Large-size Substrates Research Articles

Asymmetric competition for habitats between the temperate Japanese eel Anguilla japonica and the tropical Indo-Pacific eel A. marmorata

Habitat segregation is a common phenomenon among anguillids in rivers where multiple species coexist. However, despite the growing need to conserve their river habitats, the mechanisms underlying such segregation remain unknown. Here, we conducted tank experiments to investigate the competitive superiority for habitats between the temperate Japanese eel Anguilla japonica and the tropical Indo-Pacific eel Anguilla marmorata, which co-occur in East Asian subtropical rivers. Using eight interspecific pairs of these two species of comparable total length, we compared the use of a single pipe shelter, recorded over a 24-h experimental period, between solitary and paired conditions. The changes in shelter use patterns between conditions indicated that in the paired condition, the shelter was occupied by A. marmorata in five pairs (62.5%) by the end of the experiment while A. japonica appeared to occupy the shelter in only one pair (12.5%). Furthermore, agonistic behaviors, which occurred mainly at night, such as biting and head-butting, were observed much more frequently for A. marmorata toward A. japonica (mean ± standard deviation: 23.2 ± 36.6 times per individual) than for A. japonica toward A. marmorata (0.4 ± 0.5 times per individual), indicating an asymmetry in aggressiveness. These results suggest that A. marmorata can negatively affect the diurnal habitat use and nocturnal activities of sympatric A. japonica. These findings, combined with those from previous field studies, suggest that A. marmorata may competitively exclude A. japonica from stream habitats with large substrate sizes. This asymmetric competition can contribute to shaping their riverine distribution and composition within rivers where they co-occur.

Elimination of OISF in large-size Si substrate for low warpage and crack-free GaN epitaxial wafer

The oxygen induced stacking fault (OISF) in heavy boron-doping Si substrates causes severe warpage and surface cracks of GaN epitaxial wafers, which will lower the production yield of GaN-based power devices. In this work, high-quality 8-inch Si substrates were fabricated by using rapid thermal annealing (RTA) to eliminate OISF. RTA at 1200 °C effectively eliminated OISF, then surface cracks of 8-inch epitaxial wafers were removed fully and its bow value was decreased markedly from 45.7 μm to 14.3 μm. Consequently, the yields of high electron mobility transistors based on GaN wafers were improved up to 97 %.

P‐107: High‐Resolution Periodic Patterning for Volume Manufacturing on +300mm Size Substrates Using Displacement Talbot Lithography

The photonic device market has a need for low‐cost, high‐resolution periodic patterning that scales with product maturity to large substrate sizes. Eulitha's DTL (Displacement Talbot Lithography) technology was limited to only a single exposure field per substrate on preexisting platforms which can fully pattern 100 and 150mm substrates. The new ‘PhableS' is Eulitha's step‐and‐repeat solution to bring all the advantages of the DTL patterning to larger substrates.The PhableS tool builds on Eulitha's patented displacement Talbot lithography technology to open the way for customers to fully scale to high volume production. This tool retains the strong technical performance; including 60nm half pitch resolution (DUV version), 140x140mm2 single shot exposure field, large depth of focus (hundreds of microns), high throughput (+40wph), non‐contact, mask‐based patterning. Automated wafer and mask handling support industry expected repeatability and defect‐free patterning.

Fabrication and Application of Grinding Wheels with Soft and Hard Composite Structures for Silicon Carbide Substrate Precision Processing.

In silicon carbide processing, the surface and subsurface damage caused by fixed abrasive grinding significantly affects the allowance of the next polishing process. A novel grinding wheel with a soft and hard composite structure was fabricated for the ultra-precision processing of SiC substrates, and the grinding performance of the grinding wheel was assessed in this study. Different types of gels, heating temperatures, and composition ratios were used to fabricate the grinding wheel. The grinding performance of the grinding wheel was investigated based on the surface integrity and subsurface damage of SiC substrates. The results showed that the grinding wheel with a soft and hard composite structure was successfully fabricated using freeze-dried gel with a heating temperature of 110 °C, and the component ratio of resin to gel was 4:6. A smooth SiC substrate surface with almost no cracks was obtained after processing with the grinding wheel. The abrasive exposure height was controlled by manipulating the type and ratio of the gel. Furthermore, the cutting depth in nanoscale could be achieved by controlling the abrasive exposure height. Therefore, the fabrication and application of the grinding wheels with soft and hard composite structures is important for the ultra-precision processing of large-size SiC substrates.

