Multilayer hexagonal boron nitride (h-BN) is an ideal insulator for two-dimensional (2D) materials, such as graphene and transition metal dichalcogenides, because h-BN screens out influences from surroundings, allowing one to observe intrinsic physical properties of the 2D materials. However, the synthesis of large and uniform multilayer h-BN is still very challenging because it is difficult to control the segregation process of B and N atoms from metal catalysts during chemical vapor deposition (CVD) growth. Here, we demonstrate CVD growth of multilayer h-BN with high uniformity by using the Ni–Fe alloy film and borazine (B₃H₆N₃) as catalyst and precursor, respectively. Combining Ni and Fe metals tunes the solubilities of B and N atoms and, at the same time, allows one to engineer the metal crystallinity, which stimulates the uniform segregation of multilayer h-BN. Furthermore, we demonstrate that triangular WS₂ grains grown on the h-BN show photoluminescence stronger than that grown on a bare SiO₂ substrate. The PL line width of WS₂/h-BN (the minimum and mean widths are 24 and 43 meV, respectively) is much narrower than those of WS₂/SiO₂ (44 and 67 meV), indicating the effectiveness of our CVD-grown multilayer h-BN as an insulating layer. Large-area, multilayer h-BN realized in this work will provide an excellent platform for developing practical applications of 2D materials.

中文翻译：

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大面积均匀多层六方氮化硼作为有效2D衬底的受控生长

多层六方氮化硼（h-BN）是二维（2D）材料的理想绝缘体，例如石墨烯和过渡金属二卤化物，因为h-BN可以屏蔽周围环境的影响，从而使人们可以观察2D的固有物理特性材料。然而，合成大而均匀的多层h-BN仍然非常具有挑战性，因为在化学气相沉积（CVD）生长过程中难以控制B和N原子与金属催化剂的分离过程。在这里，我们通过使用镍铁合金膜和硼嗪（B ₃ H ₆ N ₃）分别作为催化剂和前体。结合使用镍和铁金属可调节B和N原子的溶解度，同时使人们能够控制金属的结晶度，从而刺激多层h-BN的均匀偏析。此外，我们证明了在h-BN上生长的三角形WS ₂晶粒显示出比在裸露的SiO ₂衬底上生长的三角形更强的光致发光。WS ₂ / h-BN的PL线宽度（最小宽度和平均宽度分别为24和43 meV）比WS ₂ / SiO ₂的PL线宽度窄得多（44和67 meV），表明我们的CVD生长的多层h-BN作为绝缘层的有效性。通过这项工作实现的大面积多层h-BN将为开发2D材料的实际应用提供一个极好的平台。