boundaries that are more nearly parallel to the carrier flow direction enter a point than those types of grain boundaries leaving that point. Similar arguments for thermal gradient-induced migration stal growth [15 The change in Gibbs free energy during a transformation is dG= dH - Tds Answer the following 3 questions about crystallization of Si from the melt using increases","decreases or "remains the same 1) What happens to the enthalpy(heat content) of the material [21 11) What happens to the entropy? [2 i11) What happens to the Gibbs free energy?[21 b) In the depiction of the of crystal growth shown belo 1 indicate with arrows the direction of convection in the melt. [2] 11) Why is there a maximum velocity for growth of a crystal from the melt? 4] i)What processing conditions most affect the appearance of dislocations in the crystal, and how would they be removed? 31 see tang NVAC ry 1500°C 5. a) 1) Enthalpy decreases on crystallization of Si from melt 11) Entropy, ds,(disorder) decreases; -TdS increases 111) Gibbs free energy decreases if the temperature is below the solidification temperature. D 1 See figure. 11) The thermal gradient in the solid must be than that in the liquid in order to also remove the heat of fusion ted at the solid/liquid interface. The amount of heat generated due to solidification increases with growth rate 111) Dislocations arise due to stress in crystal. Stress in crystal growth is most often due to thermal gradients in the crystal. The thermal gradients can re reduced by slower growth or smaller boule radius.3 boundaries that are more nearly parallel to the carrier flow direction enter a point than those types of grain boundaries leaving that point. Similar arguments for thermal gradient-induced migration. Crystal Growth [15] 5. a) The change in Gibbs free energy during a transformation is dG = dH - TdS. Answer the following 3 questions about crystallization of Si from the melt using “increases”, “decreases” or “remains the same” i) What happens to the enthalpy (heat content) of the material [2] ii) What happens to the entropy? [2] iii) What happens to the Gibbs free energy? [2] b) In the depiction of the of crystal growth shown below i) indicate with arrows the direction of convection in the melt. [2] ii) Why is there a maximum velocity for growth of a crystal from the melt? [4] iii) What processing conditions most affect the appearance of dislocations in the crystal, and how would they be removed? [3] 5. a) i) Enthalpy decreases on crystallization of Si from melt. ii) Entropy, dS, (disorder) decreases; -TdS increases. iii) Gibbs free energy decreases if the temperature is below the solidification temperature. b) i) See figure. ii) The thermal gradient in the solid must be larger than that in the liquid in order to also remove the heat of fusion generated at the solid/liquid interface. The amount of heat generated due to solidification increases with growth rate. iii) Dislocations arise due to stress in crystal. Stress in crystal growth is most often due to thermal gradients in the crystal. The thermal gradients can re reduced by slower growth or smaller boule radius. 1500°C seed tang VAC crystal