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Bacterial nanocellulose (BNC) is a durable, flexible, and dynamic biomaterial capable of serving a wide variety of fields, sectors, and applications within biotechnology, healthcare, electronics, agriculture, fashion, and others. BNC is produced spontaneously in carbohydrate-rich bacterial culture media, forming a cellulosic pellicle via a nanonetwork of fibrils extruded from certain genera. Herein, we demonstrate engineering BNC-based scaffolds with tunable physical and mechanical properties through postprocessing. Human skeletal muscle myoblasts (HSMMs) were cultured on these scaffolds, and in vitro electrical stimulation was applied to promote cellular function for tissue engineering applications. We compared physiologic maturation markers of human skeletal muscle myoblast development using a 2.5-dimensional culture paradigm in fabricated BNC scaffolds, compared to two-dimensional (2D) controls. We demonstrate that the culture of human skeletal muscle myoblasts on BNC scaffolds developed under electrical stimulation produced highly aligned, physiologic morphology of human skeletal muscle myofibers compared to unstimulated BNC and standard 2D culture. Furthermore, we compared an array of metrics to assess the BNC scaffold in a rigorous head-to-head study with commercially available, clinically approved matrices, Kerecis Omega3 Wound Matrix (Marigen) and Phoenix as well as a gelatin methacryloyl (GelMA) hydrogel. The BNC scaffold outcompeted industry standard matrices as well as a 20% GelMA hydrogel in durability and sustained the support of human skeletal muscle myoblasts in vitro. This work offers a robust demonstration of BNC scaffold cytocompatibility with human skeletal muscle cells and sets the basis for future work in healthcare, bioengineering, and medical implant technological development.

Interface strain significantly affects polarization in ferroelectric devices. In this paper, an innovative strategy is proposed to substantially enhance ferroelectric polarization using an ultra‐thin “soft‐buffer‐layer” (SBL), which reduces dislocation density and increases the tetragonality of ferroelectric thin films because of small elastic constants of Ti3Al along x and y axes. And in this work, it is demonstrated that PbZr0.4Ti0.6O3 (PZT) thin films are perfect c‐axis‐oriented epitaxial structures on (001) SrTiO3 (STO) substrates. The PZT capacitor with Ti3Al buffer layer exhibits a remarkable remnant polarization, reaching up to 131.93 µC cm−2 at an applied voltage of 5.00 V. Surprisingly, under the clamping effect of SrRuO3 and STO, Ti3Al films exhibit cubic structure and facilitate matching to the PZT film. It is proposed that the introduction of the Ti3Al buffer layer notably improves the tetragonality (c/a) ratio from 1.002 to 1.024, and significantly enhancing the polarization. There is no doubt that this adjustment reduces dislocation density and decreases stress influence from STO substrate. Given these advantages, the SBL method presents a compelling option for epitaxial PZT films, and also for enhancing the physical properties of other functional thin film materials. [ABSTRACT FROM AUTHOR]

Abstract Gallium oxide (Ga2O3) is an emerging ultra‐wide bandgap (UWBG) semiconductor material that has gained significant attention in the field of high voltage and high frequency power electronics. Its noteworthy attributes include a large bandgap (Eg) of 4.8 eV, high theoretical critical breakdown field strength (EC) of 8 MV cm−1, and saturation velocity (νs) of 2 × 107 cm s−1, as well as high Baliga figures of merit (BFOM) of 3000. In addition, Ga2O3 has the advantages of large‐size substrates that can be achieved by low‐cost melt‐grown techniques. This review provides a partial overview of pivotal milestones and recent advancements in the Ga2O3 material growth and device performance. It begins with a discussion of the fundamental material properties of Ga2O3, followed by a description of substrate growth and epitaxial techniques for Ga2O3. Subsequently, the contact technologies between Ga2O3 and other materials are fully elucidated. Moreover, this article also culminates with a detailed analysis of Ga2O3‐based high voltage and high frequency power devices. Some challenges and solutions, such as the lack of p‐type doping, low thermal conductivity, and low mobility are also presented and investigated in this review.

The simplicity and abundance of water sources make water-based synthesis extremely intriguing. Nb-doped ZnO nanorods was successfully grown using a straightforward and cost-effective aqueous chemical technique. The precursor of Nb-doped ZnO comprised zinc nitrate hexahydrate, hexamethylenetetramine (HMTA), and deionized water. These substances were used as starting materials, stabilisers, and solvents, respectively. Niobium chloride served as a source of niobium dopant. The intrinsic seeded substrate was submerged in a Nb-doped ZnO precursor solution in order to facilitate the epitaxial growth of nanorods. In order to investigate the influence of the dopant percentage, the amount of Nb-dopant was varied from 0 to 0.7 at. %. The presence of Nb-doped ZnO nanorods was confirmed by the utilisation of FESEM and EDAX techniques, which allowed for the verification of both the growth of nanorods and the identification of their constituent elements. The diameter obtained is between 79.76 and 134.51 nm, depending on the amount of dopant. Since the average nanorod length is 1.1086 ± 24.9187 μm, the aspect ratio estimation is about 13.9. The atomic arrangement was investigated using high-resolution transmission electron microscopy (HRTEM). The interplanar distance of 0.264 nm corresponds to plan (002) estimated via HRTEM. The estimation is in agreement with the XRD analysis. In addition, the peak of (002) is dominant for every sample. The sharpest and highest peak can be found in 0.3 at. % of dopant. As the texture coefficient (TC) has a higher value for plan (002), crystalline growth is preferred in c-orientation. [ABSTRACT FROM AUTHOR]

