Search

The lack of the vertical piezoelectricity and the corresponding internal physical mechanism of diamanes limit their applications in the piezoelectric field. The vertical piezoelectricity of the diamane doped with Si/Ge atoms is studied systematically by the first principles calculation. These monolayer diamanes can be regarded as the vertical piezoelectric nano-switches with a moderate barrier. Based on the 25 kinds of monolayers' data, the super-dipole-moment effect is found as the internal mechanism of larger vertical piezoelectricity based on the ordered phase of Born effective charges. It may deepen the understanding of the internal physical mechanism about the piezoelectricity. [ABSTRACT FROM AUTHOR]

Recently, two-dimensional (2D) piezoelectric materials are widely studied, and the vertical piezoelectric properties of 2D materials are highly required to be known in the related theory research works and experiments, so it becomes very important to explore the intrinsic mechanism of piezoelectricity in the 2D materials. Herein, we systematically study the piezoelectricity of Janus C3HFX (X = Si and Ge) monolayers with semiconductor property, which are carbon-based 2D materials, using the first-principles calculation. The remarkable enhancements on the absolute values of the vertical piezoelectric coefficient of C3HFSi-1 (e33 = 11.27 × 10−10 C/m) and C3HFGe-4 (e33 = −12.78 × 10−10 C/m) are larger than that of C4HF (e33 = −2.28 × 10−10 C/m) by 5 and 6 times, respectively. It indicates that the atom replacement at appropriate positions in the multiatomic monolayer can significantly enhance the vertical piezoelectric properties based on the appropriate distribution of polarization charge. We define the concepts, the Born effective charges center (BECs-center) and the BECs-dipole-moment in this work, to explain these large vertical piezoelectric coefficients' variation. The larger BECs-dipole-moment will enhance the vertical piezoelectricity for these C3HFX monolayers than that of the C4HF monolayer. These concepts defined in this work will deepen the understanding of the internal physical mechanism about the piezoelectricity. [ABSTRACT FROM AUTHOR]