Electronic, Elastic and Piezoelectric Properties of Two-Dimensional Group-IV Buckled Monolayers*

Abstract

Electronic, elastic and piezoelectric properties of two-dimensional (2D) group-IV buckled monolayers (GeSi, SnSi and SnGe) are studied by first principle calculations. According to our calculations, SnSi and SnGe are good 2D piezoelectric materials with large piezoelectric coefficients. The values of d 11 of SnSi and SnGe are 5.04 pm/V and 5.42 pm/V, respectively, which are much larger than 2D MoS2 (3.6 pm/V) and are comparable with some frequently used bulk materials (e.g., wurtzite AlN 5.1 pm/V). Charge transfer is calculated by the Löwdin analysis and we find that the piezoelectric coefficients (d 11 and d31) are highly dependent on the polarizabilities of the anions and cations in group-IV monolayers.

Bonding, structure, and mechanical stability of 2D materials: the predictive power of the periodic table

“…While a single vacancy has a negligible effect on the elastic modulus, it may decrease substantially with increasing density of vacancies. 128 DFT-LDA Fig. 15 The stacking orders AA, AB, and AC of bilayers of buckled hexagonal monolayers.…”

“…Table 4 provides the cohesive energies and structural data of the planar group IV carbides SiC, [112][113][114][115][116][117] GeC, 115,[118][119][120] and SnC 115,121,122 and the buckled monolayers SiGe, 115,123,124,128 SnSi, 115,122,125,126 and SnGe. 115,122,125,126 The dependence of the cohesive energy on bond length of these binary compounds is displayed in Fig.…”

“…Table 5 displays the corresponding mechanical properties of the carbides SiC, 114,118,127 GeC, 118,119 and SnC 115 and the binary monolayers SiGe, 115,118,128 SnSi, 115,128 and SnGe. 115,128 The plot of Young's moduli and ultimate strengths of the planar carbides and buckled compounds versus bond length in Fig.…”

“…Table 5 displays the corresponding mechanical properties of the carbides SiC, 114,118,127 GeC, 118,119 and SnC 115 and the binary monolayers SiGe, 115,118,128 SnSi, 115,128 and SnGe. 115,128 The plot of Young's moduli and ultimate strengths of the planar carbides and buckled compounds versus bond length in Fig. 13(b) shows a joint inverse dependence of elementary and binary compounds and reasonable agreement of the few available critical strength values with Griffith's rule.…”

Model Calculation of the Piezoelectric Coefficient of Hexagonal 2D Materials

“…A review of some of the experimental techniques for measuring the piezoelectric coefficients is given in the article by Zhang and Meguid; a typical setup involves a free‐standing film with a lateral electric field applied in an atomic force microscopy setup. Existing models and calculations of piezoelectric coefficients in 2D materials are of two kinds: a quantum‐mechanical but computationally expensive density‐functional theory (DFT)–based one and an equally computationally expensive classical lattice dynamics–based one . These methods rely on a variety of techniques and approximations such as approximations to the density functional and the Berry phase technique (which only treats the electronic contribution) or on semi‐empirical potentials; a review of these methods can be found in the article by Zhang and Meguid, and different DFT‐based techniques are discussed by Alyörük .…”