薄膜中界面相变机制的研究

Phase transformations occurred in thin solid film are different from that in bulk materials. In thin film, the Gibbs free energy change at interface plays an important and even a decisive role in the phase transformation. In this project, the investigated systems are chosen as metal/amorphous semiconductor and metal/metal thin solid films and the goal is to investigate both theoretically and experimentally the mechansims of phase transformation occurred at interface in these two systems, including the metal-induced crystallization of amorphous semiconductor and the compound formation at interface. .In theory, the Gibbs free energy values at interfaces will be first calculated based on the interfacial thermodynamical theory. Then the most stable phases and the possible procedures of phase transformation will be evaluated by comparing the changes of the interfacial Gibbs free energy under different conditions. By these theoretical calculations, the mechansims of interfacial phase transformation in thin films can be interpreted detailedly and quantitatively in the framework of a unified thermodynamics. In experiment, some designed experiments will be conducted to testify the calculation results, in particular, focusing on the requirements of nucleation and the procedures of phase transformation..The research methods developed can be applied to the interpretation of interfacial phase transformation in other thin film systems and the research results obtained can be used to provide some guidance suggestions for better use of thin film materials.

薄膜材料中的相变不同于块体材料，薄膜中界面自由能的变化对于相变的发生起着关键，甚至是决定性的作用。本项目以金属/非晶半导体及金属/金属的薄膜体系为研究对象，从理论和实验两个方面，探索发生在这两类薄膜体系中的界面相变，包括金属诱导非晶半导体晶化及界面化合物形成的机制。理论方面，通过界面热力学的方法计算体系的界面自由能，并比较在不同条件下体系自由能的变化，确定体系可能存在的最稳定相，以及随条件改变最有可能发生的相变过程，达到在一个统一的热力学框架下，全面、定量地解释发生在薄膜材料中界面相变机制的目的。实验方面，侧重于在理论计算的基础上，特别是针对相变的成核条件及界面化合物形成的过程，设计一些有针对性的实验，以验证理论计算的结果。由该项目发展起来的一套研究方法，可以推广应用于其它薄膜体系中界面相变的分析，研究结果可以为更好地利用薄膜材料提供具有指导性的建议。

本项目自2013年启动以来，一切按照申请书中制定的计划执行，顺利完成了各项任务指标，其中在发表的论文、参加的学术会议及人才培养三方面均超额完成所制定的指标。在定量表征薄膜中发生扩散的深度剖析定量分析模型，以及确定薄膜相变应满足热力学条件的界面热力学模型两方面做出了创新与拓展。提出了一个具有普适性的深度剖析定量分析模型，能适合于各种薄膜材料深度剖析实验数据的定量分析，有很好的应用价值。拓展的界面热力学模型，在科学上具有一定的创新，解释发生在界面处相变的范围更为广泛了。