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We use low-dose cryogenic transmission electron microscopy (cryo-TEM) to investigate the atomic-scale structure of antiperovskite Na2NH2BH4 crystals by preserving the room-temperature cubic phase and carefully monitoring the electron dose. Via quantitative analysis of electron beam damage using selected area electron diffraction, we find cryogenic imaging provides 6-fold improvement in beam stability for this solid electrolyte. Cryo-TEM images obtained from flat crystals revealed the presence of a new, long-range-ordered supercell with a cubic phase. The supercell exhibits doubled unit cell dimensions of 9.4 Å × 9.4 Å as compared to the cubic lattice structure revealed by X-ray crystallography of 4.7 Å × 4.7 Å. The comparison between the experimental image and simulated potential map indicates the origin of the supercell is a vacancy ordering of sodium atoms. This work demonstrates the potential of using cryo-TEM imaging to study the atomic-scale structure of air- and electron-beam-sensitive antiperovskite-type solid electrolytes.

The recent discovery of polar topological structures has opened the door for exciting physics and emergent properties. There is, however, little methodology to engineer stability and ordering in these systems, properties of interest for engineering emergent functionalities. Notably, when the surface area is extended to arbitrary thicknesses, the topological polar texture becomes unstable. Here we show that this instability of the phase is due to electrical coupling between successive layers. We demonstrate that this electrical coupling is indicative of an effective screening length in the dielectric, similar to the conductor-ferroelectric interface. Controlling the electrostatics of the superlattice interfaces, the system can be tuned between a pure topological vortex state and a mixed classical-topological phase. This coupling also enables engineering coherency among the vortices, not only tuning the bulk phase diagram but also enabling the emergence of a 3D lattice of polar textures.

The evaporation-induced self-assembly process of amphiphilic molecules (4POSS-DL-POM) in a mixed acetone/ n -decane solution is investigated using small-angle X-ray scattering. A series of scattering data analysis methods is employed to elucidate the structural evolution of heterocluster 4POSS-DL-POM from a fractal network to compact nanoclusters, followed by the formation of core–shell nanoclusters, and ultimately to hcp superlattice structure. [Display omitted] Self-assembly of nanoclusters (NCs) is an effective synthetic method for preparing functionalized nanomaterials. However, the assembly process and mechanisms in solutions still remain ambiguous owing to the limited strategies to monitor intermediate assembled states. Herein, the self-assembly process of amphiphilic molecule 4POSS-DL-POM (consisting of four polyhedral oligomeric silsesquioxanes, a dendritic linker, and one polyoxometalate) by evaporation of acetone in a mixed acetone/ n -decane solution is monitored by time-resolved synchrotron small-angle X-ray scattering (SAXS). Scattering data assessments, including Kratky analysis, pair distance distribution function, and model fitting, track the self-assembly process of 4POSS-DL-POM from a fractal network to compact NCs, then to core–shell NCs, and finally to superlattice structure. The calculated average aggregation number of a core–shell NC is 11 according to the parameters obtained from core-shell model fitting, in agreement with electron microscopy. The fundamental understanding of the self-assembly dynamics from heterocluster into NCs provides principles to control building block shape and guide target aggregation, which can further promote the design and construction of highly ordered cluster-assembled functional nanomaterials. [ABSTRACT FROM AUTHOR]

Optical phase change materials (OPCMs) hold significant promise in photonic integrated circuits (PICs) due to their non‐volatile modulation capabilities through phase transition. Recently, integrating OPCMs with silicon devices has been leveraged to achieve multi‐level modulation in neural network computing. However, the conventional OPCM Ge2Sb2Te5 (GST), faces challenges in large‐scale PICs due to its large absorption. In this work, an optimized low‐loss GST superlattice is demonstrated, which significantly lowers crystalline attenuation coefficients from 2.69 to 0.539 dB µm−1, with negligible loss in amorphous state, while retaining excellent phase modulation capability. Additionally, 15 distinguishable extinction ratio states are achieved by manipulating irradiation energy for a hybrid Si microring resonator (MRR) embedded with GST superlattice. To further explore the potential application of GST superlattice in optical computing, an all‐optical tunable temporal differentiator is empirically demonstrated with a single hybrid MRR, achieving a broad dynamic differentiation order ranging from 0.7 to 1.3. The non‐volatile nature of OPCM facilitates low energy consumption and effectively optimizes chip density. The proposed structural design strategy to reduce the absorption loss is universal for any promising OPCMs feasible for large‐scale artificial intelligence‐driven PICs, including optical analog computing, optical switching and optical neural networks. [ABSTRACT FROM AUTHOR]

The introduction of superconductivity in graphene systems is highly desirable from both fundamental physics and application perspectives. In this article, a superlattice strategy to develop a series of Li‐doped graphene is reported: deposition type‐I (Li2C6, Li2C8, LiC6, Li3C24, LiC12, LiC16, Li2C36, LiC24), intercalation type‐II (LiC4, Li2C12, LiC8, LiC12, LiC16), and coexisting deposition and intercalation type‐III (Li3C12). With increasing concentration of Li atoms, both metallicity, and electron–phonon coupling (EPC) has dramatically increased, which is favorable for the emergence of superconductivity in the screened Li–C compounds. Notably, graphene superlattice structures with intercalated Li2 atoms have higher stability, while Li1‐deposited graphene at the same concentration produces higher Tc. Among them, type‐I‐Li2C6, type‐I‐Li2C8, type‐II‐LiC4, and type‐III‐Li3C12 are phonon‐mediated superconductors with high transition temperatures (Tc) of 18, 12, 3.4, and 14 K, respectively. The EPC of type‐I‐Li2C6, type‐I‐Li2C8, and type‐III‐Li3C12 mainly arises from the coupling of the C‐2pz electron states with the low‐frequency (0–800 cm−1) deposition‐Lixy/Liz, and out‐of‐plane‐Cz vibrations. In contrast, the high‐frequency (800–1600 cm−1) vibration modes of in‐plane‐Cxy atoms are mainly responsible for the Tc of type‐II‐LiC4. The findings provide comprehensive insights into the superconductivity limit of Li‐doped graphene. [ABSTRACT FROM AUTHOR]

