稀土掺杂铁电体/纳米金属复合薄膜结构的原位可逆多重发光调控

In this project, ferroelectric materials are chosen as the doped substrates, lanthanide ions as doping activated ions, transparent conductive films as electrodes and noble nano metals as fluorescence enhanced surfaces, to prepare rare earth doped ferroelectrics/nano metals composite film with physical growth methods, such as magnetron sputtering method. Herein the piezo-effect and metal surface enhancement join together to modulate the distance between the metal surface and activated ion, and its enhanced fluorescence, in an in-situ, real-time and reversible way for the first time. Meanwhile the disadvantages of inhomogeneities and defects arising from chemical synthesis and modulation process are suppressed. Therefore the measurements of enhanced fluorescence become intimately related to the determined shape and distance of nano metals, and thus the mechanisms of metal-enhanced fluorescence are expected to be further clarified. This novel ferroelectrics/nano metals composite system facilitates a physical model to investigate the luminescence modulations. Thus the energy structures of d levels and energy transfer between lanthanide ions which are sensitive to crystal field and their distance respectively can be modulated by piezo-effect, and the advantages of the permissible parity for d-f transitions and their strong emissions with wide bands are fully performed. The effect of external electric field can be analyzed quantitatively by suitable experiment methods in this system. The external electric field acting on nano metal may lead to the change in Fermi level and plasmon resonance on metal surface, which may bring the novel phenomenon of surface enhanced d-f transition emissions in condition of multiple modulations converging on this system. On the basis of these investigations, Ferroelectric devices for luminescence modulation based on multiple physical effects will be developed to allow their applications.

选择铁电材料作为基质，稀土离子作为掺杂离子，透明导电薄膜作为电极，纳米贵金属作为增强表面，以磁控溅射等物理方法制备新型稀土掺杂铁电体/纳米金属复合薄膜增强体系。原创性地将压电效应与金属表面荧光增强效应有机结合在一起，实现了对发光离子与金属表面间距和发光过程的原位可逆实时调控。同时克服了化学制备方法与调控手段存在的体系不均匀和缺陷杂质较多的缺点，使增强的荧光测量结果与确定的间距和形貌相对应，更深入地揭示了金属表面荧光增强机制。该复合体系为研究发光调控提供了物理模型：可利用压电效应调控对晶场变化敏感的d组态能级的位置结构，以及对激活离子间距敏感的能量传递过程，进而发挥d-f跃迁宇称允许和宽带强发射的优势；能定量地分析外电场的影响；将外电场对金属表面费米能级和等离子体共振耦合的调控，与对d组态的调控相结合，有望获得d-f跃迁荧光表面增强的新发现；研发出基于多种物理效应的铁电基质复合发光调控。

项目研究体系由纳米贵金属基底、铁电隔离层、发光薄膜层、透明导电层等关键部分组成，包含了掺杂稀土离子发光过程、等离子体共振荧光增强、压电效应、晶体场调控等物理机制。为此研究工作既包括对复合结构的工艺技术开发，又包括对体系的物理机制方面的分析探讨。发展了交错溅射Ag与BaTiO3构成多层交互膜的方法，结合后续退火的方法，使Ag颗粒通过扩散达到表面，形成一定纳米银颗粒分布，产生等离子共振的纳米贵金属基底。通过控制溅射在此基底上的铁电薄膜的厚度，来调控发光离子与金属表面的距离，制备了Ag基底/ BaTiO3/发光薄膜/ITO多层复合结构。以磁控溅射NaYF4:Ln3+素靶、PLD溅射稀土掺杂铁电靶等方法制备的发光层具有良好的发光效果。透明导电层利用溅射或旋涂的方法制备，研究了AZO透明导电薄膜在105到 10-4 Pa大真空度范围退火下的电阻率变化规律，发现：电阻率的降低集中在相对狭窄的真空度范围，其中在100 Pa 到10 Pa 之间，电阻率降低了2个数量级。电阻率在10 Pa 退火时达到最小值，继续提高真空度，电阻率不再继续降低。澄清了以往对溶胶-凝胶法制备透明导电后续处理工艺的模糊认识。以上述工艺制备的Fe3O4/AlO/C60/Co/Al复合薄膜结构，磁阻率达到3%，在目前的报导中处于领先地位。研究了稀土掺杂铁电与多铁纳米结构的等离子体共振荧光增强，通过比较BaMnF4与BaMgF4:Yb3+,Tm3+纳米氟化物多铁，在等离子体共振基元下Mn2+的d-f斯托克斯发射与 Tm3+的f-f反斯托克斯发射的荧光增强效果，确定等离子体耦合是由激活离子的激发态所诱导的理论模型。应用乙醛还原银氨溶液法对铁电光催化纳米晶Bi2WO6:Yb3+,Tm3+表面进行0.5%纳米银沉积后，上转换增强7倍。研究了BaTiO3:Yb3+,Er3+反蛋白石光子晶体上转换发光过程，观测到光子带隙在抑制Er3+绿光发射的同时，红光发射得到增强。分析表明交叉弛豫过程与能量逆传递过程，在光子晶体结构中都有增强的趋势，光子晶体结构实现了对两种以上激发态过程的协同调控。利用压电效应调控光子带隙，同时达成对铁电体中的稀土离子发光过程的经典外场调控与光子带隙量子调控。

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