Nanodot to nanowire: A strain-driven shape transition in self-organized endotaxial CoSi2 on Si(100) (original) (raw)

Growth mechanisms for wire-like epitaxial gold silicide islands on Si(1 1 0) surfaces

Applied Surface Science, 2011

Epitaxial islands grown on various substrates are usually strained because of differences in lattice constants of the materials of the island and the substrate. Shape transition in the growth of strained islands has been proposed as a mechanism for strain relief and a way to form self-organized quantum wires. Shape transition usually leads to an elongated island growth. However, an elongated island growth may also be due to an anisotropic diffusion of material, the anisotropy being imposed by the symmetry of the substrate surface. In the present example, growth of gold silicide wire-like nanostructures on a Si(1 1 0) surface has been investigated by photoemission electron microscopy (PEEM). Growth of elongated unidirectional gold silicide islands, with an aspect ratio as large as 12:1, has been observed by PEEM following gold deposition on the Si substrate and subsequent annealing at the Au-Si eutectic temperature. Distribution of the width and the length of the gold silicide islands as a function of island area shows a feature similar to that for the shape transition. However, detailed investigations reveal that the elongated growth of gold silicide islands is rather mainly due to anisotropic diffusion of gold due to the twofold symmetry of the (1 1 0) surface of the Si substrate.

Self-organized trench–island structures in epitaxial cobalt silicide growth on Si(111)

Surface Science, 2014

Sub-monolayer Co deposition on clean Si(111)-(7 × 7) surfaces has been found to form nanoscale CoSi 2 islands with a surrounding trench of one Si bilayer depth and mainly hexagonal shape. The trench surface structure is largely like that of the disordered '1×1' phase of the Si(111)-7×7↔'1×1' phase transition and comprises mostly disordered Si adatoms with small ordered patches of (11 × 11), (9 × 9), c(5 × √5), c(4 × 4) and (2 × 2) structures along with some Co-ring clusters. This disordered '1 × 1' structure within the trench has formed at 600°C, the growth temperature of CoSi 2 in reactive deposition epitaxy, much below the order-disorder phase transition temperature on Si(111)-(7 × 7). The structure around the trench remains (7 × 7). Electronically the trench is semiconducting. The surrounding 7 × 7 structure being metallic, the island-trench structure forms a lateral metal-semiconductor-metal structure.

Hug-like island growth of Ge on strained vicinal Si (111) surfaces

We examine the structure and the evolution of Ge islands epitaxially grown on vicinal Si(111) surfaces by scanning tunneling microscopy. Contrary to what is observed on the singular surface, three-dimensional Ge nanoislands form directly through the elastic relaxation of step-edge protrusions during the unstable step-flow growth. As the substrate misorientation is increased, the islands undergo a shape transformation which is driven by surface energy minimization and controlled by the miscut angle.

Self-organized epitaxial growth on spontaneously nano-patterned templates

Comptes Rendus Physique, 2005

Self-ordering at crystal surfaces has been the subject of intense efforts during the last ten years, since it has been recognized as a promising way for growing uniform nanostructures with regular sizes and spacings in the 1-100 nm range. In this article we give an overview of the self-organized nanostructures growth on spontaneously nano-patterned templates. A great variety of surfaces exhibits a nano-scale order at thermal equilibrium, including adsorbate-induced reconstruction, surface dislocations networks, vicinal surfaces or more complex systems. Continuum models have been proposed where long-range elastic interactions are responsible for spontaneous periodic domain formation. Today the comparison between experiments such as Grazing Incidence X-Ray Diffraction experiments and calculations has lead to a great improvement of our fundamental understanding of the physics of self-ordering at crystal surfaces. Then, epitaxial growth on self-ordered surfaces leads to nanostructures organized growth. The present knowledge of modelization of such an heterogeneous growth using multi-scaled calculations is discussed. Such a high quality of both long-range and local ordered growth opens up the possibility of making measurements of physical properties of such nanostructures by macroscopic integration techniques. To cite this article: S. Rousset et al., C. R. Physique 6 (2005).  2004 Académie des sciences. Published by Elsevier SAS. All rights reserved.

Structural study of epitaxial growth on silicon surfaces

Thin Solid Films, 1996

Surface structures during silicon growth on an Si (Ill) 7X 7 surface were investigated by reflection high-energy electron diffraction (RHEED) and scanning tunnelling microscopy (8TM). From ananalysis ofRHEED intensity rocking curves and oscillations, we conclude that a dimer-adatorn-stacking fault (DAS) structure with 5X 5 periodicity and a metastable pyramidal cluster-type structure are formed on terraces during growth, and a7X7 DAS structure grows from step edges. From STM observations ofisolated silicon islands onSi (111)7X7 athigh temperatures, itisfound that stable small islands with a5X5 DAS structure are formed, but 7X7islands are mostly unstable, Therefore it is believed that the formation ofa 5X5 structure during growth isdue to the stability ofthe small islands. Inaddition, the formation ofthe metastable structure promotes successive epitaxial growth accompanied by slacking fault dissolution inthe dimer-stacking fault framework.

Mechanism of self-limiting epitaxial growth on nonplanar substrates

Journal of Crystal Growth, 1999

We have developed an analytic model that explains the self-ordering of nanostructures taking place during epitaxial growth on corrugated substrates. The growth rate transients leading to self-limiting growth are due to lateral gradients of the surface chemical potential on the nonplanar surface pro"le. Chemical potential variations due to both surface curvature and nonuniform alloy composition (related to the entropy of mixing) are considered. We show that a necessary condition for obtaining a self-limiting growth inside a groove or on top of a ridge is the occurrence of growth rate anisotropy between the sidewalls and the bottom or top facets, respectively. The model explains the di!erent self-limiting growth behavior observed in molecular beam epitaxy and organometallic chemical vapor deposition on corrugated surfaces of di!erent orientations.