Ambipolar MoS₂ enabled through high-ε ferroelectric P(VDF-TrFE)

The p-type and n-type transistors are the basic components for building CMOS electronic devices for logic circuits. Most two-dimensional materials are n-type due to strong electron doping by intrinsic structural defects. Notably, the p-type conductivity of MoS₂ is hardly achievable by the limited electric field modulation from the low dielectric constant of Si/SiO₂. However, through strong dielectric screening of a high dielectric constant substrate and powerful polarization electric field of ferroelectric material, the p-type transition of MoS₂ can be realized. In this paper, with the help of ferroelectric field modulation of high dielectric constant P(VDF-TrFE), a significant modulation of the band structure of MoS₂ is realized, and finally, a flexible p-type modulation of MoS₂ is obtained. The band changes and electrical properties of MoS₂ on three different dielectric constant substrates, including Si/SiO₂, hBN, and P(VDF-TrFE), were quantitatively studied with Kelvin probe force microscopy (KPFM). Fermi level changes and band n-p transitions of MoS₂ under ferroelectric modulation were also systematically investigated by KPFM. The ferroelectric modulation of the MoS₂ Fermi level can realize a wide range of flexible modulation up to nearly 900 meV. This work reveals the device physics of the realization of p-type transport from the band perspective and provides an effective and viable reference for p-type modulation of other two-dimensional materials. It also provides a boost for the application of MoS₂ in high-performance electronic and optoelectronic devices.