Piezoelectricity in two-dimensional group-III monochalcogenides

KEYWORDS piezoelectricity, two-dimensional (2D) material, monochalcogenide, density functional theory (DFT) calculation ABSTRACT It is found that several layer-phase group-III monochalcogenides, including GaS, GaSe, and InSe, are piezoelectric in their monolayer form. First-principles calculations reveal that the piezoelectric coefficients of monolayer GaS, GaSe, and InSe (2.06, 2.30, and 1.46 pm·V –1) are of the same order of magnitude as previously discovered two-dimensional (2D) piezoelectric materials such as boron nitride (BN) and MoS 2 monolayers. This study therefore indicates that a strong piezoelectric response can be obtained in a wide range of two-dimensional materials with broken inversion symmetry. The coexistence of piezoelectricity and superior photo-sensitivity in these monochalcogenide monolayer semiconductors means they have the potential to allow for the integration of electromechanical and optical sensors on the same material platform.