Lack of the critical pressure for weakening of size-induced stiffness in 3C-SiC nanocrystals under hydrostatic compression

Using in situ high-pressure x-ray diffraction methods, the compressibility of 30 nm 3C-SiC nanocrystals was studied under hydrostatic conditions while helium was used as pressure transmitting medium, as well as under nonhydrostatic conditions without pressure medium. No threshold pressure phenomenon was observed for the compressibility of the nanocrystals during compression in hydrostatic conditions, while the critical pressure around 10.5 GPa was observed during nonhydrostatic compression. These indicate that the threshold pressure phenomena, recently reported that the nanocrystals initially exhibited much higher bulk modulus below the threshold pressure during compression [Appl. Phys. Lett. 83, 3174 (2003); J. Phys. Chem. 107, 14151 (2003)], were mainly caused by the nonhydrostatic effect instead of a specific feature of nanocrystals upon compression. The bulk modulus of 3C-SiC nanocrystals is estimated as 220.6+/-0.6 GPa based on the hydrostatic compression data. (C) 2004 American Institute of Physics.