Enhanced piezoelectricity and modified dielectric screening of two-dimensional group-IV monochalcogenides

Gomes, Lídia C.; Carvalho, Alexandra; Neto, A. H. Castro

doi:10.1103/physrevb.92.214103

Cited by 202 publications

(193 citation statements)

References 37 publications

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“…Since the P nma-ML structure is piezoelectric, the application of an electric field along the polar (x) direction in a mechanically free sample induces strain as well [23]. However, here we will consider, for simplicity, the application of an electric field to a mechanically clamped sample.…”

Section: Application Of Electric Fieldmentioning

confidence: 99%

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Polarization and valley switching in monolayer group-IV monochalcogenides

et al. 2016

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Group-IV monochalcogenides are a family of two-dimensional puckered materials with an orthorhombic structure that is comprised of polar layers. In this article, we use first principles calculations to show the multistability of monolayer SnS and GeSe, two prototype materials where the direction of the puckering can be switched by application of tensile stress or electric field. Furthermore, the two inequivalent valleys in momentum space, which dictated by the puckering orientation, can be excited selectively using linearly polarized light, and this provides additional tool to identify the polarization direction. Our findings suggest that SnS and GeSe monolayers may have observable ferroelectricity and multistability, with potential applications in information storage. The discovery of 2D materials that can be isolated into single layers through exfoliation and exhibit novel properties has established new paradigms for ultrathin devices based on atomically sharp interfaces [1,2]. In particular, transition metal dichalcogenides (TMDs) have been studied extensively and have shown potential for many technological applications ranging from photovoltaics to valleytronic devices [3][4][5][6][7][8][9]. The family of monolayer 2D materials has recently grown to include other 2D semiconductors, such as phosphorene and related materials.However, one of the features thus far lacking for applications both in 2D electronics and in valleytronics is non-volatile memory. Ferromagnetism, an essential element in spintronic memories, is believed to be achievable in graphene and other 2D materials but so far remains difficult to realize and control [10]. Ferroelectric memories, in which the information is stored in the orientation of the electric dipole rather than in the magnetization are a possible option. Single-layer graphene (SLG) ferroelectric field-effect transistors (FFET) with symmetrical bit writing have been demonstrated [11], but the prototypes rely on bulk or thin film ferroelectric substrates [11] or ferroelectric polymers [12], rather than on crystalline atomically thin ferroelectric materials. An altogether different approach to information storage relies on phase change materials, where the bit value corresponds to a distinct structural phase of the material. Researchers have recently optimized the phase switching energy by using superlattice structures where the movement of the atoms is confined to only one dimension [13].In this article, we analyze the stability of group-IV monochalcogenide MX (M=Ge or Sn, and X=S or Se) monolayers, paying particular interest to their potential as memory functional materials. As prototypes, we use SnS and GeSe. In ambient conditions, bulk SnS and GeSe crystallize in the orthorhombic structure of the P nma space group. At 878 K, SnS goes through a secondorder displacive phase transition into the β-SnS phase with Cmcm symmetry [14,15], which is also a layered phase that can be viewed as a distorted rocksalt structure. For bulk GeSe, such a phase transition has not been observed. Ins...

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Section: Application Of Electric Fieldmentioning

confidence: 99%

“…In monolayer form, they feature multiple valleys, large spin-orbit splitting[21] and a piezoelectric coefficient that surpasses that of the TMDs [22,23]. Having an in-plane polar axis makes SnS and GeSe monolayers capable of a mechanical response to an applied electric field.…”

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confidence: 99%

Polarization and valley switching in monolayer group-IV monochalcogenides

et al. 2016

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“…Additionally, the proposed device based on 2D materials meets the requirement of next-generation electronic products towards miniaturization and multifunctionality. On account of the inverse piezoelectric effect [22,23], continuous tunability of band gap in monolayer GeSe can be realized via external electric fields. Thus, the more advanced polarizer with advantage of wide operating wavelength range is emerging to further widen the valleytronic applications.…”

