Electronic Properties Research Articles

Theoretical MRCI+Q study on electronic structure and spectroscopic properties of the HX+(X=F, Cl, Br, I) cations

In this work, we have systematacially investigated the electronic structure and spectroscopic properties of the HX+ (X = F, Cl, Br, I) cations by using the highly correlated MRCI+Q approach. This is the first comprehensive ab initio study on the electronic states of the HX+ cations. The SOC effect is introduced with the state interaction approach. There are total 10 Λ-S and 18 Ω states obtained in the calculation. The results show that the PECs′ shapes and structure of the electronic states of different HX+ cations exhibit the significant distinction due to the X-dependent energy-level order of the unique dissociation channel H+(1Sg)+X(2Pu). From PECs, the spectroscopic constants of the bound electronic states are determined, which are in good agreement with available observed values. Regarding HBr+ and HI+, the good agreement has been achieved only when the SOC effect is considered. The predissociation for the first excited A2Σ+ state of HCl+, HBr+, and HI+ is analyzed based on computed spin-orbit matrix elements. Around the equilibrium position, the energy splittings of X2Π are calculated to be 288 cm-1, 661 cm-1, 2691 cm-1, and 5137 cm-1 for HF+, HCl+, HBr+, and HI+, respectively. It has been demonstrated that SOC is substantial for HX+, leading to significant changes in PECs′ shapes as well as in electronic structure. Finally, the transition properties are predicted, including transition dipole moments, Franck-Condon factors, and radiative lifetimes. Both the Ω transitions A2Σ+ 1/2-X2Π3/2 and A2Σ+ 1/2-X2Π1/2 of the HX+ cations are determined to possess the radiative lifetimes at the microsecond (µs) level.

Theory of acoustic polarons in the two-dimensional SSH model applied to the layered superatomic semiconductor Re6Se8Cl2.

Layered superatomic semiconductors, whose building blocks are atomically precise molecular clusters, exhibit interesting electronic and vibrational properties. In recent work [Tulyagankhodjaev et al., Science 382, 438 (2023)], transient reflection microscopy revealed quasi-ballistic exciton dynamics in Re6Se8Cl2, which was attributed to the formation of polarons due to coupling with acoustic phonons. Here, we characterize the electronic, excitonic, and phononic properties with periodic density functional theory. We further parameterize a polaron Hamiltonian with nonlocal (Su-Schrieffer-Heeger) coupling to an acoustic phonon to study the polaron ground state binding energy and dispersion relation with variational wavefunctions. We calculate a polaron binding energy of about 10meV at room temperature, and the maximum group velocity of our polaron dispersion relation is 1.5 km/s, which is similar to the experimentally observed exciton transport velocity.

High transmission efficiency of intense sub-THz coherent phonons in strongly correlated VO2/TiO2 heterojunction

High-frequency coherent acoustic phonons hold immense value in characterizing the coupling between magnetic, lattice, and electronic properties, offering nanometer-scale spatial resolution within the ultrafast timescale. However, efficiently propagating intense sub-THz coherent acoustic phonons across diverse materials remains a formidable challenge. Here, we demonstrate that using vanadium dioxide (VO2) as a transducer can induce enhanced coherent acoustic pulses that propagate efficiently (∼90%) into TiO2 due to excellent acoustic impedance matching and minor lattice interface mismatch compared with traditional metals such as Pt, Au, and Cu. Employing time-resolved pump–probe reflectivity spectroscopy, we observe pronounced coherent phonon oscillations reaching up to 0.164 THz from the longitudinal acoustic mode along the c axis in VO2/TiO2. Furthermore, the temperature and pump fluence dependence of the coherent phonon oscillation signals suggest that the metallic state of VO2 responds to these large coherent acoustic phonons.

