Controlled Synthesis and Interfacial Bonding of Hexagonal Diamond/Wurtzite Boron Nitride Covalent Heterostructures.

Heterostructures, mediated by either weak van der Waals (vdW) coupling or chemical bonding at the heterointerface, can compensate for the inherent shortcomings of individual components and achieve exotic properties through their effective integration. The isoelectronic diamond and boron nitride (BN) can present both cubic and wurtzite polymorphs and hence prospectively form diverse heterostructures. However, synthesizing the metastable hexagonal diamond/wurtzite BN (HD/wBN) covalent heterostructures and clarifying the interfacial chemical bonds remain great challenges, despite considerable effort. In this study, we have demonstrated the direct synthesis of high-quality HD/wBN covalent heterostructures via structural transformation of graphite/hBN vdW heterostructures under high pressure and high temperature. Raman and structural characterizations evidently confirmed the sharp HD/wBN heterointerface with both C─B and C─N bonds, attributed to inversion domain boundaries within the wBN phase. The mapped pressure-temperature diagram exhibited the confined window required for HD/wBN heterostructures. Our work provides a viable pathway to prepare various covalent heterostructures through synergistic phase transitions and opens new opportunities for exploring their pronounced properties.