Self-ordering of Ge islands on step-bunched Si(111) surfaces

Sgarlata, A.; Szkutnik, Pierre-David; Balzarotti, A.; Motta, Nunzio; Rosei, Federico

doi:10.1063/1.1626260

Cited by 65 publications

(49 citation statements)

References 22 publications

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“…Examples of templates based on nanostructured surfaces are the striped periodic nanograting produced by the partial nitrogen reconstruction on Cu(001) and oxygen reconstruction of Cu (110) (discussed in Sect. 3), the self-organization of semiconductor islands on step-206 F. Cicoira et al bunched Si(111) [17,18], and the ordered growth of magnetic dots on stepped surfaces [19,20]. The most powerful and versatile technique to study the assembly of organic molecules at surfaces is scanning tunneling microscopy (STM).…”

Section: Introductionmentioning

confidence: 99%

Two-Dimensional Nanotemplates as Surface Cues for the Controlled Assembly of Organic Molecules

Cicoira

Santato

Rosei

2008

Topics in Current Chemistry

108

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Section: Introductionmentioning

confidence: 99%

Two-Dimensional Nanotemplates as Surface Cues for the Controlled Assembly of Organic Molecules

Cicoira

Santato

Rosei

2008

Topics in Current Chemistry

108

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“…[1][2][3][4]6 For example, Si magic clusters and self-assembled metal nanostructures confined in a UC over the Si͑111͒-7 ϫ 7 surface have been extensively studied. [3][4][5][6][7][8][9][10][11][12][13][14] In addition, there are many reports on the initial Ge growth in the UC of Si͑111͒-7 ϫ 7 accompanied by the formation of clusters with various shapes and sizes at submonolayer coverages, 3,4,[13][14][15][16][17][18][19][20] followed by Stranski-Krastanov ͑SK͒ growth mode with increasing Ge coverage owing to Si-Ge lattice mismatch.At present, there is a considerable controversy regarding the initial Ge adsorption site and the bonding coordination over the Si͑111͒-7 ϫ 7 surface. Dev et al have performed x-ray standing wave measurements at submonolayer Ge coverage and proposed that Ge adatoms directly bond to Si adatoms and rest atoms.…”

mentioning

confidence: 99%

Evidence of temperature dependence of initial adsorption sites of Ge atoms on Si(111)-7×7

Ansari

Tomitori

Arai

2006

Applied Physics Letters

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Small amounts of Ge atoms are deposited on Si͑111͒-7 ϫ 7 surfaces at room temperature ͑RT͒ and at 100°C to clarify the initial adsorption sites using scanning tunneling microscopy. At RT Ge atoms are adsorbed at high coordination B 2 sites around the rest atoms, as predicted by Cho and Kaxiras ͓Surf. Sci. 396, L261 ͑1998͔͒. On one hand, at 100°C Ge atoms are adsorbed on corner adatom sites. With increasing Ge coverage the corner sites are gradually occupied, followed by Ge adsorption at center adatom sites, resulting in Ge cluster growth with a size of the half unit cell. © 2006 American Institute of Physics. ͓DOI: 10.1063/1.2198109͔The stable periodic structure of a Si͑111͒-7 ϫ 7 surface with a comparatively large size unit cell ͑UC͒ offers a good template for fabricating self-assembled nanostructures. [1][2][3][4]6 For example, Si magic clusters and self-assembled metal nanostructures confined in a UC over the Si͑111͒-7 ϫ 7 surface have been extensively studied. [3][4][5][6][7][8][9][10][11][12][13][14] In addition, there are many reports on the initial Ge growth in the UC of Si͑111͒-7 ϫ 7 accompanied by the formation of clusters with various shapes and sizes at submonolayer coverages, 3,4,[13][14][15][16][17][18][19][20] followed by Stranski-Krastanov ͑SK͒ growth mode with increasing Ge coverage owing to Si-Ge lattice mismatch.At present, there is a considerable controversy regarding the initial Ge adsorption site and the bonding coordination over the Si͑111͒-7 ϫ 7 surface. Dev et al. have performed x-ray standing wave measurements at submonolayer Ge coverage and proposed that Ge adatoms directly bond to Si adatoms and rest atoms. 12 However, using first principles density-functional theory ͑DFT͒ calculations, Cho and Kaxiras suggested that a bridge ͑B 2 ͒ site among the high coordination sites has the minimum energy for Ge adsorption, even compared to those of Ge adatoms bounded with dangling bond of adatoms and rest atoms. 21 On the other hand, Wang et al. 20 explored the Ge adsorption over Si adatom sites in detail as well as sites other than the B 2 site. They concluded that Ge atoms are replaced with Si adatoms, and the kickedout Si atoms migrate to near B 2 sites within a basin on a half unit cell ͑HUC͒: This is in agreement with earlier reports. 3,4,15,20 In this letter we report on the initial stages of Ge adsorption on Si͑111͒-7 ϫ 7 at room temperature ͑RT͒ and at 100°C, which are observed by scanning tunneling microscopy ͑STM͒. The results show that Ge atoms are adsorbed over B 2 sites at RT, while they are adsorbed at corner adatom sites at 100°C by being presumably replaced with the Si adatoms, preferably over a faulted half unit cell ͑FHUC͒.Experiments were performed using a homemade ultrahigh vacuum ͑UHV͒ STM having a base pressure Ͻ2 ϫ 10 −11 Torr, equipped with a field emission microscope 22 ͑FEM͒ to evaluate STM tips, and with a resistive-type Ge evaporation source. N-type Sb-doped Si͑111͒ substrates were used ͑thickness= 375 m, = 0.02 ⍀ cm͒. Clean Si͑111͒-7 ϫ 7 surfaces were prepared by the ...

