Van der Waals Epitaxy of High‐Quality Transition Metal Dichalcogenides on Single‐Crystal Hexagonal Boron Nitride

Abstract Van der Waals (vdW) heterostructures comprising of transition metal dichalcogenides (TMDs) and hexagonal boron nitride (h‐BN) are promising building blocks for novel 2D devices. The vdW epitaxy provides a straightforward integration method for fabricating high‐quality TMDs/h‐BN vertical heterostructures. In this work, the vdW epitaxy of high‐quality single‐crystal HfSe 2 on epitaxial h‐BN/sapphire substrates by chemical vapor deposition is demonstrated. The epitaxial HfSe 2 layers exhibit a uniform and atomically sharp interface with the underlying h‐BN template, and the epitaxial relationship between HfSe 2 and h‐BN/sapphire is determined to HfSe 2 (0001)[110]//h‐BN (0001)[100]//sapphire (0001)[100]. Impressively, the full width at half maximum of the rocking curve for the epitaxial HfSe 2 layer on single‐crystal h‐BN is as narrow as 9.6 arcmin, indicating an extremely high degree of out‐plane orientation and high crystallinity. Benefitting from the high crystalline quality of HfSe 2 epilayers and the weak interfacial scattering of HfSe 2 /h‐BN, the photodetector fabricated from the vdW epitaxial HfSe 2 on single‐crystal h‐BN shows the best performance with an on/off ratio of 1 × 10 4 and a responsivity up to 43 mA W −1 . Furthermore, the vdW epitaxy of other TMDs such as HfS 2 , ZrS 2 , and ZrSe 2 is also experimentally demonstrated on single‐crystal h‐BN, suggesting the broad applicability of the h‐BN template for the vdW epitaxy.