Transition

Feb 22, 2019 - Anisotropic two-dimensional materials with direction-dependent mechanical and optical properties have attracted significant attention i...
1 downloads 0 Views 2MB Size
Download PDF
This is an open access article published under an ACS AuthorChoice License, which permits copying and redistribution of the article or any adaptations for non-commercial purposes.

Article Cite This: ACS Omega 2019, 4, 4101−4108

http://pubs.acs.org/journal/acsodf

Elastic Anisotropy and Optic Isotropy in Black Phosphorene/ Transition-Metal Trisulfide van der Waals Heterostructures Baisheng Sa,*,† Jianhui Chen,† Xuhui Yang,† Honglei Yang,† Jingying Zheng,*,† Chao Xu,‡ Junjie Li,§ Bo Wu,† and Hongbing Zhan† †

Downloaded via 46.161.58.202 on February 24, 2019 at 11:49:21 (UTC). See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles.

Key Laboratory of Eco-materials Advanced Technology, College of Materials Science and Engineering, Fuzhou University, Fuzhou 350108, P. R. China ‡ Xiamen Talentmats New Materials Science & Technology Co., Ltd., Xiamen 361015, P. R. China § School of Applied Mathematics, Xiamen University of Technology, Xiamen 361024, P. R. China S Supporting Information *

ABSTRACT: Anisotropic two-dimensional materials with direction-dependent mechanical and optical properties have attracted significant attention in recent years. In this work, based on density functional theory calculations, unexpected elastic anisotropy and optical isotropy in van der Waals (vdW) heterostructures have been theoretically proposed by assembling the well-known anisotropic black phosphorene (BP) and transition-metal trisulfides MS3 (M = Ti, Hf) together. It is interesting to see that the BP/MS3 vdW heterostructures show anisotropic flexibility in different directions according to the elastic constants, Young’s modulus, and Poisson’s ratio. We have further unraveled their physical origin of the type-II band structure nature with their conduction band minimum and valence band maximum separated in different layers. In particular, our results on the optical response functions including the excitonic effects of the BP/MS3 vdW heterostructures suggest their unexpected optical isotropies together with the enhancements of the solar energy conversion efficiency.

1. INTRODUCTION Since the successful synthesis of graphene, an artificial twodimensional (2D) atomically thin honeycomb carbon allotrope,1 the family of 2D materials has been burgeoning to hundreds of members in the past decade.2−11 Among them, low-symmetry 2D materials such as black phosphorene (BP),12−14 tellurene,15−17 monochalcogenides,18−22 dichalcogenides,23−25 and trichalcogenides26−28 have attracted global attention because of their unique asymmetric 2D crystal structures together with their intraplane mechanical, electrical, and optical anisotropies.23,29 For instance, the angle-dependent optical conductivity of BP may allow the construction of plasmonic devices where the surface plasmon polariton frequency will have a strong directional dependence on the wave vector.30 Strong anisotropy quasi-one-dimensional charge density wave states have been observed in TiS3, a typical transition-metal trisulfide.31 It is interesting to note that very different transport properties can be achieved in the field-effect transistors made from the same anisotropic material as well.32 Nevertheless, the small species and amount of 2D systems with asymmetric crystal structures limit the effective application of their anisotropic properties.33,34 Therefore, the development and investigation of novel anisotropic 2D materials is a neverending task and of considerable interest and importance. © 2019 American Chemical Society

Combing two different 2D materials together via the van der Waals (vdW) interaction to obtain the so-called vdW heterostructure is an effective way to extend the number of 2D material family.35−38 It is worth noting that the formation of a vdW heterostructure can not only combine the advantages of two 2D affiliations together but also introduce unexpected novel properties and phenomena.39−42 For instance, flexible and semitransparent devices have been fabricated by combining different 2D semiconductor materials with finetuning of the emission spectra and enhancing electroluminescence.43 By tuning the interfacial distance or applying an external electric filed, the band alignment between graphene and GaSe can be effectively modulated in the GaSe/graphene vdW heterostructure.44−46 ZrS3 and HfS3 monolayers can form a stable type-II vdW heterostructure and show high solar power conversion efficiency up to 18%.47 Superior electrical conductivity, omnidirectional flexibility, and high Li capacity can be achieved at the same time in the BP−TiC2 vdW heterostructure.48 It is noted that the single-layer structures of BP and MX3 (X = Ti, Hf) sharing the same asymmetric Received: January 2, 2019 Accepted: February 4, 2019 Published: February 22, 2019 4101

