Author:
Kondo Tomohiro,Nozaki Takamu,Kotabe Ryuya,Terai Yoshikazu
Abstract
Abstract
Bismuth selenide (Bi2Se3) epitaxial films were grown at different substrate temperatures (T
s) by molecular beam epitaxy. In the optimization of T
s, a Bi2Se3 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, Bi2Se3 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 Bi2Se3 ultrathin films.
Subject
General Physics and Astronomy,General Engineering