Magnetic and electronic properties of Cr, Mn, and Fe adatoms on Si(001): A first-principles study

Niu, Chunyao; Wang, Jiantao

doi:10.1016/j.ssc.2011.10.026

Cited by 8 publications

(8 citation statements)

References 26 publications

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“…Previous studies showed that Mn nanowires on the Si(001) surface 27,31,32 prefer to form ferromagnetic property. For the Mn clusters on Si(111) surface, our results show that the most stable Mn clusters prefer the ferromagnetic coupling for N ≤ 6 except Mn 5 , while those N ≥ 7 clusters show much more complex magnetic properties, we focus here on the discussion of two magic Mn 7 and Mn 13 clusters.…”

Section: Resultsmentioning

confidence: 99%

Size-selective self-assembly of magnetic Mn nanoclusters on Si(111)

Niu

Wang

et al. 2013

The Journal of Chemical Physics

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We show by first-principles calculations two types of magnetic magic Mn clusters on the Si(111)-(7 × 7) surface. The first is a small triangular Mn7 cluster stabilized by the solid-centered Mn-Si3 bonds on the top layer, and the second is a large hexagonal Mn13 cluster favored by the confining potential wells of the faulted half unit cells on the Si(111) surface. These two structural models are distinct from that of the planar group-III clusters on Si(111) and produce simulated scanning tunneling microscopy images in reasonable agreement with recent experimental observations. These results offer key insights for understanding the complex energetic landscape on the Si(111)-(7 × 7) surface, which is critical to precisely controlled growth of Mn nanocluster arrays with specific size, magnetic moment, and good uniformity.

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Section: Resultsmentioning

confidence: 99%

Size-selective self-assembly of magnetic Mn nanoclusters on Si(111)

Niu

Wang

et al. 2013

The Journal of Chemical Physics

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“…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)].…”

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confidence: 98%

“…Although many features seen experimentally could be reproduced in the simulated STM images, more refined models are needed to reproduce the exact appearance of the observed asymmetry. This is of particular interest in light of recent predictions of exciting spin and transport properties of Mn wires [24], which, if proven to be correct, may open the door to develop novel atomicscale spintronic devices in silicon.…”

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confidence: 99%

“…The periodic boundary conditions in the simulation further limit the appearance of wire asymmetries because the supercell has to be dipole free and charge transfer from one Mn wire edge to the other may be suppressed. Moreover, even if pure DFT simulations are accurate enough to describe the interaction and atomic structure of Mn on Si surfaces [22][23][24]28], the contraction of partially occupied d-shells is often underestimated, resulting in a modified orbital hybridization and therefore distorted simulated STM images. Nevertheless, we show that a closer look at the relaxed atom positions allows us to identify the origin of the observed asymmetry.…”

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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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“…While they also run perpendicular to the Si dimer rows, their precise structure remains unsolved. Several models, from single-atom to trimer systems, have been proposed [21][22][23]. But they all fail to reproduce a striking asymmetry of the Mn chains observed in filled state STM images [ Fig.…”

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Structure of Self-Assembled Mn Atom Chains on Si(001)

et al. 2015

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Mn has been found to self-assemble into atomic chains running perpendicular to the surface dimer reconstruction on Si(001). They differ from other atomic chains by a striking asymmetric appearance in filled state scanning tunneling microscopy (STM) images. This has prompted complicated structural models involving up to three Mn atoms per chain unit. Combining STM, atomic force microscopy, and density functional theory we find that a simple necklacelike chain of single Mn atoms reproduces all their prominent features, including their asymmetry not captured by current models. The upshot is a remarkably simpler structure for modeling the electronic and magnetic properties of Mn atom chains on Si(001).

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Magnetic and electronic properties of Cr, Mn, and Fe adatoms on Si(001): A first-principles study

Cited by 8 publications

References 26 publications

Size-selective self-assembly of magnetic Mn nanoclusters on Si(111)

Size-selective self-assembly of magnetic Mn nanoclusters on Si(111)

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

Structure of Self-Assembled Mn Atom Chains on Si(001)

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