Piezoelectricity in 2D nanomaterials-crystal structure and polarization direction

Materials that produce electric charges in response to a mechanical load are known as piezoelectric materials. Materials with a lattice structure devoid of centosymmetry exhibit piezoelectric activity. These days, non-centrosymmetric 2D nanomaterials have been used in many possible applications and have attracted a lot of attention as piezoelectric materials. The crystal structure, crystal nonsymmetry, and nonzero electronic bandgap energy values of two-dimensional nanomaterials have a significant influence on their piezoelectric capabilities. For example, it was discovered that the symmetry of certain mono- or few-layered 2D nanomaterials differed from that of their bulk counterparts. Piezoelectricity is found at the atomic thickness level in many 2D monolayer materials with structurally broken symmetry, but it gradually vanishes with increasing thickness. Secondly, there is a strong correlation between this piezoelectric action and the polarization direction. In this sense, improving the piezoelectric capabilities in 2D mono, few, and multilayer nanomaterials requires a deeper comprehension of the crystal structure and direction of polarization. Based on theoretical and experimental findings, the crystal structure and direction of polarization of various 2D nanomaterials will be the main topics of this review. We will also discuss recent developments and applications of various 2D nanomaterials.