薄膜材料因其几何尺寸特征和良好的物理性能而被广泛地应用于电子工业、航空航天、医疗设备等领域。理论和实验已表明，应力对薄膜的结构、性能和可靠性都有重要影响。薄膜材料生成制备或工作于不同物理场环境下（如温度、磁场、电场等），薄膜内的应力状态与作用物理场的关系十分复杂。因此，本文以薄膜应力为中心，从实验和理论两方面进行了如下研究工作：首先，本文利用拉伸试验机测试了多层薄膜在不同温度下的拉伸性能，同时利用三点弯和自重悬臂梁方法测试了多层薄膜的弯曲刚度，并对测试方法和实验数据进行分析。然后，本文研究了薄膜变形与应力的光测实验方法，分析了相干梯度敏感方法的精度和影响因素，并扩展其应用范围，使其能够用于高温环境测试。本文从方法的基本原理出发，研究近似条件对实验参数的限制，指出光源波长和照明范围是精度的决定因素。光束在光栅中的折射会导致测量误差，而且误差会随着光栅厚度增加而增大，本文通过光路分析，提出了考虑光栅厚度影响的修正公式，并进行了实验验证。位相型光栅可以增加光束的剪切量，提高精度。本文通过理论分析证明，当外界温度稳定时，传统的控制方程仍然适用。所得的这些结果可以为优化实验参数提供依据。此外，本文研究了薄膜/基底系统在温度、磁场等不同物理场下的应力分布。分析了置于梯度温度场的薄膜/基底系统曲率分叉行为，当热失配应变达到临界值时，系统会从等双轴变形过渡到双轴变形状态。利用位移法求解置于面内非均匀梯度温度场下的薄膜/基底系统的应力状态，建立基底曲率、薄膜应力与温度分布的关系。利用相干梯度敏感方法测量了薄膜在高温下的非均匀应力，获得了薄膜/基底界面之间的剪切应力。对于置于双向磁场的磁性薄膜，建立了薄膜磁化强度与基底非均匀曲率之间的关系。最后，本文研究在温度场下材料的高温氧化过程。对于单面氧化情况，考虑氧化生长应变，提出了弹性和蠕变两种模型，模型预测与实验结果的对比表明蠕变模型能更准确地反映实际情况。本文还考虑了应力与扩散的耦合作用，对于氧扩散为控制步骤的氧化过程，建立了氧化动力学与应力演化的耦合控制方程，揭示了应力扩散耦合作用机制，研究结果表明应力与氧化过程相互抑制。
Thin film materials, due to their size and excellent physical properties, are applied to a variety of industries such as integrated circuits, aviation and aerospace, medical equipment and so on. Such devices are usually fabricated based on thin film/substrate system. It has been described both in theory and experiment that the stresses are crucial to the structure, property and liability of the thin film. Thin film devices are often fabricated by sophisticated process or subjected to different physical fields (for instance temperature or magnetic field), and the relationship between the stresses in the film and the physical fields are complicated. Therefore, this paper focuses on the research of the stress in the film owing to the thermo-magneto-mechanical coupling effects by theoretical analysis and experiments. The main contents of this paper are as follows:The tensile property of the multilayer film at different temperatures is obtained by testing machine. The bending stiffness of the film is measured through three point bending and drape test, and the testing method and experimental results are analyzed.Second, the optical method for thin film/substrate system deformation and stress measurement is researched. The sensitivity and influential factors of the coherent gradient sensing (CGS) method are analyzed, and CGS is extended to be used at high temperature. It is pointed out in this paper that the assumptions used for CGS principle restrict the experimental parameters, and the laser wavelength and sample size determine the sensitivity. The refraction of the beam in the grating can cause error in curvature measurements, and as the grating thickness increases the error will enlarge. A modified governing equation for CGS is proposed in order to eliminate the grating thickness effects, which is demonstrated by experiments. It is showed that the phase Ronchi grating can increase the lateral shift of the beam, then the measurement sensitivity is enhanced, and the experimental operation is also simplified by using this grating. Besides the grating effects, it is proved that when the ambient temperature is stable, the conventional governing equation is still applicable. All of the above results can be used to optimize the experimental parameters.Then, the stresses in the thin film/substrate system subject to high temperature or magnetic field are analyzed in theory and experiment. It shows that, for the thin film/substrate system under the gradient temperature, as the thermal mismatch strain reaches the critical value, the deformation of the system will change from equi-biaxial condition to biaxial state, which is also referred as curvature bifurcation. The relationship between the stresses in the film and the non-uniform gradient temperature distribution is established by solving the differential equilibrium equation. Using CGS method, this paper represents the stress in the film and the interfacial shear stress at the film/substrate interface obtained at high temperature. It is pointed out in this paper that for the ferromagnetic film/substrate system in the magnetic field the magnetization of the film can be related to the substrate curvature.Finally, the stress evolution in the oxide film/substrate system during oxidation at high temperature is studied. Two models are proposed for single surface oxidation considering the growth strain. One is the elastic model the other is the creep model. The comparison between the model prediction and the experimental data demonstrates that the creep model is more consistent to the real condition. The stress diffusion coupling effect is also analyzed in this paper, and a coupled governing equation for oxidation kinetics and stress evolution is established. The results reveal the mechanism of the stress diffusion coupling effect and show that the oxidation and stress are inhibited by each other.
