晶体相场法模拟异质外延过程中界面形态演化与晶向倾侧

采用晶体相场模型研究了异质外延过程中失配应变与应力弛豫对外延层界面形态演化的影响, 并对由衬底倾角引起的外延层晶向倾侧进行了分析.研究结果表明: 在有一定倾角的衬底晶体上进行外延生长时,若衬底和外延层之间失配度较大 (ε>0.08),外延层中弹性畸变能会以失配位错的形式释放, 最终薄膜以稳定的流动台阶形式生长且外延层的晶向倾角与衬底倾角呈近似线性关系. 而当衬底和外延层之间失配度较小(ε<0.04)不足以形成失配位错时, 外延层中弹性畸变能会以表面能的形式释放,最终使薄膜以岛状形态生长. 在高过冷度条件下,衬底倾角和失配度较大时,衬底和外延层之间会形成由大量位错规则排列而成的小角度晶界从而显著改变外延层的生长位向.

Simulation of morphological evolution and crystallographic tilt in heteroepitaxial growth using phase-field crystal method

The phase-field crystal(PFC) model is employed to study the morphological evolution and the crystallographic tilt of heteroepitaxial growth on vicinal substrates.The results are as follows:for heterostructures with large misfit(ε>0.08) the crystallographic tilt of epitaxial layer is approximately proportional to the substrate miscut angle,while the elastic strain energy of the film will lead to the nucleation of dislocation,which contributes to step-flow growth mode.As for the heterostructures with small misfit(ε<0.04) the elastic strain energy will be released in the form of surface energy,and the surface profile of epitaxial film is dislocation-free island. When exposed to high undercooling,the substrate with large misfit and miscut angle will result in small-angle grain boundary between the substrate and the epitaxial layer.The small-angle grain boundary is composed of arranged dislocations,and it significantly changes the growth orientation of epitaxial layer.