Interfacial phase‐change materials (iPCM), which are alternatively stacked with GeTe and Sb2Te3 in the superlattice structure, have been highlighted as next‐generation PCM with improved overall phase‐change characteristics. However, several studies have reported that a melt‐quenching process, whereby the initial superlattice structure is not maintained within the reversible switching process, rather than the initially proposed melting‐free phase‐change mechanism, occurs during operation. Herein, GeSbTe superlattices are synthesized using molecular beam epitaxy, and the reversible phases of the superlattice obtained by irradiation with an optical pulsed laser (KrF; 280 nm, 25 ns) and re‐annealing or by applying different electrical pulses are investigated through careful structural analyses. The results revealed that Te atoms are aligned parallel to the interface regardless of the reversible phase, whereas cations and inherent vacancies are distributed differently during the phase‐change process. The stability of memory cells with cycling operations can be enhanced by enriching inherent vacancies, and the switching energy can be reduced by expanding the interspaces via doping engineering. [ABSTRACT FROM AUTHOR]

Achieving both high redox activity and rapid ion transport is a critical and pervasive challenge in electrochemical energy storage applications. This challenge is significantly magnified when using large‐sized charge carriers, such as the sustainable ammonium ion (NH4+). A self‐assembled MXene/n‐type conjugated polyelectrolyte (CPE) superlattice‐like heterostructure that enables redox‐active, fast, and reversible ammonium storage is reported. The superlattice‐like structure persists as the CPE:MXene ratio increases, accompanied by a linear increase in the interlayer spacing of MXene flakes and a greater overlap of CPEs. Concurrently, the redox activity per unit of CPE unexpectedly intensifies, a phenomenon that can be explained by the enhanced de‐solvation of ammonium due to the increased volume of 3 Å‐sized pores, as indicated by molecular dynamic simulations. At the maximum CPE mass loading (MXene:CPE ratio = 2:1), the heterostructure demonstrates the strongest polymeric redox activity with a high ammonium storage capacity of 126.1 C g−1 and a superior rate capability at 10 A g−1. This work unveils an effective strategy for designing tunable superlattice‐like heterostructures to enhance redox activity and achieve rapid charge transfer for ions beyond lithium. [ABSTRACT FROM AUTHOR]

Quantum wells and superlattices are key building blocks in the semiconductor industry, normally fabricated using epitaxial growth techniques, such as vapor phase epitaxy, metalorganic chemical vapor deposition and molecular beam epitaxy. However, these complicated preparation processes, as well as their high cost, limit their extensive applications. It is essential to develop a simple solution process for building superstructures. Here, we demonstrate an ion exchange strategy for synthesizing an all-inorganic superlattice cesium lead bromide/layered double hydroxides (CsPbBr3/LDH) in solution. At room temperature, the perovskite ions diffuse into the interlayer of LDH and assemble into layered perovskite with various thicknesses. Compared with traditional organic-inorganic hybrid perovskite superlattice, the all-inorganic perovskite superlattice CsPbBr3/LDH has weak quantum confinement, which exhibits narrow emission line-widths of 20 nm, high quantum yields of 55%, and radiative lifetimes of several ns. Our findings offer a new route to synthesize novel perovskite superlattices and enrich the perovskite supercrystal platform for electronics, photonics and optoelectronics devices. [ABSTRACT FROM AUTHOR]

Chemically ordered face-centered cubic (fcc) phases consisting mainly of Cr, Co, and Ni were synthesized by annealing a Cr26.7Co26.7Ni26.7Si10B5P5 amorphous alloy. The annealed Cr26.7Co26.7Ni26.7Si10B5P5 sample was composed of Cr4.5BP2, Cr3 Co5Si2, and fcc phases. Synchrotron radiation anomalous X-ray scattering (AXS) measurements confirmed that the annealed Cr26.7Co26.7Ni26.7Si10B5P5 sample had superlattice reflections from an L10-, and/or L12-, and D022-type ordered structure. The diffraction intensities of the superlattice reflections observed in the AXS measurements indicated strong dependence on the incident X-ray energy. The diffraction intensity of the superlattice reflection increased at the X-ray energy near the K-edge of Cr, suggesting that Cr is mainly ordered in the L10- and D022-type structures. Microstructural analysis using scanning transmission electron microscopy (STEM) revealed crystal grains with diameters of approximately 20 nm, showing diffraction spots corresponding to superlattice reflections of 001 and 110, in addition to a two-dimensional diffraction pattern corresponding to the fcc structure. Simultaneous STEM--energy dispersive X-ray spectroscopy analysis indicated that the grains had a higher Cr concentration than the mother alloy composition of Cr26.7Co26.7Ni26.7Si10B5P5. [ABSTRACT FROM AUTHOR]

The results of investigation of the gain properties of 1300 nm vertical-cavity surface-emitting lasers active regions based on In0.60Ga0.40As/In0.53Al0.20Ga0.27As superlattices and threshold characteristics comparison of superlattices and highly lattice mismatched In0.74Al0.16Ga0.10As quantum wells are presented. The heterostructure of injection lasers with an In0.60Ga0.40As/In0.53Al0.20Ga0.27As superlattice was grown by molecular beam epitaxy. Mesa structure of injection lasers was obtained by selective liquid etching followed by the application of ohmic contacts. The formation of injection lasers with various cavity lengths is performed using the method of manually cleaving mirrors. The output characteristics were measured in a pulsed mode using a large area calibrated germanium photodiode. Spectral characteristics were measured using a spectrophotometer based on monochromator. The achieved threshold characteristics (modal gain about 40 cm–1, transparency current density about 650 A/cm2, internal optical losses about 8 cm–1) of injection lasers based on In0.60Ga0.40As/In0.53Al0.20Ga0.27As superlattices with low lattice mismatch InGaAs layers are comparable to previously presented lasers based on active regions with strongly strained In0.74Al0.16Ga0.10As quantum wells. The characteristic temperatures T0 and T1 were 60 K and 87 K for injection lasers with a cavity length of 1 mm. An increase in the frequency of small-signal modulation of vertical-cavity surface-emitting lasers and their temperature stability is associated with the use of highly strained In0.74Ga0.26As/In0.53Al0.25Ga0.21As superlattices. The proposed active regions based on InGaAs-InP superlattices have the potential to be used in the development of vertical-cavity surface-emitting lasers in the 1300 nm spectral range. The findings of this work can be applied in the realization of experimental species and optimization of modulation parameters for vertical-cavity lasers operating in the 1300 nm wavelength range.

