Seed-assisted polarity control of flexible WSe2 transistors and demonstration of CMOS inverter

Polarity engineering of transition metal dichalcogenide field-effect transistors (FETs) has become a key requirement for complementary logic. Here, we report the polarity control of flexible tungsten diselenide (WSe 2 ) FETs with atomic layer deposited (ALD) top-gate dielectrics. We identify evaporated WO x as suitable seeds for ALD top-gates enabling p-channel WSe 2 FETs, while evaporated Al seeds lead to n-channel FETs. Our flexible p-channel FETs achieve good drain current on/off ratio up to 10 6 , enhancement-mode operation with a negative threshold voltage, and low off-current down to ~6 × 10 − 7 µA/µm, which are important for low-power operation. Combining both seed layers in one fabrication process, we demonstrate flexible WSe 2 complementary metal-oxide-semiconductor (CMOS) inverters. Our inverters show good switching behavior with voltage gain up to 65 and total noise margin up to ~88%. Overall, this study provides a strategy on polarity engineering of flexible WSe 2 FETs and highlights the potential of flexible complementary WSe 2 electronics.