All-Wurtzite (In,Ga)As-(Ga,Mn)As Core–Shell Nanowires Grown by Molecular Beam Epitaxy

• Published in: Nano letters Vol. 14; no. 8; pp. 4263 - 4272
• Main Authors: Šiušys, Aloyzas, Sadowski, Janusz, Sawicki, Maciej, Kret, Sławomir, Wojciechowski, Tomasz, Gas, Katarzyna, Szuszkiewicz, Wojciech, Kaminska, Agnieszka, Story, Tomasz
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 13.08.2014
• Subjects: Catalytic methods; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Magnetic properties and materials; Magnetic properties of nanostructures; Materials science; Methods of nanofabrication; Nanocrystalline materials; Nanoscale materials and structures: fabrication and characterization; Physics; Quantum wires; spintronics; wurtzite (Ga,Mn)As; molecular beam epitaxy; core−shell structures; Magnetic semiconductor nanowires; superparamagnetism; Temperature dependence; Misfit dislocations; Catalysts; Core shell structure; Ferromagnetic materials; Lattice parameters; Interfaces; Tensile stress; Transmission electron microscopy; Dislocation core; Raman scattering; Molecular beam epitaxy; Wurtzite structure; Nanowires; Nanostructured materials; Nanomaterial synthesis; Magnetic properties; Crystal structure
• ISSN: 1530-6984; 1530-6992
• DOI: 10.1021/nl500896d

Structural and magnetic properties of (In,Ga)As-(Ga,Mn)As core–shell nanowires grown by molecular beam epitaxy on GaAs(111)B substrate with gold catalyst have been investigated. (In,Ga)As core nanowires were grown at high temperature (500 °C) whereas (Ga,Mn)As shells were deposited on the {11̅00} side facets of the cores at much lower temperature (220 °C). High-resolution transmission electron microscopy images and high spectral resolution Raman scattering data show that both the cores and the shells of the nanowires have wurtzite crystalline structure. Scanning and transmission electron microscopy observations show smooth (Ga,Mn)As shells containing 5% of Mn epitaxially deposited on (In,Ga)As cores containing about 10% of In without any misfit dislocations at the core–shell interface. With the In content in the (In,Ga)As cores larger than 5% the (In,Ga)As lattice parameter is higher than that of (Ga,Mn)As and the shell is in the tensile strain state. Elaborated magnetic studies indicate the presence of ferromagnetic coupling in (Ga,Mn)As shells at the temperatures in excess of 33 K. This coupling is maintained only in separated mesoscopic volumes resulting in an overall superparamagnetic behavior which gets blocked below ∼17 K.