First-principles screening of XSbF3 (X = Ba and Ra) fluoroperovskites: an insight into structural, optoelectronic and thermal properties

This work presents a computational study of the physical properties such as structural, electronic, optical and thermal properties of XSbF3 (X = Ba and Ra) fluoroperovskites. The calculations were performed using the density functional theory (DFT) calculations in conjunction with Quantum Espresso code. The stability of the crystal structure XSbF3 compounds is determined by binding energy (Eb) computations. The Eb values for BaSbF3 and RaSbF3 compounds are −19.25 and −20.04eV respectively, indicating that both studied compounds are stable. The optimized lattice constants for BaSbF3 and RaSbF3 compounds are 5.03 and 5.06 Å, respectively. The evaluation of electronic properties is conducted by electronic band structure, total density of states (DOS), and partial density of states (PDOS). It is observed from the PDOS plots that the p-states of Sb and F whereas the d-states of X atoms have the major contribution in the formation of the band structure. Various optical properties have been computed and compared. The static value of ε10 highlights the metallic nature of the studied compounds while RaSbF3 stands out for having the highest recorded value of ε20. The maximum nω values for BaSbF3 and RaSbF3 are 8.46 and 6.86 respectively indicating their potential for photoelectric applications. Furthermore when examining the properties it is evident that the BaSbF3 compound stands out as a material for energy storage because of its higher electron energy at 2.36 KJ/N.mol and lower electron free energy of −2.55 KJ/N.mol compared to the RaSbF3 compound. On the other hand, the RaSbF3 compound is an efficient material for catalysis due to its high ability to absorb heat energy from the external source, as compared to the BaSbF3 compound. This study is the first computational investigation of XSbF3 (X is Ba and Ra) compounds, which provides valuable insights into the physical properties of sb-based fluroperovskites and their potential applications.

Structural phase transition of G-type antiferromagnetic SrMnO3 under pressure

Abstract SrMnO3 is a versatile material with applications in transistors, supercapacitors, and spintronic devices. This study employs the DFT+U calculations to investigate the electronic and magnetic properties of two polymorphs: 4H-SrMnO3 and 3C-SrMnO3 under isotropic pressure conditions up to 60 GPa. A novel approach based on density functional perturbation theory (DFPT) is employed to precisely determine the on-site Hubbard U value, yielding a computed value of 4.552 eV, consistent with experimental reports. Below P = 14 GPa, the G-AFM phase of 4H-SrMnO3 is the most favored stable, and transitioning to the G-AFM phase of 3C-SrMnO3 beyond 14 GPa. Notably, we observed significant changes in the band gaps, exhibiting an increasing trend under isotropic pressure,
while the magnetic moments of the Mn sites exhibit a decreasing trend from ≈ 2.8 μB to ≈ 2.3 μB for P = 0 GPa and 60 GPa, respectively. The projected density of states (PDOS) reveals the p-d hybridization contributions between the 3d-Mn and 2p-O covalent bonds, along with d-d Mott Hubbard interactions within the localized 3d orbitals of neighboring Mn-Mn atoms. Furthermore, a decrease in the Mn1-O-Mn2 distance prompts enhanced charge transfer which was facilitated by ligand holes, leading to a noticeable decrease in the magnetic moment of the Mn site in the G-AFM phase of SrMnO3.

Janus TiSiZ3H (Z = N, P, As) monolayers with large out-of-plane piezoelectricity and high electron mobility: first-principles study

Abstract In this paper, we propose a series of novel two-dimensional Janus structures TiSi$Z_3$H ($Z=$ N, P, As) and investigate their electronic, mechanical, piezoelectric, and transport properties using the density functional theory. The examined results demonstrated that Janus TiSi$Z_3$H monolayers are structurally stable. At the ground state, TiSiN$_3$H, TiSiP$_3$H, and TiSiAs$_3$H monolayers are all semiconductors with indirect bandgaps of 2.98, 1.06, 1.02~eV at the hybrid-functional level, respectively. The absence of vertical mirror symmetry in TiSi$Z_3$H results in the occurrence of both in-plane and out-of-plane piezoelectricity. Interestingly, TiSiAs$_3$H monolayer exhibits large out-of-plane piezoelectric response with coefficient $d_{31}$ up to $-0.45$~pm/V, that is appropriate for use in piezoelectric devices. The calculated results demonstrate that the carrier mobility in Janus TiSi$Z_3$H monolayers is high and directional anisotropic. Particularly, electron mobility in TiSiP$_3$H monolayer is observed up to 772.31~cm$^2$V$^{-1}$s$^{-1}$. Our results not only suggest and confirm some fundamental physical characteristics of new materials but also lay important premises for experimental studies as well as their application prospects in the future.

