Effect Of Biaxial Strain Research Articles

Adsorption behavior of transition metal (Pd, Pt, Ag and Au) doped SnS monolayers on SF6 decomposed species and the effects of applied electric field and biaxial strain

The adsorption behavior of SF6 characteristic decomposition products (SO2 and SOF2) on intrinsic and transition metal (TM) atom modified SnS monolayers is investigated based on the first principles. The adsorption structure, adsorption energy, density of states, electron localization function, electron density difference, work function, and desorption properties are discussed to evaluate SnS monolayers as potential candidates as adsorbents for SO2 and SOF2. Our results show that the detection performance of the intrinsic SnS monolayer is poor due to the relatively weak interaction with gas molecules. After introducing TM dopants (TM = Pd, Pt, Ag and Au) on SnS monolayer, Pd and Pt atoms tend to be adsorbed on TH sites, while Ag and Au atoms are more easily captured by TS sites. The results of adsorption energy and electronic properties showed that TM atoms could significantly improve the adsorption properties of SO2 and SOF2 molecules on SnS monolayers. Furthermore, the effects of electric field and biaxial strain on the sensing properties of gas molecules on TM-SnS monolayers are also investigated. Finally, the desorption time of gas molecules from the TM-SnS monolayer is estimated to evaluate its potential application in the detection and removal of faulty gases in SF6 power devices. The research results not only reveal the sensing mechanism of the TM-SnS monolayer for the characteristic decomposition products of SF6, but also provide theoretical guidance for the further development of SnS-based adsorbents or scavengers.

Engineering electronic structures of Janus monolayer group-III monochalcogenides via biaxial strain

We investigate the effects of biaxial strain and spin-orbit coupling on the electronic structures of Janus monolayer group-III monochalcogenides based on first-principle calculations. Due to the spin-orbit coupling and mirror symmetry breaking, Rashba band splitting appears at Γ point of the bottom conduction band and the band gap decreases significantly. The spin-orbit coupling strength and electronic structures can be greatly tuned by biaxial strain, which originate from the change of interaction between pz orbitals. As the lattice constant decreases, the interaction between pz orbitals is enhanced, leading to the decrease (increase) of the energy of corresponding bonding (anti-bonding) state, which is the origin of the indirect-direct-indirect transition of the band gap. In addition, when tensile strain is applied, the pz orbital component of Te atoms increases, leading to the enhancement of the Rashba effect. These results are of great significance for the band engineering and spin-orbitronics of two-dimensional materials.

Thermoelectric properties and the effect of biaxial strain and external electric fields on the electronics of novel 2D Lace-like O-Pd2Q3 (Q= S, Se) monolayers

Inspired by the experimental synthesis of the novel 2D O-Pd2Se3 monolayer, we performed density functional theory calculations to reveal detailed investigations of the electronics, and thermal properties of 2D O-Pd2Q3 (Q= S, Se) monolayers. The O-Pd2S3 and Pd2Se3 are semiconductors with indirect band gaps of 0.43 eV and 0.33 eV, respectively. Through strain engineering, the bulk modulus B (N/m) and young's modulus Y (N/m) are also determined to acquire a deep understanding of the elasticity of the monolayers. We find that the bandgaps tend to increase with increasing tensile biaxial strain (+ε%), and decrease with increasing compressive biaxial strain (-ε%). In particular, the O-Pd2Se3 monolayer starts to manifest a metallic feature at -5%. More importantly, we note that at room temperature, and under biaxial strain, O-Pd2S3 (O-Pd2Se3) has a high electron (hole) carrier mobility up to ∼ 766 cm2 V−1 s−1 (∼ 106 cm2 V−1 s−1). We have also tuned the band gaps of the monolayers via the application of an external electric field, along the z-direction. We find that, in the [-2.5, +2.5] V/Å range, such external electric fields reduce the bandgaps in both monolayers, transforming Pd2Se3 into a metal at a strength of ± 2.5 V/Å. Additionally, we have perceived that the thermoelectric (TE) properties of these materials exhibit an anisotropic behavior at ambient and higher temperatures. At 300K, the O- Pd2Se3 monolayers show a large thermal electronic conductivity and a power factor of about 18 (16) times that of O-Pd2S3 along the x (y) directions. At temperatures higher than 600K, these properties become more dominant in O-Pd2S3. The acquired power factor of O-Pd2S3 (O-Pd2Se3) is much higher than that of the 1T phase of PdS2 (1T PdSe2 and penta-PdSe2). By just knowing the group velocities of the three acoustical modes, we were able to determine the minimum lattice thermal conductivity, which is 0.207 W/(m.K) for both systems. If properly exploited, these characteristics make the O-Pd2Q3 monolayers excellent candidates for the fabrication of novel ultrathin electronic and TE nanodevices at ambient and higher temperatures.

