Regensburg 2013 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 69: Poster Session: II-VI semiconductors; Organic semiconductors; Heterostructures

HL 69.2: Poster

Wednesday, March 13, 2013, 16:00–20:00, Poster A

Doping of ZnO micro and nano crystals prepared by sol-gel technique — •Christoph Brodehl, Jahanzeb Azam, Tim Baumgarten, and Sigmund Greulich-Weber — University of Paderborn, 33098 Paderborn, Warburger Str. 100, Germany

Zinc oxide (ZnO) is a wide-bandgap semiconductor with promising applications in the optoelectronic domain. Our main focus is on micro and nano crystalline ZnO as a transparent conductor in solar cells and photonic crystals, and as diluted magnetic semiconductor (DMS) for development of left-handed materials. We prepared ZnO nano and micro crystals via sol-gel routes and doped them with donors, acceptors and regarding to DMS with manganese. Annealing series of doped and as-grown crystals were characterized with electron paramagnetic resonance (EPR), photoluminescence, electron microscopy, X-ray diffraction and conductivity measurements. The annealing studies investigated by EPR together with photoluminescence measurements allow an identification of the commonly observed positively charged oxygen vacancy and the positively charged interstitial zinc as intrinsic defects in as-grown nominally undoped sol-gel ZnO. Beside shallow intrinsic defects and dopants a surface-related defect was always present and determines the crystal conductivity at least at room temperature. Doping with lithium allows a partly compensation of shallow intrinsic defects. Depending on the annealing temperature, we observed changes in EPR spectra of manganese doped ZnO. The samples show paramagnetic behavior for low annealing temperatures and ferromagnetic behavior for temperatures higher than 800°C.