Department of Chemistry, Ulsan National Institute of Science and Technology (UNIST), Ulsan, Republic of Korea.
Center for Multidimensional Carbon Materials, Institute for Basic Science (IBS), Ulsan, Republic of Korea.
Nature. 2022 Jun;606(7912):88-93. doi: 10.1038/s41586-022-04745-7. Epub 2022 Jun 1.
Large-area single-crystal monolayers of two-dimensional (2D) materials such as graphene, hexagonal boron nitride (hBN) and transition metal dichalcogenides have been grown. hBN is considered to be the 'ideal' dielectric for 2D-materials-based field-effect transistors (FETs), offering the potential for extending Moore's law. Although hBN thicker than a monolayer is more desirable as substrate for 2D semiconductors, highly uniform and single-crystal multilayer hBN growth has yet to be demonstrated. Here we report the epitaxial growth of wafer-scale single-crystal trilayer hBN by a chemical vapour deposition (CVD) method. Uniformly aligned hBN islands are found to grow on single-crystal Ni (111) at early stage and finally to coalesce into a single-crystal film. Cross-sectional transmission electron microscopy (TEM) results show that a NiB interlayer is formed (during cooling) between the single-crystal hBN film and Ni substrate by boron dissolution in Ni. There are epitaxial relationships between hBN and NiB and between NiB and Ni. We also find that the hBN film acts as a protective layer that remains intact during catalytic evolution of hydrogen, suggesting continuous single-crystal hBN. This hBN transferred onto the SiO (300 nm)/Si wafer acts as a dielectric layer to reduce electron doping from the SiO substrate in MoS FETs. Our results demonstrate high-quality single-crystal multilayered hBN over large areas, which should open up new pathways for making it a ubiquitous substrate for 2D semiconductors.
大面积二维（2D）材料单晶单层，如石墨烯、六方氮化硼（hBN）和过渡金属二卤化物，已经被生长出来。hBN 被认为是 2D 材料场效应晶体管（FET）的“理想”介电材料，有潜力延长摩尔定律。尽管比单层更厚的 hBN 作为 2D 半导体的衬底更理想，但高度均匀和单晶多层 hBN 的生长尚未得到证明。在这里，我们报告了通过化学气相沉积（CVD）方法外延生长晶圆级单晶三层 hBN。在早期阶段，发现均匀排列的 hBN 岛在单晶 Ni（111）上生长，最终合并成单晶膜。横截面透射电子显微镜（TEM）结果表明，在单晶 hBN 薄膜和 Ni 衬底之间形成了 NiB 中间层（在冷却过程中），这是通过硼在 Ni 中的溶解产生的。hBN 和 NiB 之间以及 NiB 和 Ni 之间存在外延关系。我们还发现，hBN 薄膜在氢气的催化演化过程中充当保护层，保持完整，表明连续的单晶 hBN。转移到 SiO（300nm）/Si 晶片上的 hBN 充当介电层，以减少来自 SiO 衬底的电子掺杂在 MoS FET 中。我们的结果表明，大面积高质量单晶多层 hBN 已经实现，这应该为使其成为 2D 半导体普遍使用的衬底开辟新途径。
