Effect of temperature on fracture toughness in a single-crystal-silicon film and transition in its fracture mode

A change in the fracture mode of a micrometer-sized single-crystal-silicon (SCS) film was observed at a temperature slightly higher than room temperature (RT). Silicon films with a notch on one side were tested under tensile stress at temperatures ranging from RT to 500 degrees C. The mean fracture toughness was 1.28 MPa root m m at RT and the value remained similar up to 60 degrees C. However, it drastically increased to nearly twice this value above 70 degrees C. Differences in the fracture mode and dislocation activity were found by scanning and transmission electron microscopy (SEM and TEM). These results show that the fracture mode changed even at a low temperature near 70 degrees C due to the activation of dislocations at the notch tip.