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

Abstract

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.

Energetics and kinetics of Cu atoms and clusters on the Si(111)-7 × 7 surface: first-principles calculations

“…1(b) (the energy of the most stable site is set to be 0.0 eV for reference). The present results show that the adsorption energies of the Cu atom in the UHUC sites are about 0.1 eV higher than analogous energies in the FHUC, which is similar to the trend for a variety of other metals (such as Pb, Tl, Sn, Ag, Pd, Mn, Sr, and the alkali metals 4,23,[25][26][27] ) on Si(111)-(7 Â 7) as previously reported. In the FHUC, around the R site (see Fig.…”

“…Overall, from this PES, one can see that the Si(111)-(7 Â 7) surface is considerably corrugated with an energy difference of about 1.5 eV between minima (deep blue regions) and maxima (bright red regions), meanwhile, the nearest distances between them are less than 3 Å. The present results show that, for Cu adsorption, the adatom and rest atom sites have neither the local (or global) energy maxima for Mn adsorption reported by Niu et al 23 and Sr investigated by Zhachuk et al, 25 nor the local (or global) energy minimum found for H adsorption studied by Lo et al 28 In the present system, the most unfavorable adsorption position for the Cu atom localizes in the vicinity of the dimer rows (about 1.5 eV higher in energy than H 2 site), the preference of the H 2 site for Cu shows that the adsorbed Cu atoms prefer to saturate the maximum number of dangling bonds around them.…”

“…The Cu-Si ad-atom bond is always preserved in this path, leading to such a low-energy barrier. Note that for Cu, such an inter-basin diffusion path is significantly different from that for Mn 23 and Sr 25 diffusion on Si(111)-(7 Â 7) where the Mn(Sr) atom jumps through the H 3 site. The intra-basin diffusion is characterized by an energy barrier of 0.45 eV along the path H 1 -T 1 -H 2 -T 2 -H 2 , as shown in Fig.…”

“…The Brillouin zone is sampled with the Gamma-point; this approximation was used in a number of previous studies on the 7 Â 7 surface. [21][22][23] Convergence criteria employed for the electronic and ionic self-consistent relaxations are set to be 10 À4 eV and 0.02 eV Å À1 for energy and force, respectively. The convergence of total energies on energy cutoff, slab thickness, vacuum and relaxed layers has been tested, and these parameters can ensure that the total energy converges within the range of 0.02 eV.…”

Mn-Doped Sr/Si(111)-(3 × 2) HCC Surfaces: Antiferromagnetic Semiconductors for Spintronic Applications

“…For example, self-assembled Mn clusters , and nanowires − have been found on the Si(111)-(7 × 7) and Si(001)-(2 × 1) surfaces at a low coverage of Mn, respectively. Theoretical investigations indicate that these surface structures have a FM metallic characteristic. , By controlling the coverage of Mn and the temperature of growth, MnSi 1.7 silicide nanowires , and MnSi silicide thin films − were formed on the Si(111)-(7 × 7) and Si(001)-(2 × 1) surfaces, which show FM semiconducting and FM metallic properties, − respectively. Meanwhile, the magnetic FeSi 2 , nanowires grown on the Si(110) and (111) surfaces have also been reported.…”