We report on the strong pore-size-dependent optical properties of porous alumina membranes (PAMs) by using the photoluminescence and the optical spectroscopic techniques. The pore diameters of our PAMs varied from 60 to 420 nm. All samples showed a sizable violet/blue emission with a strong temperature dependence. We found that the peak position of the emission shifted to higher energies with increasing pore diameter, which was in accord with the smaller binding energy extracted from the temperature dependence of the emission intensity. From the transmission spectra, we found that the effective bandgap of the PAMs shifted significantly to lower energies with increasing pore diameter, which indicated that the impurity states within the bandgap was affected strongly by the geometry of the PAM.
Bibliographical noteFunding Information:
This work was supported by a National Research Foundation of Korea (NRF) grant funded by the Korea government (MOE) (No. 2013R1A1A2012281). SDB was supported by the Priority Research Centers Program through the funded by the Ministry of Education, Science and Technology (MEST, No. 2011-0031400). SY was supported by grants funded by the Korea government (MEST, No. 2011k000584) and the Korea government (MSIP, No. 2008-0062237).
- Optical simulation
- Pore-size dependence
- Porous alumina membrane