Biaxial strain and electric field effects on the electronic, optical, and photocatalytic properties of full hydrogenated SiSn monolayer

The electronic, optical, and photocatalytic characteristics of full hydrogenated stanene-silicene monolayer H–SiSn–H were investigated under biaxial strain and external electric field via first-principles calculations. The binding energy, phonon dispersion and ab initio molecular dynamics simulations display this material's excellent ambient stability. The obtained results show that at the equilibrium, a full hydrogenated SnSi sheet is a direct semiconductor with a gap energy of 2.62 eV by GW approximation. The analysis of band edge alignment indicates that the H– SiSn –H sheet can possess photocatalytic properties for water splitting when biaxial strain or an electric field is applied. We can tune the gap energy of the full hydrogenated SiSn sheet by biaxial strain or electric field. The direct-to-indirect bandgap transition occurs at certain compression of the biaxial strain in this binary system. Comparing to the bare SnSi sheet, the complete hydrogenation causes absorption peaks of SnSi to shift towards the higher frequency region. The optical characteristics of the full hydrogenated SiSn sheet depend greatly on the strain, while the influence of the electric field on them is negligible. These results can provide beneficial information for the potential application of the H–SnSi–H sheet in nanoelectronics and photocatalytic activities.

Strain modulated electronic and optical properties of laterally stitched MoSi2N4/XSi2N4 (X=W, Ti) 2D heterostructures

We used first-principles calculations to investigate the laterally stitched monolayered MoSi2N4/XSi2N4 (X=W, Ti) 2D heterostructures. The structural stability of such heterostructures is confirmed by the phonon spectra exhibiting no negative frequencies. From the electronic band structures, the MoSi2N4/WSi2N4-lateral heterostructure (MWLH) shows semiconducting nature with an indirect bandgap of 2.35 eV, while the MoSi2N4/TiSi2N4-lateral heterostructure (MTLH) revealed metallic behavior. Moreover, the effect of biaxial strain on the electronic and optical properties of MWLH is studied, which indicated substantial modifications in their electronic and optical spectra. In particular, an indirect to direct bandgap semiconducting transition can be achieved in MWLH via compressive strain. Besides, the absorbance, transmittance and reflectance spectra can effectively be tuned by means of biaxial strain. Our findings provide insights into the strain engineering of electronic and optical features, which could pave the way for future nano- and optoelectronic applications.

A in-plane biaxial strain tunable electronic structures and magnetic properties of Fe2C monolayer

This work intends to study the effect of a in-plane biaxial strain (ε) on the electronic structures and magnetic properties of monolayer Fe2C by first-principles calculation. The unstrained and strained Fe2C monolayer is thermally, dynamically, and mechanically stable, and unstrained Fe2C monolayer is ferromagnetic metal with the Curie temperature (TC) of 510 K. Introducing the tensile strain, the magnetic moments, spin polarization and magnetic anisotropy energy (MAE) can be significantly enhanced. Furthermore, a phase transition from ferromagnetic to antiferromagnetic ordering occurs at the ε of 12%, −10%. Especially, the result of Monte Carlo simulations demonstrates that the TC decreases with strain and Néel temperature TN increases with the tensile strain. A tensile strain applied on Fe2C monolayer with the value less than 8% facilitates the enhancement of MAE and spin polarization, and maintaining the TC above room temperature. This study provides a theoretical guide for the application of monolayer Fe2C in spintronic devices, and provides a basis for tuning the physical properties to two-dimensional MXene materials.

