柔性衬底上室温生长高附着性能ZnO基透明导电膜研究

Transparent conductive films (TCFs) require more and more flexibility, because more and more electronic devices require flexibility. Zinc oxide (ZnO), as a novel direct wide-bandgap semiconductor, has merits of a high transparence in the visible region, a room-temperature deposition, and an excellent stability in H plasma, which is an ideal material for TCFs. The flexibility of thin films can come true by using organic substrates. However, ZnO, which is an inorganic material, has the very different properties with the organic substrate. And then it will induce the bad adhesive property between ZnO and organic substrates. So preparing ZnO thin films with excellent adhesive properties is an urgent problem. In this proposal, we will study adhesive properties of flexible ZnO-based TCFs. We will improve the adhesive property to meet the devices application. Flexible ZnO based transparent conductive films will be prepared on polycarbonate (PC) substrates at room temperature by magnetron sputtering. The interface properties between ZnO films and PC substrates will be characterized by all kinds of testing instruments. And then according to the interface properties, the adhesive properties will be improved by surface treatment of PC and buffer layer. The relationship between the adhesive, optical, electrical properties of films and growth process will be found out. The films have excellent adhesive, optical and electrical properties, which will satisfy the practical applications of devices. This will be helpful to advance the development of flexible TCFs and contribute to the applications of flexible electronic devices.

电子器件的发展逐渐趋向柔性化，使得对柔性透明导电膜的需求日益迫切。ZnO作为一种新型宽带半导体，具有可见光透明、室温沉积、在氢等离子体中稳定等优点，成为制备透明导电膜的理想材料。薄膜柔性化通过使用有机衬底来实现，ZnO是无机材料，与有机衬底之间的性质差异较大，易导致两者之间的附着性不好，故高附着性能ZnO膜制备是亟待解决的科学难题。本项目以柔性ZnO基透明导电膜的附着性能为核心展开研究，采用磁控溅射法，以聚碳酸酩酯PC为柔性衬底，室温制备柔性ZnO基透明导电膜。通过各种测试手段表征ZnO膜与PC之间的界面特性，根据界面特性，采取针对性的衬底预处理技术及合适的缓冲层材料来协同提高薄膜的附着性能，与此同时，寻求薄膜附着性能和光电性能与生长工艺之间的关系，在获得优异附着性能的同时保证薄膜具有优异的光电性能，以达到器件的实际应用要求。本项目将促进柔性透明导电膜的发展，为柔性电子器件的应用提供基础。

本项目主要研究了ZnO透明导电薄膜与聚合物衬底PC之间的附着性能，揭示ZnO透明导电膜与聚合物PC衬底之间的附着机理。在保证ZnO薄膜具有优良的导电性和透明性，能够满足光电器件对透明电极的应用要求的基础上，再研究薄膜与衬底之间的附着性能。本项目采用磁控溅射法，使用Ga作为掺杂元素，在聚合物PC衬底上室温沉积Ga掺杂的ZnO透明导电薄膜。通过优化工艺参数，制备得到的薄膜透过率在可见光区域大于90%，电阻率小于10-4Ωcm，方块电阻小于8Ω/sq.，这些指标足以满足一般光电器件对透明导电薄膜的应用要求。薄膜与衬底之间的附着性能通过自动划痕仪进行定量表征。然后，采用二次离子质谱（SIMS）分析ZnO 膜与PC 衬底之间的界面成分分布情况；采用X 射线光电子能谱（XPS）深度剖析方法分析ZnO 膜与PC 衬底之间的界面化学态；采用双轴应力模型获得薄膜内部的残余应力。通过这些测试手段，来了解分析ZnO膜与PC之间的界面特性，从而获得ZnO膜与PC之间的附着机理。通过SIMS测试可知，ZnO薄膜附着在PC衬底上是存在扩散结合的，这主要表现为物理结合为主；通过XPS深度剖析可知，扩散到PC衬底的Zn元素并没有衬底之间形成化学键合，还是以物理结合为主；采用双轴应力模型，计算可知，薄膜内的残余应力为压应力。综上可知，ZnO薄膜与聚合物PC衬底之间结合主要以物理结合为主，同时，ZnO薄膜内存在很大残余压应力，所以最终导致ZnO薄膜与PC衬底之间的附着性能比较差。首次揭示了ZnO透明导电膜与聚合物PC衬底之间的附着机理。为了提高薄膜与衬底之间的附着性能，通过引入热膨胀系数介于ZnO与PC之间的MgO缓冲层及对PC衬底进行UVO预处理等方法，来提高薄膜的附着性能。本项目可促进柔性透明导电膜在柔性电子器件的实际应用。