Chemical vapor deposited monolayer MoS2 top-gate MOSFET with atomic-layer-deposited ZrO2 as gate dielectric
For the first time, ZrO2 dielectric deposition on pristine monolayer MoS2 by atomic layer deposition (ALD) is demonstrated and ZrO2/MoS2 top-gate MOSFETs have been fabricated. ALD ZrO2 overcoat, like other high-k oxides such as HfO2 and Al2O3, was shown to enhance the MoS2 channel mobility. As a result, an on/off current ratio of over 107, a subthreshold slope of 276 mV dec−1, and a field-effect electron mobility of 12.1 cm2 V−1 s−1 have been achieved. The maximum drain current of the MOSFET with a top-gate length of 4 μm and a source/drain spacing of 9 μm is measured to be 1.4 μA μm−1 at V DS = 5 V. The gate leakage current is below 10−2 A cm−2 under a gate bias of 10 V. A high dielectric breakdown field of 4.9 MV cm−1 is obtained. Gate hysteresis and frequency-dependent capacitance–voltage measurements were also performed to characterize the ZrO2/MoS2 interface quality, which yielded an interface state density of ~3 × 1012 cm−2 eV−1.