Texture development mechanisms in ion beam assisted deposition
Texture development mechanisms in ion beam assisted deposition
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DOI：
10.1063/1.368794
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发表时间：
1998-11-01
影响因子：
3.2
通讯作者：
Srolovitz, DJ
中科院分区：
文献类型：
--
作者：
Dong, L;Srolovitz, DJ
对离子束辅助沉积 (IBAD) 进行三维分子动力学模拟，以确定多晶薄膜 IBAD 过程中晶体织构选择的机制。当离子束以法向入射轰击生长的薄膜时，会生长由[111]和[110]取向晶粒组成的面心立方双晶。随着薄膜生长，界定[111]和[110]晶粒的晶界相互靠近，最终夹断[111]晶粒，使得薄膜纹理从[111]和[110]的相等密度变为纯[110]。对在离子束存在下生长的单晶的检查显示出两个重要的效果：当离子束沿晶体的沟道方向取向时，离子束引起的表面原子溅射和离子束引起的损伤显着减少。第一个观察结果表明，沟道方向与离子束平行排列的晶粒比那些未排列的晶粒生长得更快。这导致薄膜厚度的颗粒与颗粒之间的变化，并且在生长过程中其幅度增加。厚度的变化会产生阴影效应，进一步减慢较不厚（不对齐）晶粒的生长，最终导致这些晶粒的夹断。第二个观察结果表明，沟道方向平行于离子束排列的晶粒内存储的能量将低于未排列的晶粒的能量。这种存储能量的差异（以晶体缺陷的形式）被证明会导致晶界迁移，这是一个相当于初次再结晶的过程。这两种效应都会导致薄膜生长过程中晶体结构的变化，并且在双晶模拟中都可以观察到。在规定的条件下哪种机制将占主导地位仍有待界定。 (C) 1998 年美国物理研究所。 [S0021-8979(98)01020-2]。
Three-dimensional molecular dynamics simulations of ion beam assisted deposition (IBAD) are performed to determine the mechanisms of crystallographic texture selection during the IBAD of polycrystalline films. A face centered cubic bicrystal consisting of [111] and [110] oriented grains is grown while an ion beam bombards the growing film at normal incidence. As the film grows, the grain boundaries delimiting the [111] and [110] grains move towards each other, eventually pinching off the [111] grain such that the film texture changes from equal densities of [111] and [110] to purely [110]. Examination of single crystals grown in the presence of ion beams shows two important effects: ion beam induced atomic sputtering from the surface and ion beam induced damage are significantly reduced when the ion beam is oriented along channeling directions of the crystals. The first observation suggests that grains with channeling directions aligned parallel to the ion beam grow more quickly than those where they are not aligned. This leads to grain-to-grain variations in the film thickness that increase in magnitude during growth. Variations in thickness result in a shadowing effect that further slows the growth of the less thick (nonaligned) grains-eventually leading to pinch-off of these grains. The second observation suggests that the stored energies within the grains with channeling directions aligned parallel to the ion beam will be lower than that of the nonaligned grains. This difference in stored energy (in the form of crystal defects) is shown to lead to grain boundary migration-a process equivalent to primary recrystallization. Both of these effects can lead to changes in crystallographic texture during film growth and both are observed in the bicrystal simulations. Which mechanism will dominate under a prescribed set of conditions remains to be delineated. (C) 1998 American Institute of Physics. [S0021-8979(98)01020-2].