Biaxial Strain Field Research Articles

Unveiling the tunable electronic, optoelectronic, and strain-sensitive gas sensing properties of Janus ZrBrCl: Insights from DFT study

Janus monolayers materials exhibit extraordinary physical and chemical properties because of crystal field changes caused by their asymmetric structures. Here, we investigate the electronic, switching, optoelectronic, and strain-sensitive gas-sensing properties of a Janus ZrBrCl monolayer via density-functional theory and the nonequilibrium Green’s function methods. The electronic properties can be tuned by applying biaxial strain and electric fields. In particular, the band gap can be changed from indirect to direct via applied a + 8 % biaxial tensile strain. It can be transformed from a semiconductor to a metal with an applied −14 % biaxial compressive strain, with a 1011 switching ratio. In addition, a biaxial strain and an electric field can modulate visible light absorption and photocurrents. Under a −12 % biaxial compressive strain, the absorption coefficient increased to 5.26 × 105 cm−1 from the intrinsic 4.08 × 105 cm−1. Across biaxial strains from −4% to + 4 %, the photocurrent density peak displayed red and blue shifts, respectively, with increasing tensile and compressive strains. NH3, NO2, and NO physically adsorb on the Br side of the ZrBrCl monolayer. Maximum gas sensitivity values of a ZrBrCl sensor are 52 % in the zigzag direction and 21 % in the armchair direction. After application of the −14 % biaxial strain, the maximum values respectively increased to 76 % and 179 %. The biaxial compressive strain-sensitive gas-sensing properties are driven by changes in the electrostatic potential difference between the Br and Cl surfaces. These findings indicate promising candidate materials for high-performance switching and optoelectronic devices, and also provide a strategy for improved gas sensors.

Exploring tunable optoelectronic properties of two-dimensional GaS/PtSSe heterostructures under biaxial strain and external electric field

Vertically stacked heterostructures offer novel material options for designing tunable optoelectronic devices due to their adjustable electronic and optical properties. This work compares the electronic structure, charge transfer, and optical properties of two different contact faces of GaS/Janus PtSSe heterostructures using the density functional theory. The results show that GaS/PtSSe form a built-in electric field at the interface, directing from the monolayer GaS to the PtSSe. GaS/SePtS and GaS/SPtSe are determined to be indirect bandgap semiconductors with bandwidths of 1.51 eV and 1.11 eV utilizing the PBE. In this study, the band alignment of GaS/PtSSe can induce a semiconductor-to-metal transition. Notably, GaS/SePtS is highly sensitive to biaxial strain and external electric field, transitioning its energy band alignment from Type-I to Type-II. Applying tensile strain enhances the sunlight absorption of GaS/PtSSe, making it a promising candidatein the tunable electronic devices and photodetectors.

Ultra-high electron mobility in Sn-doped two-dimensional Ga2O3 modified by biaxial strain and electric field

2D Ga2O3 exhibits overwhelming advantages over its bulk counterpart, whereas manipulating the carriers is rare. We report strain-dependent electronic structures and transport properties of Sn-doped 2D Ga2O3 using first-principles calculations with deformation potential theory. The band gaps are tunable from 2.23 eV to 1.20 eV due to the strain-mediated σ* anti-bonding and π bonding state variations. Specifically, ultra-high electron mobility of 22579.32 cm2V−1s−1 is predicated under 8% tensile. Further electric field modulations suggest the retaining of band gap and effective mass. These results highlight its property manipulations and nanoscale electronic applications.

Vertical heterojunction photodetector of In2Se3/PtS2 with high polarization sensitivity and tunable electronic characteristics

A monolayer In2Se3 root number model was used with a monolayer PtS2 material 2 × 2 × 1 cell expansion to form an In2Se3/PtS2 bilayer with a lattice mismatch of 3.12 %. Utilizing first principles calculations, we systematically explore the structural, electrical, and optical characteristics of In2Se3/PtS2 heterostructures. The stabilized heterostructure displays an indirect band gap of 1.62 eV and a type I energy band arrangement. Moreover, the absorption spectra further demonstrate the heterostructure's ability to capture visible and UV light, it is significantly better than monolayer In2Se3 and monolayer PtS2, and the absorption peak at a wavelength of 185 nm is as high as 8. 07×105/cm. Using biaxial strain to change the heterojunction energy band structure, it is found that as the biaxial strain field changes, the hetero-structure of In2Se3/PtS2 transforms from a type I to a type II energy band arrangement with the applied stresses of −8 %, 2 %, 4 %, 6 %, and 8 %. Transitioning from simulations to practical applications, we model a novel photodetector based on the In2Se3/PtS2 heterojunction. Remarkably, the In2Se3/PtS2 heterojunction photodetector demonstrates high polarization sensitivity at a photon energy of 3.2 eV, boasting a maximum extinction ratio of 20, outperforming alternatives. In summary, the In2Se3/PtS2 heterostructure presents exceptional optical properties, providing a robust foundation for advanced photodetector applications.