Engineering superlattices (SLs)—which are spatially periodic potential landscapes for electrons—is an emerging approach for the realization of exotic properties, including superconductivity and correlated insulators, in two-dimensional materials. While moiré SL engineering has been a popular approach, nanopatterning is an attractive alternative offering control over the pattern and wavelength of the SL. However, the disorder arising in the system due to imperfect nanopatterning is seldom studied. Here, by creating a square lattice of nanoholes in the SiO2 dielectric layer using nanolithography, we study the SL potential and the disorder formed in hBN-graphene-hBN heterostructures. Specifically, we observe that while electrical transport shows distinct SL satellite peaks, the disorder of the device is significantly higher than graphene devices without any SL. We use finite-element simulations combined with a resistor network model to calculate the effects of this disorder on the transport properties of graphene. We consider three types of disorder: nanohole size variations, adjacent nanohole mergers, and nanohole vacancies. Comparing our experimental results with the model, we find that the disorder primarily originates from nanohole size variations rather than nanohole mergers in square SLs. We further confirm the validity of our model by comparing the results with quantum transport simulations. Our findings highlight the applicability of our simple framework to predict and engineer disorder in patterned SLs, specifically correlating variations in the resultant SL patterns to the observed disorder. Our combined experimental and theoretical results could serve as a valuable guide for optimizing nanofabrication processes to engineer disorder in nanopatterned SLs. [ABSTRACT FROM AUTHOR]

We investigate the energy band structure and transport properties of electrons in superlattice structure based on semi-Dirac material with one-dimensional periodic potentials of square barriers. The influence of different parameters on transmission probability in superlattice structure is studied. It is found that two new Dirac points are formed in the superlattice structure by adjusting the gap parameter. The position of the new Dirac points can be regulated by changing the size of the potential barrier, the ratio of well width to barrier width, and the gap parameter. Some forbidden bands appear in the transmission probability, the location and width of the forbidden bands can be regulated by changing the system parameters. [ABSTRACT FROM AUTHOR]

An efficient tapered coupling mechanism for monolithic integration of active and passive devices on InGaAsP/InP quantum well (QW) structures is theoretically analyzed and experimentally demonstrated. An easier fabrication technique using Z r O 2 impurity-free QW-intermixing is used to achieve vertical tapering, while photolithography is used to optimize horizontal tapering. The importance of designing the epitaxial layer specifically for this fabrication technique and the device combination to be used is demonstrated. First, on a regular InGaAsP/InP waveguide photodiode structure and then redesigning the same for optimization and experimental verification. The improvement is achieved by introducing an InGaAs/InP superlattice (SL)—graded index (GRIN) with a single QW absorption layer in the waveguide core. Asymmetrical InGaAs/InP SL cladding layers are used for lower optical losses and higher index contrast. While the regular structure shows a reduction in coupling and insertion loss of 1 and 3 dB, respectively, a redesign of the epitaxial structure brought down the same by 7.5 and 9.0 dB, respectively. [ABSTRACT FROM AUTHOR]

Perovskite manganites have been widely studied due to their rich magnetic and electrical properties, such as the colossal magnetoresistance (CMR) effect, ferromagnetic transition, and exchange bias effect. This work reports the preparation of five [La0.8Ca0.2MnO3/La0.5Ca0.5MnO3]20 superlattice films with different La0.8Ca0.2MnO3 layer thicknesses on (001) LaAlO3 substrate using pulsed laser deposition technology. The thickness of the La0.5Ca0.5MnO3 sublayers for all five superlattice films during one growth cycle is 48 Å. The thickness of the La0.8Ca0.2MnO3 sublayers in the superlattice films during one growth cycle is 24 Å, 48 Å, 72 Å, 96 Å, and 120 Å, designated as SL-24, SL-48, SL-72, SL-96, and SL-120, respectively. The crystal structure (lattice constants) of samples is obtained using x-ray diffraction technology, and the strain states of the samples are determined based on the lattice constant. Three superlattice samples (SL-48, SL-72, and SL-96) are in a state of strain relaxation. The SL-24 and SL-120 samples are in a strain state, which is the result of the interlayer strain effect due to the asymmetric thickness of the two components between the sublayers. The magnetic properties of samples are analyzed based on the stress state and magnetic properties. All superlattice samples show a ferromagnetism-to-paramagnetism transition, and with the increase in the thickness of the La0.8Ca0.2MnO3 sublayer, the Curie temperature (TC) shows a gradual decreasing trend. In addition to the ferromagnetic phase transition in SL-96, the presence of the Néel temperature (representing antiferromagnetic phase transition) is also observed, further indicating that the magnetic performance is affected by factors in addition to strain, such as multiple magnetic phases. There is no significant exchange bias in SL-48, SL-72, and SL-96, since the percolation of ferromagnetic clusters at the interface of ferromagnetic La0.8Ca0.2MnO3 and charge-ordered antiferromagnetic La0.5Ca0.5MnO3 in superlattices destroys the exchange coupling between ferromagnetic and antiferromagnetic layers, resulting in a very small exchange bias. On the contrary, for the SL-24 and SL-120 samples with significant strain states, the strain can suppress the percolation behaviors at the interfaces of the ferromagnetic and antiferromagnetic layers, leading to a pronounced exchange bias effect. [ABSTRACT FROM AUTHOR]

Lead halide perovskite quantum dots (LHP QDs) emerge as versatile photonic sources in electroluminescence and laser devices. Their applications in optoelectronic devices are hindered by surface distortion and ligand stripping during the purification process. In addition, the device performance roll‐off suffers from the ultrafast non‐radiative Auger recombination (AR). To address these issues, herein, CsPbBr3 QDs are prepared with sizes ranging from 6.5 to 9.2 nm and the universal surface repairing strategy is proved to efficiently increase the biexciton lifetime and quantum yield up to 1.4 and 3 times, respectively. The strategy provides a PbBrx rich surface and strong binding didodecyldimethylammonium bromide (DDAB) ligands to achieve near‐unity photoluminescence efficiency, which significantly improves their stability against anti‐solvents and aging in ambient conditions. A single‐mode laser device is realized by self‐assembling the QDs into superlattice as optical microcavity, with low threshold of 9.45 µJ cm−2, quality factor of 2187 and ultrafast lifetime of 3.22 ps. The superlattice laser is demonstrated as an optical encoder with large coding bandwidth of 0.133 THz. This work proposes new insight into the non‐radiative AR process in these single‐component CsPbBr3 QDs, and will pave the way for optoelectronic devices working in intense conditions. [ABSTRACT FROM AUTHOR]