Terahertz technology has the potential to have a large impact in myriad fields, such as biomedical science, spectroscopy, and communications. Making these applications practical requires efficient, reliable, and low‐cost devices. Photoconductive switches (PCS), devices capable of emitting and detecting terahertz pulses, are a technology that needs more efficiency when working at telecom wavelength excitation (1550 nm) to exploit the advantages this wavelength offers. ErAs:InGaAs is a semiconductor nanocomposite working at this energy; however, high dark resistivity is challenging due to a high electron concentration as the Fermi level lies in the conduction band. To increase dark resistivity, ErAs:InGaAlBiAs material is used as the active material in a PCS detecting Terahertz pulses. ErAs nanoparticles reduce the carrier lifetime to subpicosecond values required for short temporal resolution, while ErAs pins the effective Fermi level in the host material bandgap. Unlike InGaAs, InGaAlBiAs offers enough freedom for band engineering to have a material compatible with a 1550 nm pump and a Fermi level deep in the bandgap, meaning low carrier concentration and high dark resistivity. Band engineering is possible by incorporating aluminum to lift the conduction band edge to the Fermi level and bismuth to keep a bandgap compatible with 1550 nm excitation. [ABSTRACT FROM AUTHOR]

Perovskite‐oxide‐based capacitors, which exhibit high charge storage capacity, have attracted considerable attention as a potential candidate for overcoming the limitations of nanoscale integration. Unfortunately, a dead layer forms in these capacitors at the interface between the electrode and the dielectric, which degrades the charge storage capacity; thus, this layer has been extensively investigated. The dead layer in perovskite‐oxide‐based capacitors exhibits different characteristics depending on the electrode materials; however, a method for minimizing this layer is lacking. In this study, the charge storage capacity of a perovskite‐oxide‐based capacitor is evaluated considering the effect of the Ru and SrRuO3 top electrodes on the SrRuO3/Ba0.5Sr0.5TiO3 stack. Dead layers at the interface between each top electrode material and the dielectric are studied on the atomic scale. The results indicate that the Ru metal electrode causes oxygen to diffuse from the dielectric to the electrode, forming elongated perovskite oxide at the interface, which acts as a dead layer. However, minimizing the dead layer at the top interface increases the dielectric permittivity from 667 to 953. Consequently, the phenomenon and mechanism of the dead layer are intuitively identified. This study proposes a method to overcome the limitations of next‐generation dynamic random access memory (DRAM). [ABSTRACT FROM AUTHOR]

To address surface morphological defects that have a destructive effect on the epitaxial wafer from the aspect of 4H-SiC epitaxial growth, this study thoroughly examined many key factors that affect the density of defects in 4H-SiC epitaxial wafer, including the ratio of carbon to silicon, growth time, application of a buffer layer, hydrogen etching and other process parameters. Through systematic experimental verification and data analysis, it was verified that when the carbon–silicon ratio was accurately controlled at 0.72, the density of defects in the epitaxial wafer was the lowest, and its surface flatness showed the best state. In addition, it was found that the growth of the buffer layer under specific conditions could effectively reduce defects, especially surface morphology defects. This provides a new idea and method for improving the surface quality of epitaxial wafers. At the same time, we also studied the influence of hydrogen etching on the quality of epitaxial wafers. The experimental results show that proper hydrogen etching can optimize surface quality, but excessive etching may lead to the exposure of substrate defects. Therefore, it is necessary to carefully control the conditions of hydrogen etching in practical applications to avoid adverse effects. These findings have important guiding significance for optimizing the quality of epitaxial wafers. [ABSTRACT FROM AUTHOR]

The impacts of retrograde counter doping (RCD) profiles on low frequency noise (LFN) of buried channel (BC) PMOSFETs were investigated. RCD profiles were formed using heavy ion implantation. The RCD profile reduced LFN by more than 50%. The origin of LFN reduction in the RCD device was investigated using TCAD simulation. It was found that both RCD profile itself and the polarity of Si surface contributed to the deeper channel position and larger energy barrier between Si surface and channel position.

Abstract Perovskite‐oxide‐based capacitors, which exhibit high charge storage capacity, have attracted considerable attention as a potential candidate for overcoming the limitations of nanoscale integration. Unfortunately, a dead layer forms in these capacitors at the interface between the electrode and the dielectric, which degrades the charge storage capacity; thus, this layer has been extensively investigated. The dead layer in perovskite‐oxide‐based capacitors exhibits different characteristics depending on the electrode materials; however, a method for minimizing this layer is lacking. In this study, the charge storage capacity of a perovskite‐oxide‐based capacitor is evaluated considering the effect of the Ru and SrRuO3 top electrodes on the SrRuO3/Ba0.5Sr0.5TiO3 stack. Dead layers at the interface between each top electrode material and the dielectric are studied on the atomic scale. The results indicate that the Ru metal electrode causes oxygen to diffuse from the dielectric to the electrode, forming elongated perovskite oxide at the interface, which acts as a dead layer. However, minimizing the dead layer at the top interface increases the dielectric permittivity from 667 to 953. Consequently, the phenomenon and mechanism of the dead layer are intuitively identified. This study proposes a method to overcome the limitations of next‐generation dynamic random access memory (DRAM).

