表面氧压对一维铁电材料畴结构及相关特性影响机理研究

Under ambient condition, some charges may be supplied by the dissociative adsorption, yielding ionic adsorbates on the surface of ferroelectric material. These charges can compensate for the screen charge, reduce the critical thinkness, switch the polarization without domain formation. Recently, all the research are around on the electrochemical interaction between the ferroelectric thin film and ambient. However, there are no report from literature for the electrochemical interaction between one-dimension(1D) ferroelectric nanorob or nanotube and ambient. In this proposal, firstly, we apply the mechanics and thermodynamics method to develop systematically the theoretical model of the electrochemical action and analyse the stability. Secondly, The dynamic evolution of domain pattern will be simulated with the surface electrochemical in the 1D ferroelectric materials by the phase field model. For researching on the mechanism of the influence of the electrochemical on 1D ferroelectric materials, we will take advantage of first principle to investigate the ferroelectric properties, such as the phase transition, polarization, microstructure, and so on. Finally, the dynamical change of the ferroelectric properties will be characterized using XRD, PFM, TEM, etc. The results will develop the theory of the microstructure and properties evlution for 1D ferroelectric material under ambient condition, and provide the benefit of research and development of the nanodevices.

纳米铁电器件在大气或特定的化学环境中，环境物质被铁电材料解离吸附释放电荷，释放的电荷可以有效地补偿铁电材料表面未补偿电荷、降低薄膜的临界尺寸、使自发极化反转甚至极化反转过程中没有反向畴核的形成。目前，对这种电化学作用影响的研究大都集中在铁电薄膜，一维铁电材料与薄膜相比具有更大比表面积，这种电化学作用也更强烈。本项目拟运用力学、热力学、表面电化学的方法建立氧化性气氛对一维铁电纳米材料作用的理论模型并对稳定性做出分析。模拟氧分压变化情况下，铁电材料畴结构、缺陷结构和临界尺寸等铁电相关性能的动态演化过程。深入探讨氧化性气氛对纳米铁电材料相变、极化、微结构等性能影响的微观机理，结合实验数据检验理论模型和模拟结果的可靠性。研究结果将为探讨表面化学环境变化情况下一维铁电纳米线微观结构的演化规律及性能变化的机理提供基础，也为一维铁电纳米材料制作铁电器件设计开发提供理论和实验的保障。

铁电纳米材料作为重要的存储器件、传感器、调制器材料，在现代微电子工业中有着重要的应用，铁电纳米线更是铁电功能器件不可或缺的重要角色。在本项目支持下，课题组根据研究计划，建立了氧分压影响下的铁电纳米线、量子点等的热力学模型，进行了铁电材料的相场模拟，发现氧分压的变化能够有效的反转极化并对铁电畴结构具有较大的影响，并且在不同的温度下材料的铁电特性对氧分压的依赖程度也有不同。对于铁电纳米结构在柔性衬底上出现的弯曲情况，建立了相应的热力学模型，模拟了柔性铁电材料的力学载荷擦除特性、弯曲条件下铁电纳米结构的电热和热电效应，作为铁电纳米线热电效应的进一步延伸，从实验上深入研究了铁电材料的温度品质因数和热敏感性，用于铁电纳米器件的热电效应和温度特性研究。在实验上我们制备了钛酸铅纳米线并测量了其在不同氧压下的电流电压曲线，从而为氧化性气氛传感器制作提供了实验和理论的借鉴。自资助以来共发表SCI收录论文20篇，申请发明专利3项，为Materials撰写综述2篇，共培养博士生7人，硕士生2人。