Decoupling Metal Deposition from Contact Formation Enables Polarity Transformation in WSe2 Transistors

Polarity control in two-dimensional (2D) semiconductor field-effect transistors (FETs) is essential for their integration into complementary logic circuits. However, existing polarity-engineering approaches often fail to preserve high-quality contact interfaces because atomically thin 2D semiconductors are highly sensitive to fabrication processes. Here, we introduce an effective buffer-layer removal process that enables polarity transformation while preserving a high-quality contact interface. A thin semimetal layer (Bi or Sb) is deposited prior to high-work-function metal evaporation and subsequently removed by a wet chemical treatment that preserves a high-quality metal/semiconductor interface. Minimizing the contact angle of the rinsing solution suppresses wrinkle and bubble formations and reduces Fermi-level pinning. The same WSe2 transistors transform from semimetal-dominated n-type transport before treatment to high-work-function-metal-dominated p-type transport afterward. Monolayer devices exhibit a maximum two-terminal hole field-effect mobility of 313 cm2 V-1 s-1 after treatment, while also supporting a maximum electron mobility of 41 cm2 V-1 s-1 before treatment. These results demonstrate n-to-p polarity transformation in WSe2 transistors enabled by a removable semimetal layer, providing a potential doping-free route toward complementary 2D electronics.