α-In2O3 monolayer: A promising material as field-effect phototransistor and out-of-plane piezoelectric device.

The α-In 2 O 3 monolayer possesses a direct bandgap, high electrons mobility, excellent optical absorption and out-of-plane piezoelectricity. [Display omitted] • The α-In 2 O 3 monolayer possesses good structural stability and environmental stability, such as oxidation resistance. • The α-In 2 O 3 monolayer is a promising field-effect transistor material with a suitable direct bandgap and high carrier separation efficiency. • The α-In 2 O 3 monolayer is a candidate material for optoelectronic devices due to the excellent optical absorptivity. • The asymmetric α-In 2 O 3 monolayer is a piezoelectric material with superior out-of-plane piezoelectric response ability. Two-dimensional (2D) semiconductors have opened promising avenues for designing advanced functional devices due to their novel electronic features. In this work, the 2D α-In 2 O 3 monolayer is systematically studied using first-principles calculations. Our calculations show that the α-In 2 O 3 monolayer exhibits a stable configuration with good oxidation resistance. The electronic structure calculations identify that α-In 2 O 3 monolayer is a semiconductor with a direct bandgap of 1.41 eV, which makes the α-In 2 O 3 monolayer to be as a promising candidate in modern bottom/top gate technologies. Interestingly, the partial charge density shows that the valence band maximum and conduction band minimum locate at the different atomic region, and the electron carrier mobility of the α-In 2 O 3 monolayer is much larger than hole carrier mobility, indicating that the electrons and holes can be effectively separated. Additionally, the α-In 2 O 3 monolayer has excellent optical absorption coefficient among the infrared and visible range. Hence, the α-In 2 O 3 monolayer can be used as field-effect phototransistor. Moreover, the asymmetric atomic-layer configuration and strong inner covalent bond of the α-In 2 O 3 monolayer induce a superior out-of-plane piezoelectric response (e 31 = 1.81 × 10-10C·m−1, d 31 = -0.89 pm·V−1), make α-In 2 O 3 monolayer as a promising material as out-of-plane piezoelectric device. [ABSTRACT FROM AUTHOR]