Arrangement Of Si Atoms Research Articles

Prediction of the atomic structure and stability for the ensemble of silicon nanoclusters passivated by hydrogen

The total energy and geometry of nanoclusters are calculated using evolutionary structure searching and density functional theory. The calculation shows that the arrangement of Si atoms is close to the diamond crystal structure only in the cluster , while in others it is unique for each composition. We found that the ensemble of clusters remains uniform after passivation only if hydrogen concentration corresponds to one of the stable compositions – , , , or . Passivation by an arbitrary amount of hydrogen converts the ensemble into a mixture of the stable clusters having the nearest compositions. In addition there are numerous metastable cluster configurations with energies within above the ground state. These metastable configurations come into existence in synthesis at , making experimentally realizable cluster compositions even more diverse.

Theoretical Study of Si-Rich Transition-Metal Silicides with Double-Graphene-Like Structures

ABSTRACTWe propose a novel form of graphene-like Si nanostructure based on ab initio total-energy calculation and geometry optimization, (MSi12)n, with M being transition metal atom. It has a three-layer structure, where the two layers of Si atoms in graphene-like positions sandwich another layer of transition metal atoms. The electronic structure may become semiconducting or metallic, depending on the choice of M and arrangement of Si atoms. This hypothetical material can be regarded as a Si-rich phase of transition metal silicide. A potential impact of our finding in forthcoming ultra-scaled Si technology is also discussed.

Scanning tunneling microscopy study of reconstruction of 0.8 monolayers Ga on an Si (001) surface

The surface structure of 0.8 monolayers (ML) Ga on an Si (001) 2×1 surface has been studied with scanning tunneling microscopy (STM). Periodical clusters, aligned in 〈110〉 directions on an Si (001) surface and reflecting the polarity of terraces on that surface, were observed. The clusters of Ga consist of the 8×5 phase. From the line profiles of the clusters in STM images, each cluster of the 8×5 phase has been found to consist of Ga double layers, the top layer of Ga being composed of four Ga atoms. Clusters in contiguous arrays are out of phase in the direction of the arrays. Pairs of two Ga atoms exist in both longitudinal sides at each cluster along the contiguous arrays. These pairs of two Ga atoms at both sides of the valleys between the contiguous arrays are located alternatively. From the above information on positions of Ga atoms, arrangements of Ga atoms of the clusters of the 8×5 phase are presumed. Two cases are considered for the arrangements of the clusters based on the arrangements of Si atoms on the top and second layers of Si (001). It is concluded that the lateral direction of clusters is parallel to the rows of the top and second layers of Si (001).

Distribution of metalloid atoms in nanocrystalline Fe-Cu-Si-B alloys

Mossbauer spectroscopy results show that, in 30 nm-grained Fe-Cu-Si-B alloy, boron atoms exhibit two states, 9% of which are as Fe2B and the remainder boron-enriched species in the interfaces. Also, the solubility of Si atoms in body-centred cubic Fe is calculated to be about 13 at.% and the arrangement of Si atoms in the alpha -Fe(Si) phase is of short-range order. With grain growth the Mossbauer parameters of the Fe2B phase change slightly. However, the Mossbauer parameters of the alpha -Fe(Si) phase are strongly affected by grain growth, indicating variation of short-range order of silicon atoms in the body-centred cubic Fe phase with grain growth.