DOI: 10.1021/acsomega.9b00011 ACS Omega 2019, 4, 4101−4108

ACS Omega

Article

(HfS3) and BP monolayers are Δa = 10.4% and Δb = 2.4% (Δa = 13.0%, Δb = 8.2%), which are larger than the wellknown vdW heterostructures.51,52 However, because the BP monolayer can sustain very large tensile strain and retain good lattice stability,49,53 the construction of a BP−TiS3 (BP−HfS3) heterostructure is still expected. As there are many possible structural configurations between two 2D orthogonal lattices, a global total energy minimum search by combining the TiS3 (HfS3) and BP monolayers together is necessary. We first placed the original TiS3 (HfS3) and BP monolayers together in the same 2D orthogonal lattice and then we shifted the BP monolayer along the directions of lattice a and b independently by the step size of 0.1. After all, we have achieved a total of 100 stacking configurations for the BP−TiS3 (BP−HfS3) heterostructure. Herein, all the configurations were under full structural optimization with convergence criteria in terms of both energy and force. Figure 1c,d represents the cohesive energy mapping and the most energy favorable stacking configurations for the BP−TiS3 and BP−HfS3 heterostructures, respectively, after structural optimization. It is interesting to show that BP−TiS3 and BP−HfS3 heterostructures show a very different cohesive energy mapping feature and stable stacking configuration. The optB88-vdW-optimized 2D lattice parameters of BP−TiS3 and BP−HfS3 heterostructures with the most energy favorable stacking configuration are a(BP−TiS3) = 4.885 Å, b(BP−TiS3) = 3.340 Å, and a(BP−HfS3) = 4.996 Å, b(BP−HfS3) = 3.464 Å, respectively. We found that the BP monolayers sustain tensile strains in the heterostructures. On the contrary, the TiS3 and HfS3 monolayers withstand compression strains in the heterostructures. In addition, it is worth noting that the deformation of BP is much larger than that of TiS3 and HfS3 in the heterostructure, which could enhance the stability of the heterostructure due to the good tensile flexibility of BP.49,53 Furthermore, the binding energy between BP and TiS3 (HfS3) monolayers in the heterostructures is calculated to be 24.44 (22.46) meV/Å2, which is close to the typical vdW binding energy of around 20 meV/Å2 by the advanced DFT calculations.38 Hence, the BP−TiS3 (BP−HfS3) heterostructures belong to the novel growing family of vdW heterostructures.54 The calculated P−P and M− S bond length and the corresponding changes from the monolayers to heterostructures of the BP−TiS3 (BP−HfS3) vdW heterostructure with the most stable stacking configuration are also listed in Table 1. For both cases, the P−P bond length is larger than that in the BP monolayer with positive bond length change values, whereas the M−S bond length is smaller than that in the MS3 monolayer with negative bond length change values, which represent the results that the BP monolayers sustain tensile strain but the MS3 monolayers withstand compression strain in the heterostructures. It is worth noting that all the bond length changes are smaller than 0.06 Å, showing the very small structure rearrangement and good structure stability of the monolayers in the vdW heterostructures. The elastic constants were calculated by a step-by-step stress−strain method55,56 to explore the mechanical stability and biaxial/omnidirectional stretchability of the BP/MS3 vdW heterostructures. For the 2D orthogonal system, there are only four independent elastic constants, C11, C22, C12, and C44, as summarized in Table 2. The elastic coefficient matrix can be represented as

orthogonal 2D crystal structure with reasonable lattice mismatch, which are good counterparts for establishing highquality heterostructures.27,49 Hence, it is very interesting to raise the question that whether BP and MX3 monolayers can form vdW heterostructures and show attractive novel physical and chemical properties.50 Therefore, in this work, BP/MS3 vdW heterostructures were theoretically explored based on advanced vdW-corrected density functional theory (DFT) calculations in order to unravel their interesting mechanical properties, electronic structures, and optical properties. The present results reveal unexpected elastic anisotropy and optical isotropy in the BP/MS3 vdW heterostructures. We assume that these remarkable 2D materials will find their applications in nanoscaled flexible optical and photoelectrical devices.

2. RESULTS AND DISCUSSIONS BP, TiS3, and HfS3 monolayers share a similar orthogonal 2D lattice, and the corresponding structure sketches are illustrated in Figure 1a,b. As listed in Table 1, the optB88-vdW-optimized 2D lattice parameters of BP, TiS3, and HfS3 are a(BP) = 4.506 Å, b(BP) = 3.304 Å; a(TiS3) = 4.974 Å, b(TiS3) = 3.384 Å; and a(HfS3) = 5.094 Å, b(HfS3) = 3.576 Å, respectively, all of which are in excellent agreement with the previous literature.26,27 Herein, the lattice mismatches between TiS3

Figure 1. Structure sketch of (a) BP and (b) MS3. The cohesive mapping and most stable structure configuration sketch of (c) BP− TiS3 heterostructure and (d) BP−HfS3 heterostructure. Herein, the small black balls are P atoms; the small yellow balls are S atoms; and the large red and blue balls are Ti and Hf atoms, respectively. 4102

DOI: 10.1021/acsomega.9b00011 ACS Omega 2019, 4, 4101−4108

ACS Omega

Article

Table 1. Lattice Constants (Å), P−P and M−S Bond Length (Å) Range (from LsM−S to LlM−S) for the BP and MS3 Monolayers and the BP/MS3 Heterostructures, and the Corresponding Changes (Å) of the Bond Length from the Monolayers to Heterostructures ΔLsP−P

system

a

b

LsP−P

BP TiS3 HfS3 BP−TiS3 BP−HfS3

4.506 4.974 5.094 4.885 4.996

3.304 3.384 3.576 3.340 3.464

2.226

ijC11 C12 0 yz ÅÄÅ ∂σ(ε ) ÑÉÑ jj zz ÅÅ j z j Ñ Ñ ÑÑ = jjjjC12 C22 0 zzzz Cij = ÅÅÅ Ñ ÅÅ ∂εi ÑÑ j zz ÅÇ ÑÖε= 0 jj 0 z 0 C 44 k {

2.243 2.278

LlP−P

ΔLsP−P

LsM−S

0.017 0.027

2.456 2.580 2.453 2.568

ΔLsM−S

l LM−S

ΔLlM−S

−0.003 −0.012

2.641 2.699 2.607 2.661

−0.034 −0.038

2.260

0.017 0.052

2.277 2.287

Δ

E (θ ) = 4

4

C11s + C22c + (1)

(C ν(θ ) = −

11

Table 2. Estimated Elastic Constants C11, C22, C12, and C44 (N/m) for the BP and MS3 Monolayers and the BP/MS3 Heterostructures system

C11

C22

C12

C44

BP TiS3 HfS3 BP−TiS3 BP−HfS3

28.4 93.4 89.0 164.6 145.4

115.9 137.3 125.3 264.5 200.9

23.3 14.1 11.3 34.1 19.1

30.7 23.6 23.3 48.7 38.9

+ C22 −

(

Δ C44

)c s +(

Δ C44

C11s 4 + C22c 4

)

− 2C12 c 2s 2 2 2 Δ C44

(2)

− C12(s 4 + c 4)

)

− 2C12 c 2s 2

(3)

where Δ = C11C22 − c = cos θ, and s = sin θ. The corresponding polar diagrams are presented in Figure 2. For C122,

