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Title: Stability and mechanical properties of silicon nanowires

Abstract

his work focuses on the structure, stability, and mechanical properties of silicon nanowires (SiNWs) oriented along the < 111 > direction. A total energy calculation and a quenching-technique based on a non-orthogonal tight-binding molecular dynamics (MD) is used to study the equilibrium structure and relative stability of SiNWs of different diameters (d) ranging from 2 nm to 17 nm. Our study of the structural relaxation of wires of different diameters reveal the following two key findings: (i) A SiNW is composed of a crystalline core surrounded by a bond distortion-dominated surface region, and (ii) the width of the surface region is found to be similar to 1 nm and is independent of the diameter of the wire. These findings suggest that there exists a critical diameter (similar to 2 nm) below which a crystalline nanowire becomes unstable due to surface-surface interaction. We have also calculated the surface energy (E-s) for wires of different diameters (d), where the E-s versus d curve exhibits several local minima. A more careful study of the local minimum at d similar to 6 nm finds this minimum to be very sharp. The existence of local minima in the surface energy curve is indicative of themore » existence of magic diameters for SiNWs, while the sharpness of the minima is related to the existence of uniform-diameter wires. A study of the Young's modulus of the similar to 6 nm-SiNW suggests that surface effects are critically important in determining the mechanical properties of nanowires with the value of the Young's modulus reduced from its bulk value by about 40%.« less

Authors:
 [1];  [2];  [1];  [3]
  1. ORNL
  2. unknown
  3. University of Louisville, Louisville
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
931903
DOE Contract Number:
DE-AC05-00OR22725
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Computational and Theoretical Nanoscience; Journal Volume: 4; Journal Issue: 2
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; MECHANICAL PROPERTIES; RELAXATION; SILICON; STABILITY; SURFACE ENERGY; YOUNG MODULUS

Citation Formats

Liu, Shudun, Jayanthi, C. S., Zhang, Zhenyu, and Wu, S. Y.. Stability and mechanical properties of silicon nanowires. United States: N. p., 2007. Web.
Liu, Shudun, Jayanthi, C. S., Zhang, Zhenyu, & Wu, S. Y.. Stability and mechanical properties of silicon nanowires. United States.
Liu, Shudun, Jayanthi, C. S., Zhang, Zhenyu, and Wu, S. Y.. Thu . "Stability and mechanical properties of silicon nanowires". United States. doi:.
@article{osti_931903,
title = {Stability and mechanical properties of silicon nanowires},
author = {Liu, Shudun and Jayanthi, C. S. and Zhang, Zhenyu and Wu, S. Y.},
abstractNote = {his work focuses on the structure, stability, and mechanical properties of silicon nanowires (SiNWs) oriented along the < 111 > direction. A total energy calculation and a quenching-technique based on a non-orthogonal tight-binding molecular dynamics (MD) is used to study the equilibrium structure and relative stability of SiNWs of different diameters (d) ranging from 2 nm to 17 nm. Our study of the structural relaxation of wires of different diameters reveal the following two key findings: (i) A SiNW is composed of a crystalline core surrounded by a bond distortion-dominated surface region, and (ii) the width of the surface region is found to be similar to 1 nm and is independent of the diameter of the wire. These findings suggest that there exists a critical diameter (similar to 2 nm) below which a crystalline nanowire becomes unstable due to surface-surface interaction. We have also calculated the surface energy (E-s) for wires of different diameters (d), where the E-s versus d curve exhibits several local minima. A more careful study of the local minimum at d similar to 6 nm finds this minimum to be very sharp. The existence of local minima in the surface energy curve is indicative of the existence of magic diameters for SiNWs, while the sharpness of the minima is related to the existence of uniform-diameter wires. A study of the Young's modulus of the similar to 6 nm-SiNW suggests that surface effects are critically important in determining the mechanical properties of nanowires with the value of the Young's modulus reduced from its bulk value by about 40%.},
doi = {},
journal = {Journal of Computational and Theoretical Nanoscience},
number = 2,
volume = 4,
place = {United States},
year = {Thu Mar 01 00:00:00 EST 2007},
month = {Thu Mar 01 00:00:00 EST 2007}
}