Epitaxial growth of large area ZrS₂ 2D semiconductor films on sapphire for optoelectronics

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.