title: Strain and Hole Gas Induced Raman Shifts in Ge-Si(x)Ge(1-x) Core-Shell Nanowires Using Tip-Enhanced Raman Spectroscopy.
abstract: We report tip-enhanced and conventional Raman spectroscopy studies of Ge-Si0.5Ge0.5 core-shell nanowires in which we observe two distinct Ge-Ge vibrational mode Raman peaks associated with vibrations in the Ge nanowire core and at the Ge-Si0.5Ge0.5 interface at which a quantum-confined hole gas is formed. Tip enhanced Raman measurements show dramatically increased sensitivity to the modes at the Ge-Si0.5Ge0.5 interface and a shift in position of this mode due to plasmonic field localization at the tip apex and the resulting change in phonon self-energy caused by increased coupling between phonons and intervalence-band carrier transitions.
authors.affiliation: Microelectronics Research Center, University of Texas, 10100 Burnet Rd, Building 160, Austin, Texas 78758, United States.
authors.forename: Zhongjian
authors.initials: Z
authors.lastname: Zhang
authors.affiliation: Microelectronics Research Center, University of Texas, 10100 Burnet Rd, Building 160, Austin, Texas 78758, United States.
authors.forename: David C
authors.initials: DC
authors.lastname: Dillen
authors.affiliation: Microelectronics Research Center, University of Texas, 10100 Burnet Rd, Building 160, Austin, Texas 78758, United States.
authors.forename: Emanuel
authors.initials: E
authors.lastname: Tutuc
authors.affiliation: Microelectronics Research Center, University of Texas, 10100 Burnet Rd, Building 160, Austin, Texas 78758, United States.
authors.forename: Edward T
authors.initials: ET
authors.lastname: Yu
keywords: Raman spectroscopy; Tip-enhanced Raman scattering; atomic force microscopy; core−shell; germanium; heterostructure; nanowire; optical near-field spectroscopy; silicon−germanium; strain