摘要:
采用基于壳模型的分子动力学模拟方法,研究了存在外延压应变时BaTiO3铁电体的辐射位移效应,以O原子作为初冲原子(primary knock-on atom, PKA),能量为1 keV,方向为[001],分别计算了外延压应变为0,0.4%,0.8%,1.2%,1.6%,2.0%时体系的缺陷数量、分布,以及辐射前后的极化强度,比较了压应变为2%以及无应变下损伤区域、缺陷离位距离和反向外电场下PKA的迁移距离.结果表明,随外延压应变增加体系极化近似线性增加,辐射后极化降低幅度降低、缺陷产生的数量有所减小,2%压应变存在时缺陷原子的离位距离、PKA在反向外电场作用下的迁移距离和损伤区域都小于无应变的情况,说明外延压应变的存在对辐射造成的晶格损伤具有抑制作用,对辐射损伤具有改善作用,可以通过引入外延压应变来调控BaTiO3的辐射损伤.
Abstract:
Radiation displacement effect of BaTiO3 ferroelectric under epitaxial compressive strain is studied by using molecular dynamics simulations which is based on shell model. The numbers of defects, distributions and changes of polarization in the system are calculated before and after radiation under epitaxial compressive strains of 0, 0.4%, 0.8%, 1.2%, 1.6%, 2.0%respectively by using O atom of 1 keV and [001] direction as a primary konck-on atom (PKA). The damaged areas, the displacement distances of the defect, and migration distances of PKA under reverse applied electric field, obtained in the two cases: 2% compressive strain and no strain, are compared. The results show that the polarization of system increases almost linearly with increasing the epitaxial compressive strain, and that both the polarization amplitude and the number of defects decrease after irradiation. The displacement distance of defects under 2% compressive strain, migration distance of PKA under reverse applied electrical field and damaged area are all smaller than under no strain condition, which indicates that epitaxial compressive strain can suppress lattice irradiation damage, and the damage in BaTiO3 can be tuned by introducing epitaxial compressive strain.
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