To address surface morphological defects that have a destructive effect on the epitaxial wafer from the aspect of 4H-SiC epitaxial growth, this study thoroughly examined many key factors that affect the density of defects in 4H-SiC epitaxial wafer, including the ratio of carbon to silicon, growth time, application of a buffer layer, hydrogen etching and other process parameters. Through systematic experimental verification and data analysis, it was verified that when the carbon–silicon ratio was accurately controlled at 0.72, the density of defects in the epitaxial wafer was the lowest, and its surface flatness showed the best state. In addition, it was found that the growth of the buffer layer under specific conditions could effectively reduce defects, especially surface morphology defects. This provides a new idea and method for improving the surface quality of epitaxial wafers. At the same time, we also studied the influence of hydrogen etching on the quality of epitaxial wafers. The experimental results show that proper hydrogen etching can optimize surface quality, but excessive etching may lead to the exposure of substrate defects. Therefore, it is necessary to carefully control the conditions of hydrogen etching in practical applications to avoid adverse effects. These findings have important guiding significance for optimizing the quality of epitaxial wafers.

This study investigates energy harvesting by a deionized (DI) water droplet flow on an epitaxial graphene film on a SiC substrate. We obtain an epitaxial single-crystal graphene film by annealing a 4H-SiC substrate. Energy harvesting of the solution droplet flow on the graphene surface has been investigated by using NaCl or HCl solutions. This study validates the voltage generated from the DI water flow on the epitaxial graphene film. The maximum generated voltage was as high as 100 mV, which was a quite large value compared with the previous reports. Furthermore, we measure the dependence of flow direction on electrode configuration. The generated voltages are independent of the electrode configuration, indicating that the DI water flow direction is not influenced by the voltage generation for the single-crystal epitaxial graphene film. Based on these results, the origin of the voltage generation on the epitaxial graphene film is not only an outcome of the fluctuation of the electrical-double layer, resulting in the breaking of the uniform balance of the surface charges, but also other factors such as the charges in the DI water or frictional electrification. In addition, the buffer layer has no effect on the epitaxial graphene film on the SiC substrate. [ABSTRACT FROM AUTHOR]

The discovery of topological Hall effect (THE) has important implications for next‐generation high‐density nonvolatile memories, energy‐efficient nanoelectronics, and spintronic devices. Both real‐space topological spin configurations and two anomalous Hall effects (AHE) with opposite polarity due to two magnetic phases have been proposed for THE‐like feature in SrRuO3 (SRO) films. In this work, SRO thin films with and without THE‐like features are systematically Investigated to decipher the origin of the THE feature. Magnetic measurement reveals the coexistence of two magnetic phases of different coercivity (Hc) in both the films, but the hump feature cannot be explained by the two channel AHE model based on these two magnetic phases. In fact, the AHE is mainly governed by the magnetic phase with higher Hc. A diffusive Berry phase transition model is proposed to explain the THE feature. The coexistence of two Berry phases with opposite signs over a narrow temperature range in the high Hc magnetic phase can explain the THE like feature. Such a coexistence of two Berry phases is due to the strong local structural tilt and microstructure variation in the thinner films. This work provides an insight between structure/micro structure and THE like features in SRO epitaxial thin films. [ABSTRACT FROM AUTHOR]

Abstract The discovery of topological Hall effect (THE) has important implications for next‐generation high‐density nonvolatile memories, energy‐efficient nanoelectronics, and spintronic devices. Both real‐space topological spin configurations and two anomalous Hall effects (AHE) with opposite polarity due to two magnetic phases have been proposed for THE‐like feature in SrRuO3 (SRO) films. In this work, SRO thin films with and without THE‐like features are systematically Investigated to decipher the origin of the THE feature. Magnetic measurement reveals the coexistence of two magnetic phases of different coercivity (Hc) in both the films, but the hump feature cannot be explained by the two channel AHE model based on these two magnetic phases. In fact, the AHE is mainly governed by the magnetic phase with higher Hc. A diffusive Berry phase transition model is proposed to explain the THE feature. The coexistence of two Berry phases with opposite signs over a narrow temperature range in the high Hc magnetic phase can explain the THE like feature. Such a coexistence of two Berry phases is due to the strong local structural tilt and microstructure variation in the thinner films. This work provides an insight between structure/micro structure and THE like features in SRO epitaxial thin films.