Herein, the elastic constants C11 and C22 describe the response stiffness of the 2D crystal when applied uniaxial tensile strains along the x and y direction, respectively. The elastic constant C12 implies the ability of the material to resist biaxial tensile strain. The elastic constant C44 expresses the deformation resistance of the in-plane shear strain. For all the cases, the calculated elastic constants satisfy the so-called Born’s mechanical stability criteria, C11, C22, C44 > 0 and Δ = C11C22 − C122 > 0, indicating that all the monolayers and vdW heterostructures are mechanically stable. From Table 2, three general roles can be concluded for the 2D monolayers and vdW heterostructures herein: first, the strong mechanical anisotropic behaviors can be seen from the elastic constants table. The calculated elastic constants C22 of both the monolayers and vdW heterostructures are significantly larger than that of C11, indicating that all these 2D materials are stiffer against strain in the zigzag (y) direction than in the armchair (x) direction. Second, the MS3 monolayers present higher rigidity than the BP monolayer with larger elastic constants. Third, the in-plane elastic constants of vdW heterostructures are larger than those of the corresponding monolayers, which means that the 2D monolayers will strain more than the vdW heterostructures under the same applied force. Herein, under strain or deformation, the vdW heterostructures with greater elastic constant or elastic modulus can act as the scaffold material or substrate material, where the interlayer vdW interaction can be employed to introduce a driving force to deform the 2D monolayers with smaller elastic stiffness values. In order to get a further understanding of the mechanical properties of the BP/MS3 vdW heterostructures, we calculated Young’s modulus E(θ) and Poisson’s ν(θ) ratio along the arbitrary in-plane direction θ (θ identifies the angle relative to the armchair direction) from the elastic constants according to the following equations:

Figure 2. Polar diagrams of (a) Young’s modulus E(θ) and (b) Poisson’s ratio ν(θ) for the BP and MS3 monolayers and the BP/MS3 heterostructures, where the angle θ identifies the extension direction with respect to the armchair direction.

the BP monolayer, Young’s modulus and Poisson’s ratio along the y direction are about 3−4 times larger than those along the x direction. It is notable that the small negative Poisson’s ratio around 45° for the BP monolayer well represents the previous theoretical 57 and experimental results. 58 For the MS 3 monolayers, Young’s modulus along the y direction is about 2 times larger than those along the x direction. In addition, Poisson’s ratio around 45° is about 3−4 times larger than those along the axial directions. Anyway, all the monolayers show strong anisotropic mechanical properties according to the plots of Young’s moduli and Poisson’s ratios. Interestingly, although the plots of BP and MS3 monolayers show very different patterns, Young’s moduli and Poisson’s ratio plots of the BP/ MS 3 vdW heterostructures follow the feature of MS 3 monolayers very well. It is because that the rigidity of the MS3 monolayers is stronger than that of the BP monolayer. Anyway, compared with Young’s moduli of typical 2D flexible materials, such as graphene (342.2 N/m)59,60 and BN (275.8 N/m),60,61 the BP/MS3 vdW heterostructures show anisotropic flexibility in different directions. For the better understanding of the electronic structures of the BP/MS3 vdW heterostructures, we started from the initial screening of the band structure of the monolayers. The calculated band structure of BP and MS3 monolayers using the HSE06 hybrid functional based on the optB86-vdW wave 4103

DOI: 10.1021/acsomega.9b00011 ACS Omega 2019, 4, 4101−4108

ACS Omega

Article

HfS3 vdW heterostructure is originated from the Hf 5d electrons. Therefore, it can be concluded that the BP/MS3 vdW heterostructures are typical type-II vdW heterostructures where the CBM and VBM are localized in different monolayers of the heterostructures. It is worth noting that type-II heterostructures are highly desirable optical materials, where the photogenerated electrons and holes can be spatially separated from each other to different layers.37 Such a phenomenon may efficiently reduce the electron−hole recombination probability and facilitate the efficiency for light detection and harvesting.64 To understand how the excitation state and quantum confinement work on the optical properties, the optical responses were explored based on the real and imaginary parts of the time-dependent Hartree−Fock (TDHF) dielectric functions in Figure S2. TDHF simulations have been proved to provide a more accurate optical response with energydistinguished peaks.65 On the basis of the dielectric functions in Figure S2a−c, the optical absorption coefficients of the BP, TiS3, and HfS3 monolayers are presented in Figure 4a−c, respectively. It is obvious that all the monolayers show very strong optical anisotropy features. For the BP monolayer, the optical absorption along the xx direction is much stronger than the yy direction in the infrared and visible light range. In the ultraviolet range, the yy direction optical absorption peaks are

functions are illustrated in Figure S1. The results indicate that the BP and TiS3 monolayers are direct gap semiconductors, where both conduction band minimum (CBM) and valance band maximum (VBM) locate at the Γ point of the first Brillouin zone, whereas the HfS3 monolayer is an indirect gap semiconductor, where CBM locates at the Γ point and VBM locates between the Γ and K high-symmetry points. As is concluded in Table 3, the calculated band gaps using HSE06 Table 3. HSE06 Band Gap Eg (eV), Visible Light Absorption Spectrum Anisotropic Factor A, and TDHF Sunlight Energy Conversion Efficiency P (%) for the BP and MS3 monolayers and the BP/MS3 Heterostructures system

Eg

A

Px

Py

BP TiS3 HfS3 BP−TiS3 BP−HfS3

1.41 1.19 2.10 0.89 1.00

5.05 0.37 0.21 1.15 1.57

0.09 0.07 0.03 0.32 0.19

0.02 0.21 0.09 0.47 0.14

hybrid functional calculations for BP, TiS 3 , and HfS 3 monolayers are 1.41, 1.19, and 2.10 eV, respectively. All the electronic structure results agree well with previously published works.26,27,62,63 It is interesting to note that both the BP/MS3 vdW heterostructures display direct band gap nature according to their HSE06 band structure plots in Figure 3. Both VBM

