The preferential orientation of the directionally solidified Si-TaSi₂ eutectic in situ composite

The Si-TaSi₂ eutectic in situ composite is a favorable field emission material due to relatively low work function, good electron conductivity, and three-dimensional array of Schottky junctions grown in the composite spontaneously. The preferential orientation during directional solidification is determined by the growth anisotropy. In order to obtain the preferential direction of the steady-state crystal growth, the transmission electron microscopy (TEM) is used for analysis. It is found that the preferential orientation of the Si-TaSi₂ eutectic in situ composite prepared by Czochralski (CZ) technique is [3 3̄ 2̄] Si∥[0 0 0 1] TaSi₂, (2 2 0)Si∥(2 2̄ 0 0) TaSi₂. Whereas the preferential orientation of the Si-TaSi₂ eutectic in situ composite prepared by electron beam floating zone melting (EBFZM) technique is [0 1̄ 1̄ ]] Si∥[0 0 0 1] TaSi₂,(0 1̄ 1) Si∥(0 1̄ 1 1)TaSi₂. The preferential directions of the Si-TaSi₂ eutectic in situ composites prepared by two kinds of crystal growth techniques are distinctly different from each other, which results from different solid-liquid interface temperatures on account of the different crystal growth conditions, e.g. different solidification rate, different temperature gradient, different solid-liquid interface curvature and different kinetic undercooling.