Biomaterials in Cancer Therapy: Investigating the Interaction between Kaempferol and Zinc Ions through Computational, Spectroscopic and Biological Analyses

A complex of the natural flavonoid kaempferol with zinc (Kam-Zn) was synthesized, and its physicochemical properties were investigated using spectroscopic methods such as Fourier transform infrared spectroscopy (FT-IR), ultraviolet–visible (UV-Vis) spectroscopy and theoretical chemistry. Biological studies were conducted to evaluate the cytotoxic and antiproliferative effects of these complexes on MCF-7 breast cancer cells. Treatment with Kam 100 µM (84.86 ± 7.79%; 64.37 ± 8.24%) and Kam-Zn 100 µM (91.87 ± 3.80%; 87.04 ± 13.0%) showed no significant difference in proliferation between 16 h and 32 h, with the gap width remaining stable. Both Kam-Zn 100 μM and 200 μM demonstrated effective antiproliferative and cytotoxic activity, significantly decreasing cell viability and causing cell death and morphology changes. Antioxidant assays revealed that Kam (IC50 = 5.63 ± 0.06) exhibited higher antioxidant potential compared to Kam-Zn (IC50 = 6.80 ± 0.075), suggesting that zinc coordination impacts the flavonoid’s radical scavenging activity by the coordination of metal ion to hydroxyl groups. Computational studies revealed significant modifications in the electronic structure and properties of Kam upon forming 1:1 complexes with Zn2+ ions. Spectroscopy analyses confirmed structural changes, highlighting shifts in absorption peaks and alterations in functional group vibrations indicative of metal–ligand interactions. FT-IR and UV-Vis spectra analysis suggested that Zn coordinates with the 3-OH and 4C=O groups of ligand. These findings suggest that the Kam-Zn complex exhibits interesting antiproliferative, cytotoxic and modified antioxidant effects on MCF-7 cells, providing valuable insights into their structural and anticancer properties.

Role of chalcogen vacancies and hydrogen in the optical and electrical properties of bulk transition-metal dichalcogenides

Like in any other semiconductor, point defects in transition-metal dichalcogenides (TMDs) are expected to strongly impact their electronic and optical properties. However, identifying defects in these layered two-dimensional materials has been quite challenging with controversial conclusions despite the extensive literature in the past decade. Using first-principles calculations, we revisit the role of chalcogen vacancies and hydrogen impurity in bulk TMDs, reporting formation energies and thermodynamic and optical transition levels. We show that the S vacancy can explain recently observed cathodoluminescence spectra of MoS2 flakes and predict similar optical levels in the other TMDs. In the case of the H impurity, we find it more stable sitting on an interstitial site in the Mo plane, acting as a shallow donor, and possibly explaining the often observed n-type conductivity in some TMDs. We also predict the frequencies of the local vibration modes for the H impurity, aiding its identification through Raman or infrared spectroscopy.

Thickness dependence of the room-temperature ethanol sensor properties of Cu2O polycrystalline films

