In situ ultrahigh vacuum transmission electron microscopy studies of hetero-epitaxial growth I.

Hammar, Mattias; LeGoues, F. K.; Tersoff, J.; Reuter, M. C.; Tromp, R. M.

doi:10.1016/0039-6028(95)01068-8

Cited by 162 publications

(95 citation statements)

References 44 publications

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“…11,12,13 In the classical Stranski-Krastanow 14 ͑S-K͒ mode of coherent island formation, one material with a different lattice parameter and low interfacial energy is initially deposited on a substrate surface, layer by layer, forming a ''wetting layer''. When the wetting layer reaches a critical thickness ͓usually three to five monolayers for pure Ge on Si͑001͒, 3,15 island growth starts to partially release the mismatch strain energy between the epitaxial layer and the substrate. However, in the case of InAs/GaAs, recent investigations suggest that, for higher temperature growths, there is significant mass transport from both the wetting layer and the substrate to the islands.…”

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confidence: 99%

Strain relaxation by alloying effects in Ge islands grown on Si(001)

et al. 1999

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Transmission electron microscopy is used to study the morphology and the composition profile of ''pure'' Ge islands grown at high temperature on Si͑001͒ by molecular beam epitaxy. An alloying process, involving mass transport from the substrate to the islands during the island growth, was identified. It was found that, as a result of Si mass transport to the Ge islands, the island/substrate interface moves towards the substrate, and trenches form on the substrate surface around the islands. Reduction of the misfit strain at the island/substrate interface is the driving force for this process. ͓S0163-1829͑99͒00748-1͔Semiconductor quantum dots ͑QD's͒ are attracting increasing interest because of their significant optoelectronic properties. 1 Although QD's can be produced in many ways, the method of coherent island formation is of great importance for materials with large lattice mismatch ͑such as Ge͑Si͒/Si 2,3 and In x Ga 1Ϫx As/GaAs 4 because of the possible combination of the QD growth and semiconductor integration techniques. Of crucial importance in determining the optoelectronic properties of the QD's are the structural parameters of the QD's including the shape, size and composition. 5 Uniformity in and control over these parameters are a prerequisite for many applications. To achieve this goal, a complete understanding of the mechanism of the QD growth is necessary. Although many investigations have concentrated on the shape and size 6,7 and evolution 8,9,10 during the QD growth, relatively less attention has been paid to the composition. 11,12,13 In the classical Stranski-Krastanow 14 ͑S-K͒ mode of coherent island formation, one material with a different lattice parameter and low interfacial energy is initially deposited on a substrate surface, layer by layer, forming a ''wetting layer''. When the wetting layer reaches a critical thickness ͓usually three to five monolayers for pure Ge on Si͑001͒, 3,15 island growth starts to partially release the mismatch strain energy between the epitaxial layer and the substrate. However, in the case of InAs/GaAs, recent investigations suggest that, for higher temperature growths, there is significant mass transport from both the wetting layer and the substrate to the islands. 16 Furthermore, the wetting layer in InAs/GaAs systems has been reported to be an ͑In,Ga͒As alloy with temperature dependent composition. 17 The composition of the alloy wetting layer will certainly affect any subsequent island growth procedure. These points suggest that the classical S-K growth mechanism needs to be modified to explain the details of island growth. In this paper, we demonstrate evidence for mass transport from the Si substrate to the Ge islands during high temperature molecular beam epitaxy ͑MBE͒ growth of ''pure'' Ge islands on the Si͑001͒ substrate. The mass transport changes the composition of the islands, moves the Ge/Si interface below the original substrate surface, and forms a trench around each island. It is proposed that the driving force for this mechanism is a reduction...

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Strain relaxation by alloying effects in Ge islands grown on Si(001)

et al. 1999

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“…The remarkable effect is that the equilibrium shape ratio of the crystal drops during each dislocation introduction and then increases again leading to a sawtooth behavior. This phenomenon has been experimentally observed very recently, in situ, on growing silicongermanium systems [5,17]. The associated strain-stress sawtooth oscillations can easily be drawn too.…”

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confidence: 53%

Some Aspects of Coherent Epitaxial Deposits

Müller

Kern

1997

Microsc. Microanal. Microstruct.

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“…TEM studies have also been performed to study the initial growth of Ge films on Si. 7 In the initial growth of thin films, three types of growth can occur, depending on the surface free energy of the substrate (σ s ), surface free energy of the epilayer (σ f ) and the interface free energy (γ i ). If (σ f + γ i ) > σ s , the three dimensional island growth, called Volmer-Weber (VW) growth is favoured.…”

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confidence: 99%

Ultra thin films of nanocrystalline Ge studied by AFM and interference enhanced Raman scattering

et al. 2003

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Abstract. Initial growth stages of the ultra thin films of germanium (Ge) prepared by ion beam sputter deposition have been studied using atomic force microscope (AFM) and interference enhanced Raman scattering. The growth of the films follows Volmer-Weber growth mechanism. Analysis of the AFM images shows that Ostwald ripening of the grains occurs as the thickness of the film increases. Raman spectra of the Ge films reveal phonon confinement along the growth direction and show that the misfit strain is relieved for film thickness greater than 4 nm.

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In situ ultrahigh vacuum transmission electron microscopy studies of hetero-epitaxial growth I.

Cited by 162 publications

References 44 publications

Strain relaxation by alloying effects in Ge islands grown on Si(001)

Strain relaxation by alloying effects in Ge islands grown on Si(001)

Some Aspects of Coherent Epitaxial Deposits

Ultra thin films of nanocrystalline Ge studied by AFM and interference enhanced Raman scattering

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