Figure 3. Band structure characterization plots and projected DFT wave functions of VBM and CBM for (a) BP−TiS3 heterostructure and (b) BP−HfS3 heterostructure. Herein, the size of the red, blue, yellow, and black circles illustrates the projected weight of electrons from Ti, Hf, S, and P atoms, respectively. The cyan and the violet isosurfaces present the positive and negative wave functions, respectively.

and CBM of the two vdW heterostructures are located at the Γ point of the first Brillouin zone. The HSE06-predicted band gap values for BP−TiS3 and BP−HfS3 vdW heterostructures are 0.89 and 1.00 eV, respectively, which are also listed in Table 3. Further investigations on the band decomposition confirmed that the VBM of both the heterostructures is contributed by P atoms and CBM of BP−TiS3(BP−HfS3) vdW heterostructure is contributed by Ti(Hf) atoms. To provide vividly pictures for the better understanding of the role of the constituent layers in the vdW heterostructures, we have further illustrated the DFT wave functions for VBM and CBM in the real space in Figure 3 as well. As can be seen, the VBM of both heterostructures is occupied by the P 3p electrons, whereas the CBM of the BP−TiS3 vdW heterostructure is originated from the Ti 3d electrons, and the CBM of the BP−

Figure 4. Absorption coefficient α of (a) BP, (b) TiS3, and (c) HfS3 monolayers; (d) BP−TiS3 heterostructure; and (e) BP−HfS3 heterostructure obtained using TDHF@HSE06 calculations. 4104

DOI: 10.1021/acsomega.9b00011 ACS Omega 2019, 4, 4101−4108

ACS Omega

Article

higher than the xx direction. However, TiS3 and HfS3 monolayers show very opposite tendencies: the optical absorption along the xx direction is much weaker than the yy direction in the infrared and visible light range. In the ultraviolet range, the optical absorption properties are more or less isotropic. To achieve a quantitative understanding of the optical anisotropy features of the monolayers, we have integrated the optical absorption coefficients in the visible light range of 400−760 nm. The visible light absorption anisotropy factor A can be defined as A = Sxx/Syy, where Sxx and Syy are the area of the optical absorption coefficients in the visible light range along the xx and yy direction, respectively. For a 2D material, an A value of 1 denotes the optical isotropy, and any value that deviates from 1 represents the optical anisotropy. The calculated visible light absorption anisotropy factor A of the monolayers is also listed in Table 3. We observed that the BP, TiS3, and HfS3 monolayers possess strong optical anisotropy with A = 5.05, 0.37, and 0.21, respectively. We have further introduced the methods by Shi and Kioupakis66 to obtain the sunlight energy conversion efficiency P to lowest energy excitons along different directions.67 As the calculated results summarized in Table 3, the sunlight energy conversion efficiencies P of BP, TiS3, and HfS3 monolayers along the xx direction are 0.09, 0.07, and 0.03%, respectively, which are 0.02, 0.21, and 0.09% along the yy direction, respectively. The different energy conversion efficiencies along diffractions indicate strong optical anisotropy of the monolayers as well. We have further illustrated the optical absorption coefficients of the BP/MS3 vdW heterostructures in Figure 4d,e according to the TDHF dielectric functions in Figure S2d,e. It is obvious that the optical absorption of the vdW heterostructures is not simply added by that of the monolayers. Interestingly, the formation of the vdW heterostructures leads to a spectral blue shift along the xx direction and a spectral red shift along the yy direction. As a result, the optical absorption curves are homogenized in different directions. Especially in the visible light range, the difference of the optical absorption of the BP/MS3 vdW heterostructures along the xx direction and yy direction is much less than that of the monolayers. For quantitative understanding of the optical anisotropy features of the heterostructures, we have shown the visible light absorption anisotropy factor A and the sunlight energy conversion efficiency P in Table 3 as well. We have got the visible light absorption anisotropy factor A values of 1.15 and 1.57 for the BP−TiS3 and BP−HfS3 vdW heterostructures, respectively, which show very high isotropic features. The sunlight energy conversion efficiencies P of the BP−TiS3 and BP−HfS3 vdW heterostructures along the xx direction are 0.32 and 0.47%, respectively, which are 0.19 and 0.14% along the yy direction, respectively. We found that the formation of the vdW heterostructures not only leads to optical isotropy but also enhances the solar light energy conversion efficiencies.

heterostructures but show very different cohesive energy mapping features and stable stacking configurations. The elastic constants and mechanical property analyses indicate that the BP/MS3 vdW heterostructures show anisotropic flexibility in different directions. However, further optical properties guarantee their high isotropic visible light absorption features. Our findings will provide valuable insights into the exploration of these remarkable elastic anisotropic and optic isotropic 2D materials and vdW heterostructures and shed light on their applications in flexible optical and photoelectrical devices.

4. COMPUTATIONAL DETAILS Our DFT calculations of the heterostructures were performed using the Vienna Ab initio Simulation Package (VASP)68 in conjunction with the projector-augmented wave69 generalized gradient approximations70 of Perdew−Burke−Ernzerhof71 pseudopotentials. The optB88-vdW functional72 was used for all calculations to enhance the description of the vdW interactions.73 The valence electron configurations for, P, S, Ti, and Hf were 3s23p3, 3s23p4, 3d34s1, and 5d26s2, respectively. We introduced at least 20 Å thick vacuum in the z-axis direction in order to prevent the interaction between periodic images.51 The automatically generated k-point set of 14 × 20 × 1 with the Γ symmetry was used for self-consistent calculations. The relaxation convergence for ions and electrons were 1 × 10−5 and 1 × 10−6 eV, respectively, which were achieved with the cutoff energy of 600 eV. The Heyd− Scuseria−Ernzerhof (HSE06) hybrid functional74 was applied to better describe the band gaps and dielectric functions. To obtain accurate optical dielectric functions comparable with experimental results,37,75 we employed the TDHF calculations76 based on HSE06 wave functions by including the excitonic effects. The crystal structures and isosurfaces were visualized using the VESTA package.77

