hBN/Graphene 2D Heterostructures: from scalable growth to integration

石墨烯是一种2D材料，以其特殊的电子性质而闻名。然而，为了在实际器件中利用这些特性，必须大力降低与衬底和任何周围材料的电子耦合。六方氮化硼(HBN)是另一种二维材料，在这方面非常有前途。它既可用于将石墨烯与衬底绝缘，也可用作栅电介质材料。虽然通过机械剥离和转移获得的器件确实证实了石墨烯/hBN异质结构的巨大潜力，但一种可扩展和可靠的生长技术仍然有待验证：开发新的方法来制备2D异质结构是非常重要的。通过结合项目合作伙伴的技术诀窍和资源，拟议研究的目的是探索和开发在与硅微电子兼容的衬底上制备石墨烯/hBN异质结构的各种方法。为了实现这些目标，石墨烯/hBN异质结的生长主要有两种方法：分子束外延和化学气相沉积。该工艺可以通过在项目过程中开发的特定成核增强的横向图案来改进。先进的显微镜和光谱技术将被用来提供关于薄膜的形态、晶体、化学和电学性质的信息。我们将通过从头算密度泛函理论和大规模动力学蒙特卡罗模拟相结合的方法进行原子计算，以了解生长机制和最佳工艺条件。此外，在考虑到这个项目之外的最终目标，即这种异质结构的生长用于器件应用的同时，这些研究将揭示hBN在石墨烯上和石墨烯在hBN上特有的成核和生长机制。这种机制应该推广到一般范德华(VDW)体系，hBN和石墨烯都属于VDW体系。这将通过在以各种方式获得并因此包含各种成核中心的VDW衬底上进行实验，以及通过先进的成像技术深入检查典型样品并辅之以理论计算来阐明所涉及的化学反应的细节并模拟生长来实现。了解这些机理不仅具有基础性的科学意义，而且对石墨烯/hBN及类似体系的进一步发展也具有重要意义。这些实验将在与CMOS兼容的材料上进行，使这项研究变得独特，因为其结果可能直接为进一步的石墨烯/hBN集成和主流硅技术中的器件原型铺平道路。

Graphene is a 2D material, famous for its exceptional electronic properties. However, to exploit these properties in real devices, the electronic coupling with the substrate and with any surrounding material must be strongly reduced. Hexagonal boron nitride (hBN), another 2D material, is very promising for this purpose. It could be used both to insulate graphene from the substrate and as a gate dielectric material. Although devices obtained by mechanical exfoliation and transfer did confirm the strong potentialities of graphene/hBN heterostructures, a scalable and reliable growth technique remains to be demonstrated: the development of new approaches to the fabrication of 2D heterostructures is of high importance. By combining the know-how and resources of the project partners, the aim of the proposed study is to explore and develop various ways to fabricate graphene/hBN heterostructures on substrates compatible with Si microelectronics. Towards these goals, graphene/hBN heterostructures will be grown by two major methods: molecular beam epitaxy and chemical vapor deposition. The process may be improved by specific nucleation-enhanced lateral patterning to be developed in the course of the project. Advanced microscopy and spectroscopy techniques will be applied to provide information on the morphological, crystallographic, chemical and electrical properties of the films. Atomistic calculations by ab initio density functional theory complemented with large scale kinetic Monte Carlo simulations will be conducted to understand the growth mechanisms and optimal process conditions.Moreover, while keeping in mind the ultimate goal that goes beyond this project, i.e., the growth of such heterostructures for device applications, the studies will result in the disclosure of the nucleation and growth mechanisms specific to hBN on graphene and to graphene on hBN. Such mechanisms should be generalized to generic Van der Waals (VdW) systems, to which both hBN and graphene belong. This will be made possible by performing the experiments on VdW substrates obtained in various ways and thus containing various types of nucleation centers, and by in-depth examination of typical samples by advanced imaging techniques augmented by theoretical calculations to elucidate the details of the chemical reactions involved and to simulate the growth. To understand the mechanisms is not only of fundamental scientific interest, but it is as well important for further development of graphene/hBN and similar systems. The experiments will be carried out on CMOS compatible materials, making this study unique, as its results might directly pave the way to the further graphene/hBN integration and device prototyping within the mainstream Si technologies.