Strain-tunable Dzyaloshinskii-Moriya interaction and skyrmions in two-dimensional Janus Cr2X3Y3 ( X, Y = Cl, Br, I, X≠Y ) trihalide monolayers

Recently, great effort has been devoted to the search for two-dimensional (2D) ferromagnetic materials with inherent strong Dzyaloshinskii--Moriya interaction (DMI). Here, through a first-principles approach, we systematically investigate the effect of biaxial strain on the DMI, the Heisenberg exchange interaction, and the magnetic anisotropy energy (MAE) of Janus Cr$_{2}$X$_{3}$Y$_{3}$ (X, Y = Cl, Br, I, X $\neq$ Y) monolayers. Both DMI and MAE can be significantly enhanced by tensile strain, while a reversal of the chirality of DMI in Cr$_{2}$Cl$_{3}$Br$_{3}$ and a switch of MAE from off-plane to in-plane in Cr$_{2}$I$_{3}$Cl$_{3}$ are induced by a compressive strain of $2\%$. Microscopically, DMI and MAE are associated mainly with the large spin--orbit coupling of the heavy nonmagnetic halogen atoms rather than that of the magnetic Cr atoms. In particular, the peculiar magnetic transition of Cr$_{2}$I$_{3}$Cl$_{3}$ is explained by competition between direct exchange and superexchange interactions. Micromagnetic simulations show that a small external magnetic field of 65~mT stabilizes a skyrmion with a diameter of 9.8~nm in the Cr$_2$I$_3$Cl$_3$ monolayer. Our results will provide guidance for further research on DMI and skyrmions in 2D Janus materials, as well as a basis for the potential applications in spintronic devices.

First-principles insights of electronic properties of Blue Phosphorus/MoSi2N4 van der Waals heterostructure via vertical electric field and biaxial strain

Very recently, a new kind of 2D transition metal nitride , MoSi 2 N 4 , has been attracting considerable attention due to its successful synthesis and outstanding properties. To further explore its novel properties and applications for nanodevices , we have proposed a van der Waals (vdW) heterostructure composed of MoSi 2 N 4 and Blue Phosphorus (BlueP) monolayers and systematically studied its electronic properties with first-principles calculations. The results show that the heterostructure exhibits a type-II band alignment, with the conduction band minimum (CBM) and valence band maximum (VBM) located in BlueP and MoSi 2 N 4 layers, respectively. Furthermore, the electronic properties of heterostructure are not sensitive to different stacking patterns while can be significantly modulated by applying an external electric field or a biaxial strain. When applying the electronic field, the band gap shows linear variation with the electric field, and a semiconductor-to-metal transition is observed under the strong electric field. When applying the biaxial strain, the band alignment can be transformed from type-II to type-I. This work provides theoretical guidance for design of flexible nano-electronic and optoelectronic devices based on the BlueP/MoSi 2 N 4 heterostructure. • The BlueP/MoSi 2 N 4 heterostructure exhibits a type-II band alignment. • The electronic properties of heterostructure are not sensitive to diverse stacking patterns. • The electronic properties of heterostructure can be tuned by external electric field or biaxial strain. • A semiconductor-to-metal transition takes place when applying a strong electric field. • Band alignment transition from type-II to type-I has been observed under the effect of biaxial strain.

Strain engineering on the thermoelectric performance of monolayer AlP3: A first-principles study

