失配性质对面心立方外延晶体失配位错结构及其形核机制的影响

Misfit Characters Effect on the Dislocation Structure and Nucleation Mechanism in FCC Epitaxial Crystals

运用三维分子动力学方法模拟了外延铝薄膜晶体中失配位错的形成过程。结果显示：失配度为fx=4％时，位错是通过薄膜表层原子的相对滑移来形核，形成一个伯格斯矢量为1／2[101]的刃型位错，该位错形成后会迅速向界面滑移，并稳定在离界面1～2个原子层上不动，同时在薄膜表面留下一个台阶。而失配度为fx=4％时，位错形核是通过挤出一个四面体构型的原子团开始，形成一个伯格斯矢量为1／2[110]的刃型位错，该位错只能平行于界面滑移，位错稳定后离界面的距离比正失配度时的距离和热力学临界厚度都要大。

A three-dimensional molecular dynamics simulation of epitaxial growth of fcc aluminum film crystals with positive or negative misfit of 4% was carried out. The result shows that when the misfit is ＋4%, the misfit dislocation nucleation begins with the sliding of two parts of surface atoms and forms a edge dislocation with 1/2 [ 10 1] Burgers vector. Then the edge dislocation will slide quickly from the surface to the interface and stay near the interface stably. A step is left in the surface as a result. When the misfit is-4%, the dislocation nucleation begins with squeezing-out a tetrahedron consisting of four interstitial atoms. And a 1/2 [ 110 ] edge dislocation forms. This edge dislocation can only slide paralleling to the interface. So the distance from dislocation to interface is longer than the distance when a positive misfit is fixed and thermodynamic critical thickness.