Hydrophilic Substrates: A Key toward Wrinkle-Free Wet Transfer of Two-Dimensional Materials

Two-dimensional transition metal dichalcogenides (TMDs) have been recognized as next-generation semiconductor materials with tremendous potential in electronics and optoelectronics, owing to their promising electrical and optical properties. Though wafer-scale high-quality TMDs films have been achieved, a transfer method is always needed to transfer the as-synthesized TMDs from the as-grown substrate to the target substrate. The imperfect interface between the target substrate and TMDs results in poor device performance. In this study, we find that a highly hydrophilic atomic layer-deposited (ALD)-Al₂O₃ layer is beneficial to obtain transferred monolayer WS₂ films without wrinkles. Uniform photoluminescence distribution confirms the wrinkle-free transfer of the monolayer WS₂ film on the ALD-Al₂O₃-mediated substrate. Field-effect transistors based on monolayer WS₂ with ALD-Al₂O₃/SiO₂ as the gate dielectric exhibit an 80% reduction in hysteresis compared to devices with SiO₂ as the gate dielectric, along with an increased electron mobility of up to 15.81 cm²·V^-1·s^-1 achieved by directly utilizing Al₂O₃ as the high-k gate dielectric. Furthermore, the phototransistor based on the FET exhibits a responsivity as high as 1354 A·W^-1 at a gate voltage of 5 V under 405 nm light illumination with an intensity of 75 μW·cm^-2. Our results demonstrate that employing hydrophilic substrates as target substrates during wet transfer enables wrinkle-free transfer of two-dimensional materials, establishing a viable route to achieve high-quality two-dimensional material films and thereby facilitating enhanced device performance.