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

Abstract Highly ordered α-Al 2 O 3 microcones were readily generated by a facile thermal oxidation method. The α-Al 2 O 3 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 Al 2 O 3 microcones match better with single crystal than bulk Al 2 O 3 , 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 nm, 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.