Recently, the two-dimensional semiconductor AlP 3 has been proved to be a promising thermoelectric material with high carrier mobility and low thermal conductivity . By using first-principles methods combined with Boltzmann transport theory, we investigate the effect of biaxial tensile strain on the thermoelectric properties of monolayer AlP 3 . Through calculating electronic transport properties, we find that the electron mobility first increases and then drops with the increase of tensile strain. Furthermore, the power factor of monolayer AlP 3 under a 4% tensile strain has been significantly improved, indicating that strain engineering could enhance the power factor of monolayer AlP 3 . Moreover, the tensile strain will increase the electronic and lattice thermal conductivities. Compared with unstrained AlP 3 , the increase of lattice thermal conductivities of strained monolayer AlP 3 results from a higher phonon lifetime. The ZT and maximum energy conversion efficiency of n -type doping monolayer AlP 3 under a 4% tensile strain can reach 7.13 and 29.4% at 700 K. This study provides an in-depth understanding of the transport properties of monolayer AlP 3 by applying tensile strain and monolayer AlP 3 has a great potential in flexible thermoelectric applications. • The biaxial tensile strain can improve the power factor of monolayer AlP 3 . • The tensile strain can tune the thermal conductivity of monolayer AlP 3 . • The ZT of n -type doping monolayer AlP 3 under a 4% tensile strain can reach 7.13 • Monolayer AlP 3 has a great potential in flexible thermoelectric applications.

Phonon anharmonicity in multi-layered WS2 explored by first-principles and Raman studies

Anharmonicity is an essential property of two-dimensional materials due to its significant impact on lattice dynamics – involving interactions between phonons, thermal expansion of the structure, and interaction with the substrate. The effects manifest in temperature-dependent redshifts of the phonon frequencies and reduced lifetime. In this work, we investigate phonon anharmonicity in supported 1–5 layered WS2 by performing Raman measurements in the temperature range of 80–500 K and explore the results by ab-initio DFT study. An ab-initio model including three-phonon interaction processes and thermal expansion of all geometrical degrees of freedom (in-plane lattice constant, interlayer distance, and monolayer thickness) well describes the experimental temperature trends of the fundamental E2g1 (in-plane) and A1g (out-of-plane) phonon modes, giving a great promise of using simulation to quantitatively analyze phonon propagation and heat transport in multi-layered two-dimensional materials. The models predict a noticeable increase in the temperature-induced slope of A1g vibrations’ frequency with the number of layers – primarily due to the thermal expansion of interlayer distance. Additionally, we study the impact of the substrate on the phonon properties – concerning cumulated effects of induced strain and electron doping. We show that the effect of biaxial strain is the most significant in the E2g1 phonon mode and independent of the number of layers, while the excess charge is more significant in thin films and affects mainly the A1g mode. The presented studies based on a combination of ab-initio and experimental approaches can be extended to quantitatively analyze phonon evolution with structural modification and external stimuli.

Biaxial strain engineering on the superconducting properties of MgB2 monolayer

The effect of biaxial strain on the superconducting properties of MgB2 monolayer was studied by first-principles calculations. The stability analyses by phonon dispersions show that a biaxial strain of as much as 7% can be applied onto MgB2 without inducing any imaginary frequency. The superconducting property calculations based on the frame of Migdal-Eliashberg theory successfully reproduce the two-gap superconductivity of MgB2. The results show that the tensile biaxial strain can increase the critical temperature of MgB2 by as much as ∼20% while the compressive biaxial strain would decrease the critical temperature by ∼29%. The detailed microscopic mechanism of the biaxial strain effect on the superconducting properties was studied by calculations of electronic structures and phonon dispersions. The increased Tc is a combining result of the increased electron density at the Fermi level and the in-plane boron phonon softening. By means of high-throughput screening of proper substrates, it is found that most of the substrates would result in tensile strain in MgB2 film, some of which can result in tensile strain of higher than 10%, consistent with many experimental works that the MgB2 thin film has increased Tc. The results in this work provide a detailed understanding of the biaxial strain engineering mechanism and demonstrate that biaxial strain engineering can be an effective way of tuning the superconducting properties of MgB2 and other similar materials.

Effect of biaxial strain on structural, electronic, optical and thermoelectric properties of LiNbO3: Ab-initio calculations

The theoretical effects of biaxial strain on the structural, electronic, optical, and thermoelectric properties of LiNbO3 were investigated using the Wien2k and BoltzTraP programs with the GGA approximation. The lattice thermal conductivity was calculated by the GIBBS code. We demonstrate that the bandgap value decreases and increase with the tensile and compressive strain respectively. The optical absorption and the optical conductivity of LiNbO3 can be enhanced by applying tensile biaxial strain. The thermoelectric properties are also investigated. LiNbO3 pure and under the biaxial strain is a p-type material. Our compounds are promising candidates for thermoelectric applications.