Section: Introductionmentioning

confidence: 99%

Electrically tunable polarizer based on 2D orthorhombic ferrovalley materials

et al. 2017

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The concept of ferrovalley materials has been proposed very recently. The existence of spontaneous valley polarization, resulting from ferromagnetism, in such hexagonal two-dimensional materials makes nonvolatile valleytronic applications realizable. Here, we introduce a new member of ferrovalley family with orthorhombic lattice, i.e. monolayer group-IV monochalcogenides (GIVMs), in which the intrinsic valley polarization originates from ferroelectricity, instead of ferromagnetism. Combining the group theory analysis and first-principles calculations, we demonstrate that, different from the valley-selective circular dichroism in hexagonal lattice, linearly polarized optical selectivity for valleys exists in the new type of ferrovalley materials. On account of the distinctive property, a prototype of electrically tunable polarizer is realized. In the ferrovalley-based polarizer, a laser beam can be optionally polarized in x-or y-direction, depending on the ferrovalley state controlled by external electric fields. Such a device can be further optimized to emit circularly polarized radiation with specific chirality and to realize the tunability for operating wavelength. Therefore, we show that two-dimensional orthorhombic ferrovalley materials are the promising candidates to provide an advantageous platform to realize the polarizer driven by electric means, which is of great importance in extending the practical applications of valleytronics.

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“…Recently, peculiar piezoelectric properties of two-dimensional dielectric materials have been demonstrated by both experimental and theoretical studies [7][8][9][10][11]. The relaxed-ion piezoelectric stress (e11) and piezoelectric strain (d11) coefficients of single layer hexagonal BN, and transition metal dichalcogenides such as MoS2, MoSe2, WS2, and WSe2 have been determined as comparable or even better than those of conventional bulk piezoelectric materials by density functional perturbation theory calculations (DFPT) [7].…”

Section: Introductionmentioning

confidence: 99%

“…Following these studies, the piezoelectric properties of different group III [10], and group IV monochalcogenides [11] have been studied by finite displacement (FD) method based on polarization calculations via density functional theory. Quite surprisingly, the mechanical-electrical energy conversion ratio, d11 coefficients of some of these materials has been calculated to be one or two orders of magnitude larger than that of conventional bulk materials such as α-quartz (d11 = 2.3 pmV -1 ), wurtzite- [8], CdO [7], GeSe, and SnSe3 [9], respectively.…”

Section: Introductionmentioning

confidence: 99%

Assessment on The Accuracy of Piezoelectric Property Calculations of Single Layer Two Dimensional Hexagonal Crystals

Sevik¹

2017

ANADOLU UNIVERSITY JOURNAL OF SCIENCE AND TECHNOLOGY a - Applied Sciences and Engineering

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The finite difference and the density functional perturbation theory based piezoelectric property calculation methods are applied to the novel two dimensional hexagonal materials named as group II-VI monolayers and transition metal dichalcogenides for the purposes of comparison. The clamped-and relaxed-ion coefficients have been calculated separately to test the accuracy of both methods on electronic and ionic piezoelectric response contributions. While there is no significant difference between the clamped-ion piezoelectric coefficients calculated with these two methods, a notable difference between the values for relaxedion piezoelectric coefficients are determined. Considering the results of the density functional perturbation theory given in the previous applications, it has been determined that the consistency of the finite difference method in the ionic contribution calculation do not provide reliable results for some 2D materials. We have predicted that the atomic relaxation for different strain values is not adequate to achieve accurate results for ionic contribution of piezoelectric coefficient. However, on the contrary to the explicit difference in the coefficients calculated with two different approaches, our results clearly show that the piezoelectric potentials of the considered materials can be determined accurately and reliably by both methods.

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Enhanced piezoelectricity and modified dielectric screening of two-dimensional group-IV monochalcogenides

Cited by 202 publications

References 37 publications

Polarization and valley switching in monolayer group-IV monochalcogenides

Polarization and valley switching in monolayer group-IV monochalcogenides

Electrically tunable polarizer based on 2D orthorhombic ferrovalley materials

Assessment on The Accuracy of Piezoelectric Property Calculations of Single Layer Two Dimensional Hexagonal Crystals

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