Electronic Performance and Schottky Contact of 2D GeH/InSe and GeH/In2Se3 Heterostructures: Strain Engineering and Electric Field Tunability

AbstractRecent exciting developments in synthesis and properties study of the germanane (GeH) mono‐layer have inspired us to investigate the structural and electronic properties of the van der Waals heterostructures (HTS) of GeH/InSe and GeH/In2Se3 through a first‐principles methodology. In this study, structural and electronic properties of the HTS are examined thoroughly. GeH/InSe and GeH/In2Se3 are determined as n‐type Schottky with a Schottky barrier height (SBH) of 0.40 eV and n‐type ohmic, respectively. GeH/InSe turns out as a semiconductor with a direct bandgap of 0.62 eV, while GeH/In2Se3 is seen to be a metal. The results show that changing of the bandgap and SBH in very small values. For GeH/In2Se3 the effects are even less substantial, as the metallic or n‐type nature of the material does not change. The biaxial strain and electric field have more tangible effects on the characteristics of the HTS. A mixture of compressive and tensile strain is seen to have the capability of changing GeH/InSe into a metal and at the same time transform it to an n‐type/p‐type ohmic or p‐type Schottky contact. The results given here can guide future research in the field of HTS and especially GeH‐based devices.

Adsorption and gas sensing properties of Pdn(n=1–3) cluster-modified PtSe2 on transformer fault characterizing gases under biaxial strain and electric field

In this study, the adsorption behavior of three DGA gases (C2H2, C2H4, and CO) on monolayers of PtSe2 doped with metal clusters Pdn(n=1–3) was investigated using density-functional theory (DFT). The critical influence of the Pd clusters on the sensitivity of PtSe2 gas is revealed by in-depth analysis of the geometrical structure of the adsorption system, DCD, ELF, DOS and band gap. The results show that the detection performance of intrinsic PtSe2 monolayer is poor. However, the doping of Pdn(n=1–3) fundamentally changes the adsorption behavior of PtSe2 on C2H2 and C2H4 from an adsorptive to an exothermic reaction, and endows it with excellent adsorption, desorption, and gas sensitivity properties. In addition, the introduction of external electric field and biaxial strain can significantly change the charge transfer, band gap, and adsorption energy of each adsorption system, which suggests that the Pdn(n=1–3)-PtSe2 monolayer has excellent tunability and can be strain-modulated for gas detection.

First-principles study of the electronic and optical properties of two-dimensional PtS2/GaS van der Waals heterostructure

Heterostructures based on two-dimensional materials have received increasing attention due to their extraordinary properties and application potential. In this paper, the electronic and optical properties of the PtS2/GaS van der Waals (vdW) heterostructure as well as the effects of biaxial strain and external electric field are systematically investigated based on first-principles calculations. The PtS2/GaS vdW heterostructure has an interlayer distance of 3.01 Å and is a type-Ⅱ semiconductor of band gap 1.54 eV. Large optical absorption coefficients are observed in both the ultraviolet and the visible regions. Furthermore, its band structure can be effectively tuned by applying biaxial strain and external electric field. The transition between the type-Ⅱ and type-I band alignments can be realized. The absorption spectra and their peaks can be then manipulated effectively by applying biaxial strain with good stability under external electric field. The predicted tunable electronic properties and unique optical absorption properties suggests promising potential for the application of the PtS2/GaS vdW heterostructure in future optoelectronic nanodevices.

Strain and Electric Field Engineering of G-ZnO/SnXY (X, Y = S, Se) S-Scheme Heterostructures for Photocatalyst and Electronic Device Applications: A Hybrid DFT Calculation.

