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

Abstract

Inspired by the typical two-dimensional (2D) black-phosphorene-type structure with mm2 point-group symmetry, the structural stability, electronic structure, and intrinsic piezoelectricity of 2D ternary GaXY (X = Se and Te; Y = Cl, Br, and I) monolayers are systematically studied by the first-principles density functional theory. Our calculations show that these ternary monolayer compounds exhibit desirable dynamical and thermal stabilities and a large variety of bandgaps. The calculated piezoelectric coefficients d 11 is as large as 15.57 pm/V for GaTeF, and the largest d 12 reaches to 3.78 pm/V for GaSeI. It is worth noting that the e ij and d ij coefficients of GaXY monolayers display anisotropic periodic trends with respect to the constituent elements, which could be interpreted by a linear correlation between the piezoelectric coefficients and the differences in anionic polarizabilities a X or a Y . It is found that d 11 of GaXY monolayers is directly proportional to ða X À a Y Þ, while d 12 is inversely proportional to ða X À a Y Þ. Such anisotropic correlation could be applicable to elucidate the origin of the piezoelectricity in other 2D ternary compounds.

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

“…Moreover, the much larger piezoelectric coefficients in the range of 9.13–29.52 pm V −1 are obtained in CuMX 2 monolayers. For example, the CuSbSe 2 and CuBiSe 2 monolayers exhibit high coefficients of 29.52 and 26.24 pm V −1 , respectively; obviously, they exceed or approach to those of most well‐studied 2D systems, such as h ‐BN (0.60 pm V −1 ), [ 14 ] MoS 2 (3.73 pm V −1 ), [ 14 ] GaTeF (15.57 pm V −1 ), [ 26 ] SiAs 2 (–17.09 pm V −1 ), [ 22 ] CrTe 2 (17.1 pm V −1 ), [ 17 ] AgBiP 2 S 6 (17.33 pm V −1 ), [ 27 ] α‐AsN (29.14 pm V −1 ), [ 19 ] and P 4 O 2 (54.06 pm V −1 ). [ 20 ]…”

“…Numerous efforts have been made in the past decade to design and develop novel 2D piezoelectric materials for the demand of practical devices. [ 14–28 ] 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.…”

“…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.…”

“…[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. [18,25] Although the piezoelectricity in 2D systems has some advantages, they are inadequate to support the replacement of traditional 3D piezoelectric crystals by 2D counterparts.…”

Ultrahigh mechanical flexibility induced superior piezoelectricity of InSeBr-type 2D Janus materials

“…16 Previous studies suggest that such a high piezoelectric coefficient is mainly attributed to their structural instabilities that could facilitate the polarization rotation. 19,21,22 Recently, twodimensional (2D) piezoelectric materials, [23][24][25][26][27][28][29][30][31] such as SnSe (d 11 = 251 pm V À1 ), 25 SbAs (d 11 = 243 pm V À1 ), 26 and BiInTe 3 (d 11 = 362 pm V À1 ), 27 have been found to exhibit good piezoelectricity. Nonetheless, the piezoelectric properties of 2D materials are still inferior to those of optimized 3D perovskite materials, which significantly restrict the practical applications of the 2D piezoelectric materials in micro-and nano-electronic devices.…”