title: Carrier density modulation in a germanium heterostructure by ferroelectric switching.
abstract: The development of non-volatile logic through direct coupling of spontaneous ferroelectric polarization with semiconductor charge carriers is nontrivial, with many issues, including epitaxial ferroelectric growth, demonstration of ferroelectric switching and measurable semiconductor modulation. Here we report a true ferroelectric field effect-carrier density modulation in an underlying Ge(001) substrate by switching of the ferroelectric polarization in epitaxial c-axis-oriented BaTiO3 grown by molecular beam epitaxy. Using the density functional theory, we demonstrate that switching of BaTiO3 polarization results in a large electric potential change in Ge. Aberration-corrected electron microscopy confirms BaTiO3 tetragonality and the absence of any low-permittivity interlayer at the interface with Ge. The non-volatile, switchable nature of the single-domain out-of-plane ferroelectric polarization of BaTiO3 is confirmed using piezoelectric force microscopy. The effect of the polarization switching on the conductivity of the underlying Ge is measured using microwave impedance microscopy, clearly demonstrating a ferroelectric field effect.
authors.affiliation: Department of Physics, The University of Texas at Austin, Austin, Texas 78712, USA.
authors.forename: Patrick
authors.initials: P
authors.lastname: Ponath
authors.affiliation: Department of Physics, The University of Texas at Austin, Austin, Texas 78712, USA.
authors.forename: Kurt
authors.initials: K
authors.lastname: Fredrickson
authors.affiliation: Department of Physics, The University of Texas at Austin, Austin, Texas 78712, USA.
authors.forename: Agham B
authors.initials: AB
authors.lastname: Posadas
authors.affiliation: Department of Physics, The University of Texas at Austin, Austin, Texas 78712, USA.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Ren
authors.affiliation: Department of Physics, The University of Texas at Austin, Austin, Texas 78712, USA.
authors.forename: Xiaoyu
authors.initials: X
authors.lastname: Wu
authors.affiliation: Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
authors.forename: Rama K
authors.initials: RK
authors.lastname: Vasudevan
authors.affiliation: Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
authors.forename: M Baris
authors.initials: MB
authors.lastname: Okatan
authors.affiliation: Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
authors.forename: S
authors.initials: S
authors.lastname: Jesse
authors.affiliation: Center for Solid State Science, Arizona State University, Tempe, Arizona 85287, USA.
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Aoki
authors.affiliation: Department of Physics, Arizona State University, Tempe, Arizona 85287, USA.
authors.forename: Martha R
authors.initials: MR
authors.lastname: McCartney
authors.affiliation: Department of Physics, Arizona State University, Tempe, Arizona 85287, USA.
authors.forename: David J
authors.initials: DJ
authors.lastname: Smith
authors.affiliation: Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
authors.forename: Sergei V
authors.initials: SV
authors.lastname: Kalinin
authors.affiliation: Department of Physics, The University of Texas at Austin, Austin, Texas 78712, USA.
authors.forename: Keji
authors.initials: K
authors.lastname: Lai
authors.affiliation: Department of Physics, The University of Texas at Austin, Austin, Texas 78712, USA.
authors.forename: Alexander A
authors.initials: AA
authors.lastname: Demkov