In this paper we present the study of the features of epitaxial growth highly stressed superlattices based on highly stressed thin InGaAs/InAlAs layers on InP substrates by the molecular beam epitaxy. It was shown that the growth rates of the InGaAs and InAlAs bulk layers lattice-matched to InP substrates do not allow us to precisely determine the growth rates of thin highly stressed In0.36Al0.64As/In0.67Ga0.33As strain compensated superlattices and the error is about 10 percent. The effect is related to the difference in the growth temperatures of InGaAs and InAlAs bulk layers, which affects the intensity of indium evaporation from the growth surface. [ABSTRACT FROM AUTHOR]

The electronic properties of calcium-intercalated graphite (CaC6) as a function of pressure are revisited using density functional theory (DFT). The electronic band structures of CaC6, like many other layered superconducting materials, display cosine-shaped bands at or near the Fermi level (FL). Such bands encompass bonding/antibonding information with a strong connection to superconducting properties. Using a hexagonal cell representation for CaC6, the construction of a double supercell in the c-direction effects six-folding in the reciprocal space of the full cosine function, explicitly revealing the bonding/antibonding relationship divide at the cosine midpoint. Similarly, folding of the Fermi surface (FS) reveals physical phenomena relevant to electronic topological transitions (ETTs) with the application of pressure. The ETT is characterised by a transition of open FS loops to closed loops as a function of pressure. As the highest transition temperature is reached with pressure, the dominant continuous, open FS loops shift to a different region of the FS. For CaC6, the peak value for the superconducting transition temperature, Tc, occurs at about 7.5 GPa, near the observed pressure of the calculated ETT. At this pressure, the radius of the nearly spherical Ca 4s-orbital FS coincides with three times the distance from the Γ centre point to the Brillouin zone (BZ) boundary of the 2c supercell. In addition, the ETT coincides with the alignment of the nonbonding (inflection) point of the cosine band with the FL. At other calculated pressure conditions, the Ca 4s-orbital FS undergoes topological changes that correspond and can be correlated with experimentally determined changes in Tc. The ETT is a key mechanism that circumscribes the known significant drop in Tc for CaC6 as a function of increasing pressure. Consistent calculated responses of the ETT to pressure match experimental measurements and validate the examination of superlattices as important criteria for understanding mechanisms driving superconductivity. [ABSTRACT FROM AUTHOR]

The superconductivity of CaC6 as a function of pressure and Ca isotopic composition was revisited using DFT calculations on a 2c–double hexagonal superlattice. The introduction of superlattices was motivated by previous synchrotron absorption and Raman spectroscopy results on other superconductors that showed evidence of superlattice vibrations at low (THz) frequencies. For CaC6, superlattices have previously been invoked to explain the ARPES data. A superlattice along the hexagonal c-axis direction is also illustrative of atomic orbital symmetry and periodicity, including bonding and antibonding s-orbital character implied by cosine-modulated electronic bands. Inspection of the cosine band revealed that the cosine function has a small (meV) energy difference between the bonding and antibonding regions, relative to a midpoint non-bonding energy. Fermi surface nesting was apparent in an appropriately folded Fermi surface using a superlattice construct. Nesting relationships identified phonon vectors for the conservation of energy and for phase coherency between coupled electrons at opposite sides of the Fermi surface. A detailed analysis of this Fermi surface nesting provided accurate estimates of the superconducting gaps for CaC6 with the change in applied pressure. The recognition of superlattices within a rhombohedral or hexagonal representation provides consistent mechanistic insight on superconductivity and electron−phonon coupling in CaC6. [ABSTRACT FROM AUTHOR]

Epitaxially-fused superlattices of colloidal quantum dots (QD epi-SLs) may exhibit electronic minibands and high-mobility charge transport, but electrical measurements of epi-SLs have been limited to large-area, polycrystalline samples in which superlattice grain boundaries and intragrain defects suppress/obscure miniband effects. Systematic measurements of charge transport in individual, highly-ordered epi-SL grains would facilitate the study of minibands in QD films. Here, we demonstrate the air-free fabrication of microscale field-effect transistors (μ-FETs) with channels consisting of single PbSe QD epi-SL grains (2-7 μm channel dimensions) and analyze charge transport in these single-grain devices. The eight devices studied show p-channel or ambipolar transport with a hole mobility as high as 3.5 cm2 V-1 s-1 at 290 K and 6.5 cm2 V-1 s-1 at 170-220 K, one order of magnitude larger than that of previous QD solids. The mobility peaks at 150-220 K, but device hysteresis at higher temperatures makes the true mobility-temperature curve uncertain and evidence for miniband transport inconclusive.

Spin‐orbit torque resulting from non‐magnetic materials with strong spin‐orbit coupling enables electrically controlled magnetization switching, offering potential applications in ultralow‐power memory and logic devices. However, such switching of perpendicular magnetization usually requires an in‐plane magnetic field along the applied current direction, which limits its use. To address this challenge, an all‐oxide superlattice is designed and fabricated that show both the perpendicular magneto‐crystalline anisotropy and in‐plane magnetic anisotropies induced by interfacial engineering. The results demonstrate that the coexistence of perpendicular and in plane magnetic anisotropy breaks the symmetry and thus enables the pure electrical switching of perpendicular magnetization. [ABSTRACT FROM AUTHOR]

A novel defect control approach based on laminated HfO2/ZrO2 with multifunctional TiN/Mo/TiO x N y electrode is proposed to significantly improve the endurance and data retention in HZO-based ferroelectric capacitor. The O-rich interface reduces leakage current and prolong the endurance up to 1011 cycles while retaining a 2Pr value of 34 (μ C cm–2) at 3.4 MV cm−1. Using first-principles calculations and experiments, we demonstrate that the enhancement of endurance is ascribed to the higher migration barrier of oxygen vacancies within the laminated HZO film and higher work function of MoO x /TiO x N y between top electrode and the insulating oxide. This 2.5 nm thick TiO x N y barrier further increase the grain size of HZO, lowering the activation field and thus improving polarization reversal speed. This interfacial layer further decreases the overall capacitance, increases the depolarization field, thereby enhancing the data retention. By fitting the data using the Arrhenius equation, we demonstrate a 10 years data retention is achieved at 109.6 °C, surpassing traditional SS-HZO of 78.2 °C with a 450 °C rapid thermal annealing (required by backend-of-the-line). This work elucidates that interfacial engineering serves as a crucial technology capable of resolving the endurance, storage capability, and high-temperature data retention issues for ferroelectric memory. [ABSTRACT FROM AUTHOR]

