Wavy and rough cracks in silicon.
Single-crystal silicon exhibits a strong preference to cleave along a few certain planes, but in experiments we observe wavy cracks with almost no evidence of a preferred fracture direction. Furthermore, we find that the fracture surface is an anisotropic and self-affine fractal over five decades in length scale in the direction of the crack with a roughness exponent of 0.78. In our experiments a 1-4 cm wide strip of single-crystal silicon is heated to 378 degrees C and lowered into a 20 degrees C water bath at speeds of 0.2-5 cm/s. The thermal gradient produces cracks that, depending on the speed, are straight, wavy with amplitude 0.1-0.5 cm and wavelength 0.3-1 cm, or multibranched. The transition from one mode of fracture to another is discontinuous and hysteretic.
Deegan
Robert D
RD
Center for Nonlinear Dynamics, Department of Physics, The University of Texas, Austin, Texas 78712, USA.
Chheda
Shilpa
S
Patel
Lisa
L
Marder
M
M
Swinney
Harry L
HL
Kim
Jeehoon
J
de Lozanne
Alex
A