Role of Buffer Layer and Building Unit in the Monolayer CrI₃ Growth: A First-Principles Perspective

CrI₃, a two-dimensional layered material, has recently attracted a lot of research interest due to its exotic magnetic property. However, the synthesis of a CrI₃ monolayer (ML) by vapor-phase deposition has not been achieved by current experimental endeavors, which require a better understanding of the vapor-phase growth mechanism involved. In this study, we theoretically simulate the growth of the CrI₃ ML on the Si(111) surface by using a first-principles calculation. Our key finding is that an iodine buffer layer on the Si surface is crucial to the formation of the CrI₃ ML by stabilizing the precursor and also reacting with the precursor. Moreover, our simulation reveals that the CrI₂ cluster as the growth building unit, which can be formed by controlling the chemical potential of the I source, is preferred for the formation of CrI₃ ML. We think that our work will provide insightful guidance for the experimental synthesis of CrI₃ ML in the future.