title: Coherently Strained Si-SixGe1-x Core-Shell Nanowire Heterostructures.
abstract: Coherently strained Si-SixGe1-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-SixGe1-x core-shell heterostructures through the vapor-liquid-solid mechanism for the Si core, followed in situ by the epitaxial SixGe1-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 SixGe1-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-SixGe1-x core-shell nanowires as channel are demonstrated.
authors.affiliation: Microelectronics Research Center, The University of Texas at Austin , 10100 Burnet Road, Bldg. 160, Austin, Texas 78758, United States.
authors.forename: David C
authors.initials: DC
authors.lastname: Dillen
authors.affiliation: Microelectronics Research Center, The University of Texas at Austin , 10100 Burnet Road, Bldg. 160, Austin, Texas 78758, United States.
authors.forename: Feng
authors.initials: F
authors.lastname: Wen
authors.affiliation: Microelectronics Research Center, The University of Texas at Austin , 10100 Burnet Road, Bldg. 160, Austin, Texas 78758, United States.
authors.forename: Kyounghwan
authors.initials: K
authors.lastname: Kim
authors.affiliation: Microelectronics Research Center, The University of Texas at Austin , 10100 Burnet Road, Bldg. 160, Austin, Texas 78758, United States.
authors.forename: Emanuel
authors.initials: E
authors.lastname: Tutuc
keywords: Nanowire; Raman spectroscopy; core−shell; elastic strain; field-effect transistor; silicon−germanium