title: Mapping carrier diffusion in single silicon core-shell nanowires with ultrafast optical microscopy.
abstract: Recent success in the fabrication of axial and radial core-shell heterostructures, composed of one or more layers with different properties, on semiconductor nanowires (NWs) has enabled greater control of NW-based device operation for various applications. (1-3)  However, further progress toward significant performance enhancements in a given application is hindered by the limited knowledge of carrier dynamics in these structures. In particular, the strong influence of interfaces between different layers in NWs on transport makes it especially important to understand carrier dynamics in these quasi-one-dimensional systems. Here, we use ultrafast optical microscopy (4)  to directly examine carrier relaxation and diffusion in single silicon core-only and Si/SiO(2) core-shell NWs with high temporal and spatial resolution in a noncontact manner. This enables us to reveal strong coherent phonon oscillations and experimentally map electron and hole diffusion currents in individual semiconductor NWs for the first time.
authors.affiliation: Center for Integrated Nanotechnologies, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States. minahseo@lanl.gov
authors.forename: M A
authors.initials: MA
authors.lastname: Seo
authors.forename: J
authors.initials: J
authors.lastname: Yoo
authors.forename: S A
authors.initials: SA
authors.lastname: Dayeh
authors.forename: S T
authors.initials: ST
authors.lastname: Picraux
authors.forename: A J
authors.initials: AJ
authors.lastname: Taylor
authors.forename: R P
authors.initials: RP
authors.lastname: Prasankumar
mesh_terms: D004058:Diffusion; D004867:Equipment Design; D008853:Microscopy / Q000191:economics / Q000295:instrumentation*; D053770:Nanowires / Q000737:chemistry* / Q000648:ultrastructure; D012825:Silicon / Q000737:chemistry*; D012822:Silicon Dioxide / Q000737:chemistry*; D013997:Time Factors
chemical_list: D012822:Silicon Dioxide; D012825:Silicon