Correlation between birefringence and absorption mapping in large-size Sapphire substrates for gravitational-wave interferometry

In high-sensitive laser interferometers, such as the gravitational-wave detector KAGRA, ultra-high-quality mirrors are essential. In the case of KAGRA, where cavity mirrors are cooled down to 20 K, large-size Sapphire crystals are used as the substrate for the main mirrors to achieve both a good optical quality (i.e., low absorption and uniform refractive index) and optimized thermal behavior under cryogenic temperatures. To implement the very tight optical specifications required by this demanding application, it is mandatory to test the optical homogeneity of different substrates. In order to characterize refractive-index inhomogeneities of large-size uniaxial samples such as the KAGRA Sapphire test masses, we developed a dedicated setup, allowing to resolve birefringence changes with a sensitivity in the order of Δn≈2×10-10\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Delta n\\approx 2 \ imes 10^{-10}$$\\end{document} and a spatial resolution of 1mm2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$1\\,{{{\\hbox {mm}}}}^{2}$$\\end{document}. Moreover, the same setup allows us to simultaneously record residual absorption maps, thus allowing for a comparison between birefringence and absorption features. In this paper, we will present for the first time measurements on a KAGRA-sized Sapphire substrate which has been characterized in terms of absorption already in an earlier work. Both birefringence inhomogeneities and absorption distributions will be compared and correlations discussed.

Antireflective coatings of chitin nanofibers on glass fabricated through electric field deposition

Due to their wide variety of practical applications, antireflective coatings have been studied intensively. In this paper, we developed a novel approach to fabricate antireflective coatings on glass substrate by using charged chitin nanofibers (ChNFs) and electric field deposition. The ChNFs were obtained via ultrasonic treatment of the modified chitin through partial deacetylation, esterification and esterification followed partial deacetylation (dual modification), respectively. The ChNF coatings prepared by applying electric field deposition and using aqueous dispersions of the dual modified ChNFs had antireflective capacity. The effects of electric field intensity, electric field application time and ChNF dispersion concentration on antireflective capacity of the ChNF coatings were studied. The coating obtained by applying 55 V electric field for 5 min and using the dispersion of the dual modified ChNFs with concentration of 0.05 wt% yielded increase in transmittance of a glass substrate (∼ 2.4% at wavelength of 550 nm). The results of this study demonstrate that electric field deposition is a high efficiency and low cost approach to prepare antireflective coatings on large size and nonplanar substrates with charged nanofibers.

Recycled clay bricks and palm kernel shell as constructed wetland substrate for wastewater treatment: An engineered closed circuit circular economy approach

Wastewater treatment using green technologies contributes significantly to a circular economy. Constructed wetlands (CW) using green substrates or recycled materials are low-cost cleaner technologies that further contribute to a closed circuit. This study assessed the performance of two recycled materials, Waste Clay Brick (WCB) and Palm Kernel Shells (PKS), as suitable substrates in a CW for wastewater treatment. Five (5) horizontal subsurface flow constructed wetlands (HSSF CW), designed and fabricated using galvanized steel, were set up for the treatment of domestic wastewater (sewage). The wetland cells were packed with small (WCBS, PKSS) or large (WCBL or PKSL) particle size substrates with one cell using sand as control. The CW operated under two hydraulic loading rates (HLR), 50l/d (HLR-1) and 80l/d (HLR-2). Overall, the effluent quality of HLR-1 was relatively better than HLR-2. pH and turbidity of effluent were satisfactory and within the Ghana Environmental Protection Agency (EPA) guidelines for discharge of wastewater into surface water bodies. For both hydraulic loading rates, the highest removal efficiencies of BOD5 (73.97%), COD (71.89%), TSS (90.82%), TP (71.13%), TN (49.41%) were recorded for WCB. Coliform removal was highest in the Palm Kernel Shell (98.6%), followed by the control (97.39%). Wastewater treatment efficiency decreased with increasing wastewater loading rates for all parameters in Waste Clay Brick and BOD5 and TP in Palm Kernel Shell. WCB demonstrated superior treatment potential compared to PKS for all parameters except coliform removal.

