Improved Photoluminescence and Ferroelectric Properties of (Bi3.6Eu0.4)Ti3O12 Thin Films Via Li+ Doping

(Bi3.6Eu0.4)Ti3O12 (BEuT) thin films with different Li+ doping contents were prepared on fused silica and Pt/Ti/SiO2/Si substrates by chemical solution deposition, and the effects of Li+ doping contents on the photoluminescence and ferroelectric properties of the thin films were investigated in detail. The results showed that an appropriate amount of Li+ doping could effectively improve emission intensities for two characteristic Eu3+ emission transitions of D-5(0)-> F-7(1) (594 nm) and D-5(0)-> F-7(2) (617 nm) compared with BEuT thin films without Li doping. This photoluminescence improvement can be attributed to the dual roles of Li+ ions, one of which is that Li ions can act as co-activators which are helpful to the energy transfer from the host to the Eu3+ ions, leading to a higher quantum yield; the other is that Li ion doping can induce local distortion of crystal field surrounding the Eu3+ activator because Bi3+ and Li+ ions have different ionic radii. In addition, the Li+-doped BEuT thin films had larger remanent polarization than BEuT thin films without Li doping prepared under the same experimental conditions. These results suggest that Li+ doping is an effective way to improve photoluminescence and ferroelectric properties of the (Bi,Eu)(4)Ti3O12 thin films.