This study investigates the fabrication process of copper thin films via thermal evaporation, with precise control over film thickness achieved through Z-position adjustment. Analysis of the as-fabricated copper films reveals a discernible relationship between grain size (〈D〉) and Z-position, characterized by a phenomenological equation 〈D〉XRDn(Z)=〈D〉0n1+32rZ2+158rZ4 , which is further supported by a growth exponent (n) of 0.41 obtained from the analysis. This value aligns well with findings in the literature concerning the growth of copper films, thus underlining the validity and reliability of our experimental outcomes. The resulting crystallites, ranging in size from 20 to 26 nm, exhibit a resistivity within the range of 3.3–4.6 μΩ · cm. Upon thermal annealing at 200 °C, cuprite Cu2O thin films are produced, demonstrating crystallite sizes ranging from ∼9 to ∼24 nm with increasing film thickness. The observed monotonic reduction in Cu2O crystallites relative to film thickness is attributed to a recrystallization process, indicating amorphization when oxygen atoms are introduced, followed by the nucleation and growth of newly formed copper oxide phase. Changes in the optical bandgap of the Cu2O films, ranging from 2.31 to 2.07 eV, are attributed mainly to the quantum confinement effect, particularly important in Cu2O with size close than the Bohr exciton diameter (5 nm) of the Cu2O. Additionally, correlations between refractive index and extinction coefficient with film thickness are observed, notably a linear relationship between refractive index and charge carrier density. Electrical measurements confirm the presence of a p-type semiconductor with carrier concentrations of ∼1014 cm−3, showing a slight decrease with film thickness. This phenomenon is likely attributed to escalating film roughness, which introduces supplementary scattering mechanisms for charge carriers, leading to a resistivity increase, especially as the roughness approaches or surpasses the mean free path of charge carriers (8.61 nm). Moreover, ab-initio calculations on the Cu2O crystalline phase to investigate the impact of hydrostatic strain on its electronic and optical properties was conducted. We believe that our findings provide crucial insights that support the elucidation of the experimental results. Notably, thinner cuprite films exhibit heightened sensitivity to ethanol gas at room temperature, indicating potential for highly responsive gas sensors, particularly for ethanol breath testing, with significant implications for portable device applications.

Prediction of Single-Layer Antimony Oxyselenide (Sb2O2Se2): Metal-to-Semiconductor Transition via Hydrogenation.

In this study, the structural, electronic, vibrational, and mechanical properties of single-layer
Antimony Oxyselenide (Sb 2 O 2 Se 2 ) and its hydrogenated structure (Sb 2 O 2 Se 2 H 2 ) are investigated
by performing density functional theory-based first principles calculations. Geometry optimizations
reveal that single-layer Sb 2 O 2 Se 2 crystallizes in tetragonal structure which is shown to possess
dynamical stability by means of phonon band dispersions. In addition, the mechanical stability of
the predicted single layer is satisfied via the linear-elastic parameters. Electronically, it is revealed
that single-layer Sb 2 O 2 Se 2 exhibits metallic behavior whose highest occupied states are found to
arise from the surface Se atoms, may be an indication for tuning the electronic features via surface
functionalization. For the surface modification of Sb 2 O 2 Se 2 , top of each Se atom is saturated with
a H atom and fully hydrogenated single-layer Sb 2 O 2 Se 2 H 2 is shown to be an in-plane anisotropic
structure. In addition, it is found that the existence of tilted H atoms on the surface can be detected
via Scanning Tunneling Microscopy (STM) images. Phonon band dispersion calculations indicate the
dynamical stability of Sb 2 O 2 Se 2 H 2 . Mechanically stable Sb 2 O 2 Se 2 H 2 is found to possess anisotropic
linear-elastic behavior, which is much softer than its pristine structure. Moreover, electronically a
metallic-to-semiconducting transition is shown to occur as the unoccupied Se-orbitals are saturated
via H atoms. Our work offers insights into prediction of a novel single-layer material, namely
Sb 2 O 2 Se 2 , and reports the chemically-driven semiconducting behavior via hydrogenation, which may
lead to the use of hydrogenated structure in solar cell, photoelectrode, or photocatalyst applications.

