Uniaxial strain observed in solid/liquid interface during crystal growth from melted Si: a molecular dynamics study

We have performed molecular dynamics (MD) simulations of crystal growth from melted Si using a MD cell immersed in a thermal bath with various temperature gradients. Based on the analysis of changes in the distance between the (0 0 1) atomic planes, it was found that uniaxial strain was induced along the [0 0 1] direction near the solid/liquid interface. The induced strain is essentially the same as equilibrium thermal expansion corresponding to the local temperature when the temperature gradient is low. However, as the temperature gradient increases, the tensile strain becomes smaller than equilibrium thermal expansion and it gradually changes to being compressive. This is consistent with the experimental trend that interstitial-type grown-in defects are formed in higher-temperature gradients. We have also examined oxygen effects on the strain by introducing an oxygen atom in melted Si and found that the oxygen atom is taken into the interstitial site of crystal Si resulting in an enhancement of the tensile strain. (C) 2000 Elsevier Science B.V. All rights reserved.