Flexure Strength and Failure Probability of Silicon Nanowires
Open Access
- Author:
- Kirkpatrick, Rebecca
- Graduate Program:
- Materials Science and Engineering
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- June 21, 2010
- Committee Members:
- Christopher Muhlstein, Dissertation Advisor/Co-Advisor
Christopher L Muhlstein, Committee Chair/Co-Chair
Joan Marie Redwing, Committee Member
James Hansell Adair, Committee Member
Srinivas A Tadigadapa, Committee Member - Keywords:
- silicon
mechanical characterization
nanowire
bend testing
Weibull statistics - Abstract:
- Silicon nanowires are used in a variety of small scale applications where mechanical reliability predictions are based on bulk, instead of length-scale dependent materials properties. This research presents a study of the mechanical behavior of silicon nanowires using an atomic force microscope to fracture samples in centrally loaded, fixed-fixed beam bending. Silicon nanowires 43-83 nm in diameter were grown using the vapor-liquid-solid technique, and the crystallographic orientation of each nanowire ([100], [110], [111], and [112] growth directions) was characterized using electron backscatter diffraction patterns (EBSD). Nanowires in flexure exhibited large deflection, nonlinear elastic behavior followed by brittle fracture. Flexure strengths ranged from 5.10 to 20.01 GPa, with an average value of 13.74 GPa, and displayed no clear dependence on diameter or single crystal orientation. Numerical analyses were also used to evaluate the effect of the boundary conditions and the implications of weakest link statistical theories on the measurement of mechanical properties. For the flexible beams loaded in fixed-fixed bending it is not possible to achieve a high localization of stresses, therefore there is a lower probability of approaching the theoretical strength of materials.