Berlin 2015 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 35: Nanostructures at Surfaces

O 35.13: Poster

Dienstag, 17. März 2015, 18:15–21:00, Poster A

Does the band structure picture hold for Si Nanocrystals of few nm in size? — Prokop Hapala, •Ante Šiljić, Pavel Jelínek, Pingo Mutombo, Katerina Kusova, and Ivan Pelant — Institute of Physics of the ASCR, v.v.i. Cukrovarnicka 10, Prague 6, Czech Republic

There has been a long-standing discussion on whether or not an electronic band structure concept. i.e. energy-to-wavevector dispersion, can be assigned to zero-dimensional objects such as quantum dots (nanocrystals) (see e.g. [1]). To answer this question, we developed a general method [2], which allows reconstruction of electronic band structure of nanocrystals from ordinary real-space electronic structure calculations. We combine the method with fully relaxed large-scale Density Functional Theory calculations of a realistic Si nanocrystals of up to 3 nm in size with different surface passivations including hydrogen, hydroxyl and methyl groups [3]. To demonstrate character of the band structure of Si nanocrystals, we calculate band dispersion along the Γ-X direction to compare it with a bulk counterpart. Based on this comparison, we conclude that the band structure concept is applicable to silicon nanocrystals with diameter larger than ~2 nm with certain limitations. In addition we will discuss impact of polarized surface hydroxyl groups or geometric distortion on momentum space selection rules important for light emission.

[1] M. S. Hybertsen, Phys. Rev. Lett. 72, 1514 (1994)

[2] P. Hapala, et al., Phys. Rev. B 87, 195420 (2013)

[3] K. Kůsová et al., ACS Nano 4, 4495 (2010)