Tuning the electronic properties through phase engineering of two-dimensional transition metal dichalcogenides (TMDCs) is promising for their applications in electronic devices, energy conversion, and so on. Here, we establish a phase-field continuum mechanics model that accounts for both the finite deformation and mechanically induced phase transition of monolayer molybdenum disulfide (MoS₂) and molybdenum ditelluride (MoTe₂). Informed by first-principle calculations, our model can accurately describe not only the nonlinear mechanical behavior but also the phase transition criteria and processes driven by the mechanical energy. Applied to the nanoindentation tests on MoS₂ drum specimens, the model reproduces well the force vs. depth curves and provides rich details on how the phase transition initiates and develops near the contact region. Further, based on the mechanical instability analysis, our study suggests that MoS₂ monolayers under indentation tests would fail prematurely due to the mechanical instability in shear mode before the phase transition completes. In comparison, MoTe₂ can finish the phase transition without worrying about mechanical instability, as observed in the indentation experiments. The model and methodology developed herein would serve as a powerful tool to guide the phase engineering of two-dimensional TMDCs.

通过二维过渡金属二硫属化物（TMDCs）的相工程来调整电子特性对于它们在电子器件、能量转换等方面的应用很有前景。在这里，我们建立了一个相场连续介质力学模型，该模型解释了单层二硫化钼 (MoS ₂ ) 和二碲化钼 (MoTe ₂ ) 的有限变形和机械诱导的相变。通过第一性原理计算，我们的模型不仅可以准确地描述非线性机械行为，还可以准确地描述由机械能驱动的相变标准和过程。应用于 MoS ₂鼓样品的纳米压痕测试，该模型很好地再现了力与压力的关系。深度曲线，并提供有关相变如何在接触区域附近开始和发展的丰富细节。此外，基于机械不稳定性分析，我们的研究表明，在相变完成之前，由于剪切模式的机械不稳定性，压痕测试下的 MoS _{2单层会过早失效。}相比之下，MoTe ₂可以完成相变而不用担心机械不稳定性，正如在压痕实验中观察到的那样。本文开发的模型和方法将作为指导二维 TMDC 相位工程的有力工具。