Electronic, elastic, and thermodynamic properties of complex hydrides XAlSiH (X = Sr, Ca, and Ba) intended for hydrogen storage: an ab-initio study

The mechanical and thermodynamic properties of polyanionic hydrides XAlSiH (X = Sr, Ca, and Ba) were evaluated using density functional theory (DFT). The thermal parameters of XAlSiH hydrides, such as the Grüneisen parameter γ, heat capacity, and thermal expansion coefficient, were computed for the first time. The quasi-harmonic Debye model was used to determine these parameters over a range of pressures (0–40 GPa) and temperatures (0–1000 K). The gravimetric hydrogen storage capacities for BaAlSiH, SrAlSiH, and CaAlSiH were found to be 0.52%, 0.71%, and 1.05%, respectively. The hydrogen desorption temperatures for these compounds were also simulated at 748.90 K, 311.57 K, and 685.40 K. Furthermore, semiconducting behavior with an indirect bandgap value between 0.2 and 0.7 eV was exhibited by these compounds using the GGA and LDA approximation, and between 0.7 and 1.2 eV using the mBJ-GGA and mBJ-LDA approximation. Accurate elastic constants for single crystals were obtained from the calculated stress–strain relationships. The elastic constants for the XAlSiH compounds were significantly higher than those for other hydrides. The [001] direction was more compressible than the [100] direction in the hexagonal structure of XAlSiH. A lower bulk modulus than metallic hydrides was exhibited by these materials, indicating that XAlSiH compounds (X = Sr, Ca, and Ba) were highly compressible. The melting temperature for CaAlSiH was higher than that for SrAlSiH and BaAlSiH. Consequently, the decomposition temperature for XAlSiH (X = Sr and Ba) at which hydrogen was released from a fuel cell was lower than that for CaAlSiH. The bonding behavior of CaAlSiH was more directional than that of SrAlSiH and BaAlSiH. Brittle materials were XAlSiH (X = Sr, Ca, and Ba). Our PBE calculations yield linear compressibility and orientation-dependent Young’s modulus. Materials composed of hexagonal XAlSiH (where X represents Sr, Ca, or Ba elements) exhibit anisotropy in Young’s modulus but isotropy in bulk modulus.

Electrostatic doping tunable magnetic transition and half-metallicity in the monolayer CrCTe3.

The electrical manipulation of the magnetic transition and spinpolarized states has attracted extensive attention in the field of spintronics. In this work, we perform a detailed study on the electronic and magnetic properties of the carrier-doped monolayer CrCTe3by using first-principles calculation. It is found that, the magnetic transition from Néel-antiferomagnetic (nAFM) to ferromagnetic (FM) is observed in the case of the electron doping, while for hole doping a magnetic transition sequence of nAFM → zigzag-AFM → FM is observed in the monolayer CrCTe3. Interestingly, the carrier doping induced FM ground state always exhibits half-metallicity with full spin polarization. Moreover, the spin polarity of the half-metallic electronic states is opposite for electron and hole doping, meaning that the spin polarization direction can be tuned by manipulating a gate voltage. The Monte Carlo calculations show that the magnetic transition temperature of the doped FM CrCTe3is rapidly increased with the increasing doping concentration and is extremely expected to achieve room temperature at a suitable doping concentration. These findings demonstrate that the monolayer AFM system possesses a potential application in spintronic devices with electrically tunable spin polarization.

Comparative Analysis of Hydrogen Molecule Interaction with B-Au and N-Au Co-Doped Graphene Nanoribbons: DFT Insights

In the present study, B and N atoms are co-doped with Au atom in graphene nanoribbons and has been analysed for hydrogen molecule interaction with the aid of Density Functional Theory. A comparative analysis is carried out between N-AuG and B-AuG substrate towards H2 molecule. The structural as well as electronic properties of the optimized structures have been studied. Different theoretical parameters which include adsorption energy, charge redistribution, and bandgap analysis have been computed to determine the effectiveness of substrate.

