Composition redistribution of self-assembled Ge islands on Si (001) during annealing

Lee, S.W.; Chang, Hsiang-Szu; Lee, C.H.; Cheng, Sheng-Tzong; C, Liu

doi:10.1016/j.tsf.2009.10.087

Cited by 9 publications

(8 citation statements)

References 20 publications

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“…1(c). This crescent shaped Ge-core has been observed experimentally by Lee et al 36 Experimentally, the Si-capping layer is used not only to prevent Ge atoms from being oxidized during the control oxide growth, 8 but also to preserve the dome shape and size during growth. 60,61 Prior experimental studies of Ge-Si heterostructures demonstrated sharp interfaces with minimal intermixing.…”

Section: Introductionsupporting

confidence: 58%

“…[29][30][31][32][33] Researchers have recently been successful in fabricating high quality Ge-Si NCs of different lateral dimensions and shapes in both single and multiple layers. 19,[34][35][36][37] Of the various experimentally observed NC shapes, hut-shaped and dome-shaped Ge-Si NCs have unique electronic and optical properties. 38 Dome-shaped Ge-Si NCs with the curved bounding facets can relieve strain more efficiently compared to the hut, pyramid, or ring shaped NCs.…”

Section: Introductionmentioning

confidence: 99%

“…30 A decrease in the aspect ratio corresponds to a morphological transition from a dome to an energetically favorable superdome resulting from excessive Ge deposition. 36,53,54 Recently, good control over the height of a Ge-Si NC system has been demonstrated with less control over the diameter. [55][56][57][58][59] This motivates our study of the diameter dependent properties of Ge-Si NCs.…”

Section: Introductionmentioning

confidence: 99%

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Effect of strain on the electronic and optical properties of Ge–Si dome shaped nanocrystals

Neupane

Rahman

Lake

2015

Phys. Chem. Chem. Phys.

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The effects of strain and confinement on the energy levels and emission spectra of dome-shaped, Ge-core-Si-shell nanocrystals (NCs) with diameters ranging from 5 to 45 nm are investigated with atomistic models. For NCs with base diameters ≥15 nm, the strain-induced increase in the energy gap is ∼100 meV. The increase in the energy gap is primarily the result of the downward shift in the occupied states confined in the Ge core. The fundamental energy gap varies from 960 meV to 550 meV as the NC diameter increases from 5 nm to 45 nm. Confinement and strain break the degeneracy of the lowest excited state and split it into two states separated by a few meV. For the smaller NCs, one of these states can be localized in the Si core and the other state can be in the Si cap. For diameters ≥20 nm, both of these states are localized in the Si cap. The electronic states are calculated using an atomistic sp(3)d(5)s* tight-binding model including spin-orbit coupling, and geometry relaxation is performed using a valence force field model.

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Section: Introductionsupporting

confidence: 58%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Effect of strain on the electronic and optical properties of Ge–Si dome shaped nanocrystals

Neupane

Rahman

Lake

2015

Phys. Chem. Chem. Phys.

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“…18,19 A further increase in the QD volume even results in the appearance of dislocated superdomes as a result of strain relaxation by dislocation injection. Also during the growth of thin-lm-like SK QD materials, too thin a Si spacer or excessive Ge deposition is prone to Ge QDs coarsening and defect generation, 20,21 thus deteriorating the TE performance. Another challenge on TE materials is accurate tailoring of TE properties of thin-lm-like QD materials with high spatial resolution which is crucial for thermal management of nanoelectronics, or for nanoscale energy conversion.…”

Section: Introductionmentioning

confidence: 99%

Designer Ge/Si composite quantum dots with enhanced thermoelectric properties

2014

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An otherwise random, self-assembly of Ge/Si composite quantum dots (CQDs) on Si was controlled by inserting a layer of Si, sub-dot stacks, and post-annealing to produce micron-scale-thick QD layers with desired QD morphology, interface density, and composition distribution. A heterostructure consisting of a deliberate insertion of Si between Ge sub-dots is shown to improve the epitaxial coherence of the Ge QDs by suppression of the Ge surface interdiffusion and coarsening. As compared to regular-QD materials, the thin-film-like multifold-CQD materials are found to exhibit both reduced cross-plane thermal conductivity and enhanced electrical conductivity, and 1.5 times higher ZT value by calculation, providing a promising building block for practical thermoelectric applications in micro- or nanoelectronics.

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“…[13][14][15] Many different isocompositional profiles have been discovered and explained by different island-formation mechanisms. [16][17][18] In this work, utilizing this technique, we observed that the etched Ge/Si/Ge islands exhibited pyramid structures, which differed from the ring-like isocompositional profiles observed in conventional Ge islands. We attempt to elucidate the possible islandformation mechanism on the basis of low surface diffusivity and strain adjustment of the thin Si layer in composite islands.…”

mentioning

confidence: 79%

Formation Mechanism of Self-Assembled Ge∕Si∕Ge Composite Islands

Lee

Chang

et al. 2011

J. Electrochem. Soc.

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This study investigated the formation mechanism of Ge/Si/Ge composite islands on Si(001) using a combination of selective wet chemical etching, atomic force microscopy and high-resolution transmission electron microscopy. After upper Ge-rich parts were removed by selective etching, the etched Ge/Si/Ge composite islands exhibited pyramid structures, which differed from the ring-like isocompositional profiles observed in conventional Ge islands. Experimental results demonstrated that the multilayered Ge/Si/Ge composite islands were almost defect-free and suffered from a serious SiGe intermixing during growth. The shape and size distribution of composite islands can be further controlled by tuning the island parameters. We elucidate these phenomena on the basis of low surface diffusivity and strain adjustment of the thin Si layer in composite islands. These composite islands were also found to exhibit an apparent enhancement and blueshift in photoluminescence emission. These results indicated that Ge/Si/Ge composite islands would be potentially useful as an optoelectronic material operating in the telecommunication range.

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Composition redistribution of self-assembled Ge islands on Si (001) during annealing

Cited by 9 publications

References 20 publications

Effect of strain on the electronic and optical properties of Ge–Si dome shaped nanocrystals

Effect of strain on the electronic and optical properties of Ge–Si dome shaped nanocrystals

Designer Ge/Si composite quantum dots with enhanced thermoelectric properties

Formation Mechanism of Self-Assembled Ge∕Si∕Ge Composite Islands

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