Omnidirectional antireflective coatings prepared with chitin nanofibers via layer-by-layer self-assembly

Antireflective coatings play an important role in various optical devices. Herein, we developed omnidirectional antireflective coatings fabricated with charged chitin nanofibers (ChNFs) through layer-by-layer (LbL) self-assembly technology. The charged ChNFs were prepared from chitin with modifications of esterification (negatively charged) and esterification followed partial deacetylation (positively charged), respectively, through ultrasonic treatment. The effects of concentration of the ChNF suspensions and number of bilayers on thickness, refractive index and antireflective capacity of the ChNF coatings were investigated. Refractive index of the ChNF coatings can be manipulated by changing concentration of the ChNF suspensions. Thickness of the ChNF coatings depends on number of bilayers and concentration of the ChNF suspensions. The ChNF coating on a glass substrate with 5 bilayers fabricated using the suspensions with concentration 0.1% had a refractive index of 1.36 and yielded 4% gain in transmittance compared to the glass at the wavelength of 550 nm. This work demonstrates that charged ChNFs are promising building blocks to fabricate antireflective coatings on large size substrates with high efficiency and low cost through LbL self-assembly.

8‐1: Invited Paper: High Mobility Poly‐Crystalline Oxide TFT Achieving Mobility over 50 cm2/Vs and High Level of Uniformity on the Large Size Substrates

We have successfully developed stable poly‐crystalline oxide semiconductor (Poly‐OS) as channels of TFT on Gen.6 glass substrates. This technology has significantly improved mobility and stability at the same time, achieving both extremely low off‐state current similar to conventional oxide TFTs and high on‐state current equivalent to LTPS TFTs.

State-of-the-art and prospective progress of growing AlN substrates by physical vapor transport

SiC, GaN, diamond, and AlN known as wide band-gap semiconductors, integrate the advantages of microelectronics, optoelectronics, and power electronics. The ultra-wide bandgap semiconductor AlN crystal has a direct bandgap of 6.1 eV at room temperature. AlN has led to a burgeoning research interest in the fabrication of devices due to its outstanding structure and fascinating physiochemical (microelectronics, optoelectronics and power-electronics, etc.) properties. In this review, we summarize some recent advances in growing physical vapor transport AlN substrates. First, we introduce the primary seed growth of AlN using two disparate growth strategies: on heterogeneous substrate and spontaneous nucleation. We then elaborate on their advantages and disadvantages for subsequent homogeneous growth. Second, we highlight ultramodern advances that have been made in the preparation of high-quality and large-size AlN substrates, discuss the optical properties of AlN. In the end, the current challenges and new opportunities for PVT grown AlN substrates in improving the quality are also discussed.

Die-embedded packaging using Corning® multi-layered glass

Die-embedded (DE) packaging technologies in recent years have ventured into advanced packaging structures, such as fan-out wafer level packages (FOWLPs) or package-on-packages (PoPs). They offer higher density at lower costs, despite many challenges, such as the die-shift and warpage problems often observed during the molding process, caused by the high shrinkage and high coefficients of thermal expansion (CTEs) of the molding materials. This in turn makes it difficult to accurately mount the high-density fine-pitch bumps and adversely affects the overall yield, especially in processes using large-size substrates. Glass, known for its superior dimensional and thermal stability and its low or tunable CTEs, can be advantageous in reducing die-shift and warpages as opposed to other alternative material solutions for the molding process. In this paper, we propose a packaging solution based on a glass substrate incorporating a plurality of precisely dimensioned cavities, with a chip positioned in each cavity to prevent them from shifting during processing. Corning® Adaptive Formed Glass (AFG), a laminate glass with a unique clad/core/clad structure, allows for effectively forming cavities with high dimensional precision and positional accuracies as well as surface flatness through a wet etch process. Using a 0.5mm thick laminate Corning® AFG glass, we successfully designed and fabricated three types of DE packages with lab scale tools at Korea Electronics Technology Institute (KETI): single- and double-sided DE packages, and package-on-packages (POPs). High etching selectivity over 20:1, which was achieved by carefully designing the core and clad glass compositions, enabled a wet-etch cavity forming process with accurate cavity depths and flat bottom surfaces (< ± 2.5μm) with relative ease. A double-sided DE package with a total thickness of 600μm was fabricated with two 125μm-thick IC chips, one embedded on each side of the substrate, and connected by metallized through glass vias (TGVs). A POP measured at 5.1×5.1×1.27 mm3 was also successfully demonstrated by using two built-in double-sided DE packages joined by flip-chip bonding, equivalent to stacking four layers of conventional single-sided DE packages. The double-sided DE packages and POPs presented in this paper are believed to be the world’s first demonstration on glass. The work also manifests the immense potential of Corning® AFG glass in enabling higher density IC packaging and large-size panel-level (or wafer-level) packaging.

