Zinc oxide single-crystal microtubes

ZnO single-crystal microtubes were fabricated using an encapsulated microwave growth method. The ZnO crystals are grown in hexagonal hollow tube form with a well faceted end and side surfaces, which have cross-sectional dimensions of 100 to 250 mum, lengths of 3-5 mm, and wall thickness of 1-2 mum. Under optical excitation, a strong near-band-edge emission was obtained at a peak wavelength of 377.8 nm with a full width at half maximum of 11 nm. The ZnO microtubes exhibited a highly selective UV light response with a cut-off wavelength at similar to370 nm, and excellent electron field emission properties with an emission current density of 11 mA/cm(2) at an applied field of similar to20 V/mum. (C) 2004 American Institute of Physics.