Dresden 2009 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 9: Poster 1

HL 9.67: Poster

Monday, March 23, 2009, 14:30–17:00, P2

Structure and optical properties of ZnO nanocrystals embedded in amorphous SiO₂ — •Gillian Mayer¹, Mikail Fonin¹, Ulrich Rüdiger¹, Reinhard Schneider², Dagmar Gerthsen², Nils Janßen³, and Rudolf Bratschitsch³ — ¹Fachbereich Physik, Universität Konstanz, 78457 Konstanz, Germany — ²Laboratorium für Elektronenmikroskopie, Universität Karlsruhe, 76128 Karlsruhe, Germany — ³Fachbereich Physik, Universität Konstanz and Center for Applied Photonics, 78457 Konstanz, Germany

Zinc oxide (ZnO) is a wide gap semiconductor with a broad range of optoelectronic applications due to its direct band gap and high exciton binding energy. ZnO quantum dots have attracted attention since their spins might be used as qubits in quantum information technology.

In this study, ZnO nanocrystals (NCs) were grown by radio-frequency magnetron sputtering as a SiO₂/ZnO/SiO₂ layer stack on Si(100) and Al₂O₃(0001) substrates with an intermediate in situ annealing step. Structural properties were investigated by transmission electron microscopy (TEM), which reveals a uniform dispersion of ZnO NCs with sizes up to 16 nm in the amorphous SiO₂ matrix. High resolution TEM shows a well-defined hexagonal close packed wurtzite structure for individual NCs with lattice parameters close to those of bulk ZnO. Statistics of the NC sizes lead to a grain size of 5 ± 2 nm for more than 70 % of the NCs. The chemical separation of the ZnO NCs from the surrounding SiO₂ matrix is corroborated by energy-filtered TEM. Measurements of the optical transmittance confirm the results obtained by TEM.