Structural and electronic properties of Mo-decorated graphene, reduced graphene and reduced graphene oxide: a DFT calculation

The structural and electronic properties of pure graphene, graphene with a vacancy, graphene with two vacancies and molybdenum-doped graphene were investigated. In addition, the adsorption of Mo atoms on graphene (G), reduced graphene (rG) and reduced graphene oxide (rGO) was examined. The possible energies of different active adsorption sites of nanostructured Mo-decorated G, rG and rGO have been calculated using density functional theory (DFT). Mo atoms are predicted to create bonds with six C atoms in G, three C atoms in rG, and both C and O atoms in rGO sheets after geometry optimizations. The study focused on changing the electronic structure of G, including opening the zero band gap and controlling the band structure, which was done by creating defects and adding impurities. The present study revealed a significant correlation between the adsorption of the Mo atom and the characteristics exhibited by frontier orbitals. The results indicated that the adsorption characteristics of Mo atoms in pure G, rG and rGO are different, despite chemisorption being the common mechanism. Specifically, Mo-decorated rG exhibited higher adsorption energy, while Mo-decorated G demonstrated a lower adsorption energy. According to these findings, it is reasonable to anticipate that Mo-decorated rG could be applied as a novel adsorbent for the removal of pollutants.

Erratum: Structural, elastic, optic, and electronic properties of strontium oxide under pressure studied by first-principles calculations

Erratum: Structural, elastic, optic, and electronic properties of strontium oxide under pressure studied by first-principles calculations

Computational Investigation of a Reversible Energy Storage Medium in g-B5N3 Decorated by Lithium.

Graphene-like materials in two dimensions hold great promise for energy storage and transformation applications owing to their distinctive features, such as lightweight composition, porous geometry, etc. Among these materials, a recently discovered unit known as g-B5N3 has demonstrated high performance in energy storage and transformation. In our efforts to enhance its applicability in adsorbing energy gases, we propose a novel composite structure by decorating Li atoms on the surface of pristine g-B5N3. The electronic properties of this composite have been comprehensively investigated using a first-principles method. Our findings reveal that the added Li atoms can be securely anchored on the g-B5N3 with an adsorption energy of -3.01 eV. Furthermore, the Li atom transfers its partial 2s electrons to the g-B5N3, exhibiting considerable electropositivity. These metallic sites effectively polarize the adsorbed H2 molecules, enhancing the mutual electrostatic interactions. Each primitive cell of Li-doped g-B5N3 can adsorb up to 13 H2 molecules, resulting in a storage capacity up to 6.3 wt %. This capacity significantly surpasses the goal of 4.5 wt % set by the U.S. Department of Energy. Furthermore, the typical adsorption energy of -0.209 eV per molecule of H2 aligns with the energy range suitable for reversible hydrogen storage. This study underscores the potential of Li-doped g-B5N3 for energy gas adsorption, shedding light on further advancements in this field.

Emergence of two distinct phase transitions in monolayer CoSe2 on graphene

Dimensional modifications play a crucial role in various applications, especially in the context of device miniaturization, giving rise to novel quantum phenomena. The many-body dynamics induced by dimensional modifications, including electron-electron, electron-phonon, electron-magnon and electron-plasmon coupling, are known to significantly affect the atomic and electronic properties of the materials. By reducing the dimensionality of orthorhombic CoSe2 and forming heterostructure with bilayer graphene using molecular beam epitaxy, we unveil the emergence of two types of phase transitions through angle-resolved photoemission spectroscopy and scanning tunneling microscopy measurements. We disclose that the 2 × 1 superstructure is associated with charge density wave induced by Fermi surface nesting, characterized by a transition temperature of 340 K. Additionally, another phase transition at temperature of 160 K based on temperature dependent gap evolution are observed with renormalized electronic structure induced by electron-boson coupling. These discoveries of the electronic and atomic modifications, influenced by electron-electron and electron-boson interactions, underscore that many-body physics play significant roles in understanding low-dimensional properties of non-van der Waals Co-chalcogenides and related heterostructures.Graphical Two different pseudo-gaps and corresponding phase transitions are observed in monolayer orthorhombic CoSe2 grown on graphene substrates.

Choice of the Right Supporting Electrolyte in Electrochemical Reductions: A Principal Component Analysis.