The epitaxial organization of nano-objects with different compositions and structures into superlattice nanorods holds great promise for photocatalytic biomass oxidation as it can make full use of sunlight and improve carrier transport efficiency. Here, we construct type II photocatalytic heterojunctions using α-Fe2O3 and Nb2O5, both of which are alternately grown in situ to form superlattice nanorod structures. Due to the interlaced growth of thin layers of α-Fe2O3 and Nb2O5, the phase interface between α-Fe2O3 and Nb2O5 is greatly increased, which effectively improves the catalytic activity of the catalyst. The selective oxidation of HMF was achieved by superlattice α-Fe2O3/Nb2O5/C nanorod photoelectrocatalysts with 96.6% FDCA selectivity, which was 2.3 times higher than that of α-Fe2O3 and 3.5 times higher than that of Nb2O5, respectively, and the conversion of HMF was close to 100%. This work provides a new idea for the design of catalysts with superlattice structure and used for biomass conversion. [ABSTRACT FROM AUTHOR]

This work investigated the impact of periodic thickness and doping region on the doping efficiency of the P-type AlGaN superlattice. In this paper, the band structure of the simulated superlattice was analyzed. The superlattice structure of Al0.1Ga0.3N/Al0.4Ga0.6N, and the AlGaN buffer on the sapphire substrate, achieved a resistivity of ~3.3 Ω·cm. The results indicate that barrier doping and low periodic thickness offer significant advantages in introducing a reduction of the resistivity of P-type AlGaN superlattice structures. [ABSTRACT FROM AUTHOR]

[Display omitted] Achieving a controlled preparation of nanoparticle superstructures with spatially periodic arrangement, also called superlattices, is one of the most intriguing and open questions in soft matter science. The interest in such regular superlattices originates from the potentialities in tailoring the physicochemical properties of the individual constituent nanoparticles, eventually leading to emerging behaviors and/or functionalities that are not exhibited by the initial building blocks. Despite progress, it is currently difficult to obtain such ordered structures; the influence of parameters, such as size, softness, interaction potentials, and entropy, are neither fully understood yet and not sufficiently studied for 3D systems. In this work, we describe the synthesis and characterization of spatially ordered hierarchical structures of coated cerium oxide nanoparticles in water suspension prepared by a bottom-up approach. Covering the CeO 2 surface with amphiphilic molecules having chains of appropriate length makes it possible to form ordered structures in which the particles occupy well-defined positions. In the present case superlattice arrangement is accompanied by an improvement in photoluminescence (PL) efficiency, as an increase in PL intensity of the superlattice structure of up to 400 % compared with that of randomly dispersed nanoparticles was observed. To the best of our knowledge, this is one of the first works in the literature in which the coexistence of 3D structures in solution, such as face-centered cubic (FCC) and Frank-Kasper (FK) phases, of semiconductor nanoparticles have been related to their optical properties. [ABSTRACT FROM AUTHOR]

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Intercalation of layered materials offers an effective approach for tunning their structures and generating unprecedented properties. The multiple van der Waals (vdW) gap combined with long‐range ordering guests can change the interaction of layered host materials and electromagnetic field. Herein, a chemical‐scissor intercalation protocol medicated by molten salt is proposed for tailing the electromagnetic properties of transitional metal dichalcogenides (TMDCs). NbS2 is functional intercalated by heteroatoms (Fe, Co, Ni). The intercalated NbS2 with superlattice exhibit improved dielectric properties due to the reduced Brillouin zone size and the local electron distribution. Both the computational and experimental investigations indicate enhanced electron transport and additional polarized centers caused by intercalation. Overall, this work shows the great potential of structure editing of vdW materials, whilst intercalation via the chemical scissor in molten salts is considered a feasible intercalation strategy to further enrich their applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • Domain reconstruction imposes honeycomb and kagome superstructures in twisted MoS 2 bilayer with small twist angles. • Superstructures introduce valence bands resembling band structures of graphene (θ → 0 °) and hexagonal boron nitride (θ → 60 °). • Flat bands emerge for small twist angles. For twists close to 60°, super-heavy fermions govern the valence band. Angeli and MacDonald reported a superlattice-imposed Dirac band in twisted bilayer molybdenum disulphide (tBL MoS 2) for small twist angles towards the R h M (parallel) stacking. Using a hierarchical set of theoretical methods, we show that the superlattices differ for twist angles with respect to metastable R h M (0°) and lowest-energy H h h (60°) configurations. When approaching R h M stacking, identical domains with opposite spatial orientation emerge. They form a honeycomb superlattice, yielding Dirac bands and a lateral spin texture distribution with opposite-spin-occupied K and K' valleys. Small twist angles towards the H h h configuration (60°) generate H h h and H h X stacking domains of different relative energies and, hence, different spatial extensions. This imposes a symmetry break in the moiré cell, which opens a gap between the two top-valence bands, which become flat already for relatively small moiré cells. The superlattices impose electronic superstructures resembling graphene and hexagonal boron nitride into trivial semiconductor MoS 2. [ABSTRACT FROM AUTHOR]

In this study, the focus revolves around the synthesis, characterization, and subsequent evaluation of CuMM'O 4 (M, M' = Al, Ga, In) photoelectrocatalysts, notable for their distinct spinel- and delafossite-like structures. These novel materials are derived from a pseudobinary CuMO 2 -based solid solution. Specifically, the delafossite-like CuAlInO 4 and CuGaInO 4 manifest a trigonal superstructure within the R 3 ‾ m space group, defined by structural motifs comprising [InO 6 ] octahedra, [CuO 5 ] hexahedra, and [AlO 5 ] or [GaO 5 ] hexahedra. This study spans a comprehensive analysis encompassing optical properties, electrical characteristics, electronic structure, and the ensuing photoelectrochemical performancer. This exploration integrates experimental analyses and density functional theory calculations to discern the intricacies of these materials. The assessed CuMM'O 4 samples display favorable optical traits and band-edge positions conducive to facilitating visible-light-driven photoelectrochemical water-splitting. Among the evaluated samples, the delafossite-like CuGaInO 4 photocathode stands out due to its notably elevated carrier density and reduced resistance for carrier transport, distinguishing it from CuAlGaO 4 and CuAlInO 4. Consequently, it exhibits superior photoelectrochemical activity. CuGaInO 4 , serving as an unadorned photocathode, demonstrates a noteworthy photocurrent density of 8.6 μA/cm2 under 0.61V RHE and 102.05 μA/cm2 at 0.15 V RHE. Moreover, it achieves a peak incident photon-to-current efficiency of approximately 1.86 % at 0.61 V RHE under a 480 nm wavelength. [Display omitted] [ABSTRACT FROM AUTHOR]

