title: Size effects in mechanical deformation and fracture of cantilevered silicon nanowires.
abstract: Elastic modulus and fracture strength of vertically aligned Si [111] nanowires (ø = 100-700 nm) in an as-grown state have been measured using a new, multipoint bending protocol in an atomic force microscope. All wires showed linear elastic behavior, spring constants which scale with (length)(3), and brittle failure at the wire-substrate junction. The "effective" Young's modulus increased slightly (100 --> 160-180 GPa) as wire diameter decreased, but fracture strength increased by 2-3 orders of magnitude (MPa --> GPa). These results indicate that vapor-liquid-solid grown wires are relatively free of extended volume defects and that fracture strength is likely controlled by twinning and interfacial effects at the wire foot. Small wires (100 nm) grown with a colloidal catalyst were the best performers with high modulus ( approximately 180 GPa) and fracture stress >1 GPa.
authors.affiliation: Department of Chemical Engineering, University of California, Santa Barbara, California 93106-5080, USA. mjgordon@engr.ucsb.edu
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Gordon
authors.forename: Thierry
authors.initials: T
authors.lastname: Baron
authors.forename: Florian
authors.initials: F
authors.lastname: Dhalluin
authors.forename: Pascal
authors.initials: P
authors.lastname: Gentile
authors.forename: Pierre
authors.initials: P
authors.lastname: Ferret