Using hybrid density functional theory calculations, we systematically study the biaxial strain and electric field modulated electronic properties of g-ZnO/SnS2, g-ZnO/SnSe2, and g-ZnO/SnSSe S-scheme van der Waals heterostructures (vdWHs). g-ZnO/SnS2 and g-ZnO/SnSSe are found to be promising photocatalysts for water splitting with high solar-to-hydrogen efficiencies, even under acidic, alkaline, and high-stress conditions. The strain effect on the bandgaps of g-ZnO/SnXY is explained in detail according to the correlation between geometry structure and orbital hybridization of SnXY, which could help understand the strain-induced band structure evolutions in other SnXY (X, Y = S, Se)-based vdWHs. It is surprising that under an external electric field, g-ZnO/SnS2, g-ZnO/SnSe2, and g-ZnO/SnSSe can offer the occupied nearly free-electron (NFE) states. In many materials, NFE states are usually unoccupied and is not conducive to the charge transport. The NFE state in g-ZnO/SnSe2 is the most sensitive to the electric field and might be promising electron transport channel in nanoelectronic devices. g-ZnO/SnSe2 might also have application potential in gas sensors and high-temperature superconductors.

Softened membrane model for shear of ultra-high-performance concrete (SMM-UHPC)

Understanding the shear behavior of Ultra-High-Performance (UHPC) is crucial to prevent undesired responses that could be induced by diagonal shear cracks. Hence, the ability of analytical models to predict shear responses of UHPC members is of paramount importance, which is addressed in this paper by the Softened Membrane Model (SMM). Since the SMM is a two-dimensional shear modeling framework developed for reinforced concrete, a parametric investigation was conducted to assess its suitability for UHPC, namely SMM-UHPC. Through this assessment, a softening coefficient for the biaxial behavior of UHPC was developed and new constitutive laws were integrated in SMM. Comparisons with shear panel tests were used to evaluate the accuracy of SMM-UHPC and quantify the significance of key model parameters. Sensitivity analyses showed that the decomposition between biaxial and uniaxial strain fields, which is used in SMM to capture the Poisson effect, has a negligible influence on UHPC shear. Combining experimental and analytical data, the tensile localization strain was identified to be of most significance for predicting the shear stress-strain response of UHPC.

Two-dimensional type-II BlueP/GaN heterostructure for solar cells: A first-principles study

The geometric structure, electronic and optical properties, power conversion efficiency (PCE) of the BlueP/GaN heterostructure and its response to biaxial strain and electric field are systematically studied based on first-principles calculations. The results show that all configurations are found to be semiconductors with indirect band gaps of 1.34, 1.79, 1.20 and 1.40 eV, respectively. The BlueP/GaN heterostructure possesses excellent carrier mobility. The electron mobility of AA' configuration is up to 3.329 m2 V−1 s−1, while the hole mobility can reach 1.707 m2 V−1 s−1. The visible light absorption intensity of the BlueP/GaN heterostructure can significantly improve compared with the corresponding monolayers. The maximum adsorption coefficient of AA configuration can attain to 1.01 × 105 cm−1 at the 422 nm visible light. Especially, the tunable band gap and type-II band alignment are achieved through biaxial strains and external electric fields. The BlueP/GaN heterostructure can achieve 24.13 % PCE at 4 % tension strain. External electric fields can more accurately modulate the band gap to dynamically control electronic properties of BlueP/GaN heterostructure. Hence, the results not only provide theoretical basis for sustainable energy application of BlueP/GaN heterostructure, but also provide motivation to experimentally explore BlueP/GaN heterostructure for harvesting green, abundant and clean solar energy.

Shubnikov–de Haas oscillations of biaxial-strain-tuned superconductors in pulsed magnetic field up to 60 T

Two-dimensional (2D) materials have gained increasing prominence not only in fundamental research but also in daily applications. However, to fully harness their potential, it is crucial to optimize their properties with an external parameter and track the electronic structure simultaneously. Magnetotransport over a wide magnetic field range is a powerful method to probe the electronic structure and, for metallic 2D materials, quantum oscillations superimposed on the transport signals encode Fermi surface parameters. In this manuscript, we utilize biaxial strain as an external tuning parameter and investigate the effects of strain on the electronic properties of two quasi-2D superconductors, MoTe2 and RbV3Sb5, by measuring their magnetoresistance in pulsed magnetic fields up to 60 T. With a careful selection of insulating substrates, we demonstrate the possibility of both the compressive and tensile biaxial strains imposed on MoTe2 and RbV3Sb5, respectively. For both systems, the applied strain has led to superconducting critical temperature enhancement compared to their free-standing counterparts, proving the effectiveness of this biaxial strain method at cryogenic temperatures. Clear quantum oscillations in the magnetoresistance—the Shubnikov–de Haas (SdH) effect—are obtained in both samples. In strained MoTe2, the magnetoresistance exhibits a nearly quadratic dependence on the magnetic field and remains non-saturating even at the highest field, whereas in strained RbV3Sb5, two SdH frequencies showed a substantial enhancement in effective mass values, hinting at a possible enhancement of charge fluctuations. Our results demonstrate that combining biaxial strain and pulsed magnetic field paves the way for studying 2D materials under unprecedented conditions.

