Regensburg 2010 – scientific programme

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O: Fachverband Oberflächenphysik

O 46: Density functional theory and beyond for real materials I

O 46.11: Talk

Wednesday, March 24, 2010, 13:00–13:15, H34

Time dependent hybrid density functional calculations on semiconductor nanocrystallites — Marton Voros and •Adam Gali — Budapest University of Technology and Economics

Recent technological developments allow the preparation of nanometer sized semiconductor nanocrystals [1-2]. Due to the small size, these nanocrystals exhibit several special features [2-4], therefore understanding the electronic and optical properties at the molecular level is crucial for applications. We show that by using a hybrid functional based TDDFT approach the calculated absorption spectrum of small diamond nanocrystals (diamondoids) near quantitatively agrees with recent experiments [5-6]. We show that Rydberg transititions rule the low energy part of the absorption spectra even in relatively large diamondoids [6] which is not common in other group IV type semiconductor nanocrystals. This property makes it computationally hard to get a well-converged result using supercell based methods. Applying the same technique we show that the low energy part of the absorption spectrum of biologically inert silicon carbide nanocrystals strongly depends on the actual type of surface reconstruction. This would allow the identification of surface reconstruction by comparing the experimental and calculated absorption spectra.

[1] J. E. Dahl et al., Science 299, 96 (2003) [2] X. L. Wu et al., Phys. Rev. Lett. 94, 026102 (2005) [3] Jiyang Fan et al., Small 4, No. 8, 1058 (2008) [4] W. L. Yang et al., Science 316, 1460 (2007) [5] Lasse Landt et al., Phys. Rev. Lett. 103, 047402 (2009) [6] Márton Vörös and Adam Gali, Phys. Rev. B 80, 161411(R)(2009)