Knowledge of the mechanical properties and stability of thin film structures is important for device operation. Potential failures related to crack initiation and growth must be identified early, to enable healing through e.g. annealing. Here, three square suspended membranes, formed from a thin layer of cubic silicon carbide (3C-SiC) or germanium (Ge) on a silicon substrate, were characterised by their response to ultrasonic excitation. The resonant frequencies and mode shapes were measured during thermal cycling over a temperature range of 20–100 °C. The influence of temperature on the stress was explored by comparison with predictions from a model of thermal expansion of the combined membrane and substrate. For an ideal, non-cracked sample the stress and Q-factor behaved as predicted. In contrast, for a 3C-SiC and a Ge membrane that had undergone vibration and thermal cycling to simulate extended use, measurements of the stress and Q-factor showed the presence of damage, with the 3C-SiC membrane subsequently breaking. However, the damaged Ge sample showed an improvement to the resonant behaviour on subsequent heating. Scanning electron microscopy showed that this was due to a self-healing of sub-micrometer cracks, caused by expansion of the germanium layer to form bridges over the cracked regions, with the effect also observable in the ultrasonic inspection. [2020-0017]

中文翻译：

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Ge 和 3C-SiC 半导体膜的超声波检测和自修复

了解薄膜结构的机械性能和稳定性对于器件操作很重要。必须及早识别与裂纹萌生和扩展相关的潜在故障，以便通过退火等方式进行修复。在这里，三个方形悬浮膜由硅衬底上的立方碳化硅 (3C-SiC) 或锗 (Ge) 薄层形成，其特征在于它们对超声波激发的响应。在 20–100 °C 的温度范围内的热循环过程中测量了谐振频率和模式形状。通过与组合膜和基板的热膨胀模型的预测进行比较，探讨了温度对应力的影响。对于理想的无裂纹样品，应力和 Q 因子的表现与预测一致。相比之下，对于经过振动和热循环以模拟长期使用的 3C-SiC 和 Ge 膜，应力和 Q 因子的测量表明存在损坏，随后 3C-SiC 膜破裂。然而，损坏的 Ge 样品在随后的加热中显示出共振行为的改善。扫描电子显微镜显示，这是由于亚微米裂纹的自我修复，由锗层膨胀在裂纹区域上形成桥而引起，在超声波检测中也可以观察到这种影响。[2020-0017] 损坏的 Ge 样品在随后的加热中显示出共振行为的改善。扫描电子显微镜显示，这是由于亚微米裂纹的自我修复，由锗层膨胀在裂纹区域上形成桥而引起，在超声波检测中也可以观察到这种影响。[2020-0017] 损坏的 Ge 样品在随后的加热中显示出共振行为的改善。扫描电子显微镜显示，这是由于亚微米裂纹的自我修复，由锗层膨胀在裂纹区域上形成桥而引起，在超声波检测中也可以观察到这种影响。[2020-0017]