The multiple topological phases in a new family of compounds ACrTe (A = Na, K, Rb, Cs) predicted by first-principles calculations.

Based on first-principles calculations, we predict a new family of chromium-based compounds, ACrTe (A = Na, K, Rb, Cs), which share the same structure as the iron-based superconductor LiFeAs. We show that all these materials are narrow-gap antiferromagnetic (AFM) semiconductors. The AFM order is of the checkerboard type within Cr layers, while the interlayer coupling changes from ferromagnetic (FM) for NaCrTe to AFM for KCrTe, RbCrTe and CsCrTe. Interestingly, we find that the small gap is sensitive to in-plane biaxial strain and magnetic fields, which can tune the bulk compounds to become Dirac and Weyl semimetals and tune the monolayer case to exhibit quantum spin and anomalous Hall effects. Significantly, both Dirac and Weyl semimetals show clean topological structures with a long-sought single pair of Dirac and Weyl points at the Fermi level. Our studies may provide an ideal candidate material to study Dirac and Weyl physics and to realize clean quantum spin and anomalous Hall effects.

Band alignment in CdS-α-Te van der Waals heterostructures for photocatalytic applications: Influence of biaxial strain and electric field

We present a comprehensive theoretical analysis of the structural and electronic properties of a van der Waals heterostructure composed of CdS and α-Te single layers (SLs). The investigation includes an...

Tunability of electronic properties in the 2D MoS2/α-tellurene/WS2 heterotrilayer via biaxial strain and electric field.

Alpha-tellurene (α-Te), a two-dimensional (2D) material that has been theoretically predicted and experimentally verified, has garnered significant attention due to its unique properties. In this study, we investigated the 2D trilayer MoS2/α-Te/WS2 van der Waals heterostructure with different stacking orders using first-principles calculations. Our results indicate that this heterotrilayer exhibits an intrinsic type-I band alignment and an indirect band gap similar to that of monolayer α-Te. Notably, the band edges of the heterostructure can be modulated by biaxial strain and an external electric field, enabling these edges to arise from different monolayers. This controlled manipulation facilitates the effective separation of photogenerated electron-hole pairs and prolongs the carrier lifetime. Moreover, the heterostructure can undergo a transition from an indirect to a direct band gap under biaxial compressive strain or a moderate negative electric field, and semiconductor-to-metal transition can also be achieved by intensifying the biaxial strain and external electric field. Overall, our research provides valuable theoretical insights into the potential applications of α-Te-based heterostructures, rendering them promising candidates for the next generation of nanodevices.

Modulation of electronic and optical properties of BlueP/MoSSe heterostructures via biaxial strain and vertical electric field

Constructing van der Waals heterostructures (vdWHs) is an efficient approach for enhancing the desirable properties of two-dimensional (2D) materials and greatly expanding the range of applications of the original monolayer materials. The structure, stability, electronic and optical properties of BlueP/MoSSe heterostructures are explored by density functional theory (DFT) calculations. The different configurations of BlueP/MoSSe vdWHs are all indirect bandgap semiconductors and have similar energy band structures, with the bandgap of about 1.0 eV under the PBE method. The bandgap of the A3 (B3) configuration calculated with HSE06 method is 1.608 (1.377) eV. The A3 configuration exhibits type-II band alignment while the B3 configuration shows type-I band alignment, both of which have high stability. The bandgap and band edge of A3 (B3) configuration can be modulated effectively by biaxial strain and vertical electric field (Efield). The BlueP/MoSSe vdWHs have broader absorption range and higher absorption intensity than their monolayers. The optical absorption intensity of heterostructures is gradually improved with increasing compressive strain, and the optical absorption spectrum is red-shifted under tensile strain. We hope that our findings will provide meaningful theoretical guidance for the preparation and potential application of BlueP/MoSSe vdWHs.