β‐(AlxGa1−x)2O3 films have several critical properties of interest to the research community, including a wide bandgap that may be used in the development of new electronic, optoelectronic, and photonic devices. Here we demonstrate the first time fabricated metal‐alkoxide‐based spin‐coated single‐phase epitaxial β‐(AlxGa1−x)2O3 films on c‐sapphire substrates with (2¯01)$(\bar{2}\,0\,1)$ orientation and good crystallinity that is comparable to the films fabricated using other film deposition techniques, such as molecular beam epitaxy and chemical vapor deposition. Using this technique, we generated films with broad Al compositions (x) of 0.3, 0.5, and 0.7 with bandgap energies of 5.15, 5.56, and 6.16 eV, respectively, estimated from the X‐ray photoelectron spectroscopy inelastic energy‐loss spectra. Photoluminescence emission spectra in the ultraviolet and visible (blue) wavelength range highlighted several intrinsic defects in the film structure that functioned as luminescence centers, including self‐trapped exciton and recombining donor‐to‐acceptor band. Detailed analysis of the structural and optical properties of β‐(AlxGa1−x)2O3 epitaxial films revealed that this low‐cost and scalable solution‐deposition approach coupled with a spin‐coating technique could be used to fabricate β‐(AlxGa1−x)2O3 films with tunable properties. [ABSTRACT FROM AUTHOR]

Atomically thin transition metal dichalcogenides (TMDs), like MoS2 with high carrier mobilities and tunable electron dispersions, are unique active material candidates for next generation opto-electronic devices. Previous studies on ion irradiation show great potential applications when applied to two-dimensional (2D) materials, yet have been limited to micron size exfoliated flakes or smaller. To demonstrate the scalability of this method for industrial applications, we report the application of relatively low power (50 keV) 4He+ ion irradiation towards tuning the optoelectronic properties of an epitaxially grown continuous film of MoS2 at the wafer scale, and demonstrate that precise manipulation of atomistic defects can be achieved in TMD films using ion implanters. The effect of 4He+ ion fluence on the PL and Raman signatures of the irradiated film provides new insights into the type and concentration of defects formed in the MoS2 lattice, which are quantified through ion beam analysis. PL and Raman spectroscopy indicate that point defects are generated without causing disruption to the underlying lattice structure of the 2D films and hence, this technique can prove to be an effective way to achieve defect-mediated control over the opto-electronic properties of MoS2 and other 2D materials. [ABSTRACT FROM AUTHOR]

Tantalum disulfide (1T-TaS 2 ), being a Mott insulator with strong electron correlation, is highlighted for diverse collective quantum states in the 2D lattice, including charge density wave (CDW), spin liquid, and unconventional superconductivity. The Mott physics embedded in the 2D triangular CDW lattice has raised debates on stacking-dependent properties because interlayer interactions are sensitive to van der Waals (vdW) spacing. However, control of interlayer distance remains a challenge. Here, spiral lattices in the epitaxial TaS 2 spirals are studied to probe collective properties with tunable interlayer interactions. A scalable synthesis of epitaxial TaS 2 spirals is presented. A more than 50%-increased interlayer spacing enables prototype decoupled monolayers for enhanced electronic correlation exhibiting Mott physics at room-temperature and a simplified system to explore collective properties in vdW materials., (© 2024 Wiley‐VCH GmbH.)

The synthesis of graphene by the graphitization of SiC surface has been driven by a need to develop a way to produce graphene in large quantities. With the increased use of thermal treatments of commercial SiC substrates, a comprehension of the surface restructuring due to the formation of a terrace-stepped nanorelief is becoming a pressing challenge. The aim of this paper is to evaluate the utility of X-ray reflectometry and grazing-incidence off-specular scattering for a non-destructive estimate of depth-graded and lateral inhomogeneities on SiC wafers annealed in a vacuum at a temperature of 1400–1500 °C. It is shown that the grazing-incidence X-ray method is a powerful tool for the assessment of statistical parameters, such as effective roughness height, average terrace period and dispersion. Moreover, these methods are advantageous to local probe techniques because a broad range of spatial frequencies allows for faster inspection of the whole surface area. We have found that power spectral density functions and in-depth density profiles manifest themselves differently between the probing directions along and across a terrace edge. Finally, the X-ray scattering data demonstrate quantitative agreement with the results of atomic force microscopy. [ABSTRACT FROM AUTHOR]

GaN and its alloys with InN and AlN are of technological importance for a variety of optical, electronic, and optoelectronic devices due to its high thermal conductivity, wide band gap, high breakdown voltage and high saturation velocity. GaN-based devices now provide superior performance for a variety of high power, high frequency, high temperature, and optical applications. The major roadblock for the full realization of Nitride semiconductor potential is still the availability of affordable large-area and high-quality native substrates with controlled electrical properties. Despite the impressive accomplishments recently achieved by techniques such as hydride vapor phase epitaxy and ammonothermal for GaN growth, much more must be attained before establishing a fully satisfactory bulk growth method for this material. Recent results suggest that ammonothermal GaN wafers can be successfully used as seeds to grow thick freestanding GaN wafers by hydride vapor phase epitaxy. A brief review of defect-sensitive optical and paramagnetic spectroscopy techniques employed to evaluate structural, optical, and electronic properties of the state-of-the-art bulk and thick-film (quasi-bulk) Nitride substrates and homoepitaxial films is presented. Defects control the performance of devices and feeding back knowledge of defects to growth efforts is key to advancing technology. [ABSTRACT FROM AUTHOR]

