is Part Of: Japanese journal of applied physics. Volume 62:Number SD(2023)
• Publication Date: 2023-05-01
• Subjects: Bi2Se3 -- MBE -- thin film; Physics -- Periodicals; 621.05
• DOI: 10.35848/1347-4065/acaab3
• Languages: English
• ISSNs: 0021-4922

Abstract

Abstract: Bismuth selenide (Bi2 Se3 ) epitaxial films were grown at different substrate temperatures ( T s ) by molecular beam epitaxy. In the optimization of T s, a Bi2 Se3 film with the smallest root mean square roughness (Rq) and the lowest electron density was grown at T s = 120 °C. In the optimized growth condition, Bi2 Se3 epitaxial films with 3−85 quintuple layers (QL: 1 QL ≈ 1 nm) were grown. In unpolarized Raman spectra, the positions of A 1 1g and E 2 g -modes shifted to the low wavenumbers at film thickness below 10 QL. The polarized Raman spectra showed that the depolarization ratio ρ also changed with film thickness. The change in ρ was more significant than the change in the position shift. This indicates that the measurement of ρ is an effective method to evaluate the thickness of Bi2 Se3 ultrathin films.