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

V. S. Baturin, S. V. Lepeshkin, N. L. Matsko, Artem R. Oganov, Yu. A. Uspenskii
2014 Europhysics letters  
PACS 73.22.-f -Electronic structure of nanoscale materials and related systems PACS 61.46.Bc -Structure of clusters (e.g., metcars; not fragments of crystals; free or loosely aggregated or loosely attached to a substrate) PACS 64.75.Jk -Phase separation and segregation in nanoscale systems Abstract -The total energy and geometry of nanoclusters Si10H2m (m = 0-12) are calculated using evolutionary structure searching and density functional theory. The calculation shows that the arrangement of Si
more » ... e arrangement of Si atoms is close to the diamond crystal structure only in the cluster Si10H16, while in others it is unique for each composition. We found that the ensemble of Si10 clusters remains uniform after passivation only if hydrogen concentration corresponds to one of the stable compositions -Si10, Si10H14, Si10H16 Si10H20, or Si10H22. 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 ∼ 0.1 eV above the ground state. These metastable configurations come into existence in synthesis at T ≥ 500 K, making experimentally realizable cluster compositions even more diverse. Introduction. -The physical and chemical properties of silicon nanoclusters (Si-NCs) have been subject of extensive research for over two decades. Owing to their strong photoluminescence and their optical spectrum depending on cluster size, geometry and passivation (thus allowing to tune spectra to the desired wavelengths), Si-NCs are considered highly promising for opto-and nanoelectronics, solar cells, biosensors, etc. For applications of Si-NCs in nanodevices, their size and shape should be carefully controlled, since deviations in cluster structure greatly impair working characteristics. Such deviations can originate from both imperfect fabrication technology and intrinsic nanocluster instability. In practice, these two factors are entangled. The situation with instability is more difficult, as in this case even improved fabrication technology will not eliminate the problem. At present, the atomic structure and stability of Si-NCs are known insufficiently. Most of experimental information relates to small clusters Si n with n ≤ 10 (a)
doi:10.1209/0295-5075/106/37002 fatcat:f57le323o5bk3a6eryaoqy5viu