生长铜膜中孪晶形成与出现几率的分子动力学模拟

运用分子动力学和静力学方法对(111)生长铜膜中孪晶形成的原子过程与能量进行了模拟研究.所用的原子间相互作用势为Finnis-Sinclair型镶嵌原子法(EAM)势.模拟和计算分析结果表明,(111)生长铜膜表面沉积原子在不同局部可形成正常排列的fcc畴或错排的hcp畴;沉积原子处于hcp位置时体系的能量比fcc位置时要高,其增量决定了孪晶面出现几率.沉积原子错排能还受相邻{111}孪晶面的影响,其间距小于3个原子层厚时,沉积原子错排能与不形成孪晶的Al晶体表面沉积原子错排能相当,此时形成孪晶面的几率极低;随间距的增加,表面沉积原子错排能迅速降低,在间距达到约12个原子层厚以后,降到略低于完整Cu晶体{111}表面的沉积原子错排能,这表明此时出现孪晶面的几率比在完整晶体表面形成一个新的孪晶面的几率要大.

MOLECULAR DYNAMICS SIMULATION OF FORMATION AND PROBABILITY OF TWINNING IN (111) GROWN COPPER FILMS

Molecular dynamics/statics study of the atom process and relevant energy for formation of the twins in (111) grown copper films have been carried out. An embedded atom method (EAM) potential of Finnis-Sinclair type was employed. The results show that the deposited atoms on (111) grown copper films can form fcc domains or hcp domains in different localities. When atoms deposited at hcp positions, the energy of the system is higher than that at fcc positions. The increment decides the probability of twin formation. It is further indicated that the mismatch energy of the deposited atom is greatly affected by previously formed {111} twin plane. When the distance between surface and the twin plane underneath is smaller than three atomic layers, the mismatch energy is as high as that for perfect crystal of aluminum which does not form twins in (111) growth, and hence the probability for formation of twin is very low. As the distance increases, the mismatch energy rapidly decreases, and even becomes slightly lower than that on {111} plane of perfect copper crystal after the distance reaches twelve atomic layers, implying that the probability for formation of twin plane is higher than that on {111} surface of perfect crystal.