Bound states in the continuum (BICs) are localized electromagnetic modes within the continuous spectrum of radiating waves. Due to their infinite lifetimes without radiation losses, BICs are driving research directions in lasing, non‐linear optical processes, and sensing. However, conventional methods for converting BICs into leaky resonances, or quasi‐BICs, with high‐quality factors typically rely on breaking the in‐plane inversion symmetry of the metasurface and often result in resonances that are strongly dependent on the angle of the incident light, making them unsuitable for many practical applications. Here, an emerging class of BIC‐driven metasurfaces is numerically analyzed and experimentally demonstrated, where the coupling to the far field is controlled by the displacement of individual resonators. In particular, both all‐dielectric and metallic as well as positive and inverse displacement‐mediated metasurfaces sustaining angular‐robust quasi‐BICs are investigated in the mid‐infrared spectral region. Their optical behavior with regard to changes in the angle of incidence is investigated and experimentally shows their superior performance compared to two conventional alternatives: silicon‐based tilted ellipses and cylindrical nanoholes in gold. These findings are anticipated to open exciting perspectives for bio‐sensing, conformal optical devices, and photonic devices using focused light. [ABSTRACT FROM AUTHOR]

Machine learning (ML) methods have gained widespread attention in optimizing nanostructures for target transport properties and discovering unexpected physics. Here, an ML method is developed to discover and experimentally confirm binary CeO2‐MgO aperiodic multilayers (AMLs) for thermal barrier coatings with significantly enhanced reflectance. The effect of varying AML design parameters like total thickness, average period, and randomness in layer thicknesses, on the spectral and total reflectance is demonstrated. Introducing aperiodicity in layer thicknesses is shown to lead to a broadband increase in spectral reflectance due to photon localization. Since the number of possible AML structures increases exponentially with total thickness, a Genetic Algorithm optimizer is developed to efficiently discover AMLs with enhanced reflectance, for total thicknesses of 5–50 µm. Surprisingly, all the optimized structures show an odd number of layers with a CeO2 layer at both ends, deviating from the traditional way of designing binary superlattices with paired layers. The optimized AML and a reference periodic superlattice of 5 µm thickness are fabricated by Pulsed Laser Deposition and characterized by optical reflectance measurements. The fabricated AML, despite considerable fabrication uncertainty, still enhances the reflectance to 48% from 40% of the reference superlattice, validating the effectiveness of our ML‐based optimization process. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) materials have attracted more and more attention due to their excellent properties. In this work, we systematically explore the heat transport properties of Graphene-C3B (GRA-C3B) superlattices and van der Waals (vdW) heterostructures using molecular dynamics method. The effects of interface types and heat flow directions on the in-plane interfacial thermal resistance (ITRip) are analyzed. Obvious thermal rectification is detected in the more energy stable interface, GRA zigzag-C3B zigzag (ZZ) interface, which also has the minimum value of ITRip. The dependence of the superlattices thermal conductivity (k) of the ZZ interface on the period length (l p ) is investigated. The results show that when the l p is 3.5 nm, the k reaches a minimum value of 35.52 W m−1 K−1, indicating a transition stage from coherent phonon transport to incoherent phonon transport. Afterwards, the effects of system size, temperature, coupling strength and vacancy defect on the out-of-plane interfacial thermal resistance (ITRop) are evaluated. With the increase of temperature, coupling strength and vacancy defect, ITRop are found to reduce effectively due to the enhanced Umklapp phonon scattering and increased probability of energy transfer. Phonon density of states and phonon participation ratio is evaluated to reveal phonon behavior during heat transport. This work is expected to provide essential guidance for the thermal management of nanoelectronics based on 2D monolayer GRA and C3B. [ABSTRACT FROM AUTHOR]

The mixed-valence perovskite manganites attracted much attention because of their interesting electro-magnetic properties, and strain modulation on magnetic properties of perovskite manganites is worth exploring. In this paper, [La 0. 8 Ca 0. 2 MnO3/La 0. 5 Ca 0. 5 MnO3] 2 0 superlattice films with different La 0. 8 Ca 0. 2 MnO3 layer thicknesses are prepared by pulsed laser deposition (PLD). The crystal structures (lattice constants) of samples are measured by X-ray diffraction (XRD). The strain of the films is determined according to their crystal structures. The magnetic hysteresis loops (M-H loops) and magnetization versus temperature (M-T) curves of these superlattice films are measured by the physical property measurement system (PPMS). From the M-H loops, the coercive field (H C) of the samples can be measured. From the M-T curves, the Curie temperature (T C) of the samples can be obtained. All samples show a ferromagnetic to paramagnetic transition at TC, and the [La 0. 8 Ca 0. 2 MnO3/La 0. 5 Ca 0. 5 MnO3] 2 0 sample with the La 0. 8 Ca 0. 2 MnO3 layer thicknesses of 72 Å has an antiferromagnetic Néel transition at TN. According to the strain state and magnetic phases, the magnetic properties are comprehensively analyzed. It is found that with the increase of ferromagnetic La 0. 8 Ca 0. 2 MnO3 layer thickness, the ferromagnetic phase is increased, and the double exchange effect can also be enhanced, resulting in the increase of TC. When the thickness of La 0. 8 Ca 0. 2 MnO3 reaches 96 Å, the uneven strain distribution in the superlattice can induce the reduction of ferromagnetic phase compared with antiferromagnetic phase (even antiferromagnetic phase starts to appear), and the double exchange effect can be weakened, and finally leading to the decrease of TC. In addition, with increasing the La 0. 8 Ca 0. 2 MnO3 layer thickness, HC gradually decreases. The change of HC is related to strain states and magnetic phase interactions in the samples. The analysis of the strain and magnetism can contribute to the understanding of perovskite manganite superlattice films. [ABSTRACT FROM AUTHOR]