Mechanical chemical polishing of large-size single-crystal diamond substrates with a sol-gel polishing tool

To process large-size single-crystal diamond (SCD) substrates efficiently, we proposed a method that utilises mechanical action to induce a chemical reaction for SCD polishing. In this study, a novel semi-fixed abrasive polishing tool suitable for high-speed polishing was fabricated using the sol-gel technique. A single-diamond abrasive and a mixed abrasive of diamond and CuO were selected for the SCD (100) plane polishing. After polishing for 2.5 h, the surface roughness of the SCD was reduced from approximately Ra 80 nm to approximately Ra 9 nm. The material removal rate (MRR) was measured quantitatively, and it was found that the mixed abrasive polishing performance was superior. In addition, the amorphous carbon content on SCD surface/subsurface after mixed abrasive polishing was significantly lower than single-diamond abrasive diamond abrasive. These results indicate that the scratching of the SCD surface by diamond abrasives induced the transformation of the carbon into amorphous carbon, which could then react with CuO powder. The wear debris morphology indicates that the surface material of the SCD was peeled off with a slice shape during single-diamond abrasive polishing, while it was removed with a slag-shape by the chemical reaction and slightly crushed during the mixed abrasive polishing. The material removal process for the mixed abrasive polishing was CDia→MechanicalCAmo→CuOCu+CO, which is a mechanical chemical polishing process. Experiments confirmed that the synergistic effects of the mechanical action and chemical reaction could increase the MRR and produce a smoother surface and less damage to the subsurface of the SCD, which provides inspiration for the processing of large-size SCD substrates.

High-quality (001) β-Ga2O3 homoepitaxial growth by metalorganic chemical vapor deposition enabled by in situ indium surfactant

(001) β-Ga2O3 homoepitaxy on commercially available large-size (001) β-Ga2O3 substrates remains a significant challenge for the wide bandgap semiconductor community. In this Letter, high-quality homoepitaxial (001) β-Ga2O3 films were grown via metalorganic chemical vapor deposition (MOCVD) with the assistance of an in situ indium surfactant, where the growth modes and mechanisms were also elucidated. During the growth of β-Ga2O3, an etching process occurred by the desorption of the suboxide Ga2O, resulting in rough surface morphology with streaky grooves oriented along the [010] direction. It is postulated that the parallel grooves were associated with the surface desorption and anisotropic diffusion characteristics of β-Ga2O3. To suppress the desorption, indium surfactant was introduced into the growth environment. A 2D-like growth feature was prompted subsequently by the coadsorption of In and Ga atoms, accompanied by relatively smooth surface morphology. The crystal quality had no degradation despite the incorporation of indium in the epitaxial film. The O II peak of the β-Ga2O3 film shifted ∼0.5 eV toward higher binding energy due to an increasing number of oxygen vacancies originating from the indium incorporation. This work provides a systemic investigation on the growth of high-quality (001) β-Ga2O3 homoepitaxial films by MOCVD, which is critical for the development of β-Ga2O3 electronic devices for future power switching and RF applications.

Identifying potential drivers of distribution patterns of invasive Corbicula fluminea relative to native freshwater mussels (Unionidae) across spatial scales.

This study aimed to identify the importance of ecological factors to distribution patterns of the invasive Clam (Corbicula fluminea) relative to native mussels (family: Unionidae) across seven rivers within the Mobile and Tennessee basins, Southeast United States. We quantitatively surveyed dense, diverse native mussel aggregations across 20 river reaches and estimated mussel density, biomass, and species richness along with density of invasive C. fluminea (hereafter Corbicula). We measured substrate particle size, velocity, and depth in quadrats where animals were collected. Additionally, we characterized reach scale environmental parameters including seston quantity and quality (% Carbon, % Nitrogen, % Phosphorous), water chemistry (ammonium [NH4+], soluble reactive phosphorous [SRP]), and watershed area and land cover. Using model selection, logistic regression, and multivariate analysis, we characterized habitat features and their association to invasive Corbicula within mussel beds. We found that Corbicula were more likely to occur and more abundant in quadrats with greater mussel biomass, larger substrate size, faster water velocity, and shallower water depth. At the reach scale, Corbicula densities increased where particle sizes were larger. Mussel richness, density, and biomass increased with watershed area. Water column NH4+ increased at reaches with more urban land cover. No land cover variables influenced Corbicula populations or mussel communities. The strong overlapping distribution of Corbicula and mussels support the hypothesis that Corbicula are not necessarily limited by habitat factors and may be passengers of change in rivers where mussels have declined due to habitat degradation. Whether Corbicula is facilitated by mussels or negatively interacts with mussels in these systems remains to be seen. Focused experiments that manipulate patch scale variables would improve our understanding of the role of species interactions (e.g., competition, predation, facilitation) or physical habitat factors in influencing spatial overlap between Corbicula and native mussels.

