FeIn₂S₄ Nanocrystals: A Ternary Metal Chalcogenide Material for Ambipolar Field-Effect Transistors

An ambipolar channel layer material is required to realize the potential benefits of ambipolar complementary metal-oxide-semiconductor field-effect transistors, namely their compact and efficient nature, reduced reverse power dissipation, and possible applicability to highly integrated circuits. Here, a ternary metal chalcogenide nanocrystal material, FeIn₂S₄, is introduced as a solution-processable ambipolar channel material for field-effect transistors (FETs). The highest occupied molecular orbital and the lowest unoccupied molecular orbital of the FeIn₂S₄ nanocrystals are determined to be -5.2 and -3.75 eV, respectively, based upon cyclic voltammetry, X-ray photoelectron spectroscopy, and diffraction reflectance spectroscopy analyses. An ambipolar FeIn₂S₄ FET is successfully fabricated with Au electrodes (E_F = -5.1 eV), showing both electron mobility (14.96 cm² V^-1 s^-1) and hole mobility (9.15 cm² V^-1 s^-1) in a single channel layer, with an on/off current ratio of 10⁵. This suggests that FeIn₂S₄ nanocrystals may be a promising alternative semiconducting material for next-generation integrated circuit development.