■

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acsomega.9b00011. Band structure plots for the monolayers and real and imaginary parts of dielectric functions for the monolayers and vdW heterostructures (PDF)

■

AUTHOR INFORMATION

Corresponding Authors

*E-mail: [email protected] (B.S.). *E-mail: [email protected] (J.Z.). ORCID

Baisheng Sa: 0000-0002-9455-7795 Hongbing Zhan: 0000-0002-8748-6642

3. CONCLUSIONS In summary, based on DFT calculations, we have systematically studied the mechanical properties, electronic structures, and optical properties of BP, TiS3, and HfS3 monolayers together with the corresponding heterostructures. The most energetic favorable stacking configurations of the BP−TiS3 and BP−HfS3 heterostructures have been determined by global total energy minimum searching. We have found that the BP− TiS3 and BP−HfS3 heterostructures belong to typical vdW

Notes

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS This work was supported by the National Key Research and Development Program of China (Materials Gnome initiative no. 2017YFB0701701), the National Natural Science Foundation of China (nos. 51872048 and 61504028), the Natural Science Foundation of Fujian Province (nos. 2016J01040, 4105

DOI: 10.1021/acsomega.9b00011 ACS Omega 2019, 4, 4101−4108

ACS Omega

Article

(19) Zhao, L.-D.; Tan, G.; Hao, S.; He, J.; Pei, Y.; Chi, H.; Wang, H.; Gong, S.; Xu, H.; Dravid, V. P.; Uher, C.; Snyder, G. J.; Wolverton, C.; Kanatzidis, M. G. Ultrahigh power factor and thermoelectric performance in hole-doped single-crystal SnSe. Science 2015, 351, 141−144. (20) Huang, S.; Tatsumi, Y.; Ling, X.; Guo, H.; Wang, Z.; Watson, G.; Puretzky, A. A.; Geohegan, D. B.; Kong, J.; Li, J.; Yang, T.; Saito, R.; Dresselhaus, M. S. In-Plane Optical Anisotropy of Layered Gallium Telluride. ACS Nano 2016, 10, 8964−8972. (21) Wang, C.; Yang, S.; Cai, H.; Ataca, C.; Chen, H.; Zhang, X.; Xu, J.; Chen, B.; Wu, K.; Zhang, H.; Liu, L.; Li, J.; Grossman, J. C.; Tongay, S.; Liu, Q. Enhancing light emission efficiency without color change in post-transition metal chalcogenides. Nanoscale 2016, 8, 5820−5825. (22) Lee, C. H.; Krishnamoorthy, S.; O’Hara, D. J.; Brenner, M. R.; Johnson, J. M.; Jamison, J. S.; Myers, R. C.; Kawakami, R. K.; Hwang, J.; Rajan, S. Molecular beam epitaxy of 2D-layered gallium selenide on GaN substrates. J. Appl. Phys. 2017, 121, 094302. (23) Liu, E.; Fu, Y.; Wang, Y.; Feng, Y.; Liu, H.; Wan, X.; Zhou, W.; Wang, B.; Shao, L.; Ho, C.-H.; Huang, Y.-S.; Cao, Z.; Wang, L.; Li, A.; Zeng, J.; Song, F.; Wang, X.; Shi, Y.; Yuan, H.; Hwang, H. Y.; Cui, Y.; Miao, F.; Xing, D. Integrated digital inverters based on twodimensional anisotropic ReS2 field-effect transistors. Nat. Commun. 2015, 6, 6991. (24) Island, J. O.; Barawi, M.; Biele, R.; Almazán, A.; Clamagirand, J. M.; Ares, J. R.; Sánchez, C.; van der Zant, H. S. J.; Á lvarez, J. V.; D’Agosta, R.; Ferrer, I. J.; Castellanos-Gomez, A. TiS3 Transistors with Tailored Morphology and Electrical Properties. Adv. Mater. 2015, 27, 2595−2601. (25) Li, Y.-L.; Li, Y.; Tang, C. Strain engineering and photocatalytic application of single-layer ReS2. Int. J. Hydrogen Energy 2017, 42, 161−167. (26) Dai, J.; Zeng, X. C. Titanium Trisulfide Monolayer: Theoretical Prediction of a New Direct-Gap Semiconductor with High and Anisotropic Carrier Mobility. Angew. Chem. Int. Ed. 2015, 54, 7572− 7576. (27) Jin, Y.; Li, X.; Yang, J. Single layer of MX3 (M = Ti, Zr; X = S, Se, Te): a new platform for nano-electronics and optics. Phys. Chem. Chem. Phys. 2015, 17, 18665−18669. (28) Miao, N.; Zhou, J.; Sa, B.; Xu, B.; Sun, Z. Few-layer arsenic trichalcogenides: Emerging two-dimensional semiconductors with tunable indirect-direct band-gaps. J. Alloys Compd. 2017, 699, 554− 560. (29) Nemilentsau, A.; Low, T.; Hanson, G. Anisotropic 2D Materials for Tunable Hyperbolic Plasmonics. Phys. Rev. Lett. 2016, 116, 066804. (30) Xia, F.; Wang, H.; Jia, Y. Rediscovering black phosphorus as an anisotropic layered material for optoelectronics and electronics. Nat. Commun. 2014, 5, 4458. (31) Huang, C.; Zhang, E.; Yuan, X.; Wang, W.; Liu, Y.; Zhang, C.; Ling, J.; Liu, S.; Xiu, F. Tunable charge density wave in TiS3 nanoribbons. Chin. Phys. B 2017, 26, 067302. (32) Xue, D.-J.; Tan, J.; Hu, J.-S.; Hu, W.; Guo, Y.-G.; Wan, L.-J. Anisotropic Photoresponse Properties of Single Micrometer-Sized GeSe Nanosheet. Adv. Mater. 2012, 24, 4528−4533. (33) Tan, C.; Cao, X.; Wu, X.-J.; He, Q.; Yang, J.; Zhang, X.; Chen, J.; Zhao, W.; Han, S.; Nam, G.-H.; Sindoro, M.; Zhang, H. Recent Advances in Ultrathin Two-Dimensional Nanomaterials. Chem. Rev. 2017, 117, 6225−6331. (34) Liu, G.; Zhen, C.; Kang, Y.; Wang, L.; Cheng, H.-M. Unique physicochemical properties of two-dimensional light absorbers facilitating photocatalysis. Chem. Soc. Rev. 2018, 47, 6410−6444. (35) Geim, A. K.; Grigorieva, I. V. Van der Waals heterostructures. Nature 2013, 499, 419−425. (36) Liu, Y.; Weiss, N. O.; Duan, X.; Cheng, H.-C.; Huang, Y.; Duan, X. Van der Waals heterostructures and devices. Nat. Rev. Mater. 2016, 1, 16042. (37) Guo, Z.; Miao, N.; Zhou, J.; Sa, B.; Sun, Z. Strain-mediated type-I/type-II transition in MXene/Blue phosphorene van der Waals

