STRUCTURE AND GROWTH OF CRYSTALLINE SUPERLATTICES - FROM MONOLAYER TO SUPERLATTICE
STRUCTURE AND GROWTH OF CRYSTALLINE SUPERLATTICES - FROM MONOLAYER TO SUPERLATTICE
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DOI：
10.1103/physrevb.33.3657
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发表时间：
1986-03-15
影响因子：
3.7
通讯作者：
VANDERMERWE, JH
中科院分区：
文献类型：
--
作者：
BAUER, E;VANDERMERWE, JH
我们讨论了理解晶体超晶格的结构和生长的基本物理现象：（i）由表面能，过饱和度和晶格失配确定的生长模式;和（ii）在（111）fcc/（110）bcc界面外延的局部情况下，外延取向对晶格匹配，原子键合和膜厚度的依赖性。为了均匀性，需要单层接单层[Frank-van der Merwe（FM）]生长。这可能会受到失配位错形成的不利影响。如果表面能γ A和γ B是相容的，在中等过饱和度下交替的A和B层可以实现连续的FM生长。认为在足够高的过饱和度下也有可能的建议是一种误解。目前情况下的主要外延取向--西山-瓦瑟曼（NW）和库尔德朱莫夫-萨克斯（KS）取向--之前已经单独在几何关系的（能量上合理的）基础上预测过。该模型的预测能力证明为六边形接口。理想情况下，为了预测生长（增厚）膜的结构和取向的演变，必须考虑原子力。我们通过薄膜的结晶度和谐性以及截断傅立叶级数吸附物-基底相互作用来模拟这些力。各种形式的均匀和振荡膜应变，影响取向和结构，图示。我们的结论是，超晶格形成的一个很好的指导方针是：（a）在适度的过饱和度下生长的金属对具有可比的γ在唯一的NW方向（0.8 <$B/a <$1.0，a和B是最近邻距离）;或者，可能的话，（B）沿着单向步骤的成核和生长。
We discuss the physical phenomena fundamental to the understanding of the structure and growth of crystalline superlattices:(i) the growth mode as determined by surface energies, supersaturation, and lattice misfit; and (ii) the dependence of epitaxial orientation on lattice matching, atomic bonding, and film thickness, in the topical case of epitaxy at (111) fcc/(110) bcc interfaces. For uniformity monolayer-by-monolayer [Frank–van der Merwe (FM)] growth is desirable. This may be adversely affected by the formation of misfit dislocations. Continued FM growth may be achieved with alternate A and B layers at moderate supersaturation, provided that the surface energies γ A and γ B are compatible. The suggestion that it is possible otherwise at sufficiently high supersaturation is a misconception. The main epitaxial orientations in the present case—the Nishiyama-Wassermann (NW) and the Kurdjumov-Sachs (KS) orientations—have been previously predicted on the (energetically justified) basis of geometrical relationships alone. The predictive power of this model is demonstrated for hexagonal interfaces. Ideally, to predict the evolution of the structure and orientation of a growing (thickening) film atomic forces must be allowed for. We model these forces by means of crystallinity and harmonicity of film, and by a truncated–Fourier-series adsorbate-substrate interaction. Various forms of homogeneous and oscillatory film strains, affecting orientation and structure, are illustrated graphically. We conclude that a good guideline for superlattice formation is the following:(a) growth at moderate supersaturations of metal pairs with comparable γ’s in the unique NW orientation (0.8≲ b/a≲ 1.0, a and b are nearest-neighbor distances); or, possibly,(b) nucleation and growth along unidirectional steps.