Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States.
University of Tennessee , Knoxville, Tennessee 37996, United States.
Nano Lett. 2017 Dec 13;17(12):7306-7314. doi: 10.1021/acs.nanolett.7b02841. Epub 2017 Nov 21.
Chemical vapor deposition (CVD) has been established as the most effective way to grow large area two-dimensional materials. Direct study of the etching process can reveal subtleties of this competing with the growth reaction and thus provide the necessary details of the overall growth mechanism. Here we investigate hydrogen-induced etching of hBN and graphene and compare the results with the classical kinetic Wulff construction model. Formation of the anisotropically etched holes in the center of hBN and graphene single crystals was observed along with the changes in the crystals' circumference. We show that the edges of triangular holes in hBN crystals formed at regular etching conditions are parallel to B-terminated zigzags, opposite to the N-terminated zigzag edges of hBN triangular crystals. The morphology of the etched hBN holes is affected by a disbalance of the B/N ratio upon etching and can be shifted toward the anticipated from the Wulff model N-terminated zigzag by etching in a nitrogen buffer gas instead of a typical argon. For graphene, etched hexagonal holes are terminated by zigzag, while the crystal circumference is gradually changing from a pure zigzag to a slanted angle resulting in dodecagons.
化学气相沉积（CVD）已被确立为生长大面积二维材料的最有效方法。直接研究刻蚀过程可以揭示与生长反应竞争的细微差别，从而为整体生长机制提供必要的细节。在这里，我们研究了氢诱导的 hBN 和石墨烯的刻蚀，并将结果与经典的动力学 Wulff 结构模型进行了比较。在 hBN 和石墨烯单晶的中心观察到各向异性刻蚀孔的形成，同时晶体周长也发生了变化。我们表明，在规则刻蚀条件下形成的 hBN 晶体中三角形孔的边缘与 B 端锯齿形平行，与 hBN 三角形晶体的 N 端锯齿形边缘相反。在刻蚀过程中，由于 B/N 比例失衡，hBN 孔的形貌会受到影响，并且可以通过在氮气缓冲气体中而不是典型的氩气中刻蚀来向预期的 Wulff 模型 N 端锯齿形移动。对于石墨烯，刻蚀的六边形孔由锯齿形终止，而晶体周长则逐渐从纯锯齿形变为倾斜角，从而形成十二边形。
