State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics and Engineering, Sun Yat-Sen University, Guangzhou, P. R. China.
IEEE Trans Ultrason Ferroelectr Freq Control. 2010 Oct;57(10):2134-7. doi: 10.1109/TUFFC.2010.1669.
(Bi(3.6)Eu(0.4))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 ⁵D₀→⁷F₁ (594 nm) and ⁵D₀→⁷F₂ (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)₄Ti₃O₁₂ thin films.
掺 Li+ 的（Bi，Eu）₄Ti₃O₁₂ 薄膜的制备及其光电性能研究
采用化学溶液沉积法在熔融石英和 Pt/Ti/SiO₂/Si 衬底上制备了不同 Li+掺杂浓度的（Bi，Eu）₄Ti₃O₁₂（BEuT）薄膜，详细研究了 Li+掺杂浓度对薄膜的光致发光和铁电性能的影响。结果表明，适量 Li+掺杂可以有效提高 BEuT 薄膜中两个特征 Eu³+发射跃迁的发射强度，即 ⁵D₀→⁷F₁（594nm）和 ⁵D₀→⁷F₂（617nm）。这种光致发光增强可以归因于 Li+离子的双重作用，一方面 Li 离子可以作为共激活剂，有助于能量从基质转移到 Eu³+离子，从而提高量子产率；另一方面，Li 离子掺杂可以诱导 Eu³+激活剂周围晶体场的局部变形，因为 Bi³+和 Li+离子具有不同的离子半径。此外，在相同实验条件下制备的无 Li 掺杂 BEuT 薄膜相比，Li+掺杂的 BEuT 薄膜具有更大的剩余极化强度。这些结果表明，Li+掺杂是提高（Bi，Eu）₄Ti₃O₁₂ 薄膜光致发光和铁电性能的有效途径。