2016J01216, and 2018J01754), and the Talents Program Foundation for the Distinguished Young Scholars of the Higher Education Institutions of Fujian Province (2017).

■

REFERENCES

(1) Novoselov, K. S.; Geim, A. K.; Morozov, S. V.; Jiang, D.; Zhang, Y.; Dubonos, S. V.; Grigorieva, I. V.; Firsov, A. A. Electric field effect in atomically thin carbon films. Science 2004, 306, 666−669. (2) Wang, X.; Maeda, K.; Thomas, A.; Takanabe, K.; Xin, G.; Carlsson, J. M.; Domen, K.; Antonietti, M. A metal-free polymeric photocatalyst for hydrogen production from water under visible light. Nat. Mater. 2008, 8, 76−80. (3) Naguib, M.; Mochalin, V. N.; Barsoum, M. W.; Gogotsi, Y. 25th Anniversary Article: MXenes: A New Family of Two-Dimensional Materials. Adv. Mater. 2013, 26, 992−1005. (4) Lee, J.-H.; Lee, E. K.; Joo, W.-J.; Jang, Y.; Kim, B.-S.; Lim, J. Y.; Choi, S.-H.; Ahn, S. J.; Ahn, J. R.; Park, M.-H.; Yang, C.-W.; Choi, B. L.; Hwang, S.-W.; Whang, D. Wafer-Scale Growth of Single-Crystal Monolayer Graphene on Reusable Hydrogen-Terminated Germanium. Science 2014, 344, 286−289. (5) Sa, B.; Sun, Z.; Wu, B. The development of two dimensional group IV chalcogenides, blocks for van der Waals heterostructures. Nanoscale 2016, 8, 1169−1178. (6) Zhao, J.; Liu, H.; Yu, Z.; Quhe, R.; Zhou, S.; Wang, Y.; Liu, C. C.; Zhong, H.; Han, N.; Lu, J.; Yao, Y.; Wu, K. Rise of silicene: A competitive 2D material. Prog. Mater. Sci. 2016, 83, 24−151. (7) Li, Y.; Li, Y.-L.; Sa, B.; Ahuja, R. Review of two-dimensional materials for photocatalytic water splitting from a theoretical perspective. Catal. Sci. Technol. 2017, 7, 545−559. (8) Hu, D.; Xu, G.; Xing, L.; Yan, X.; Wang, J.; Zheng, J.; Lu, Z.; Wang, P.; Pan, X.; Jiao, L. Two-Dimensional Semiconductors Grown by Chemical Vapor Transport. Angew. Chem. Int. Ed. 2017, 56, 3611− 3615. (9) Si, C.; Zhou, J.; Sun, Z. Half-Metallic Ferromagnetism and Surface Functionalization-Induced Metal-Insulator Transition in Graphene-like Two-Dimensional Cr2C Crystals. ACS Appl. Mater. Interfaces 2015, 7, 17510−17515. (10) Sang, X.; Xie, Y.; Yilmaz, D. E.; Lotfi, R.; Alhabeb, M.; Ostadhossein, A.; Anasori, B.; Sun, W. W.; Li, X. F.; Xiao, K.; Kent, P. R. C.; van Duin, A. C. T.; Gogotsi, Y.; Unocic, R. R. In situ atomistic insight into the growth mechanisms of single layer 2D transition metal carbides. Nat. Commun. 2018, 9, 2266. (11) Miao, N.; Xu, B.; Zhu, L.; Zhou, J.; Sun, Z. 2D Intrinsic Ferromagnets from van der Waals Antiferromagnets. J. Am. Chem. Soc. 2018, 140, 2417−2420. (12) Li, L.; Yu, Y.; Ye, G. J.; Ge, Q.; Ou, X.; Wu, H.; Feng, D.; Chen, X. H.; Zhang, Y. Black phosphorus field-effect transistors. Nat. Nanotechnol. 2014, 9, 372−377. (13) Liu, H.; Neal, A. T.; Zhu, Z.; Luo, Z.; Xu, X.; Tománek, D.; Ye, P. D. Phosphorene: An Unexplored 2D Semiconductor with a High Hole Mobility. ACS Nano 2014, 8, 4033−4041. (14) Qiao, J.; Kong, X.; Hu, Z.-X.; Yang, F.; Ji, W. High-mobility transport anisotropy and linear dichroism in few-layer black phosphorus. Nat. Commun. 2014, 5, 4475. (15) Huang, X.; Guan, J.; Lin, Z.; Liu, B.; Xing, S.; Wang, W.; Guo, J. Epitaxial Growth and Band Structure of Te Film on Graphene. Nano Lett. 2017, 17, 4619−4623. (16) Huang, X.; Liu, B.; Guan, J.; Miao, G.; Lin, Z.; An, Q.; Zhu, X.; Wang, W.; Guo, J. Realization of In-Plane p-n Junctions with Continuous Lattice of a Homogeneous Material. Adv. Mater. 2018, 30, 1806025. (17) Wang, Y.; Qiu, G.; Wang, R.; Huang, S.; Wang, Q.; Liu, Y.; Du, Y.; Goddard, W. A., III; Kim, M. J.; Xu, X.; Ye, P. D.; Wu, W. Fieldeffect transistors made from solution-grown two-dimensional tellurene. Nat. Electron. 2018, 1, 228−236. (18) Safdar, M.; Wang, Q.; Mirza, M.; Wang, Z.; Xu, K.; He, J. Topological Surface Transport Properties of Single-Crystalline SnTe Nanowire. Nano Lett. 2013, 13, 5344−5349. 4106