Biaxial strain engineering of the electronic and optical properties of Ge2SeS monolayer: Promising for optoelectronic applications

Biaxial strain effects on the electronic and optical properties of the Ge2SeS monolayer were studied using the first-principles calculations in the present work. The band gap calculations show that the G2eSeS monolayer is a semiconductor at equilibrium state with an indirect band gap of 1.47 eV calculated by generalized gradient approximation (GGA) of Perdew Burke Ernzerhof (PBE) functional, which can be modulated by applying the biaxial strain changing from −6% to +6%. The optical properties such as dielectric constant, reflectivity, extinction coefficient, and absorption coefficient rise with the compression strain and reduce with tensile strain. Interestingly, it's confirmed that biaxial compression strain results in a high absorption coefficient in visible light. The anticipated results could make the Ge2SeS monolayer a candidate for optoelectronic applications.

Electric field and strain-induced band-gap engineering and manipulation of the Rashba spin splitting in Janus van der Waals heterostructures

The compositional as well as structural asymmetries in Janus transition metal dichalcogenides (J-TMDs) and their van der Waals heterostructures (vdW HSs) induce an intrinsic Rashba spin-splitting. We investigate the variation of band-gaps and the Rashba parameter in three different Janus heterostructures having AB-stacked Mo$XY$/W$XY$ ($X$, $Y$ = S, Se, Te; $X\neq Y$) geometry with a $Y-Y$ interface, using first-principles calculations. We consider the effect of external electric field and in-plane biaxial strain in tuning the strength of the intrinsic electric field, which leads to remarkable modifications of the band-gap and the Rashba spin-splitting. In particular, it is found that the positive applied field and compressive in-plane biaxial strain can lead to a notable increase in the Rashba spin-splitting of the valence bands about the $\Gamma$-point. Moreover, our \textit{ab-initio} density functional theory (DFT) calculations reveal the existence of a type-II band alignment in these heterostructures, which remains robust under positive external field and biaxial strain. These suggest novel ways of engineering the electronic, optical, and spin properties of J-TMD van der Waals heterostructures holding a huge promise in spintronic and optoelectronic devices. Detailed $\mathbf{k\cdot p}$ model analyses have been performed to investigate the electronic and spin properties near the $\Gamma$ and K points of the Brillouin zone.

Strain Effects on the Band Structures of Monolayer GaN from the Density Functional Theory

We perform the density functional theory calculations (DFT) to study the effect of biaxial strain on the band structures of monolayer GaN. We apply compressive and tensile strains up to 10%. There is no change of bandgap for the applied tensile strains below 8%. The compressive strains have a constant bandgap which is slightly smaller than that of the zero strain. We find that the applied tensile strain above 8% affects its electronic structure and decreases its bandgap energy by about 0.05 eV while the compressive strain above 4% decreases its bandgap about 0.22 eV.

Effects of biaxial strain on thermal conductivity of novel puckered C2N2 monolayer: A first-principles study

Strain engineering is an effective way to tune thermal and electrical properties in two-dimensional (2D) material. In this work, we systematically investigated the strain dependent lattice thermal conductivity of novel puckered C2N2 monolayer by solving the phonon Boltzmann transportation equation (BTE) with interatomic force constants extracted from first-principles calculations. At 300 K, the unstrained puckered C2N2 monolayer exhibit a high thermal conductivity of 587 W m−1K−1 and 355 W m−1K−1 along the zigzag and armchair direction, respectively. At 8% biaxial tensile strain, the thermal conductivity along the zigzag direction is 61 W m−1K−1, which is reduced by 89.6%. The underlying mechanism for such a remarkable decline of thermal conductivity in puckered C2N2 was correlated to the fact that stretch reduces both group velocity and phonon relaxation time. Our findings offer insight into the influence of strain on 2D materials and will be helpful for applications of these materials in nanoelectronics devices.

