Growth mechanisms in Ge/Si(111) heteroepitaxy with and without Bi as a surfactant

Paul, Neelima; Asaoka, Hidehito; Mysliveček, Josef; Voigtländer, Bert

doi:10.1103/physrevb.69.193402

Cited by 24 publications

(12 citation statements)

References 24 publications

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“…Secondly, we Ge/Ge(1 1 1)-(7 · 7) 290 0.090 5.5 ± 1 Ge/Ge(1 1 1)-(5 · 5) 290 0.090 5.9 ± 1 found surface undulations on top of 3D islands indicative of a strain relieving dislocation network at the Si/Ge interface. The distance between the dislocation lines indicates a relaxation of $75% [17]. On the other hand the presence of the (7 · 7) reconstruction indicates that a small residual strain is still present [16].…”

Section: Resultsmentioning

confidence: 96%

Size of small Si and Ge clusters on Si(111) and Ge(111) surfaces

2005

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Section: Resultsmentioning

confidence: 96%

Size of small Si and Ge clusters on Si(111) and Ge(111) surfaces

2005

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“…In comparison with the islands of the pre-annealed surface, these islands are clearly facetted. The change in the surface morphology shows that the equilibrium minimum free energy configuration, even in presence of a surfactant, is a rough surface where 3D islanding is the preferred mode of strain relaxation [28]. …”

Section: Relaxed Mesa-like Islandsmentioning

confidence: 99%

Comparison between surfactant-mediated Bi/Ge/Si(111) epitaxy and Ge/Si(111) epitaxy

2004

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“…In standard surfactant mediated epitaxy, materials are deposited under a constant supply of the surfactant to maintain the ͑saturated͒ 1 ML surfactant coverage. 13,16 However, performing the Ge deposition in the standard way at F Ge = 0.08 ML/ min, T s = 450°C, and Bi flux F Bi = 3 ML/ min does not yield straight Ge nanowires of homogenous width. In Fig.…”

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Optimized Ge nanowire arrays on Si by modified surfactant mediated epitaxy

Romanyuk¹,

Mysliveček

Cherepanov³

et al. 2007

Phys. Rev. B

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We demonstrate the formation of Ge nanowire arrays on highly ordered kink-free Si stepped surfaces. The nanowires are grown using Bi surfactant mediated epitaxy. The nanowires are single crystalline and feature minimal kink densities, allowing them to span lengths larger than 1 m at a width of Ϸ4 nm. To achieve desired growth conditions for the formation of such nanowire arrays, we explore a full parameter space of surfactant mediated epitaxy. We show that controlling the surfactant coverage in the surface and/or at step edges modifies the growth properties of surface steps in a decisive way. DOI: 10.1103/PhysRevB.75.241309 PACS number͑s͒: 61.46.Ϫw, 81.16.Dn, 81.15.Hi, 68.37.Ef In order to fabricate ever-smaller nanoscale device structures, there is an enormous interest in finding ways to build devices from the bottom up rather than fabricate from the top down. Using the bottom-up approach, the size of the structures is not limited by lithography; however, the uniformity and the ability to position the nanostructures are still challenges. Specifically, nanowires are desirable as nanoscale interconnects.1 One of the concepts followed in the bottom-up formation of nanowire arrays is to create a highly ordered atomic-step template on a vicinal single-crystal surface and to form the wires along the step edges, decorating the step edges with a selected material.2-4 A suitable template is the vicinal surface of a Si͑111͒ single crystal, since the structure of the step train on this surface can be controlled to a large extent. [5][6][7] Steps on Si͑111͒ vicinal surfaces have been decorated by metals, 3,8 semiconductors, 4,9 and organic molecules. 10 The challenge is to improve the homogeneity of the nanowire array and the crystallinity and the aspect ratio of the wires.Recently, we made two contributions to these efforts. First, we developed a method to grow high-aspect-ratio single-crystalline Ge nanowires at Si͑111͒ step edges. 4 We used surfactant mediated epitaxy 9 where the surfactant ͑Bi͒ always floats at the growth front, covering both the Si surface and the Ge nanowires. The surfactant prevented mutual Ge-Si intermixing and mediated a chemical contrast between Si and Ge, allowing observation of the lateral Ge-Si nanostructures in a scanning tunneling microscope ͑STM͒. Second, we developed a method to obtain an improved ordering of the step train on the Si͑111͒-7 ϫ 7 surface by precise mechanical polishing of Si wafers and subsequent controlled annealing in vacuum. 7 We obtain surface steps that are kinkfree, atomically straight, and largely equidistant at scales of 1 ϫ 1 m 2 ͓Figs. 1͑a͒ and 1͑b͔͒. 7In this work we show how it is possible to create a highly ordered array of Ge nanowires on the Bi-covered Si͑111͒ surface ͓Figs. 1͑c͒-1͑f͔͒. A straightforward combination of the above two techniques 4,7 does not yield the desired result. The important point is to conserve the long-range order of the initial Si template, which is usually lost during the nanowire preparation process using standard surfactant media...

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Growth mechanisms in Ge/Si(111) heteroepitaxy with and without Bi as a surfactant

Cited by 24 publications

References 24 publications

Size of small Si and Ge clusters on Si(111) and Ge(111) surfaces

Size of small Si and Ge clusters on Si(111) and Ge(111) surfaces

Comparison between surfactant-mediated Bi/Ge/Si(111) epitaxy and Ge/Si(111) epitaxy

Optimized Ge nanowire arrays on Si by modified surfactant mediated epitaxy

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