Temperature-Dependent Photoluminescence of ZnO Thin Films Grown on Off-Axis SiC Substrates by APMOCVD

The growth of high-quality ZnO layers with optical properties congruent to those of bulk ZnO is still a great challenge. Here, for the first time, we systematically study the morphology and optical properties of ZnO layers grown on SiC substrates with off-cut angles ranging from 0 degrees to 8 degrees by using the atmospheric pressure meta-organic chemical vapor deposition (APMOCVD) technique. Morphology analysis revealed that the formation of the ZnO films on vicinal surfaces with small off-axis angles (1.4 degrees-3.5 degrees) follows the mixed growth mode: from one side, ZnO nucleation still occurs on wide (0001) terraces, but from another side, step-flow growth becomes more apparent with the off-cut angle increasing. We show for the first time that the off-cut angle of 8 degrees provides conditions for step-flow growth of ZnO, resulting in highly improved growth morphology, respectively structural quality. Temperature-dependent photoluminescence (PL) measurements showed a strong dependence of the excitonic emission on the off-cut angle. The dependences of peak parameters for bound exciton and free exciton emissions on temperature were analyzed. The present results provide a correlation between the structural and optical properties of ZnO on vicinal surfaces and can be utilized for controllable ZnO heteroepitaxy on SiC toward device-quality ZnO epitaxial layers with potential applications in nano-optoelectronics.Funding Agencies|Swedish Research Council (VR) Marie Sklodowska Curie International Career Grant [2015-0067900 GREEN 2D FOX]</p

Solar Explosive Evaporation Growth of ZnO Nanostructures

For the first time, we present a novel method of explosive evaporation (MEE) for the deposition of ZnO nanostructures using concentrated solar radiation for precursor evaporation. Zinc acetylacetonate powder and a mixture of ZnO with graphite powders are used as precursors for the deposition of ZnO nanostructures. ZnO nanostructures are deposited on Au/Si, Ag/Si, and unpolished Si substrates by MEE. The scanning electron microscopy, energy dispersive X-ray analysis, X-ray diffraction, Raman scattering, photoluminescence, and Fourier transformed infrared spectroscopy are used for sample characterization. We demonstrate that the changing of precursors and the substrate types allows ZnO nanostructures to be grown with diverse morphologies: hexagons, spheres, and needles. The properties of ZnO nanostructures deposited on unpolished, coated by Ag and Au silicon substrates are discussed. MME using concentrated solar radiation is promising method for applications in the semiconductor industry as an economically efficient environmentally-friendly method for the growth of nanostructures