Spontaneous hydrogen production on well-designed two-dimensional MoSi2N2P2 Janus structure: N-face versus P-face tuning

Based on the recently discovered two-dimensional non-Janus MoSi2N4 structure, we here study a well-designed two-dimensional Janus structure (MoSi2N2P2) for potential application in hydrogen evolution reaction (HER) via water splitting. We first confirm the stability of the MoSi2N2P2 structure using first-principles’ calculations in the framework of density functional theory by calculating cohesive energy, phonon dispersion, and ab-initio molecular dynamics evolution. We then investigate electronic and transport properties of the structure. The MoSi2N2P2 Janus structure exhibits an indirect (Γ→M) band gap of only 0.22 eV using PBE and 0.89 eV using the HSE06 hybrid functional. We also find that there is a large intrinsic electric field across the Janus structure, which tends to gather electrons at the P face. We also calculate the mobility of the Janus structure, showing that it has a high electron mobility (409 cm2/Vs) along the zigzag direction. We then show that compared with the P face, the N face gives a lower overpotential against HER, but not sufficient to activate HER process. Therefore, we investigate how the electronic properties and the HER overpotential of the Janus MoSi2N2P2 monolayer are affected by applying biaxial strain and external perpendicular electric field. Thus, the N face exhibits a higher degree of tunability than the P face toward HER overpotential. In particular by applying an electric field of 2.7 V/Å directing from the P face to the N face, the overpotential against the HER reaction on the N face can be adjusted to zero, showing that the well-designed Janus structure can exhibit a potential application for spontaneous HER water splitting.

Tunable electronic structures in C3N/WSe2 van der Waals heterostructure by biaxial strain and external electric field

Tunable electronic structures in C3N/WSe2 van der Waals heterostructure by biaxial strain and external electric field

Modulation of contact type in BAs/Hf3C2 heterostructure via surface functionalization and strain

The exploration of contact property is greatly vital to improve the performance of transistors based on two-dimensional (2D) materials. In this work, we construct 2D BAs/Hf3C2 vdW heterostructure to explore its contact property based on first-principles calculations. We find that the BAs layer shows metallic feature in the BAs/Hf3C2 heterostructure, suggesting Hf3C2 destroys the band dispersion of BAs due to the appearance of strong interfacial coupling. Therefore, the pristine Hf3C2 is not ideal electrode material. The functionalization of Hf3C2 can weaken the interlayer interaction and make BAs maintain its semiconductor feature. Here, we select chalcogens and halogens to functionalize the Hf3C2, forming Hf3C2X2 (X = O, S, Se, Te, F, Cl, Br, and I). Furthermore, we investigate the contact type, Schottky barrier, charge transfer, and tunneling probability of BAs/Hf3C2X2 heterostructures. Ohmic contact is formed in the most BAs/Hf3C2X2 systems, suggesting that they possess high performance with a view to the application for the transistors. The biaxial strain and external electric field are utilized to modulate the contact type and barrier height in the BAs/Hf3C2O2 and BAs/ Hf3C2F2 heterostructures.

Large-band-gap non-Dirac quantum spin Hall states and strong Rashba effect in functionalized thallene films

The quantum spin Hall state materials have recently attracted much attention owing to their potential applications in the design of spintronic devices. Based on density functional theory calculations and crystal field theory, we study electronic structures and topological properties of functionalized thallene films. Two different hydrogenation styles (Tl2H and Tl2H2) are considered, which can drastically vary the electronic and topological behaviors of the thallene. Due to the C3v symmetry of the two systems, the px and py orbitals at the Γ point have the non-Dirac band degeneracy. With spin–orbit coupling (SOC), topological nontrivial band gaps can be generated, giving rise to non-Dirac quantum spin Hall states in the two thallium hydride films. The nontrivial band gap for the monolayer Tl2H is very large (855 meV) due to the large on-site SOC of Tl px and py orbitals. The band gap in Tl2H2 is, however, small due to the band inversion between the Tl px/y and pz orbitals. It is worth noting that both the Tl2H and Tl2H2 monolayers exhibit strong Rashba spin splitting effects, especially for the monolayer Tl2H2 (αR = 2.52 eVÅ), rationalized well by the breaking of the structural inversion symmetry. The Rashba effect can be tuned sensitively by applying biaxial strain and external electric fields. Our findings provide an ideal platform for fabricating room-temperature spintronic and topological electronic devices.

High carrier mobility and broad spectrum GaSe/SnSe van der Waals heterostructure optoelectronic devices: First-principles study

GaSe is widely used in optoelectronics, and its nanosheets exhibit excellent on–off current ratios and photoresponsivity. However, its large band gap limits visible light absorption. Here, through constructing GaSe/SnSe heterojunction, we found the hole and electron mobility can reach 5916 and 483.53 cm2V−1s−1, 846 and 1.4 times higher than mono-SnSe, respectively, due to it forming type-II band alignment reducing the recombination. In addition, the absorption spectrum can be broadened to the near-infrared spectrum (the band gap can be decreased to 0) through a biaxial strain or electrical field. This work provides a method to highly improve the efficiency and application scope of GaSe optoelectronic devices.