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HL: Halbleiterphysik

HL 50: Poster II

HL 50.96: Poster

Donnerstag, 30. März 2006, 16:30–19:00, P3

Size dependence of quantum confinement effects in HgTe nanocrystals determined by spectroscopic ellipsometry — •Veronika Rinnerbauer¹, Maksym Kovalenko², Ventsislav Lavchiev¹, Wolfgang Heiss², and Kurt Hingerl¹ — ¹Christian Doppler Labor für oberflächenoptische Methoden, Universität Linz, 4040 Linz, Austria — ²Institut für Halbleiter- und Festkörperphysik, Universität Linz, 4040 Linz, Austria

We have explored the optical properties of HgTe nanocrystals which were prepared from a colloidal solution. These nanocrystals show strong luminescence in the near infrared (λ=1550 nm), which makes them an interesting material for the telecommunication area. The emission wavelength can efficiently be tuned by controlling the size of the nanocrystals.

We report spectroscopic ellipsometry measurements, which show clearly an energy shift of the critical points in the dielectric function of these HgTe nanocrystals when compared to the HgTe bulk properties. This shift δ of the E1 and E1+ Δ1 transitions to higher energies is caused by the quantization effect due to the small size of the crystals. The exact peak energies of the transitions were fitted with line-shape models for critical points (CP). We observe not only a shift of the oscillator energies, but also the inhomogeneous broadening of the peaks due to the size distribution of the nanocrystals. The size dependence of the energy shift was studied for samples with nanocrystals of different sizes (3-10 nm). It can be seen that the energy of the CPs shifts from near bulk level for the biggest nanocrystals to higher energies with decreasing size.