硅晶体生长固液界面形貌研究

结合杰克逊界面理论、分子动力学模拟(MD)和密度泛函理论(DFT),对硅晶体(100)和(111)面生长过程中固液界面形貌进行研究,包括界面自由能变化、结构变化和生长位置吸附能等。通过杰克逊界面理论计算,发现(100)界面晶相原子和流体相原子在表面各占约50%时吉布斯自由能达到极小值,而(111)界面在表面占比约0%或100%时达到极小值,说明当热力学平衡时,(100)面趋向于粗糙面,(111)面趋向于光滑面;分子动力学模拟显示,随着生长的进行,初始光滑的固液界面在(100)面上会逐渐转变为粗糙界面,而(111)面则始终保持光滑界面生长;且在生长过程中,(100)面的生长速率明显高于(111)面,因为(100)面始终为粗糙面生长;DFT计算发现,(100)面上的所有生长位置吸附能接近,可以实现连续生长,(111)面吸附能则存在明显的差值,生长原子需要吸附在台阶处才能进行层状生长。

Study on Solid-liquid Interface Morphology of Silicon Crystal Growth

Combined with Jackson interface theory,molecular dynamics simulation(MD)and density functional theory(DFT),the solid-liquid interface morphology during the growth of silicon crystals(100)and(111)planes was studied,including changes in interface free energy,structure change and growth position adsorption energy.According to the calculation of Jackson interface theory,it is found that the Gibbs free energy of(100)interface crystal phase atom and fluid phase atom reaches a minimum value when they account for about 50%of the surface,while(111)interface reaches a minimum value when they account for about 0%or 100%of the surface,which indicates that(100)plane tends to rough surface and(111)plane tends to smooth surface when the thermodynamics is in equilibrium.Molecular dynamics simulations show that as growth progresses,the initial smooth solid-liquid interface at the(100)plane will gradually transform into a rough interface,while the(111)plane will always maintain a smooth interface growth.And during the growth process,the growth rate of the(100)plane is significantly higher than that of the(111)plane,because the(100)plane growth is always rough surface.DFT calculation shows that the adsorption energy of all growth on(100)plane is close,and continuous growth can be achieved,while the adsorption energy of(111)surface is stored in the obvious difference,the growth atoms need to be adsorbed on the steps to carry out layered growth.