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This study reports the growth of aligned monolayer molybdenum disulfide (MoS2) ribbons on a sapphire substrate viaNaOH-assisted chemical vapor deposition. The length of MoS2ribbon is up to 400 μm. The MoS2ribbon has excellent single crystal properties, a carrier mobility of {150 cm2V−1s−1, and a optical response of 103 mA W−1at a wavelength of 550 nm. The growth model of MoS2ribbons was given. NaOH reacts with MoO3to form sodium molybdate droplets, which increase the fluidity of the molybdenum source on the substrate, realizing the vapor–liquid–solid growth of MoS2on sapphire. The monolayer MoS2ribbons have two kinds of arrangements on the sapphire substrate, one is the oriented growth affected by the interlayer van der Waals force and the lattice, and the other is the aligned growth constrained by the sapphire step. Our results promote the basic research and device applications of MoS2, and introduce a new way of synthesizing other one dimensional (1D) and 2D nanostructures.

Doping is crucial for improving the properties of transition metal dichalcogenide (TMD) monolayers. However, most existing studies have focused on doping ability, and the research on doping distribution is rare. Recently, differences in the spatial distribution of dopants using chemical vapor deposition based on the spin-coating method have been investigated. Most of these doped TMDs are grown through a vapor–liquid–solid (VLS) growth mechanism. The doping distribution of TMD generated by the vapor–solid–solid (VSS) growth mechanism has not been studied extensively. Herein, various precursors such as Na2WO4, NaVO3, NaOH (Na-Pre), (NH4)2WO4, and NH4VO3(NH4-Pre) are used to synthesize V–WS2. An entirely reversed doping distribution of the central and marginal regions is observed. Moreover, an interface where the concentration changes substantially is also observed. The spatial concentration of dopants is accurately confirmed through transmission electron microscope. According to the results from density functional theory, the difference in the doping distribution is caused by the initial state, which is related to the VLS and VSS growth mechanisms. This research provides a new method to control the distribution of dopants and is important for applications of doped TMD in microelectronic and nanoelectronic devices.

Phosphorus (P) is typically associated with iron (Fe) hydroxides in paddy soils. Our study investigated the impact of different fertilization treatments on the availability of P regulated by Fe redox transformation in a rice (Oryza sativaL.)–wheat (Triticum aestivumL.) cropping system in the mid‐low reaches of the Yangtze River. Five fertilization treatments were examined: control (CK), chemical fertilizer (CF), 35% CF (P) plus pig manure compost (CFM), 100% CF (P) plus straw (CFS), and 35% CF (P) plus pig manure compost and straw (CFMS). Nine‐year rice–wheat rotations increased the oxalate‐extractable poorly crystalline Fe hydroxides (i.e., Feo) by 33%–87% compared with the initial soil, while fertilization further accelerated this process. Compost application increased the proportion of labile P by 75%–108% and decreased the proportion of non‐labile P by 14%–22% compared with the single chemical fertilization treatment. Furthermore, organic fertilization increased the mass proportions of macroaggregates and macroaggregate‐associated labile P. The Feo was positively correlated with the content of labile P but negatively correlated with the proportion of non‐labile P. Moreover, the reductive dissolution of Fe hydroxides was accompanied by the transformation of P from NaOH‐extractable to NaHCO3‐ and H2O‐extractable phases. These results indicate that seasonal alternation of drying and wetting can progressively drive the redox transformation of Fe hydroxides and promote the formation of Feo, thereby affecting the availability of P. Therefore, we suggested that P fertilizer should be reduced in the rice season due to the reduction of Fe hydroxides, particularly in the compost‐amended soils in the temperate rice–wheat cropping system. Fertilization accelerated the poorly crystalline iron hydroxide formation.Organic fertilization enhanced the availability of phosphorus.Poorly crystalline iron hydroxide formation contributed to the increase in phosphorus availability.

All-inorganic cesium lead triiodide (CsPbI3) perovskite has received increasing attention due to its intrinsic thermal stability and suitable band gap for photovoltaic applications. However, it is difficult to deposit high-quality pure-phase CsPbI3films using CsI and PbI2as precursors due to the rapid nucleation and crystal growth by the solution coating method. Here, a simple cation-exchange approach is employed to fabricate all-inorganic 3D CsPbI3perovskite, where 1D ethylammonium lead (EAPbI3) perovskite is first solution-deposited and then transformed to 3D CsPbI3via ion exchange between EA+and Cs+during thermal annealing. The large space between the PbI3–skeletons in 1D EAPbI3favors the cation interdiffusion and exchange for the formation of pure-phase 3D CsPbI3with full compactness and high crystallinity and orientation. The resulting CsPbI3film exhibits a low trap density of state and high charge mobility, and the perovskite solar cell shows a power-conversion efficiency of 18.2% with enhanced stability. This strategy provides an alternative and promising fabrication route for the fabrication of high-quality all-inorganic perovskite devices.