Alloying-type metal sulfides with high sodiation activity and theoretical capacity are promising anode materials for high energy density sodium ion batteries. However, the large volume change and the migratory and aggregation behavior of metal atoms will cause severe capacity decay during the charge/discharge process. Herein, a robust and conductive TiS2 framework is integrated with a high-capacity SbS layer to construct a single phase (SbS)1.15TiS2 superlattice for both high-capacity and fast Na+ storage. The metallic TiS2 sublayer with high electron activity acts as a robust and conductive skeleton to buffer the volume expansion caused by conversion and alloying reaction between Na+ and SbS sublayer. Hence, high capacity and high rate capability can be synergistically realized in a single phase (SbS)1.15TiS2 superlattice. The novel (SbS)1.15TiS2 anode has a high charge capacity of 618 mAh g−1 at 0.2 C and superior rate performance and cycling stability (205 mAh g−1 at 35 C after 2,000 cycles). Furthermore, in situ and ex situ characterizations are applied to get an insight into the multi-step reaction mechanism. The integrity of robust Na-Ti-S skeleton during (dis)charge process can be confirmed. This superlattice construction idea to integrate the Na+-active unit and electron-active unit would provide a new avenue for exploring high-performance anode materials for advanced sodium-ion batteries. [ABSTRACT FROM AUTHOR]

Abstract—The analysis of internal optical loss and internal quantum efficiency in 1.3 μm-range InAlGaA-sP/AlGaAs a composite n+-InGaAs/p+-InGaAs/p+-InAlGaAs tunnel junction obtained in the frame of molecular-beam epitaxy and wafer fusion technology. The level of internal optical losses in the lasers under study was varied by depositing a dielectric layer on the surface of the output mirror. It is shown that it is possible in principle to achieve low internal optical loss of less than 0.08 and 0.14% per one pass (round-trip) at temperatures of 20 and 90°C, respectively. [ABSTRACT FROM AUTHOR]

The paper presents the results of studying the dark currents of nB(SL)n structures with a superlattice (SL) in the barrier region based on Hg1 – xCdxTe grown by molecular beam epitaxy (MBE) in a wide range of experimental conditions. Dark currents were measured in the temperature range from 11 to 300 K for mesa structures with different cross-sectional diameters. The temperature dependences of the bulk component of the dark current density and the surface leakage current density are determined. It is shown that in the studied structures the current-voltage characteristics (CVCs) are formed by both the bulk and surface components of the current depending on the temperature and bias voltage. [ABSTRACT FROM AUTHOR]

X-ray structural analysis and photoluminescence spectroscopy techniques were used to study heterostructures based on InGaAs/InAlGaAs superlattice for active regions of 1300 nm range lasers grown by molecular beam epitaxy. It is shown that the grown heterostructures have a high crystal quality. The perpendicular lattice mismatch of the average crystal lattice constant of the InGaAs/InAlGaAs superlattice with respect to the crystal lattice constant of the InP substrate is estimated at ~ +0.01%. An analysis of the photoluminescence spectra made it possible to conclude that the contribution of Auger recombination is insignificant in the studied range of excitation power density. Studies of vertical-cavity surface-emitting lasers with an active region based on the InGaAs/InAlGaAs superlattice made it possible to estimate the gain coefficient at a level of 650 cm–1 for the standard logarithmic approximation of the dependence of the gain on the current density. The transparency current density of the laser was 400–630 A/cm2, which is comparable to the record low values for the case of highly strained InGaAs–GaAs and InGaAsN–GaAs quantum wells in the spectral ranges of 1300 nm, respectively. [ABSTRACT FROM AUTHOR]

We study superlattices in non-uniform electric field to obtain mid infrared laser. We exploit the transfer matrix method and the transmission coefficient to find the suitable parameters that lead to resonant energy levels that are appropriate for generating three and four-level laser. In particular, we consider superlattice of GaAs/Al0.45Ga0.55 As consisting of four barriers, and we apply a graduated electric field. Our calculations predict that under the effect of the electric field equal to 10KV/cm and its graduation step equals to 1.26 KV/cm with the condition of the transition resonant with LO phonon, the obtained electronic transitions are shown to have wavelengths of 23.49 µm and 32.15 µm. We found that the variation of the electric field has an influence on the energy profile of the electron in the superlattice. [ABSTRACT FROM AUTHOR]

The structure and phenomena arising from charge transfer in cold field emission mode in a single closed carbon nanotube (CNT) under cold field emission conditions are studied. Inhomogeneities of the structure of CNT in the form of two types of superlattices are found by studying microphotographs obtained by AFM, SEM, and TEM. The features of charge transfer in a quasi-one-dimensional carbon nanotube emitter with a small gap between the anode and cathode are studied under conditions of low-voltage field emission. It is established that the I - V characteristics reveal voltage thresholds and resonant peaks, which are associated with the opening of conduction channels in the region of van Hove singularities. In the region of peaks in the I - V characteristics, the emission current exceeds the one calculated using the Fowler–Nordheim ( F - N ) function by one to three orders of magnitude. The I - V characteristic is not that the curve straightens in F-N coordinates. It is found that the peaks in the I - V characteristics have distinct regions of negative differential conductivity. [ABSTRACT FROM AUTHOR]

Efficient and eco-friendly disinfection of air-borne human respiratory RNA viruses is pursued in both public environment and portable usage. The AlGaN-based deep ultraviolet (DUV) light-emission diode (LED) has high practical potentials because of its advantages of variable wavelength, rapid sterilization, environmental protection, and miniaturization. Therefore, whether the emission wavelength has effects on the disinfection as well as whether the device is feasible to sterilize various respiratory RNA viruses under portable conditions is crucial. Here, we fabricate AlGaN-based DUV LEDs with different wavelength on high-temperature-annealed (HTA) AlN/Sapphire templates and investigate the inactivation effects for several respiratory RNA viruses. The AlN/AlGaN superlattices are employed between the template and upper n-AlGaN to release the strong compressive stress (SCS), improving the crystal quality and interface roughness. DUV LEDs with the wavelength of 256, 265, and 278 nm, corresponding to the light output power of 6.8, 9.6, and 12.5 mW, are realized, among which the 256 nm-LED shows the most potent inactivation effect in human respiratory RNA viruses, including SARS-CoV-2, influenza A virus (IAV), and human parainfluenza virus (HPIV), at a similar light power density (LPD) of ~0.8 mW/cm2 for 10 s. These results will contribute to the advanced DUV LED application of disinfecting viruses with high potency and broad spectrum in a portable and eco-friendly use.