Abstract Nb-doped SrSnO3 (SSNO) thin films were epitaxially grown on LaAlO3(001) single-crystal substrates using pulsed laser deposition under various oxygen pressures and substrate temperatures. The crystalline structure, electrical, and optical properties of the films were investigated in detail. X-ray diffraction results show that the cell volume of the films reduces gradually with increasing oxygen pressure while preserving the epitaxial characteristic. X-ray photoelectron spectroscopy analysis confirms the Nb5+ oxidation state in the SSNO films. Hall-effect measurements were performed and the film prepared at 0.2 Pa with the 780 °C substrate temperature exhibits the lowest room-temperature resistivity of 31.3 mΩcm and Hall mobility of 3.31 cm2/Vs with a carrier concentration at 6.03 × 1019/cm3. Temperature-dependent resistivity of this sample displays metal-semiconductor transition and is explained mainly by electron-electron effects. Optical transparency of the films is more than 70% in the wavelength range from 600 to 1800 nm. The band gaps increase from 4.35 to 4.90 eV for the indirect gap and 4.82 to 5.29 eV for the direct by lowering oxygen pressure from 20 to 1 × 10−3 Pa, which can be interpreted by Burstein-Moss effect and oxygen vacancies generated in the high vacuum.

The integration of metal oxides and GaAs semiconductors is quite attractive for its potential applications, but interfacial diffusion and lattice mismatch usually cause huge challenges toward achieving high-performance electronic devices. In this article, we reported a thin layer of epitaxial TiO2 (110) on a GaAs (001) substrate with significant compressive strain, lattice distortion, and oxygen vacancies, where the oxygen vacancies proved to be the critical factor to induce the compressive strain and lattice distortion. In this case, the lattice mismatches between this compressed TiO2 (110) and GaAs (001) surface were calculated to be as small as 1.3 and 0.24% along the [110] and [001] orientations of TiO2, respectively. Further, no Ga-oxides or As-oxides were found at the interface, indicating that the TiO2 layer inhibited the diffusion of Ga and As atoms effectively. In summary, TiO2 film can be grown epitaxially on GaAs (001) substrates with non-negligible compressive strain, lattice distortion, oxygen vacancies, and a high-quality interface. This study also provides an approach to integrate different functional oxides on TiO2-buffered GaAs for various GaAs-based electronic devices with higher reliability and performance.

We report on the spin Hall effect in epitaxial Pt films with well-defined crystalline (200), (220), and (111) orientations and smooth surfaces. The magnitude of the spin Hall effect has been determined by spin–torque ferromagnetic resonance measurements on epitaxial Pt/Py heterostructures. We observed a 54% enhancement of the charge-to-spin conversion efficiency of the epitaxial Pt when currents are applied along the in-plane direction. Temperature-dependent harmonic measurements on epitaxial Pt/Co/Ni heterostructures compared to a polycrystalline Pt/Co/Ni suggest the extrinsic mechanism underlying spin Hall effect in epitaxial Pt. Our work contributes to the development of energy-efficient spintronic devices by engineering the crystalline anisotropy of non-magnetic metals.

[Display omitted] • Highly epitaxial indium and aluminum doped Ga 2 O 3 thin-films are deposited by using the novel CSD technique. • The 2θ, rocking curve, and φ-scan modes of XRD measurements, together with the HR-TEM all suggest the obtained thin films have pure beta-phase with good in-plane and out-of-plane crystallization qualities. • The results indicate the indium and aluminum doping can making the crystallization of the thin films shifted to lower temperature and higher temperature, respectively. • Additionally, the ultraviolet–visible (UV–vis) spectroscopy measurements indicate by using the mixed precursor solution of In: Ga = 3:7 and Al: Ga = 3: 7, the bandgap of the sintered thin films can be tuned in a range from 4.05 to 5.03 eV. • Correspondingly, the photodetectors based on the (InGa) 2 O 3 sample, pure Ga 2 O 3 sample, and (AlGa) 2 O 3 sample show the maximum photocurrent at 280, 255, and 230 nm, respectively. Compared to the vacuum-required deposition techniques, the chemical solution deposition (CSD) technique is superior in terms of low cost and ease of cation adjustment and upscaling. In this work, highly epitaxial indium- and aluminum-doped Ga 2 O 3 thin films are deposited using a novel CSD technique. The 2θ, rocking curve, and φ-scan modes of x-ray diffraction (XRD) measurements and high-resolution transmission electron microscopy suggest that these thin films have a pure beta phase with good in- and out-of-plane crystallization qualities. The effect of incorporating indium and aluminum into the crystallization process is studied using high-temperature in situ XRD measurements. The results indicate that indium and aluminum doping can shift the crystallization of the thin films to lower and higher temperatures, respectively. Additionally, ultraviolet-visible spectroscopy measurements indicate that the bandgap of the sintered thin films can be tuned from 4.05 to 5.03 eV using a mixed precursor solution of In:Ga = 3:7 and Al:Ga = 3:7. The photodetectors based on the (InGa) 2 O 3 , pure Ga 2 O 3 , and (AlGa) 2 O 3 samples exhibit the maximum photocurrents at 280, 255, and 230 nm, respectively. The results suggest that the described CSD technique is promising for producing high-quality bandgap tunable deep-ultraviolet photoelectrical and high-power devices. [ABSTRACT FROM AUTHOR]

