Chemical vapor deposition of monolayer MoS₂ directly on ultrathin Al₂O₃ for low-power electronics

Monolayer MoS₂ has recently been identified as a promising material for high-performance electronics. However, monolayer MoS₂ must be integrated with ultrathin high-κ gate dielectrics in order to realize practical low-power devices. In this letter, we report the chemical vapor deposition (CVD) of monolayer MoS₂ directly on 20 nm thick Al₂O₃ grown by atomic layer deposition (ALD). The quality of the resulting MoS₂ is characterized by a comprehensive set of microscopic and spectroscopic techniques. Furthermore, a low-temperature (200 °C) Al₂O₃ ALD process is developed that maintains dielectric integrity following the high-temperature CVD of MoS₂ (800 °C). Field-effect transistors (FETs) derived from these MoS₂/Al₂O₃ stacks show minimal hysteresis with a sub-threshold swing as low as ∼220 mV/decade, threshold voltages of ∼2 V, and current I_ON/I_OFF ratio as high as ∼10⁴, where I_OFF is defined as the current at zero gate voltage as is customary for determining power consumption in complementary logic circuits. The system presented here concurrently optimizes multiple low-power electronics figures of merit while providing a transfer-free method of integrating monolayer MoS₂ with ultrathin high-κ dielectrics, thus enabling a scalable pathway for enhancement-mode FETs for low-power applications.