DOI: 10.1021/acsomega.9b00011 ACS Omega 2019, 4, 4101−4108

ACS Omega

Article

heterostructures for flexible optical/electronic devices. J. Mater. Chem. C 2017, 5, 978−984. (38) Liao, J.; Sa, B.; Zhou, J.; Ahuja, R.; Sun, Z. Design of HighEfficiency Visible-Light Photocatalysts for Water Splitting: MoS2/ AlN(GaN) Heterostructures. J. Phys. Chem. C 2014, 118, 17594− 17599. (39) Chiu, M.-H.; Zhang, C.; Shiu, H.-W.; Chuu, C.-P.; Chen, C.H.; Chang, C.-Y. S.; Chen, C.-H.; Chou, M.-Y.; Shih, C.-K.; Li, L.-J. J. N. c. Determination of band alignment in the single-layer MoS2/WSe2 heterojunction. Nature 2015, 6, 7666. (40) Pierucci, D.; Henck, H.; Naylor, C. H.; Sediri, H.; Lhuillier, E.; Balan, A.; Rault, J. E.; Dappe, Y. J.; Bertran, F.; Le Fèvre, P. J. S. r. Large area molybdenum disulphide-epitaxial graphene vertical Van der Waals heterostructures. Sci. Rep. 2016, 6, 26656. (41) Nourbakhsh, A.; Zubair, A.; Dresselhaus, M. S.; Palacios, T. Transport properties of a MoS2/WSe2 heterojunction transistor and its potential for application. Nano Lett. 2016, 16, 1359−1366. (42) Pierucci, D.; Henck, H.; Avila, J.; Balan, A.; Naylor, C. H.; Patriarche, G.; Dappe, Y. J.; Silly, M. G.; Sirotti, F.; Johnson, A. T. C.; Asensio, M. C.; Ouerghi, A. Band Alignment and Minigaps in Monolayer MoS2-Graphene van der Waals Heterostructures. Nano Lett. 2016, 16, 4054−4061. (43) Withers, F.; Del Pozo-Zamudio, O.; Mishchenko, A.; Rooney, A. P.; Gholinia, A.; Watanabe, K.; Taniguchi, T.; Haigh, S. J.; Geim, A. K.; Tartakovskii, A. I.; Novoselov, K. S. Light-emitting diodes by band-structure engineering in van der Waals heterostructures. Nat. Mater. 2015, 14, 301−306. (44) Si, C.; Lin, Z.; Zhou, J.; Sun, Z. Controllable Schottky barrier in GaSe/graphene heterostructure: the role of interface dipole. 2D Mater 2016, 4, 015027. (45) Aziza, Z. B.; Henck, H.; Pierucci, D.; Silly, M. G.; Lhuillier, E.; Patriarche, G.; Sirotti, F.; Eddrief, M.; Ouerghi, A. van der Waals epitaxy of GaSe/graphene heterostructure: electronic and interfacial properties. ACS Nano 2016, 10, 9679−9686. (46) Aziza, Z. B.; Zólyomi, V.; Henck, H.; Pierucci, D.; Silly, M. G.; Avila, J.; Magorrian, S. J.; Chaste, J.; Chen, C.; Yoon, M. J. P. R. B. Valence band inversion and spin-orbit effects in the electronic structure of monolayer GaSe. Phys. Rev. B 2018, 98, 115405. (47) Zhao, Q.; Guo, Y.; Zhou, Y.; Yao, Z.; Ren, Z.; Bai, J.; Xu, X. Band alignments and heterostructures of monolayer transition metal trichalcogenides MX3 (M = Zr, Hf; X = S, Se) and dichalcogenides MX2 (M = Tc, Re; X = S, Se) for solar applications. Nanoscale 2018, 10, 3547−3555. (48) Peng, Q.; Hu, K.; Sa, B.; Zhou, J.; Wu, B.; Hou, X.; Sun, Z. Unexpected elastic isotropy in a black phosphorene/TiC2 van der Waals heterostructure with flexible Li-ion battery anode applications. Nano Res. 2017, 10, 3136−3150. (49) Sa, B.; Li, Y.-L.; Qi, J.; Ahuja, R.; Sun, Z. Strain Engineering for Phosphorene: The Potential Application as a Photocatalyst. J. Phys. Chem. C 2014, 118, 26560−26568. (50) Phuc, H. V.; Hieu, N. N.; Hoi, B. D.; Nguyen, C. V. Interlayer coupling and electric field tunable electronic properties and Schottky barrier in a graphene/bilayer-GaSe van der Waals heterostructure. Phys. Chem. Chem. Phys. 2018, 20, 17899−17908. (51) Peng, Q.; Wang, Z.; Sa, B.; Wu, B.; Sun, Z. Blue Phosphorene/ MS2 (M = Nb, Ta) Heterostructures As Promising Flexible Anodes for Lithium-Ion Batteries. ACS Appl. Mater. Interfaces 2016, 8, 13449−13457. (52) Yuan, J.; Yu, N.; Wang, J.; Xue, K.-H.; Miao, X. Design lateral heterostructure of monolayer ZrS2 and HfS2 from first principles calculations. Appl. Surf. Sci. 2018, 436, 919−926. (53) Wei, Q.; Peng, X. Superior mechanical flexibility of phosphorene and few-layer black phosphorus. Appl. Phys. Lett. 2014, 104, 251915. (54) Novoselov, K. S.; Mishchenko, A.; Carvalho, A.; Neto, A. H. C. 2D materials and van der Waals heterostructures. Science 2016, 353, aac9439.