Well-tailored nanomaterials with a single-crystal character provide ideal building blocks for on-chip plasmonic devices. Although colloidal methods have demonstrated mastery over the synthesis of such structures, it has proven quite difficult to deploy these same nanomaterials on substrate surfaces in a highly deterministic manner where precise control over position and orientation is ensured. Herein, we demonstrate a room-temperature two-reagent liquid-phase seed-mediated synthesis of gold nanoplates directly on substrate surfaces in arrays over a square-centimeter area. The synthesis is reliant on benchtop lithographic and directed-assembly processes that give rise to single-crystal seeds of gold that express both an epitaxial relationship with the underlying substrate and the internal defect structure required to promote a two-dimensional growth mode. The resulting structures are highly faceted and, because seed-substrate epitaxy is imposed upon the growing nanoplates, are identically aligned on the substrate surface. Nanoplate yields are increased to values as high as 95% using a post-processing sonication procedure that selectively removes a small population of irregularly shaped nanostructures from the substrate surface, and in doing so, gives rise to an uncompromised plasmonic response. The work, therefore, advances the techniques needed to integrate single-crystal nanomaterials with wafer-based technologies and provides leading-edge capabilities in terms of defining large-area arrays of plasmonic structures with the nanoplate geometry. [ABSTRACT FROM AUTHOR]

GaN and its alloys with InN and AlN are of technological importance for a variety of optical, electronic, and optoelectronic devices due to its high thermal conductivity, wide band gap, high breakdown voltage and high saturation velocity. GaN-based devices now provide superior performance for a variety of high power, high frequency, high temperature, and optical applications. The major roadblock for the full realization of Nitride semiconductor potential is still the availability of affordable large-area and high-quality native substrates with controlled electrical properties. Despite the impressive accomplishments recently achieved by techniques such as hydride vapor phase epitaxy and ammonothermal for GaN growth, much more must be attained before establishing a fully satisfactory bulk growth method for this material. Recent results suggest that ammonothermal GaN wafers can be successfully used as seeds to grow thick freestanding GaN wafers by hydride vapor phase epitaxy. A brief review of defect-sensitive optical and paramagnetic spectroscopy techniques employed to evaluate structural, optical, and electronic properties of the state-of-the-art bulk and thick-film (quasi-bulk) Nitride substrates and homoepitaxial films is presented. Defects control the performance of devices and feeding back knowledge of defects to growth efforts is key to advancing technology.

Graphene grown with less grain boundaries, larger grain sizes and transfer‐free feature by chemical vapor deposition (CVD) is of significant importance to fulfill practical applications. Sapphire has readily emerged as an ideal substrate for graphene growth owing to its relatively low cost, good mechanical strength and physical/chemical stability under CVD conditions. In this minireview, recent advance in the CVD preparation of graphene over sapphire substrates is summarized. The graphene growth on epitaxial metal (111) film derived from c‐plane sapphire and direct fabrication over sapphire are respectively discussed. Application sectors of graphene/sapphire hybrid materials are further reviewed. Finally, perspectives on the synthesis of graphene over sapphire are given. [ABSTRACT FROM AUTHOR]

The micro- and nanostructures of III-nitride semiconductors captivate strong interest owing to their distinctive properties and myriad potential applications. Nevertheless, challenges endure in managing the damage inflicted on crystals through top-down processes or achieving extensive control over the large-area growth of these microstructures via bottom-up methods, thereby impacting their optical and electronic properties. Here, we present novel epitaxially grown 3D GaN truncated pyramid arrays (TPAs) on patterned Si substrates, devoid of any catalyst. These GaN TPAs feature highly ordered, large-scale structures, attributed to the utilization of 3D Si substrates and thin AlN interlayers to alleviate epitaxial strains and limit dislocation formation. Comprehensive characterization via scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and cathodoluminescence attests to the superior structural and optical attributes of these crystals. Furthermore, photoluminescence and ultraviolet (UV)-visible diffuse reflectance spectroscopy reveal sharp band-edge emission and significant light trapping in the UV bands. Employing these GaN TPAs, we constructed metal-semiconductor-metal visible-blind UV photodetectors (PDs) incorporating Ti 3 C 2 MXene as Schottky electrodes. These PDs display exceptional responsivity, achieving 5.32 × 10 3 mA/W at 255 nm and an ultrahigh UV/visible rejection ratio ( R 255nm / R 450nm ) approaching 10 6 , which are 1-2 orders of magnitude higher than most recently reported works. This exploration showcases novel GaN-based microstructures characterized by uniformity, ordered geometry, and exemplary crystalline integrity, paving the way for developing optoelectronic applications.

X-ray photoelectron spectroscopy (XPS) is used to analyze the chemistry of the Ru(0001) film surface and the Ru/SiO2 interfacial region at different annealing conditions. The XPS spectra are collected under ultrahigh vacuum (base pressure of ∼5 × 10−10 Torr) condition using a SPECS electron spectrometer with a PHOIBOS 100 hemispherical energy analyzer and an XR 50 Al Kα x-ray source (1486.67 eV). High-resolution spectra of O 1s, Ru 3d/C 1s, and Si 2p together with survey scans are presented. The presence of 1 × 1 low energy diffraction pattern, collected from a 950 °C Ar/H2 step-annealed Ru(0001) sample, confirms the hexagonal periodicity of Ru(0001) surfaces. [ABSTRACT FROM AUTHOR]

