Morphological instabilities induced by foreign particles and Ehrlich-Schwoebel effect during the two-dimensional growth of crystalline Ti3SiC2
Résumé
Atomic step edges can exhibit a morphological instability under step-flow conditions (the so-called Bales-Zangwill instability). Such instabilities are ascribed to the fact that adatoms approaching a step from opposite directions do not see the same energy barrier to step incorporation (Ehrlich-Schwoebel or ES effect). Due to the very low solubility of carbon in the melt, Ti3SiC2 grown from a Ti-Si liquid phase is an experimental example of two-dimensional (2D) growth. In addition, the ratio between the incorporation rates at a step from the lower terrace and from the upper terrace is probably very high. The latter particularity makes the steps lying below a terrace including an unstable step independent from the forming instability, so that an instability front may appear just on one terrace, whereas the neighboring steps remain stable. Besides, foreign-particle-assisted growth can result in the production of extremely elongated islands or peninsulas on a given terrace, which then form very long grooves between the island edge and the upper terrace step. This provides the ability to test the respective stability of lines and grooves on a single terrace, and to verify that shrinking grooves are more stable than simple steps, as recently demonstrated by another author.