title: Polar Second-Harmonic Imaging to Resolve Pure and Mixed Crystal Phases along GaAs Nanowires.
abstract: In this work, we report an optical method for characterizing crystal phases along single-semiconductor III-V nanowires based on the measurement of polarization-dependent second-harmonic generation. This powerful imaging method is based on a per-pixel analysis of the second-harmonic-generated signal on the incoming excitation polarization. The dependence of the second-harmonic generation responses on the nonlinear second-order susceptibility tensor allows the distinguishing of areas of pure wurtzite, zinc blende, and mixed and rotational twins crystal structures in individual nanowires. With a far-field nonlinear optical microscope, we recorded the second-harmonic generation in GaAs nanowires and precisely determined their various crystal structures by analyzing the polar response for each pixel of the images. The predicted crystal phases in GaAs nanowire are confirmed with scanning transmission electron and high-resolution transmission electron measurements. The developed method of analyzing the nonlinear polar response of each pixel can be used for an investigation of nanowire crystal structure that is quick, sensitive to structural transitions, nondestructive, and on-the-spot. It can be applied for the crystal phase characterization of nanowires built into optoelectronic devices in which electron microscopy cannot be performed (for example, in lab-on-a-chip devices). Moreover, this method is not limited to GaAs nanowires but can be used for other nonlinear optical nanostructures.
authors.affiliation: Optical Nanomaterial Group, Institute for Quantum Electronics, Department of Physics, ETH Zurich , Auguste-Piccard Hof 1, 8093 Zurich, Switzerland.|ITMO University , Kronverkskiy 49, 197101 Saint Petersburg, Russia.
authors.forename: Maria
authors.initials: M
authors.lastname: Timofeeva
authors.affiliation: St. Petersburg Academic University , Khlopina 8/3, 194021 Saint Petersburg, Russia.|Ioffe Institute , Politekhnicheskaya 29, 194021 Saint Petersburg, Russia.
authors.forename: Alexei
authors.initials: A
authors.lastname: Bouravleuv
authors.affiliation: St. Petersburg Academic University , Khlopina 8/3, 194021 Saint Petersburg, Russia.|ITMO University , Kronverkskiy 49, 197101 Saint Petersburg, Russia.|Ioffe Institute , Politekhnicheskaya 29, 194021 Saint Petersburg, Russia.
authors.forename: George
authors.initials: G
authors.lastname: Cirlin
authors.affiliation: St. Petersburg Academic University , Khlopina 8/3, 194021 Saint Petersburg, Russia.|Ioffe Institute , Politekhnicheskaya 29, 194021 Saint Petersburg, Russia.
authors.forename: Igor
authors.initials: I
authors.lastname: Shtrom
authors.affiliation: St. Petersburg Academic University , Khlopina 8/3, 194021 Saint Petersburg, Russia.|Ioffe Institute , Politekhnicheskaya 29, 194021 Saint Petersburg, Russia.
authors.forename: Ilya
authors.initials: I
authors.lastname: Soshnikov
authors.affiliation: Optical Nanomaterial Group, Institute for Quantum Electronics, Department of Physics, ETH Zurich , Auguste-Piccard Hof 1, 8093 Zurich, Switzerland.
authors.forename: Marc
authors.initials: M
authors.lastname: Reig Escalé
authors.affiliation: Optical Nanomaterial Group, Institute for Quantum Electronics, Department of Physics, ETH Zurich , Auguste-Piccard Hof 1, 8093 Zurich, Switzerland.
authors.forename: Anton
authors.initials: A
authors.lastname: Sergeyev
authors.affiliation: Optical Nanomaterial Group, Institute for Quantum Electronics, Department of Physics, ETH Zurich , Auguste-Piccard Hof 1, 8093 Zurich, Switzerland.
authors.forename: Rachel
authors.initials: R
authors.lastname: Grange
keywords: GaAs; Nanowires; crystal phase; far-field microscopy; high-resolution transmission electron microscopy; polar second-harmonic imaging; polarization-dependent; scanning electron microscopy; second-harmonic generation; twins; wurtzite; zinc blende