Hydrothermal synthesis and optical properties of ZnO single-crystal hexagonal microtubes

ZnO micrortubes were successfully synthesized by employing zinc acetate dihydrate as the starting material under hydrothermal condition. The ZnO microtubes were characterized by X-ray diffraction, scanning electron microscopy and high-resolution transmission electron microscopy. The results showed that the as-prepared ZnO microtubes were hexagonal and single crystal in nature and grew on Si (1 1 1) substrates along the 1000 21 direction, which have diameters of about 3 mu m, lengths of 10-20 mu m, and wall thickness of 80 nm. Optical properties of the ZnO microtubes were investigated by temperature-dependent photoluminescence (PL) spectroscopy. The PL spectrum at 82.2 K shows a strong UV emission from the near band-edge with a negligible visible emission from deep level, and donor bound exciton ((DX)-X-0). free exciton (FX) and its phonon replica were observed in the UV-region. The PL spectra were dominated by the FX emission throughout the whole temperature range, and the energies of FX transitions and (DX)-X-0 transitions are close to that of the bulk values of ZnO. (C) 2009 Elsevier B.V. All rights reserved.