Optical emission from LiNbO3(:Fe)/porous Si structures

Using pulsed laser deposition, a layer of LiNbO3(:Fe) film with a thickness of 180 nm was coated onto porous Si (PS) stored in air for 1 year. A photoluminescence (PL) band enhanced about three times was observed at ∼625 nm with a same peak position as that of the stored PS. It is revealed that a new PL excitation band occurs at ∼363 nm, which is nearly equal to the fundamental optical absorption edge position of LiNbO3. The X-ray diffraction results disclose that the enhancement of the PL intensity is closely related to formation of a textured LiNbO3 film. Based on spectral analysis, we attribute the enhanced PL to optical transition in the E′ defect centers localized at the surfaces of PS nanocrystals, whereas the photoexcited carriers mainly come from the coated LiNbO3 film. This kind of LiNbO3(:Fe)/PS structures is expected to have important applications in modern ferroelectric optoelectronics.