Unique features of laterally aligned GeSi nanowires self-assembled on the vicinal Si (001) surface misoriented toward the [100] direction

Abstract

We demonstrate laterally aligned and catalyst-free GeSi nanowires (NWs) via self-assembly of Ge on miscut Si (001) substrates toward the [100] direction by an angle θ (θ < 11°). The NWs are bordered by (001) and (105) facets, which are thermodynamically stable. By tuning the miscut angle θ, the NW height can be easily modulated with a nearly constant width. The thickness of the wetting layer beneath the NWs also shows a peculiar behavior with a minimum at around 6°. An analytical model, considering the variation of both the surface energy and the strain energy of the epilayer on vicinal surfaces with the miscut angle and layer thickness, shows good overall agreement with the experimental results. It discloses that both the surface energy and stain energy of the epilayer on vicinal surfaces can be considerably affected in the same trend by the surface steps. Our results not only shed new light on the growth mechanism during heteroepitaxial growth, but also pave a prominent way to fabricate and meanwhile modulate laterally aligned and dislocation-free NWs.

Surface step terrace tuned microstructures and dielectric properties of highly epitaxial CaCu3Ti4O12 thin films on vicinal LaAlO3 substrates

“…1(c). The sizes of the nanosteps will be determined by the miscut angle and the surface step terrace energy under different growth temperatures2829.…”

Entropy-controlled fully reversible nanostructure formation of Ge on miscut vicinal Si(001) surfaces

“…On vicinal surfaces, the four-fold symmetry of the Si (001) surface is broken and as a result, asymmetric nanostructures are created [14,22,[34][35][36]. In the extreme case, one-dimensional nanowires are formed [34,37] that can be parallel [38,39] or perpendicular [40,41] to the miscut direction. It is noted that similar 1D structures can be obtained by prepattering of the substrate surface [42,43] or by anisotropic incorporation of adatoms, in which case, micrometer long Ge hut nanowires [44,45] can be produced.…”

Formation of Self-Connected Si0.8Ge0.2 Lateral Nanowires and Pyramids on Rib-Patterned Si(1 1 10) Substrate

“…Nevertheless, there has not been any convenient solution available to transfer/arrange these vertically grown nanowires yet, which limits its potential application in microelectronics [6]. On the other hand, recently laterally aligned heteroepitaxial in-plane Ge nanowires on Si substrate have been regarded as an alternative solution on both singular [8–12] and miscut [13, 14] Si (0 0 1) and Si (1 1 1) [15, 16] substrates, especially the Si (1 1 10) surface [17–19], where the lateral nanowires can naturally extend along the [5 5 −1] direction. The mechanism behind the formation and stability of these nanowires are attributed to abnormal faceting of the wetting layer [6, 13] or extended huts [10, 20], which is driven by the low surface energy of their {1 0 5} side facets under equilibrium phase.…”

“…On the other hand, recently laterally aligned heteroepitaxial in-plane Ge nanowires on Si substrate have been regarded as an alternative solution on both singular [8–12] and miscut [13, 14] Si (0 0 1) and Si (1 1 1) [15, 16] substrates, especially the Si (1 1 10) surface [17–19], where the lateral nanowires can naturally extend along the [5 5 −1] direction. The mechanism behind the formation and stability of these nanowires are attributed to abnormal faceting of the wetting layer [6, 13] or extended huts [10, 20], which is driven by the low surface energy of their {1 0 5} side facets under equilibrium phase. These lateral nanowires have shown potential applications for nano-electronics [10, 21], spintronic devices [22, 23], and optoelectronics [24, 25].…”