Dark excitons in group VI transition metal dichalcogenides (TMDCs) have garnered significant interest due to their extended charge lifetime, spin lifetime, and diffusion length compared to bright excitons, presenting exciting opportunities for quantum communication and optoelectronic devices. However, their optical insensitivity poses challenges for investigation and manipulation. Here, we employ a strain engineering approach to introduce localized strain in monolayer WSe₂ using a substrate with prepatterned holes, resulting in the hybridization of dark excitons with bright defect states. This hybridization significantly enhances photoluminescence (PL) intensity and reduces the linewidths of dark excitons by orders of magnitude. Additionally, the hybridized states exhibit unique features in temperature-dependent and linearly polarized PL spectra, with stable localization across a broad excitation power range (up to 0.4 mW) and tunable circular polarization under a magnetic field (87% at −9 T). These findings underscore strain engineering as an effective method for enhancing dark excitons and provide new insights into exciton physics in TMDCs, paving the way for advanced optoelectronic technologies.

Integrating β-Ga₂O₃ with two-dimensional (2D) hexagonal boron nitride (h-BN) into heterostructures is of significant importance for achieving high-power device applications. The 2D-materials-assisted epitaxy provides a straightforward integration method for fabricating β-Ga₂O₃/h-BN vertical heterostructures. In this work, the β-Ga₂O₃ films were deposited on both polycrystalline and single-crystalline h-BN layers with different thicknesses, and two growth modes of β-Ga₂O₃ films on h-BN, remote epitaxy and van der Waals (vdW) epitaxy, were investigated. The results show that the potential of the sapphire substrate can penetrate the monolayer and bilayer h-BN to obtain the remote epitaxy of β-Ga₂O₃ films, regardless of the crystallinity of h-BN. The vdW epitaxy of β-Ga₂O₃ film can be realized by on the monocrystalline h-BN substrate. Compared with the conventional and remote epitaxial β-Ga₂O₃ films on sapphire substrate, the vdW epitaxial β-Ga₂O₃ films on the single-crystalline h-BN substrate exhibit higher crystallinity. This work indicates that the 2D-materials-assisted epitaxy provides a feasible scheme for the heterogeneous integration of β-Ga₂O₃ films.

As a very promising epitaxy technology, the remote epitaxy has attracted extensive attention in recent years, in which graphene is the most used interlayer material. As an isomorphic of graphene, two-dimensional (2D) hexagonal boron nitride (h-BN), is another promising interlayer for the remote epitaxy. However, there is a current debate on the feasibility of using h-BN as interlayer in the remote epitaxy. Herein, we demonstrate that the potential field of sapphire can completely penetrate monolayer h-BN, and hence the remote epitaxy of ZrS₂ layers can be realized on sapphire substrates through monolayer h-BN. The field of sapphire can only partially penetrate the bilayer h-BN and result in the mixing of remote epitaxy and van der Waals (vdWs) epitaxy. Due to the weak interfacial scattering and high crystalline quality of ZrS₂ epilayer, the ZrS₂ photodetector with monolayer h-BN shows the best performance, with an on/off ratio of more than 2 × 10⁵ and a responsivity up to 379 mA·W⁻¹. This work provides an efficient approach to prepare single-crystal transition metal dichalcogenides and their heterojunctions with h-BN, which have great potential in developing large-area 2D electronic devices.

Recently, group-IVB semiconducting transition metal dichalcogenides (TMDs) of ZrS₂ have attracted significant research interest due to its layered nature, moderate band gap, and extraordinary physical properties. Most device applications require a deposition of high quality large-area uniform ZrS₂ single crystalline films, which has not yet been achieved. In this work, for the first time, we demonstrate the epitaxial growth of high quality large-area uniform ZrS₂ films on c-plane sapphire substrates by chemical vapor deposition. An atomically sharp interface is observed due to the supercell matching between ZrS₂ and sapphire, and their epitaxial relationship is found to be ZrS₂ (0001)[ $10\overline{1}0$]||Al₂O₃ (0001)[ $11\overline{2}0$]. The epitaxial ZrS₂ film exhibits n-type semiconductor behavior with a room temperature mobility of 2.4 cm²·V⁻¹·s⁻¹, and the optical phonon is the dominant scattering mechanism at room temperature or above. Furthermore, the optoelectronic applications of ZrS₂ films are demonstrated by fabricating photodetector devices. The ZrS₂ photodetectors exhibit the excellent comprehensive performance, such as a light on/off ratio of 10⁶ and a specific detectivity of 2.6 × 10¹² Jones, which are the highest values compared with the photodetectors based on other group-IVB two-dimensional TMDs.