title: Single crystalline and core-shell indium-catalyzed germanium nanowires-a systematic thermal CVD growth study.
abstract: Germanium nanowires were synthesized using thermal chemical vapor deposition (CVD) and indium as a catalyst. The process parameter space for successful growth was studied. By optimizing the growth temperature and gas pressure, high aspect ratio germanium nanowires have been obtained. Scanning electron microscopy investigations indicate that the final diameter of the nanowires is strongly influenced by the growth temperature and the germane partial pressure. High resolution transmission electron microscopy reveals that nanowires grow either as high quality single crystalline, or with a high quality single-crystalline core and a concentric amorphous shell. The occurrence of these two morphologies is found to only depend on the wire diameter. Chemical analysis of the nanowire tip indicates the presence of indium, validating its role as a catalyst. Raman spectroscopy measurements reveal a higher incidence of core-shell structures for nanowires synthesized at 30 Torr and indicate the presence of tensile strain. These results are important towards obtaining high quality germanium nanowires without the use of gold as a catalyst, which is known to degrade the wires' electrical and optical properties.
authors.affiliation: Walter Schottky Institut, Technische Universität München, Am Coulombwall 3, D-85748 Garching, Germany.
authors.forename: Ying
authors.initials: Y
authors.lastname: Xiang
authors.forename: Linyou
authors.initials: L
authors.lastname: Cao
authors.forename: Sonia
authors.initials: S
authors.lastname: Conesa-Boj
authors.forename: Sonia
authors.initials: S
authors.lastname: Estrade
authors.forename: Jordi
authors.initials: J
authors.lastname: Arbiol
authors.forename: Francesca
authors.initials: F
authors.lastname: Peiro
authors.forename: Martin
authors.initials: M
authors.lastname: Heiss
authors.forename: I
authors.initials: I
authors.lastname: Zardo
authors.forename: Joan R
authors.initials: JR
authors.lastname: Morante
authors.forename: Mark L
authors.initials: ML
authors.lastname: Brongersma
authors.forename: Anna
authors.initials: A
authors.lastname: Fontcuberta I Morral
mesh_terms: D002384:Catalysis; D003460:Crystallization / Q000379:methods*; D005740:Gases; D005857:Germanium / Q000737:chemistry*; D006358:Hot Temperature; D007204:Indium / Q000737:chemistry*; D046911:Macromolecular Substances / Q000737:chemistry; D008422:Materials Testing; D008968:Molecular Conformation; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure*; D036103:Nanotechnology / Q000379:methods*; D010316:Particle Size; D013499:Surface Properties
chemical_list: D005740:Gases; D046911:Macromolecular Substances; D005857:Germanium; D007204:Indium