Scalable Fabrication of Metallic Nanogaps at the Sub-10nm Level.

Metallic nanogaps with metal–metal separations of less than 10 nm have many applications in nanoscale photonics and electronics. However, their fabrication remains a considerable challenge, especially for applications that require patterning of nanoscale features over macroscopic length‐scales. Here, some of the most promising techniques for nanogap fabrication are evaluated, covering established technologies such as photolithography, electron‐beam lithography (EBL), and focused ion beam (FIB) milling, plus a number of newer methods that use novel electrochemical and mechanical means to effect the patterning. The physical principles behind each method are reviewed and their strengths and limitations for nanogap patterning in terms of resolution, fidelity, speed, ease of implementation, versatility, and scalability to large substrate sizes are discussed.

(Invited) Recent Progress in Large Area MOCVD Growth of 2D Materials

Metal-organic chemical vapor deposition (MOCVD) has developed to a mature production technology for state-of-the-art (opto)electronic devices such as LEDs, lasers, solar cells and transistors. Current multi-wafer MOCVD systems allow for scalable processes with precise control of growth parameters ensuring excellent uniformity of deposition rates, dopant concentrations and layer thicknesses. All of these properties are of crucial importance for reproducibly obtaining high-quality ultra-thin films required for next-generation nano-electronic devices. One of the most promising materials for the fabrication of such devices are layered transition-metal dichalcogenides (TMDCs), e.g. molybdenum disulfide (MoS2) or tungsten disulfide (WS2), graphene (Gr) or hBN. Due to their 2D structure, these materials possess unique optical, electrical and magnetic characteristics, and monolayers are considered as material system for several future applications. Moreover, the properties and functionality of a single monolayer can be even further improved by forming heterostructures of several two-dimensional materials. Such complex structures which require control on the atomic level strongly limit the number of available fabrication options, especially for volume production, leaving MOCVD as the most reliable industrial deposition method.In this work, we present wafer-scale MOCVD of high-quality monolayers of MoS2, WS2, hBN and graphene (Gr) on single-crystalline C-plane (0001) sapphire deposited in commercial AIXTRON reactors. Our upscaling effort from 2 inch wafer up to growth on 200 mm wafer supports the industrial demand. Molybdenum hexacarbonyl, tungsten hexacarbonyl and di-tert-butyl sulfide are employed as precursors. By optimizing growth conditions, fully-coalesced MoS2 and WS2 samples without parasitic carbon-related Raman peaks were obtained. XPS analysis indicates only Mo-S and W-S bonds for MoS2 and WS2 samples, respectively, with no indications of any side reactions with either the substrate, impurities or oxygen and demonstrates a high layer quality suitable for research on all kind of devices including advanced transistors and memresistive devices. Samples were characterized using Raman/photoluminescence spectroscopy, SEM and AFM to understand the correlation of growth parameter and material properties. As an example a WS2 growth duration series at 700°C temperature was performed. The intensity ratio of about 2 for the Raman E2g/A1g peaks for the optimized WS2 samples suggests deposition of monolayer WS2 with some admixture of bilayer, as confirmed by AFM. The WS2 monolayer film growth has been successfully upscaled from 2” to 200mm sapphire wafers. hBN thin films have been also grown from borazine precursor both on 2” and 200 mm sapphire substrates. Thickness uniformity of 9 nm hBN films was 3% on 200 mm wafers, as determined by XRR. High-quality monolayer graphene layers grown from CH4/H2 on 2” and 200mm sapphire wafers demonstrated good performance by Raman (2D/G peak ratio >1.5 and low D/G peak ratio (<0.25), as well as low sheet resistance (~1300-1500 Ohm/sq). The grown films had smooth surface morphology with the expected graphene wrinkles visible by AFM). These results demonstrate the applicability of AIXTRON systems for the growth of TMDC, hBN and graphene films on large size substrates. The growth could be easily upscaled from 2” to 200 mm wafer growth with only minor adjustment of the growth parameters. More details on the growth process and material properties as well as results on hBN/Gr, TMDC/Gr and TMDC/hBN heterostructures will be discussed in detail. Figure 1

A Transferrable, Adaptable, Free-Standing, and Water-Resistant Hyperbolic Metamaterial.

