Raman and photoluminescence properties of α-Al2O3 microcones with hierarchical and repetitive superstructure

Highly ordered alpha-Al2O3 microcones were readily generated by a facile thermal oxidation method. The alpha-Al2O3 superstructured microcones are composed of a large amount of nanocones, indicating a complex form and remarkable repetitive growth patterns of the superstructure microcones. Raman spectrum displays that the Al2O3 microcones match better with single crystal than bulk Al2O3, revealing a good crystalline nature. The photoluminescence (PL) spectrum reveals a strong red luminescence at 693 nm and three small-shoulder emission bands at 677, 706 and 712 turn, respectively. We deduce that variation in inhomogeneous tensile stress of the microcones that results in differences in local symmetry of the crystal should be responsible for the three unusual emission bands. (C) 2009 Elsevier B.V. All rights reserved.