Herein, we have reported domain engineering of epitaxial (001) Bi 2 Te 3 thin films by miscut (100) substrates. On a nominal flat (100) GaAs substrate, two-variant domains that were in-plane rotated by 60°, including the 60° domain boundaries, were formed in the epitaxial Bi 2 Te 3 film, such that the symmetry elements of two-fold rotational and/or mirror symmetries of the GaAs substrate were preserved. The domain variants were successfully reduced to obtain mono-domain Bi 2 Te 3 thin films without any domain boundaries using the 2°-miscut GaAs substrates, where a particular step-and-terrace structure on the vicinal surface macroscopically broke the intrinsic symmetry of GaAs, lowering the number of possible domains. Depending on the miscut directions, the in-plane orientations of the mono-domain Bi 2 Te 3 films were varied with respect to the GaAs substrate. A model was proposed to explain the effect of miscut substrate on the domain structure of Bi 2 Te 3 thin films. Low-temperature Hall measurements revealed that in the intrinsic regime (10 K) the electron concentration of the mono-domain Bi 2 Te 3 films (~2 × 1018 cm−3) was significantly lower than that of the two-domain films (~1019 cm−3). This was attributed to the donor-like effect of the 60° domain boundaries. These results provide an opportunity not only to integrate the single-crystalline, mono-domain, layered-chalcogenides on semiconductor single crystals, but also to manipulate their electronic transport properties by domain engineering. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Inverse spinel Zn2SnO4 (ZTO) films have been grown on MgO(001) and MgAl2O4(001) substrates by pulsed laser deposition. Detailed structural investigation by high-resolution X-ray diffraction, including conventional θ–2θ linear scans, φ scans and reciprocal space mappings, revealed the epitaxial characteristics of the ZTO films. Meanwhile, the in-plane and out-of-plane lattice parameters were extracted to be about a = b=8.615 Å and c = 8.629 Å from the symmetry and asymmetry reflections. The surface morphologies of ZTO films were examined by atomic force microscopy, and all the films exhibit very smooth surfaces. X-ray photoelectron spectroscopy measurement was taken to disclose the oxidation states of elements. The optical properties of ZTO films were probed by measuring the optical transmittances. The band gaps of ZTO films grown on MgO(001) and MgAl2O4(001) were extracted to be 4.26 eV and 4.30 eV by extrapolating the absorption edge, respectively. Theoretically, the band structure was also calculated using density functional theory. The results show that ZTO film is a direct band gap semiconductor with the band gap value of 2.64 eV. Such a wide band gap semiconductor with an inverse spinel structure should be of high interest for epitaxial heterojunction and optical device application. [ABSTRACT FROM AUTHOR]

There is a growing interest in the exploration of the nitride material family for radically scaled, high frequency, ultrasonic devices by epitaxial growth techniques. Furthermore, the introduction of epitaxial growth techniques to conventional nitride‐based acoustic technology opens the door to exciting new families of structures for phonon confinement. As the need for higher frequency communications increases, both piezoelectrics and electrodes must scale to smaller dimensions. It has recently become possible to epitaxially grow single‐crystalline, wurtzite AlN/NbN piezoelectric/metal heterostructures. The epitaxial NbN films maintain high crystalline quality and electrical conductivity down to several nanometers thickness. This study demonstrates preliminary results on the feasibility of an all‐epitaxial bulk acoustic wave technology by growing and characterizing the radio frequency (RF) properties of an epitaxial AlN/NbN heterostructure. [ABSTRACT FROM AUTHOR]

Graphene was reported as the first-discovered two-dimensional material, and the thermal decomposition of SiC is a feasible route to prepare graphene films. However, it is difficult to obtain a uniform single-layer graphene avoiding the coexistence of multilayer graphene islands or bare substrate holes, which give rise to the degradation of device performance and becomes an obstacle for the further applications. Here, with the assistance of nitrogen plasma, we successfully obtained high-quality single-layer and bilayer graphene with large-scale and uniform surface via annealing 4H-SiC(0001) wafers. The highly flat surface and ordered terraces of the samples were characterized using in situ scanning tunneling microscopy. The Dirac bands in single-layer and bilayer graphene were measured using angle-resolved photoemission spectroscopy. X-ray photoelectron spectroscopy combined with Raman spectroscopy were used to determine the composition of the samples and to ensure no intercalation or chemical reaction of nitrogen with graphene. Our work has provided an efficient way to obtain the uniform single-layer and bilayer graphene films grown on a semiconductive substrate, which would be an ideal platform for fabricating two-dimensional devices based on graphene.

In this study, we fabricated three-dimensional (3D) hierarchical plasmo-photonic nanoarchitectures by epitaxially integrating semiconducting zinc oxide (ZnO) nanowires with vertically oriented plasmonic gold (Au) and silver (Ag) nanoplatforms and investigated their growth mechanisms in detail. We synthesized 3D hierarchical Au–ZnO nanostructures via a vapor–solid mechanism leading to the epitaxial growth of ZnO nanowires on vertically oriented single-crystalline Au nanowires on a strontium titanate (SrTiO3) substrate. The elongated half-octahedral Au nanowires with a rhombus cross-section were transformed into thermodynamically stable elongated cuboctahedral Au nanowires with a hexagonal cross-section during the reaction. After the transformation, ZnO thin films with six twinned domains were formed on the side planes of the elongated cuboctahedral Au nanowire trunks, and six ZnO nanowire branches were grown on the ZnO thin films. Further, 3D hierarchical Ag–ZnO nanostructures were obtained via the same vapor–solid mechanism leading to the epitaxial growth of ZnO nanowires on vertically oriented Ag nanoplates on an aluminum oxide (Al2O3) substrate. Therefore, the growth mechanism developed herein can be generally employed to fabricate 3D hierarchical plasmo-photonic nanoarchitectures.