We present an analysis of a set of molecular, electrical, and electronic properties for a large number of the cations of quaternary ammonium salts usually employed as supporting electrolytes in cathodic reduction reactions. The goal of the present study is to define a measure for the quality of a supporting electrolyte in terms of the yield of the reaction considered. We performed a principal component analysis using the normalized values of the properties in order to lower the number of relevant reaction coordinates and find that the integral variance of 13 properties can well be represented by three principal components. The yield of the electrochemical hydrodimerization of acrylonitrile employing different quaternary ammonium salts as supporting electrolytes was determined in a series of experiments. We found only a very weak correlation between the yield and the values of the properties but a strong correlation between the yield and the values of the most important principal component. Very similar results are obtained for two further existing systematic experimental studies of the impact of the supporting electrolyte on the yield of cathodic reductions. For all three example reactions, a supervised regression using the two most important principal components as variables yields excellent values for the coefficients of determination. For comparison, we also applied our methodology to sets of purely structure-based features that are usually employed in cheminformatics and obtained results of almost similar quality. We therefore conjecture that our methodology in combination with a small number of experiments can be used to predict the yield of a given cathodic reduction on the basis of the properties of the supporting electrolyte.

Transport properties in ABC-ABA-ABC trilayer graphene junctions

Abstract Trilayer graphene consists of three layers of graphene arranged in a particular stacking order. In the case of ABC-ABA-ABC stacking, the layers are arranged in an A-B-C sequence, followed by an A-B-A sequence, and again an A-B-C sequence. This stacking arrangement introduces specific electronic properties and band structures due to the different stacking configurations. We focus on elucidating the transport properties of a p-n-p junction formed with ABC-ABA-ABC stacking TLG. Employing the transfer matrix method and considering continuity conditions at the junction boundaries, we establish transmission and reflection probabilities, along with conductance. Notably, electron transport through the ABC-ABA-ABC junction exhibits Klein tunneling, resulting in substantial conductance even in the absence of a potential barrier $V_0$. This effect arises from the effective barrier induced by our specific stacking, facilitating the passage of a maximal number of electrons. However, the presence of $V_0$ diminishes Klein tunneling, leading to conductance minima. Furthermore, our findings highlight that interlayer bias $\delta$ induces a hybridization of the linear and parabolic bands of ABA-TLG within the junction, reducing resonances. In cases where $\delta\neq0$ and $V_0\neq0$, we observe a suppression of the gap, contrary to the results obtained in ABC tunneling studies where a gap exists.

Strain and Piezoelectric Control of Electronic and Photonic Properties of p − n Diodes

Abstract Piezoelectricity is a well-known effect in a vast number of technologically important insulators and semiconductors and exists in $20$ out of the $32$ three-dimensional crystal classes. The piezoelectric effect is the driving mechanism behind several classical sensors and transmitters, and also most recently, in many nanodevices. Zhong Lin Wang coined the fields piezotronics and piezo-phototronics where the piezoelectric effect plays a dominant role. Piezoelectricity couples in a linear fashion mechanical strain to electrical fields and vice versa. In solids, there is another linear coupling between strain and the electric potential, known as the deformation potential effect. While linear in its coupling nature, this effect does not require the solid to be non-centrosymmetric in contrast to the piezoelectric effect. Moreover, the deformation potential effect is quantitatively huge and leads to changes in the conduction and valence band edges of III-V and II-VI materials of, typically, $50-100$~meV in the presence of $1$~\% strain. Therefore, the deformation potential effect is essential to determine the electronic and photonic properties of bulk and nanostructure semiconductors in the presence of strain. In this work, we compute the relative importance of piezoelectricity and the deformation potential effect in the presence of lattice mismatch and external strain. We choose $p-n$ junctions of ZnO/GaN structures but anticipate that the general conclusions can be carried over to other material structures. The main result of the present work is that both the inclusion of the deformation potential effect and piezoelectricity is crucial to correctly compute the effect of strain on $p-n$ junction current-voltage curves and photonic properties. In our analysis of wurtzite heterostructures, the spontaneous polarization effect is also included but this effect appears to play a minor role for electronic and photonic properties.