Hyperbolic metamaterials (HMMs) have attracted significant attention due to the profound manipulation of the photonic density of states, resulting in the efficient optoelectronic devices with the enhanced light-matter interaction. HMMs are conventionally built on rigid large-size substrates with poor conformability and the absence of flexibility. Here, we demonstrate a grating collageable HMM (GCHMM), which is composed of eight alternating layers of Au and poly(methyl methacrylate) (PMMA) and PMMA grating nanostructure containing quantum dots (QDs). The QDs serve as a scattering gain medium performing a random laser action, and the grating nanostructure enhances the extraction of light from QDs. The GCHMM enhances laser action by 13 times, reduces lasing threshold by 46%, and increases differential quantum efficiency by 1.8 times as compared to a planar collageable HMM. In addition, the GCHMM can be retransferred multiple times to other substrates as well as provide sufficient protection in water and still retain an excellent performance. It also shows stable functionality even when transferred to a dental floss. The GCHMM, therefore, promises to become a versatile platform for foldable, adaptable, free-standing, and water-resistant optoelectronic device applications.

Mass-producible slit coating for large-area electrochromic devices

The recent trend of some countries opting to ban the sale of new gasoline and diesel vehicles has led to an increase in the use of electric vehicles and automated driving. In an automobile, windows are the largest source of heat energy between the interior and exterior of the vehicle. By modulating the window material, we can precisely control the amount of heat from sunlight that is allowed to enter the car, reduce the load on heating and cooling. Thus, suppress the energy loss associated with air conditioning by introducing technology to control heat energy in windows, which can also help reduce electricity costs. To this end, our research group has been developing complementary electrochromic devices (ECDs) using Prussian blue and tungsten oxide, which consist of nanoparticles dispersed in aqueous solvents to make inks. Spin coating is used for film deposition at the laboratory level; however, it has a major limitation in terms of uniformity. Therefore, in this study, we fabricated functional thin films by using these inks with slit coating, which is a commercial process. The results obtained confirm that slit coating can be used to deposit approximately 1-μm-thick films as fast as within 20 s and even on large G2 size substrates; further, the uniformity of the films measured based on chromaticity and haze is high. In addition, this effect improves the response time of the ECD. As a future direction, this can be applied to flexible ECD, etc.

Substrate Engineering for CVD Growth of Single Crystal Graphene.

Single crystal graphene (SCG) has attracted enormous attention for its unique potential for next-generation high-performance optoelectronics. In the absence of grain boundaries, the exceptional intrinsic properties of graphene are preserved by SCG. Currently, chemical vapor deposition (CVD) has been recognized as an effective method for the large-scale synthesis of graphene films. However, polycrystalline films are usually obtained and the present grain boundaries compromise the carrier mobility, thermal conductivity, optical properties, and mechanical properties. The scalable and controllable synthesis of SCG is challenging. Recently, much attention has been attracted by the engineering of large-size single-crystal substrates for the epitaxial CVD growth of large-area and high-quality SCG films. In this article, a comprehensive and comparative review is provided on the selection and preparation of various single-crystal substrates for CVD growth of SCG under different conditions. The growth mechanisms, current challenges, and future development and perspectives are discussed.

Особенности согласования нижнего электрода с высокочастотным генератором смещения при реактивно-ионном травлении массивных подложек

This paper presents theoretical and experimental results on reactive ion etching of massive substrates in freon-14 with RF bias at the lower electrode. A hypothesis is proposed according to which a large-sized substrate violates the matching of the lower electrode with the RF generator by adding an additional reactive component to the impedance of the lower electrode. A numerical simulation of reactive ion etching with substrates of various sizes in a CF4 environment is performed . The simulation results showed a significant increase in the reactive component of RF power at the lower electrode if the substrate area exceeds 50% of the area of the lower electrode, which is consistent with the proposed hypothesis. It has been experimentally shown that the etching of massive substrates violates the matching of the lower electrode with the RF generator. A special design of the substrate holder for massive substrates has been developed. It is shown that such a substrate holder significantly improves the matching of the RF generator with the lower electrode, especially when adding 0.3-0.9 l/h argon to the plasma-forming mixture.