Abstract Room‐temperature magnetoelectric (ME) coupling is developed in artificial multilayers and nanocomposites composed of magnetostrictive and electrostrictive materials. While the coupling mechanisms and strengths in multilayers are widely studied, they are largely unexplored in vertically aligned nanocomposites (VANs), even though theory has predicted that VANs exhibit much larger ME coupling coefficients than multilayer structures. Here, strong transverse and longitudinal ME coupling in epitaxial BaTiO3:CoFe2O4 VANs measured by both optical second harmonic generation and piezoresponse force microscopy under magnetic fields is reported. Phase field simulations have shown that the ME coupling strength strongly depends on the vertical interfacial area which is ultimately controlled by pillar size. The ME coupling in VANs is determined by the competition between the vertical interface coupling effect and the bulk volume conservation effect. The revealed mechanisms shed light on the physical insights of vertical interface coupling in VANs in general, which can be applied to a variety of nanocomposites with different functionalities beyond the studied ME coupling effect.

The scale-free ferroelectricity with superior Si compatibility of HfO 2 has reawakened the feasibility of scaled-down nonvolatile devices and beyond the complementary metal-oxide-semiconductor (CMOS) architecture based on ferroelectric materials. However, despite the rapid development, fundamental understanding, and control of the metastable ferroelectric phase in terms of oxygen ion movement of HfO 2 remain ambiguous. In this study, we have deterministically controlled the orientation of a single-crystalline ferroelectric phase HfO 2 thin film via oxygen ion movement. We induced a topotactic phase transition of the metal electrode accompanied by the stabilization of the differently oriented ferroelectric phase HfO 2 through the migration of oxygen ions between the oxygen-reactive metal electrode and the HfO 2 layer. By stabilizing different polarization directions of HfO 2 through oxygen ion migration, we can gain a profound understanding of the oxygen ion-relevant unclear phenomena of ferroelectric HfO 2 .

Vapor-pressure mismatched materials such as transition metal chalcogenides have emerged as electronic, photonic, and quantum materials with scientific and technological importance. However, epitaxial growth of vapor-pressure mismatched materials are challenging due to differences in the reactivity, sticking coefficient, and surface adatom mobility of the mismatched species constituting the material, especially sulfur containing compounds. Here, a novel approach is reported to grow chalcogenides-hybrid pulsed laser deposition-wherein an organosulfur precursor is used as a sulfur source in conjunction with pulsed laser deposition to regulate the stoichiometry of the deposited films. Epitaxial or textured thin films of sulfides with variety of structure and chemistry such as alkaline metal chalcogenides, main group chalcogenides, transition metal chalcogenides, and chalcogenide perovskites are demonstrated, and structural characterization reveal improvement in thin film crystallinity, and surface and interface roughness compared to the state-of-the-art. The growth method can be broadened to other vapor-pressure mismatched chalcogenides such as selenides and tellurides. This work opens up opportunities for broader epitaxial growth of chalcogenides, especially sulfide-based thin film technological applications., (© 2024 The Authors. Advanced Materials published by Wiley‐VCH GmbH.)

Preventing ferroelectric materials from losing their ferroelectricity over a low thickness of several nanometers is crucial in developing multifunctional nanoelectronics. Epitaxially grown 5 at. % yttrium-doped Hf 0.5 Zr 0.5 O 2 (YHZO) thin films exhibit an atomically smooth surface, an ability to maintain ferroelectricity even at a thickness of 10 nm, and excellent insulating properties, making them suitable for use as gate oxides in ferroelectric thin film transistors (FeTFTs). Through the epitaxial growth of a YHZO/La 0.67 Sr 0.33 MnO 3 (LSMO)/SrTiO 3 (STO) heterostructure, YHZO effectively retains its ferroelectricity and orthorhombic single phase, leading to enhancing electron mobility (∼19.74 cm 2 V -1 s -1 ) and memory window (3.7 V) in the amorphous InGaZnO 4 (a-IGZO)/YHZO/LSMO/STO FeTFTs. These FeTFTs demonstrate a consistent memory function with remarkable endurance (∼10 6 cycles) and retention (∼10 4 s). Furthermore, they sustain a constant memory window even under ±6 V bias stress for 10 4 s and exhibit excellent stability even under ±6 V/1 ms pulse cycling for 10 7 cycles. For comparison, a transistor with the same structure was fabricated using epitaxial nonferroelectric LaAlO 3 (LAO) and epitaxial undoped Hf 0.5 Zr 0.5 O 2 (HZO) as alternatives to YHZO. This study presents a novel approach to exploit the potential of YHZO in FeTFTs, contributing to the development of next-generation logic-in-memory.