Adatom Pairing Structures for Ge on Si(100): The Initial Stage of Island Formation

Qin, X. R.; Lagally, M. G.

doi:10.1126/science.278.5342.1444

Cited by 57 publications

(69 citation statements)

References 15 publications

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“…This indicates higher filling of the Si dimer states near the wire. A similar shift in contrast was observed for Ge [26] and Al [10] wires, even though in these cases the hollow site is not occupied by a wire atom.…”

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confidence: 73%

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Atomic Structure of Mn Wires on Si(001) Resolved by Scanning Tunneling Microscopy

et al. 2012

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At submonolayer coverage, Mn forms atomic wires on the Si(001) surface oriented perpendicular to the underlying Si dimer rows. While many other elements form symmetric dimer wires at room temperature, we show that Mn wires have an asymmetric appearance and pin the Si dimers nearby. We find that an atomic configuration with a Mn trimer unit cell can explain these observations due to the interplay between the Si dimer buckling phase near the wire and the orientation of the Mn trimer. We study the resulting four wire configurations in detail using high-resolution scanning tunneling microscopy (STM) imaging and compare our findings with STM images simulated by density functional theory.The large magnetic moment related to a half-filled d-shell renders Mn atoms attractive building blocks for fascinating magnetic nanostructures [1][2][3]. Tunable ferromagnetism in Mn-doped semiconductors has been achieved for GaAs,. For silicon this effort has not been as successful because of strong segregation and the interstitial diffusion of Mn in the Si crystal during overgrowth or annealing, even though Mn implanted Si samples exhibit very high Curie temperatures [8]. During submonolayer deposition at room temperature (RT) however, Group III (Al, Ga, In), Group IV (Sn, Pb) and a few other metals (e.g. Sb and Mg) are known to form 1D wires perpendicular to the Si dimer rows on the Si(100)-2×1 surface [9][10][11][12][13][14][15][16][17]. These wires consist of metal atoms in the parallel-dimer configuration linking up to form atomic chains [18][19][20]. Recent experiments show that similar wire formation occurs for Mn [21]. Density functional theory (DFT) calculations proposed several possible structures for these wires [22][23][24] with one, two or three Mn atoms per Si dimer row [see Fig. 1(a)].We show that high-resolution STM imaging at RT reveals a unique appearance of Mn wires. In contrast to other metal wires, their signature is characterized by the pinning of nearby Si dimers in addition to two independent asymmetric realizations of the Mn wire. We find that only an extended trimer model can explain our findings and identify a total of four wire configurations based on the relative orientation of the Si dimers and an asymmetric Mn trimer unit cell. We confirm our model using a sequence of STM images, where we observe sequential changes of the Si dimer and Mn trimer configuration. Our results are important for the successful integration of Mn atoms into future silicon spintronics devices.The filled-state STM image in Fig. 1(b) shows Mn wires near a step edge of the Si(001) surface. Here, about a tenth of a monolayer of Mn was deposited at RT with a rate of 55 pm/min. The wires, with typical lengths ranging from 5 nm to 50 nm, frequently nucleate at defect sites or step edges, where clustering of Mn wires is observed (dashed ellipse). This reflects the high mobility of Mn on the Si(001) surface at RT [21]. Even at these low-temperature growth conditions, a number of larger clusters are found (dashed circles). In the following...

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supporting

confidence: 73%

“…Comparing this behavior to that of other metal wires on Si [9,11,13] or to initial stages of Si and Ge growth on Si(001) [26], it is clear that Mn is quite unique in its asymmetric appearance. All other metal wires are attributed to the parallel dimer wire model [see II in Fig.…”

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confidence: 79%

Atomic Structure of Mn Wires on Si(001) Resolved by Scanning Tunneling Microscopy

et al. 2012

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“…These are in agreement with large-scale experimental STM images of the parallel perfect dimer chains in the high-quality Si(001) and Ge(001) surfaces [4,5]. Generally speaking, such a dimer chain can be broken into several segments, but these segments are still completely in the same line [4,5,2,3,6,7] and can be considered to be an infinitely long dimer chain in the sense of averaging along the line. Actually, there is either type-S A or type-S B dimerized phases in high-quality (001) surfaces [4,5].…”

Section: Applied To the (2×1)-(1×1) Phase Transitions Of Si(001) And supporting

confidence: 84%

“…• rotation [4,5]. Because the dimerization takes place only in the top layer, it is reasonable to describe both of the Si(001) and Ge(001) dimerized surface phases by a 2D model.…”

Section: Phase-field-crystal Modelingmentioning

confidence: 99%

Phase-field-crystal modelling of the (2 × 1)–(1 × 1) phase transitions of Si(0 0 1) and Ge(0 0 1) surfaces

Liu

2008

J. Phys. D: Appl. Phys.

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Abstract. We propose a two-dimensional phase-field-crystal model for the (2×1)-(1×1) phase transitions of Si(001) and Ge(001) surfaces. The dimerization in the 2×1 phase is described with a phase-field-crystal variable which is determined by solving an evolution equation derived from the free energy. Simulated periodic arrays of dimerization variable is consistent with scanning-tunnelling-microscopy images of the two dimerized surfaces. Calculated temperature dependence of the dimerization parameter indicates that normal dimers and broken ones coexist between the temperatures describing the charactristic temperature width of the phase-transition, T L and T H , and a first-order phase transition takes place at a temperature between them. The dimerization over the whole temperature is determined. These results are in agreement with experiment. This phase-field-crystal approach is applicable to phase-transitions of other reconstructed surface phases, especially semiconductor n×1 reconstructed surface phases.

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“…During the ' I initial stages of Si and Ge growth by MBE on (001) Si and Ge rows of dimers have been observed by STM to form along C310> directions [58][59][60]. These examples all suggest that the <310> direction of modulations is a result of a sm$ace roughening mechanism such as faceting, / step bunching, or a preferred shape of 2D or 3D islands or trenches occurring probably on the AIAs layer surfaces which are under tension.…”

Section: ]mentioning

confidence: 91%

The Nature and Origin of Lateral Composition Modulations in Short-Period Strained-Layer Superlattices

et al. 1999

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Adatom Pairing Structures for Ge on Si(100): The Initial Stage of Island Formation

Cited by 57 publications

References 15 publications

Atomic Structure of Mn Wires on Si(001) Resolved by Scanning Tunneling Microscopy

Atomic Structure of Mn Wires on Si(001) Resolved by Scanning Tunneling Microscopy

Phase-field-crystal modelling of the (2 × 1)–(1 × 1) phase transitions of Si(0 0 1) and Ge(0 0 1) surfaces

The Nature and Origin of Lateral Composition Modulations in Short-Period Strained-Layer Superlattices

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