Formation of island chains in SiGe/Si heteroepitaxy by elastic anisotropy

Meixner, M.; Schöll, Eckehard; Schmidbauer, M.; Raidt, H.; Köhler, R.

doi:10.1103/physrevb.64.245307

Cited by 61 publications

(37 citation statements)

References 14 publications

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“…An averaged island base of 130 nm along a mean island height of 65 nm yields a geometric aspect ratio base vs. height of two. Moreover, the islands self-assemble in a strain-driven process into extended chains along the elastically soft h1 0 0i directions [7]. Naturally scattering from nanoscale objects is expected to appear rather weak in contrast to bulky objects.…”

Section: Methodsmentioning

confidence: 99%

On the various impact of chemical composition and elastic strain in SiGe nanoscale islands to the diffuse X-ray scattering

Hanke

Boeck

2006

Physica E: Low-dimensional Systems and Nanostructures

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High-resolution X-ray diffraction in combination with kinematical scattering simulations based on finite element calculations for the elastic strain field has been utilized to investigate the chemical composition of SiGe/Si(0 0 1) Stranski-Krastanov islands. Therefore, the intensity distribution in the vicinity of the symmetric (0 0 4) reflection has been three dimensionally measured and compared with respective simulations. Around an asymmetrical reflection, e.g. Si(1 1 3), the impact of lateral and vertical strain tensor components on the diffraction pattern decouples. This allows to distinguish between tetragonally distorted regions at the island bottom and elastically relaxed unit cells of cubic shape at the island apex in accordance with finite element calculations. Artificially switching off and on the various scattering abilities of silicon and germanium in otherwise equivalent simulations yields practically no difference in the resulting scattering. Thus, at X-ray energies far from absorption edges, the diffuse scattering is dominated by elastic strain which is caused by the chemical profile. r

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Section: Methodsmentioning

confidence: 99%

On the various impact of chemical composition and elastic strain in SiGe nanoscale islands to the diffuse X-ray scattering

Hanke

Boeck

2006

Physica E: Low-dimensional Systems and Nanostructures

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“…It may also arise due to the fact that the stress inhomogeneities induced by the islands lead to a local increase in the strain at the island edge. In fact, finite element calculations show that the strain close to an island 17,18 can be twice as high as the nominal mismatch. This strain concentration at the island edge would increase E, pushing the system into regime IB.…”

Section: Comparison To Experimentsmentioning

confidence: 99%

“…In general E is a function of the strain, and near islands the strain is enhanced 17,18 . However, as discussed in the introduction, the analysis presented here will focus on the effect of adatom concentrations.…”

Section: The Energetics Of Island and Pit Nucleationmentioning

confidence: 99%

“…There are two primary effects that could account for these inhomogeneities: a stress concentration near three-dimensional islands and a variation in adatom concentration on the surface. 16 The former effect has been studied using the finite element method, 17,18 but no analytical form of the strain in the film exists, which makes the integration of these results difficult. The latter effect, to our knowledge, has not been addressed in detail and provides the subject of our analysis.…”

Section: Introductionmentioning

confidence: 99%

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Pit nucleation in the presence of three-dimensional islands during heteroepitaxial growth

2004

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We present a model in which pit nucleation in thin films is considered to arise from a nearequilibrium nucleation process. In this model the adatom concentration plays a central role in controlling the morphological development of the surface. Although pits relieve elastic energy more efficiently than islands, pit nucleation can be prevented by a high adatom concentration.Three-dimensional islands act as adatom sinks and the lower adatom density in their vicinity promotes pit nucleation. Thermodynamic considerations predict several different growth regimes in which pits may nucleate at different stages of growth depending on the growth conditions and materials system. However direct comparisons to experimental observations require that kinetics be taken into account as well. The model predicts a wide range of possible morphologies: planar films, islands alone, islands nucleation followed by pit nucleation, and pits alone. The model shows good agreement with experimental observations in III-V systems given the uncertainties in quantifying experimental parameters such as the surface energy.

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“…Here, the elastic energy present at heteroepitaxial strained layer growth is decreased by the formation of nanoscale islands allowing for elastic strain relaxation. This process is often accompanied by lateral, 2,3 vertical, 4 or even three-dimensional 5 positional correlation. Structural investigations of QDs usually start with direct imaging techniques such as scanning electron microscopy, atomic force microscopy and transmission electron microscopy.…”

Section: Introductionmentioning

confidence: 99%

Lateral correlation of SiGe Stranski-Krastanow islands on silicon as probed by high resolution x-ray diffraction

Hanke

Schmidbauer

Köhler

2004

Journal of Applied Physics

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We describe a procedure to consider the impact of lateral positional correlation of SiGe nanoscale islands onto the diffuse scattering within a high resolution x-ray diffraction experiment. The samples have been grown by means of liquid phase epitaxy which provides monodisperse island ensembles containing up to 10 9 equivalent objects. It is shown that a proper numerical simulation of the x-ray diffuse scattering pattern requires careful consideration of the partial coherence of x rays. An appropriate numerical procedure consists of coherent summation over sample areas with lateral dimensions as given by the coherence properties of the radiation and subsequent incoherent summation over a large enough number of such areas. For the given case an effective lateral coherence length of Ϸ1 m has been used, which is derived taking into account also the detector resolution. The according simulation is in good agreement with the experimentally observed x-ray diffuse intensity pattern.

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Formation of island chains in SiGe/Si heteroepitaxy by elastic anisotropy

Cited by 61 publications

References 14 publications

On the various impact of chemical composition and elastic strain in SiGe nanoscale islands to the diffuse X-ray scattering

On the various impact of chemical composition and elastic strain in SiGe nanoscale islands to the diffuse X-ray scattering

Pit nucleation in the presence of three-dimensional islands during heteroepitaxial growth

Lateral correlation of SiGe Stranski-Krastanow islands on silicon as probed by high resolution x-ray diffraction

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