The enhanced vertical piezoelectricity in Janus C3HFX (X = Si and Ge) monolayers based on the born effective charges dipole-moment

Abstract

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.

Strong Vertical Piezoelectricity and Broad-pH-Value Photocatalyst in Ferroelastic Y2Se2BrF Monolayer

“…They can be converted by piezoelectric materials and photocatalytic technology, respectively. For one thing, piezoelectric materialwhich can achieve the mutual conversion of mechanical and electronic signalshas been extensively investigated due to its applications in collecting water flow, human movement, and walking energy harvesting technology. − Notably, the unique vertical polarization brought about by vertical piezoelectricity holds a significant potential in self-powered batteries, skin patches, and tactile sensors . For another, photocatalysis technology offers a new paradigm for harnessing solar energy.…”