Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, USA.
Center for 2-Dimensional and Layered Materials, The Pennsylvania State University, University Park, Pennsylvania 16802, USA.
Nat Mater. 2016 Nov;15(11):1166-1171. doi: 10.1038/nmat4742. Epub 2016 Aug 29.
The spectrum of two-dimensional (2D) and layered materials 'beyond graphene' offers a remarkable platform to study new phenomena in condensed matter physics. Among these materials, layered hexagonal boron nitride (hBN), with its wide bandgap energy (∼5.0-6.0 eV), has clearly established that 2D nitrides are key to advancing 2D devices. A gap, however, remains between the theoretical prediction of 2D nitrides 'beyond hBN' and experimental realization of such structures. Here we demonstrate the synthesis of 2D gallium nitride (GaN) via a migration-enhanced encapsulated growth (MEEG) technique utilizing epitaxial graphene. We theoretically predict and experimentally validate that the atomic structure of 2D GaN grown via MEEG is notably different from reported theory. Moreover, we establish that graphene plays a critical role in stabilizing the direct-bandgap (nearly 5.0 eV), 2D buckled structure. Our results provide a foundation for discovery and stabilization of 2D nitrides that are difficult to prepare via traditional synthesis.
二维（2D）和层状材料“超越石墨烯”的光谱为凝聚态物理中新现象的研究提供了一个显著的平台。在这些材料中，具有较宽能带隙能量（~5.0-6.0 eV）的层状六方氮化硼（hBN）已明确表明，2D 氮化物是推进 2D 器件的关键。然而，2D 氮化物“超越 hBN”的理论预测与这种结构的实验实现之间仍存在差距。在这里，我们利用外延石墨烯展示了通过迁移增强封装生长（MEEG）技术合成二维氮化镓（GaN）的方法。我们从理论上预测并从实验上验证了通过 MEEG 生长的二维 GaN 的原子结构与已报道的理论有显著不同。此外，我们确定石墨烯在稳定直接带隙（接近 5.0 eV）、二维褶皱结构方面起着至关重要的作用。我们的研究结果为发现和稳定传统合成方法难以制备的 2D 氮化物提供了基础。
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