(55) Sun, Z.; Ahuja, R.; Lowther, J. E. Mechanical properties of vanadium carbide and a ternary vanadium tungsten carbide. Solid State Commun. 2010, 150, 697−700. (56) Sa, B.; Zhou, J.; Ahuja, R.; Sun, Z. First-principles investigations of electronic and mechanical properties for stable Ge2Sb2Te5 with van der Waals corrections. Comput. Mater. Sci. 2014, 82, 66−69. (57) Jiang, J.-W.; Park, H. S. Negative Poisson’s ratio in single-layer black phosphorus. Nat. Commun. 2014, 5, 4727. (58) Du, Y.; Maassen, J.; Wu, W.; Luo, Z.; Xu, X.; Ye, P. D. Auxetic Black Phosphorus: A 2D Material with Negative Poisson’s Ratio. Nano Lett. 2016, 16, 6701−6708. (59) Lee, C.; Wei, X.; Kysar, J. W.; Hone, J. Measurement of the elastic properties and intrinsic strength of monolayer graphene. Science 2008, 321, 385−388. (60) Andrew, R. C.; Mapasha, R. E.; Ukpong, A. M.; Chetty, N. Mechanical properties of graphene and boronitrene. Phys. Rev. B: Condens. Matter Mater. Phys. 2012, 85, 125408. (61) Song, L.; Ci, L.; Lu, H.; Sorokin, P. B.; Jin, C.; Ni, J.; Kvashnin, A. G.; Kvashnin, D. G.; Lou, J.; Yakobson, B. I.; Ajayan, P. M. Large Scale Growth and Characterization of Atomic Hexagonal Boron Nitride Layers. Nano Lett. 2010, 10, 3209−3215. (62) Henck, H.; Aziza, Z. B.; Pierucci, D.; Laourine, F.; Reale, F.; Palczynski, P.; Chaste, J.; Silly, M. G.; Bertran, F.; Le Fèvre, P. J. P. R. B. Electronic band structure of Two-Dimensional WS2/Graphene van der Waals Heterostructures. Phys. Rev. B 2018, 97, 155421. (63) Wilson, N. R.; Nguyen, P. V.; Seyler, K.; Rivera, P.; Marsden, A. J.; Laker, Z. P. L.; Constantinescu, G. C.; Kandyba, V.; Barinov, A.; Hine, N. D. M.; Xu, X.; Cobden, D. H. Determination of band offsets, hybridization, and exciton binding in 2D semiconductor heterostructures. Sci. Adv. 2017, 3, No. e1601832. (64) Peng, Q.; Wang, Z.; Sa, B.; Wu, B.; Sun, Z. Electronic structures and enhanced optical properties of blue phosphorene/transition metal dichalcogenides van der Waals heterostructures. Sci. Rep. 2016, 6, 31994. (65) Guo, Z.; Zhou, J.; Zhu, L.; Sun, Z. MXene: a promising photocatalyst for water splitting. J. Mater. Chem. A 2016, 4, 11446− 11452. (66) Shi, G.; Kioupakis, E. Anisotropic Spin Transport and Strong Visible-Light Absorbance in Few-Layer SnSe and GeSe. Nano Lett. 2015, 15, 6926−6931. (67) Peng, Q.; Xiong, R.; Sa, B.; Zhou, J.; Wen, C.; Wu, B.; Anpo, M.; Sun, Z. Computational mining of photocatalysts for water splitting hydrogen production: two-dimensional InSe-family monolayers. Catal. Sci. Technol. 2017, 7, 2744−2752. (68) Hafner, J. Ab-initio simulations of materials using VASP: Density-functional theory and beyond. J. Comput. Chem. 2008, 29, 2044−2078. (69) Perdew, J. P.; Wang, Y. Accurate and simple analytic representation of the electron-gas correlation energy. Phys. Rev. B: Condens. Matter Mater. Phys. 1992, 45, 13244−13249. (70) Kresse, G.; Hafner, J. Ab initio molecular dynamics for openshell transition metals. Phys. Rev. B: Condens. Matter Mater. Phys. 1993, 48, 13115−13118. (71) Perdew, J. P.; Burke, K.; Wang, Y. Generalized gradient approximation for the exchange-correlation hole of a many-electron system. Phys. Rev. B: Condens. Matter Mater. Phys. 1996, 54, 16533− 16539. (72) Thonhauser, T.; Cooper, V. R.; Li, S.; Puzder, A.; Hyldgaard, P.; Langreth, D. C. Van der Waals density functional: Self-consistent potential and the nature of the van der Waals bond. Phys. Rev. B: Condens. Matter Mater. Phys. 2007, 76, 125112. (73) Yang, X.; Sa, B.; Zhan, H.; Sun, Z. Electric field-modulated data storage in bilayer InSe. J. Mater. Chem. C 2017, 5, 12228−12234. (74) Paier, J.; Marsman, M.; Hummer, K.; Kresse, G.; Gerber, I. C.; Á ngyán, J. G. Screened hybrid density functionals applied to solids. J. Chem. Phys. 2006, 124, 154709. (75) Mak, K. F.; Lee, C.; Hone, J.; Shan, J.; Heinz, T. F. Atomically Thin MoS2: A New Direct-Gap Semiconductor. Phys. Rev. Lett. 2010, 105, 136805. 4107

DOI: 10.1021/acsomega.9b00011 ACS Omega 2019, 4, 4101−4108

ACS Omega

Article

(76) Furche, F.; Ahlrichs, R. Adiabatic time-dependent density functional methods for excited state properties. J. Chem. Phys. 2002, 117, 7433−7447. (77) Momma, K.; Izumi, F. VESTA 3for three-dimensional visualization of crystal, volumetric and morphology data. J. Appl. Crystallogr. 2011, 44, 1272−1276.

4108

DOI: 10.1021/acsomega.9b00011 ACS Omega 2019, 4, 4101−4108