Highly ordered epitaxially fused colloidal quantum dot (QD) superlattices (epi-SLs) promise to combine the size-tunable photophysics of QDs with the efficient charge transport of bulk semiconductors. However, current epi-SL fabrication methods are crude and result in structurally and chemically inhomogeneous samples with high concentrations of extended defects that localize carriers and prevent the emergence of electronic mini-bands. Needed fabrication improvements are hampered by inadequate understanding of the ligand chemistry that causes epi-SL conversion from the unfused parent SL. Here we show that epi-SL formation by the conventional method of amine injection into an ethylene glycol subphase under a floating QD film occurs by deprotonation of glycol by the amine and subsequent exchange of oleate by glycoxide on the QD surface. By replacing the amine with hydroxide ion, we demonstrate that any Brønsted-Lowry base that creates a sufficient dose of glycoxide can produce the epi-SL. We then introduce an epi-SL fabrication method that replaces point injection of a base with contactless and uniform illumination of a dissolved photobase. Quantitative mapping of multilayer (3D) films shows that our photobase-made epi-SLs are chemically and structurally uniform and have much lower concentrations of bulk defects compared to the highly inhomogeneous and defect-rich epi-SLs produced by amine point injection. The structural-chemical uniformity and structural perfection of photobase-made epi-SLs make them leading candidates for achieving emergent mini-band charge transport in a self-assembled mesoscale solid.

Semi-Dirac crystals with a weak periodic modulation of the energy gap has been considered. The formation of minibands in such crystals has been studied when the latter are placed in a quantizing magnetic field. The width of the formed magnetic minibands has been shown to depend not only on the magnetic field intensity, but also on the band gap of the initial sample in contrast to gap graphene. The effect of this feature on the magneto conductivity of studied material has been investigated. [ABSTRACT FROM AUTHOR]

The electronic properties of calcium-intercalated graphite (CaC6) as a function of pressure are revisited using density functional theory (DFT). The electronic band structures of CaC6, like many other layered superconducting materials, display cosine-shaped bands at or near the Fermi level (FL). Such bands encompass bonding/antibonding information with a strong connection to superconducting properties. Using a hexagonal cell representation for CaC6, the construction of a double supercell in the c-direction effects six-folding in the reciprocal space of the full cosine function, explicitly revealing the bonding/antibonding relationship divide at the cosine midpoint. Similarly, folding of the Fermi surface (FS) reveals physical phenomena relevant to electronic topological transitions (ETTs) with the application of pressure. The ETT is characterised by a transition of open FS loops to closed loops as a function of pressure. As the highest transition temperature is reached with pressure, the dominant continuous, open FS loops shift to a different region of the FS. For CaC6, the peak value for the superconducting transition temperature, Tc, occurs at about 7.5 GPa, near the observed pressure of the calculated ETT. At this pressure, the radius of the nearly spherical Ca 4s-orbital FS coincides with three times the distance from the Γ centre point to the Brillouin zone (BZ) boundary of the 2c supercell. In addition, the ETT coincides with the alignment of the nonbonding (inflection) point of the cosine band with the FL. At other calculated pressure conditions, the Ca 4s-orbital FS undergoes topological changes that correspond and can be correlated with experimentally determined changes in Tc. The ETT is a key mechanism that circumscribes the known significant drop in Tc for CaC6 as a function of increasing pressure. Consistent calculated responses of the ETT to pressure match experimental measurements and validate the examination of superlattices as important criteria for understanding mechanisms driving superconductivity.

Structural versatility and multifunctionality of biological materials have resulted in countless bioinspired strategies seeking to emulate the properties of nature. The nanostructured egg case of swell sharks is one of the toughest permeable membranes known and, thus, presents itself as a model system for materials where the conflicting properties, strength and porosity, are desirable. The egg case possesses an intricately ordered structure that is designed to protect delicate embryos from the external environment while enabling respiratory and metabolic exchange, achieving a tactical balance between conflicting properties. Herein, structural analyses revealed an enabling nanolattice architecture that constitutes a Bouligand-like nanoribbon hierarchical assembly. Three distinct hierarchical architectural adaptations enhance egg case survival: Bouligand-like organization for in-plane isotropic reinforcement, noncylindrical nanoribbons maximizing interfacial stress distribution, and highly ordered nanolattices enabling permeability and lattice-governed toughening mechanisms. These discoveries provide fundamental insights for the improvement of multifunctional membranes, fiber-reinforced soft composites, and mechanical metamaterials.

In one-dimensional phononic crystals, as a result of multiple destructive interferences of a mechanical wave, the phononic band gap phenomenon occurs, i.e., the lack of propagation of a wave of a given frequency through the structure due to internal reflections at the layer boundary and destructive interference. In dynamic phononic crystals, the incident monochromatic mechanical wave at the boundary of the media does not propagate according to Fresnel's relations, but is transformed into a wave spectrum, which affects the phononic properties of the examined structures and allows them to be dynamically controlled. The paper analyzes the transmission and influence of the frequency of changes in the properties of the elements of the finite phononic structure described by sinusoidal functions on the propagation of mechanical waves. [ABSTRACT FROM AUTHOR]

Moiré patterns result from setting a 2D material such as graphene on another 2D material with a small twist angle or from the lattice mismatch of 2D heterostructures. We present a continuum model for the elastic energy of these bilayer moiré structures that includes an intralayer elastic energy and an interlayer misfit energy that is minimized at two stackings (disregistries). We show by theory and computation that the displacement field that minimizes the global elastic energy subject to a global boundary constraint gives large alternating regions of one of the two energy-minimizing stackings separated by domain walls. We derive a model for the domain wall structure from the continuum bilayer energy and give a rigorous asymptotic estimate for the structure. We also give an improved estimate for the L 2 -norm of the gradient on the moiré unit cell for twisted bilayers that scales at most inversely linearly with the twist angle, a result which is consistent with the formation of one-dimensional domain walls with a fixed width around triangular domains at very small twist angles. [ABSTRACT FROM AUTHOR]

The Green's function method is recognized to be a very powerful tool for modelling quantum transport in nanoscale electronic devices. As atomistic calculations are generally expensive, numerical methods and related algorithms have been developed accordingly to optimize their computation cost. In particular, recursive techniques have been efficiently applied within the Green's function calculation approach. Recently, with the discovery of Moiré materials, several attractive superlattices have been explored using these recursive Green's function techniques. However, numerical difficulty issues were reported as most of these superlattices have relatively large supercells, and consequently a huge number of atoms to be considered. In this article, improvements to solve these issues are proposed in order to keep optimizing the recursive Green's function calculations. These improvements make the electronic structure calculations feasible and efficient in modelling large superlattice-based devices. As an illustrative example, twisted bilayer graphene superlattices are computed and presented to demonstrate the efficiency of the method. [ABSTRACT FROM AUTHOR]