The structure and optical properties of ZnO nanocrystals embedded in SiO₂fabricated by radio-frequency sputtering

Abstract

Zinc oxide (ZnO) nanocrystals (NCs) with high crystalline quality were prepared via radio-frequency magnetron sputtering as a SiO 2 /ZnO/SiO 2 trilayer on Si(100) and Al 2 O 3 (0001) substrates with an intermediate in situ annealing step. Transmission electron microscopy reveals a uniform dispersion of ZnO NCs in the amorphous SiO 2 matrix with typical sizes up to 16 nm with a larger fraction of smaller crystals. The size distribution analysis yields a mean grain size of 5 nm for small particles. Individual ZnO NCs show a well-defined hexagonal close packed wurtzite structure and lattice parameters close to those of bulk ZnO, confirming their high crystalline quality. Mapping of the Zn distribution by means of energy-filtered transmission electron microscopy reveals a strongly non-uniform distribution of Zn within the SiO 2 matrix, corroborating the chemical separation of ZnO NCs from surrounding SiO 2 . Optical transmittance measurements confirm the findings of the electron microscopy analysis. The fabrication technique described opens up new possibilities in the preparation of ZnO NCs with high crystalline quality, including growth in monolithic optical cavities without intermediate ex situ fabrication steps.

Size and defect related broadening of photoluminescence spectra in ZnO:Si nanocomposite films

“…Thus it becomes clear that the compositional ratio of ZnO to Silicon which inturn means the neighbourhood offered to ZnO nanoparticles is deterimental in bringing desired changes in optical properties of the nanocomposites and should be given its due concern. Nanocomposites based on ZnO and Si have been fabricated by sol gel [15,16,17,18,19], RF sputtering [20,21,22,23], pulsed laser deposition [24], via chemical routes [25,26,27,28], reverse micelle method [29]and their optical properties studied. These research calls for more systematic work to optimize the parameteres for tailoring the properties and for a better understanding of interface and defect mechanism of ZnO:Si nanocomposites Hence to this effect, we have started systematic study of Zinc Oxide grains in nano regime embedded in amorphous Silicon matrix.…”

X-Ray Spectroscopic Investigations of Zn$_{0.94}$Co$_{0.06}$O Thin Films

“…In our earlier investigations, strong ferromagnetic behavior of the Al O single crystals after annealing under vacuum conditions was found [29]. In order to minimize the substrate contribution to the ferromagnetic signal of the sample, one reference substrate was treated in the same way as the samples, but without the sputter deposition of Zn Co O, and measured by SQUID magnetometry.…”

Ultrafast Semiconductor Quantum Optics

“…ZnO quantum dots have shown long electron spin dephasing times even at room temperature (Liu et al, 2007) and have been successfully doped with magnetic ions (Kittilstved & Gamelin, 2006). In the future, the quantum dot ensemble used in this study may be replaced by sputtered ZnO quantum dots (Mayer et al, 2009), magnetically doped ZnO nanocrystals, or other UV emitters.…”