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“…[1][2][3] Quantum confinement effect in these islands is useful for optoelectronic device applications based on the Si technology. [3][4][5][6][7][8][9][10][11][12][13][14][15] The homoepitaxial Si/Si growth is also important because isotopically controlled Si structures are expected to serve as building blocks of novel application devices, such as a quantum computer utilizing Si nuclear spin. 16 Himpsel and co-workers have experimentally demonstrated that vicinal Si͑111͒ surfaces can serve as templates for self-assembly of one-dimensional ͑1D͒ nanostructures, 17,18 because a regular array of straight steps can be obtained on these surfaces.…”

Section: Introductionmentioning

confidence: 99%

Self-assembly of periodic nanoclusters of Si and Ge along atomically straight steps of a vicinal Si(111)

Sekiguchi

Yoshida

Shiren

et al. 2007

Journal of Applied Physics

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The very initial stage of the molecular beam epitaxy of Si and Ge on Si͑111͒ −7ϫ 7 substrates with atomically straight steps has been studied by scanning tunneling microscopy and spectroscopy. The atomically straight steps have been prepared on a miscut Si͑111͒ substrate by annealing at 830°C with kink-up direct current. The length of the steps can be maximized by selecting a proper annealing time. The steps have a well-defined U͑2, 0͒ step-edge structure. The growth of both Si and Ge at temperatures between 250 and 400°C starts with formation of a single-adatom-row nanowire ͑0.67 nm in width͒ along the lower edge of each U͑2, 0͒ step. Subsequent growth of Si and Ge at temperatures between 250 and 300°C results in formation of one-dimensional arrays of nanoclusters ͑less than 2.0 nm in width͒ in the unfaulted halves of the 7 ϫ 7 structure along the upper step edges. Scanning tunneling spectroscopy reveals localized electronic states of the nanoclusters. Differences between the growth of Si and Ge nanoclusters are discussed.

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Self-ordering of Ge islands on step-bunched Si(111) surfaces

Cited by 65 publications

References 22 publications

Two-Dimensional Nanotemplates as Surface Cues for the Controlled Assembly of Organic Molecules

Two-Dimensional Nanotemplates as Surface Cues for the Controlled Assembly of Organic Molecules

Evidence of temperature dependence of initial adsorption sites of Ge atoms on Si(111)-7×7

Self-assembly of periodic nanoclusters of Si and Ge along atomically straight steps of a vicinal Si(111)

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