Self-assembled nanodot arrays on<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi mathvariant="normal">Si</mml:mi><mml:mo>(</mml:mo><mml:mn>111</mml:mn><mml:mo>)</mml:mo><mml:mn /><mml:mo>−</mml:mo><mml:mo>(</mml:mo><mml:mn>7</mml:mn><mml:mn /><mml:mo>×</mml:mo><mml:mn>7</mml:mn><mml:mo>)</mml:mo></mml:math>surfaces

Yoon, Moon Soo; Lin, Xiuzhu; Chizhov, Ilya; Mai, H.; Willis, R. F.

doi:10.1103/physrevb.64.085321

Cited by 44 publications

(25 citation statements)

References 18 publications

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“…The clusters are possibly formed by adsorption of extra Ge atoms to the same potential well through the weak Ge-Ge interaction. Similar phenomena have been reported for various metals, [5][6][7][8][9][10][11] and, in particular, for Pb ͑Ref. 8͒ and Au ͑Ref.…”

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confidence: 58%

“…19 It is also clear that Ge atoms are preferably adsorbed to FHUC at low coverages in agreement to the results reported for different metals. [5][6][7][8][9][10] The preference is possibly attributed to the adsorption energy difference between the faulted and the unfaulted halves, which is reported as 0.05-0.1 eV. 2,11,20,21,23,24 Figure 2͑a͒ shows a STM image of ϳ0.005 ML Ge deposited at 100°C.…”

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confidence: 99%

“…[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.…”

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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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confidence: 99%

mentioning

confidence: 99%

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

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Tomitori

Arai

2006

Applied Physics Letters

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“…Growth of the identical clusters is mediated by the existence of particular magic sizes of atom clusters that are more stable than the others. In case of Tl [3], Sn [4] and Ag [5,6] more or less ordered island arrays were reported but magic clustering was not observed. Preparation of ordered structures requires a delicate control of deposition conditions.…”

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confidence: 99%

Self-organized growth of Ag islands on Si(1 1 1)-(7 × 7)-optimization of an STM experiment by means of KMC simulations

et al. 2004

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A growth model and parameters obtained in our previous experimental (STM) and theoretical (Kinetic Monte Carlo simulations) studies of Ag/ Si(111)-(7×7) heteroepitaxy were used to optimise growth conditions (temperature and deposition rate) for the most ordered self-organized growth of Ag island arrays on the (7×7) reconstructed surface. The conditions were estimated by means of KMC simulations using the preference in occupation of half unit cells (HUCs) of F-type as a criterion of island ordering. Morphology of experimentally prepared island structures was studied by STM. High degree of experimentally obtained island ordering is compared with the simulated data and results are discussed with respect to the model and parameters used at the KMC simulations. IntroductionA lot of effort has been paid to prepare ordered arrays of metal nanoclusters because of interesting possible applications in the field of microelectronics. Reconstructed Si(111)-(7× 7) surface was used as a template for spontaneous ordering. Recently ordered arrays of In, Al, Ga identical clusters have been prepared [1,2]. Highly ordered arrays of identical bimetal clusters of In/Ag and In/Mn were also reported in [2]. Growth of the identical clusters is mediated by the existence of particular magic sizes of atom clusters that are more stable than the others. In case of Tl [3], Sn [4] and Ag [5,6] more or less ordered island arrays were reported but magic clustering was not observed. Preparation of ordered structures requires a delicate control of deposition conditions. Kinetics of self-ordering of clusters on the reconstructed surface depends on many parameters and theoretical description of a role of deposition conditions is difficult and still not available. Kinetic Monte Carlo simulation (KMC) of the growth represents an effective approach for theoretical study of important processes involved. We used the KMC simulations together with growth experiments for studying nucleation and heteroepitaxial growth of Ag on the Si(111)-(7×7) surface [5,6,7,8].The (7×7) reconstructed surface consists of triangular half-unit cells (HUCs), which represent potential wells for adsorbed atoms hopping on the surface [9,10]. Each HUC contains six Si adatoms of a top layer. The HUCs are of two types, one containing structural fault (FHUC), the other is unfaulted (UHUC) [11]. It results in different reactivities and consequently in preferential nucleation of Ag in FHUCs. The Ag adatom hopping between various adsorption positions within a HUC at room and higher temperatures is easy but the mobility of the Ag adatoms on the surface -important for growth processes -is determined by the hopping rate between HUCs (depends on barrier height). In a coarse grained model, we used for the simulations, the surface is represented by adsorption sites of two types (FHUCs, UHUCs) with different barrier heights. The preference in FHUC occupancy, P F , (ratio of number of FHUCs occupied by Ag clusters to number of all occupied HUCs) is determined by the barrier difference...

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“…For the STM experiment, a thin In film represents a perfect comparison object for yet another reason: room-temperature deposition of both Pb and In on Si(111) yields nanostructures of very similar geometry, i.e. (111)-oriented flat-top islands with the face-centered cubic lattice 12,13 . Moreover, in both cases the 7x7 reconstruction of Si(111) remains unchanged upon burial.…”

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confidence: 99%