Two nano-sized amorphous layers were created within a crystalline cell to study anisotropic expitaxial recrystallization using molecular dynamics (MD) methods in 4H-SiC. Both amorphous layers were created with the normal of the amorphous–crystalline (a–c) interfaces along the [0001] direction, but one had a microscopic extension along the [\bar {1}2\bar {1}0 ] direction, i.e. the dimension along the [\bar {1}2\bar {1}0 ] direction is much larger than that along the [\bar {1}010 ] direction (Ix model), and the other had a microscopic extension along the [\bar {1}010 ] direction (Iy model). The amorphous layer within the Ix model can be completely recrystallized at 2000 K within an achievable simulation time, and the recrystallization is driven by a step-regrowth mechanism. On the other hand, the nucleation and growth of secondary ordered phases are observed at high temperatures in the Iy model. The temperature for recrystallization of the amorphous layer into high-quality 4H-SiC is estimated to be below 1500 K. Compared with other models, it is found that the regrowth rates and recrystallization mechanisms depend strongly on the orientation of 4H-SiC, whereas the activation energy spectra for recrystallization processes are independent of any specific polytypic structure, with activation energies ranging from 0.8 to 1.7 eV.
Source:IOPscience
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