Effects of high-temperature annealing on structural and optical properties of highly ordered porous alumina membranes

We report on the structural and optical properties of highly ordered porous alumina membranes (PAMs) under different annealing temperatures up to 1100 degreesC. Clear structural transition from amorphous to gamma- and then to alpha-Al2O3 has been demonstrated in PAMs through x-ray diffraction and micro-Raman scattering measurements. The crystallization of the PAMs under an annealing temperature above 800 degreesC results in the appearance of two absorption structures in the transmission spectra ranging from 1500 to 1700 cm(-1) due to the formation of stable carboxylic impurities. We have presented convincing evidence that the blue photoluminescence band in PAMs originates from the coactions of the singly ionized oxygen vacancies (F+ centers) and the luminescent centers transformed from oxalic impurities. (C) 2004 American Institute of Physics.