Size- and temperature-dependent Young's modulus of SiC nanowires determined by a laser-Doppler vibration measurement

Young's modulus of Fe-catalyzed silicon carbide (SiC) nanowires was measured in the temperature range of 300–575 K by the use of a laser Doppler vibrometer. The nanowires have a face-centered cubic structure grown along the [111] direction and exhibit different cross-sectional geometries, including circle, rectangle, hexagon, ellipse, trapezoid, and triangle. When the effective diameters of the nanowires decrease from 200 to 55 nm, their room-temperature Young's modulus decreases from ∼550 GPa (the bulk value) to ∼460 GPa, i.e., a reduction of ∼16%, and their temperature coefficient of Young's modulus varies from $−47.4 ± 1.7$ ppm/K (the bulk value) to $−78.1 ± 5.9$ ppm/K, i.e., a change of ∼65%. The size and temperature dependency of the modulus would greatly benefit the design and fabrication of high-temperature mechanical sensors based on SiC nanostructures.