Coherently Strained Si–SixGe1–x Core–Shell Nanowire Heterostructures

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• 作者：David C. Dillen ; Feng Wen ; Kyounghwan Kim ; Emanuel Tutuc
• 刊名：Nano Letters
• 出版年：2016
• 出版时间：January 13, 2016
• 年：2016
• 卷：16
• 期：1
• 页码：392-398
• 全文大小：435K
• ISSN：1530-6992

文摘

Coherently strained Si–Si_xGe_1–x core–shell nanowire heterostructures are expected to possess a positive shell-to-core conduction band offset, allowing for quantum confinement of electrons in the Si core. We report the growth of epitaxial, coherently strained Si–Si_xGe_1–x core–shell heterostructures through the vapor–liquid–solid mechanism for the Si core, followed in situ by the epitaxial Si_xGe_1–x shell growth using ultrahigh vacuum chemical vapor deposition. The Raman spectra of individual nanowires reveal peaks associated with the Si–Si optical phonon mode in the Si core and the Si–Si, Si–Ge, and Ge–Ge vibrational modes of the Si_xGe_1–x shell. The core Si–Si mode displays a clear red-shift compared to unstrained, bare Si nanowires thanks to the lattice mismatch-induced tensile strain, in agreement with calculated values using a finite-element continuum elasticity model combined with lattice dynamic theory. N-type field-effect transistors using Si–Si_xGe_1–x core–shell nanowires as channel are demonstrated.