Magnesium niobate as a high-κ gate dielectric for two-dimensional electronics
摘要
Integrated circuits based on two-dimensional semiconductors require ultrathin gate insulators that can provide high interface quality and dielectric reliability, minimized electrically active traps and efficient gate controllability. However, existing two-dimensional insulators do not provide a good trade-off in terms of bandgap, breakdown strength, dielectric constant, leakage current and bias temperature stability. Here, we show that single crystals of magnesium niobate (MgNb2O6) can be obtained through a buffer-controlled epitaxial growth process on a mica substrate. The atomically thin MgNb2O6 crystals have a wide bandgap (around 5.0 eV), high dielectric constant (around 20), large breakdown voltage (around 16 MV cm−1) and good thermal reliability. The MgNb2O6 can form a van der Waals interface with monolayer molybdenum disulfide (MoS2) with an extremely low density of trap states. MoS2 field-effect transistors with MgNb2O6 gate dielectrics exhibit a hysteresis under 0.9 mV (MV cm−1)−1, a subthreshold swing of 62 mV dec−1, an on/off current ratio of up to 4 × 107 and high electrical reliability at 500 K. The excellent electrostatic controllability of MgNb2O6 allowed us to create graphene-contacted transistors and inverter circuits with a channel length of 50 nm.