Combine effect of doping and strain on the thermodynamics, ferroelectric, electronic, and magnetic properties of PbTiO3

Multiferroic materials become prominent as they utilize both the charge and spin degree of electrons, which have tremendous scope in solid-state electronic-based devices. Herein, the combined effect of transition metals (TM = Fe, Co, and Ni) doping and biaxial ([110]) strain on the thermodynamics, electronic, and multiferroic properties of PbTiO3 (PTO) perovskite oxide is investigated by the inclusion of Hubbard parameter U. Formation energetics computed by utilizing the Convex Hull analysis, confirm the structural stability of the TM-doped motifs, while elastic properties affirm the mechanical regularity. In addition, positive frequencies of the phonon dispersion bands maintained the dynamical cohesion of the systems. Our results revealed that the magnitude of spontaneous polarization (P) decreases from 84.3 μCcm−2 to 70.2/67.8/63 μCcm−2 due to the reduction of the structural distortions when Fe/Co/Ni ions are doped at Ti site, which agrees well with the recent experiment [J. Phys. Chem. C 125, 12342 (2021)]. Strikingly, all the strained systems exhibit a higher P amplitude than that of the unstrained one. The most striking feature of the present study is that the Co-doped motif predicted a metallic behavior for −5% biaxial ([110]) strain. Along with this, the Ni-doped structure demonstrates a reasonable amplitude of spin-polarization with respect to strain. A high to low (2.0–0.5)/low to high (0.5–1.0) spin-state transition is observed at a critical strain of −1%/−2% in Fe/Ni, while Co lies in a low spin state with S = 0.5. Finally, spin-magnetization isosurfaces plots established that magnetism mainly arises from the admixture of 3dz2, 3dx2−y2, 3dyz + xz, and 3dxy orbitals.

Strain enhanced electronic and optical properties in Janus monolayers AsMC3 (M: Sb, Bi)

In this work, first-principles calculations were employed to investigate the biaxial strain effects on the electronic structure and optical properties of As2C3 and AsMC3 (M: Sb, Bi) Janus monolayers. The band structure calculations show that the As2C3 and AsBiC3 monolayers, and Janus AsSbC3 structure are semiconductors with a bandgap of 1.44, 0.99, and 1.16 eV, respectively. Moreover, the optical properties such as the real ε1(ω) and imaginary ε2(ω) parts of the dielectric constant, refractive index n(ω), reflectivity R(ω), extinction coefficient K(ω) and absorption coefficient α(ω), under different biaxial strain levels and versus the energy are predicted. Interestingly, it is found that the biaxial strain improved the optical properties of the studied Janus monolayers, suggesting their potential for photovoltaic and optoelectronic applications.

Effect of biaxial strain on the electronic structure and transport properties of AlX (X $$=$$ S or Se) monolayer

Effect of biaxial strain on the electronic structure and transport properties of AlX (X $$=$$ S or Se) monolayer

Optimizing the thermoelectric transmission of monolayer HfSe2 by strain engineering

The demand for clean energy is driving enhancements in the efficiency of conversion of thermoelectric materials. The electronic and phononic properties of thermoelectric materials can be adjusted through straining to improve their figure of merit. In this work, the authors systematically examine the effects of biaxial strain on the phononic, electronic, and thermoelectric properties of monolayer 1T-HfSe2 by using first-principles calculations combined with semi-classical Boltzmann transport theory. The results show that the monolayer HfSe2 is a good n-type thermoelectric material. The tensile strain caused the valence band to converge and increased the Seebeck coefficient to induce the transition of HfSe2 from n-type to p-type thermoelectric material. The thermal conductivity κl of the lattice decreased from 5.54 Wm-1κ−1 to 1.16 Wm-1κ−1 at 300 K owing to stronger phonon scattering and lower velocity of the phonon group as the tensile strain increased the bond distance and weakened the bonds. Due to improvements in electrical and thermal transport, ZTmax significantly increased from 0.16 to 2.41 for the p-type material, and from 0.53 to 1.91 for the n-type material. This shows that strain engineering can improve electrical transport and reduce thermal conductivity to improve thermoelectric performance.