Origin of the Stability of Ge(105) on Si: A New Structure Model and Surface Strain Relaxation

Fujikawa, Y.; Akiyama, Kazuo; Nagao, Tadaaki; Sakurai, T.; Lagally, M. G.; Hashimoto, Tamotsu; Morikawa, Yoshitada; Terakura, Kiyoyuki

doi:10.1103/physrevlett.88.176101

Cited by 106 publications

(97 citation statements)

References 21 publications

(31 reference statements)

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“…The PTMC study [10] indicates that the SR structure is the lowest surface energy even in the absence of strain, although there are several other reconstructions with very similar surface energies. It is interesting to note that the number of reported reconstructions for the (105) orientation has increased very rapidly from two (models SU and SR [13,14,15]), to a total of fourteen reported in Refs. [10,16].…”

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confidence: 99%

“…Since the interactions are modelled by empirical potentials, it is generally desirable to check the relative stability of different model structures using higher-level calculations based on density functional theory. Here we test the genetic procedure on the (105) surface, which, at least in conditions of compressive strain, is known to have a single-height rebonded step structure SR [13,14,15,16,17]. The PTMC study [10] indicates that the SR structure is the lowest surface energy even in the absence of strain, although there are several other reconstructions with very similar surface energies.…”

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confidence: 99%

“…The single-height rebonded structure SR [13,14,15] is retrieved in less than 400 mating operations. The SR model is in fact the global minimum for Si(105), as found recently in an exhaustive PTMC search [10].…”

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confidence: 99%

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Finding the reconstructions of semiconductor surfaces via a genetic algorithm

et al. 2004

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In this article we show that the reconstructions of semiconductor surfaces can be determined using a genetic procedure. Coupled with highly optimized interatomic potentials, the present approach represents an efficient tool for finding and sorting good structural candidates for further electronic structure calculations and comparison with scanning tunnelling microscope (STM) images. We illustrate the method for the case of Si (105), and build a database of structures that includes the previously found low-energy models, as well as a number of novel configurations.

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Finding the reconstructions of semiconductor surfaces via a genetic algorithm

et al. 2004

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“…2 More investigations followed, demonstrating that the Ge͑105͒ surface is indeed an optimal alternative to ͑001͒: owed to a peculiar rebonded-step ͑RS͒ reconstruction, the ͑105͒ surface energy competes with the ͑001͒ one, particularly so under the compressive-strain conditions experienced by Ge on Si. [3][4][5][6][7][8][9] In order to get more insights into the kinetics of ͕105͖ Ge islands growth, also Ge-adatom mobility at such facets was investigated, [10][11][12] and a step-flow model allowing for fast facet enlargement was proposed. 13 Nowadays it is well known that, despite the deposition of pure Ge on Si͑001͒, islands tend to be alloyed with temperature-dependent SiGe distributions.…”

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confidence: 99%

Si/Ge exchange mechanisms at the Ge(105) surface

Cereda

Montalenti

2010

Phys. Rev. B

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Kinetic pathways for Si adatoms incorporation into Ge͑105͒ are explored by density-functional theory. A very low activation energy ͑between ϳ0.6 and ϳ0.84 eV, depending on strain͒ for Si/Ge exchanges is found. Consequences on the Ge distribution within SiGe islands on Si͑001͒ are discussed, illustrating why the above processes can influence strain relaxation. Fast exchange processes are shown to take place also in the presence of Si ad-dimers, further facilitating the creation of a Ge floating layer under Si deposition, lowering the surface energy of the exposed facet.

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“…Moreover, molecular models using realistic semiconductor atomic potentials have provided better understanding of island stress distribution [34] and facet structures [35] in static calculations. Finally, first principles calculations focus on the statics of fewer atoms but are able to provide important estimates for the surface energies of relevant facets bounding the islands [36,37,38].…”

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confidence: 99%

Fast Kinetic Monte Carlo Simulation of Strained Heteroepitaxy in Three Dimensions

2008

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Accelerated algorithms for simulating the morphological evolution of strained heteroeptiaxy based on a ball and spring lattice model in three dimensions are explained. We derive exact Green's function formalisms for boundary values in the associated lattice elasticity problems. The computational efficiency is further enhanced by using a superparticle surface coarsening approximation. Atomic hoppings simulating surface diffusion are sampled using a multi-step acceptance-rejection algorithm. It utilizes quick estimates of the atomic elastic energies from extensively tabulated values modulated by the local strain. A parameter controls the compromise between accuracy and efficiency of the acceptance-rejection algorithm. PACS numbers:Epitaxial growth techniques enable deposition of a dislocation-free thin film on a substrate of a different material with a mismatched lattice constant. For film-substrate combinations such as Ge/Si, InAs/GaAs and InAs/InP, arrays of three-dimensional (3D) coherent islands self-assemble spontaneously beyond certain film thicknesses under appropriate growth conditions [1,2,3,4]. These studies are of much current interest since they are expected to find applications in future microelectronic devices.One of the most widely studied examples is Ge/Si(100) with a 4% lattice misfit. Relatively flat islands called pre-pyramids start to emerge at 3 monolayers (MLs) of Ge coverage [5,6,7]. Upon further deposition, they quickly grow into truncated pyramids bounded by four (105) facet planes on the sides and subsequently into fully grown pyramids which are also called hut islands. Upon still further deposition, they become dome islands bounded mainly by (113) facet planes. Finally, large dislocated islands appear. For the closely related alloy variant Si 1−x Ge x /Si(100) with a generally lower 4x% misfit, the development is rather similar and goes through stages characterized by ripples, hut islands, dome islands and finally dislocated islands [8,9,10]. The structures are however larger and each transition is postponed to occur at a larger film thickness. The islands are also more closely packed.Islands self-assemble because they can relieve the elastic stress in the heteroepitaxial films. There is theory for island formation that emphasizes nucleation. It suggests that islands must overcome an energy barrier associated with a critical size so that the elastic energy gained can balance the extra surface energy cost [11]. The theory is reasonably consistent with experiments at relatively high misfit. At low misfit, the critical island size and hence the energy barrier are expected to increase and make nucleation prohibitively difficult. Island formation mechanisms which do not have a barrier then offer a more promising explanation. For example, according to the Asaro-Tiller-Grinfeld (ATG) theory [12,13,14], strained surfaces are unstable at sufficiently long wavelengths. Therefore, shallow ripples first develop from small random initial perturbations and then into islands. For this mechanism to oper...

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Origin of the Stability of Ge(105) on Si: A New Structure Model and Surface Strain Relaxation

Cited by 106 publications

References 21 publications

Finding the reconstructions of semiconductor surfaces via a genetic algorithm

Finding the reconstructions of semiconductor surfaces via a genetic algorithm

Si/Ge exchange mechanisms at the Ge(105) surface

Fast Kinetic Monte Carlo Simulation of Strained Heteroepitaxy in Three Dimensions

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