Intrinsic piezoelectricity of monolayer group IV–V MX2: SiP2, SiAs2, GeP2, and GeAs2

Abstract

The intrinsic piezoelectric effect of the monolayer group IV–V MX2 (M = Si, Ge and X = P, As) is systematically investigated using the density functional theory based on first-principles calculations and the modern theory of polarization. We find that the piezoelectric coefficients d112D of the compounds are approximately one order of magnitude larger than those of other 2D materials, such as hexagonal boron nitride and MoS2, which have been widely studied both experimentally and theoretically. Furthermore, the coefficients d112D are always one order of magnitude larger than d122D, showing obvious anisotropy. Such strong anisotropy can be easily understood by the C2v symmetry and puckered configuration along the a direction, which leads to considerable flexibility. Our results show that these monolayers of group IV–V MX2 have potential for applications in nanosized sensors, piezotronics, and energy-harvesting in portable electronic nanodevices. Owing to the recent advances in synthesis technologies, it is expected that these monolayers may be put to a wide practical use in the future.

Anisotropic correlation between the piezoelectricity and anion-polarizability difference in 2D phosphorene-type ternary GaXY (X = Se, Te; Y = F, Cl, Br, I) monolayers

“…For example, the calculated piezoelectric coefficient of MoS 2 monolayer has been verified exactly by the subsequent experiments [12]. Although the piezoelectric properties of a lot of 2D materials without centrosymmetry have been systematically investigated and those with very large piezoelectric coefficients have been reported [5,10,[16][17][18][19][20][21], it is still quite difficult to accurately determine the origin of piezoelectricity in the 2D materials. Empirical formulas have been proposed to explain the mechanisms of the periodic trend of piezoelectric response in some 2D piezoelectric materials, such as transition-metal dichalcogenide [18], group III-V compounds [18], and group II-VI compounds [22].…”

Anomalous Anisotropy of the Piezoelectric Response in 2D Copper‐Based Ternary Chalcogenides CuMX2

“…Moreover, the much larger piezoelectric coefficients d 12 in the range of 9.13-29.52 pm V À1 are obtained in CuMX 2 monolayers. For example, the CuSbSe 2 and CuBiSe 2 monolayers exhibit high coefficients d 12 of 29.52 and 26.24 pm V À1 , respectively; obviously, they exceed or approach to those of most well-studied 2D systems, such as h-BN (0.60 pm V À1 ), [14] MoS 2 (3.73 pm V À1 ), [14] GaTeF (15.57 pm V À1 ), [26] SiAs 2 (-17.09 pm V À1 ), [22] CrTe 2 (17.1 pm V À1 ), [17] AgBiP 2 S 6 (17.33 pm V À1 ), [27] α-AsN (29.14 pm V À1 ), [19] and P 4 O 2 (54.06 pm V À1 ). [20] Anisotropic piezoelectricity with respect to different-direction strain or stress almost exists in every previously studied 2D systems with C 2v point-group symmetry, such as group IV monochalcogenides, [16] group V binary compounds, [19] and group IV-V binary monolayers.…”

“…Numerous efforts have been made in the past decade to design and develop novel 2D piezoelectric materials for the demand of practical devices. [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28] It is worth noting that the calculated piezoelectric coefficient of the MoS 2 monolayer has been confirmed by subsequent experiment, [14,18] indicating that theoretical calculation is an effective approach in evaluating piezoelectricity and will play a significant and unique role in studying 2D materials. At the same time, some unique characteristics and mechanisms in 2D piezoelectric materials have been proposed successively, such as anisotropic and multidirectional piezoelectricity, [16,19,24] coexistence of out-of-plane and in-plane piezoelectricity, [15,23] direct correlation between the piezoelectricity and atom polarizability, [15,19,26,28] and layer-dependent piezoelectricity.…”

Multidirectional Intrinsic Piezoelectricity of 2D Metal Chalcogen–Diphosphate ABP2X6 Monolayers

“…For example, the AgBiP 2 S 6 and AgBiP 2 Se 6 monolayers exhibited high d 11 coefficients of 17.33 and 17.25 pm V −1 , respectively; these are generally superior to those of well‐studied 2D materials, such as h‐BN (0.61 pm V −1 ) [ 17 ] and MoS 2 (3.65 pm V −1 ), [ 17 ] and comparable with previously reported CrTe 2 (17.1 pm V −1 ) [ 42 ] and SiAs 2 (–17.09 pm V −1 ). [ 43 ] Furthermore, most of the d 11 coefficients of the monolayers were positive, except for AgInP 2 Se 6 , because of the negative value of e 11 ; this reflects that the polarization changes of the AgInP 2 Se 6 monolayer along the x ‐direction decrease with increasing strain, ε 11 . From Table 1, it can be observed that the displacement, ΔL , between Ag and In atoms in the AgInP 2 Se 6 monolayer is only 0.12 Å.…”