The rapid increase in the artificial syntheses of organic pollutants has raised widespread concern. However, the mechanisms by which fungi degrade these new organic pollutants in the environment and adapt to environmental stressors remain unclear. In this study, Phanerochaete chrysosporium, a model white rot fungus, was used to explore the interfacial processes and mechanisms for synergistic degradation of 4,4′-dichlorobiphenyl (PCB15) with magnetite nanoparticles. The results showed that after 3 and 5 days of cultivation with Phanerochaete chrysosporiumalone, the rates for PCB15 degradation were 32% and 65%, respectively, indicating that the white rot fungus itself was able to degrade the organic pollutant. Moreover, the addition of magnetite nanoparticles significantly enhanced the degradation of PCB15 by Phanerochaete chrysosporium. After cocultivation for 3 and 5 days, the rates for PCB15 degradation increased to 42% and 84%, respectively. Synchrotron radiation-based Fourier transform infrared spectromicroscopy (SR-FTIR) showed that the magnetite particles were tightly adhered to the fungal hyphae and were unevenly distributed on the hyphal surfaces. Furthermore, cocultivation of the fungus and magnetite nanoparticles significantly enhanced the nanozymatic activity of magnetite. A linear regression model provided a significantly negative correlation (r=−0.96, p<0.001) between the nanozymatic activity of the magnetite and the concentration ratio of the PCB15, supporting the hypothesis that white rot fungi degraded the PCB15 by enhancing the nanozyme activity of magnetite. High-resolution X-ray photoelectron spectroscopy (XPS) revealed that the nanozymatic activity of magnetite was mainly governed by oxygen vacancies on the mineral surfaces rather than the iron valence. Together, these findings increase our understanding of the powerful capabilities of fungi in terms of stress resistance and adaptation to extreme environments and provide new insights into fungal-mediated degradation of organic pollutants for soil remediation in contaminated sites.

Aeration plays a crucial role in maintaining the overall health and sustainability of the recirculating aquaculture system. Conventional aeration operates continuous and consumes 35.06 % of equipment energy consumption. How to optimize aeration while ensuring normal fish growth remains a great challenge. To address these challenges, this research paper established a coupled model of computational fluid dynamics and species transport model (CFD-STM). Aeration tests were carried out in a 33.3 m3culture tank using a 0.31 m diameter aerator to find out the impacts of operating variables (aeration flow rate, bubble diameter, inlet velocity, and aerator position) on oxygen transfer using a microporous aeration system. A CFD-STM model was coupled to obtain the optimum values of aeration parameters. Results revealed that the Standard Aeration Efficiency (SAE) reductions by 32.1 % for 50 % larger aeration flow rate and 86.4 % for 50 % larger bubble diameter, as well as SAE achieved 5.67 kg/kWh with an aerator position scale factor equal to 0.48. In addition, the energy consumption of the Roots blower was compared for a single aeration and dissolved oxygen saturation. Results indicated that smaller bubbles microbubbles can effectively improve oxygen transfer coefficient. The energy consumption was reduced by 15.7 % for 50 % larger aeration flow rate and 38.6 % for 50 % lower bubble diameter. Based on the results, this study demonstrated that CFD is a useful tool to optimize the aeration system design and operation in order to enhance aeration efficiency. It provides a theoretical foundation the future optimization of energy conservation through intermittent aeration practices.

A mechanistic understanding of interactions between atomically thin two-dimensional (2D) transition-metal dichalcogenides (TMDs) and their growth substrates is important for achieving the unidirectional alignment of nuclei and seamless stitching of 2D TMD domains and thus 2D wafers. In this work, we conduct a cross-sectional scanning transmission electron microscopy (STEM) study to investigate the atomic-scale nucleation and early stage growth behaviors of chemical vapor deposited monolayer (ML-) MoS2and molecular beam epitaxy ML-MoSe2on a Au(111) substrate. Statistical analysis reveals the majority of as-grown domains, i.e., ∼88% for MoS2and 90% for MoSe2, nucleate on surface terraces, with the rest (i.e., ∼12% for MoS2and 10% for MoSe2) on surface steps. Moreover, within the latter case, step-associated nucleation, ∼64% of them are terminated with a Mo-zigzag edge in connection with the Au surface steps, with the rest (∼36%) being S-zigzag edges. In conjunction with ab initiodensity functional theory calculations, the results confirm that van der Waals epitaxy, rather than the surface step guided epitaxy, plays deterministic roles for the realization of unidirectional ML-MoS2(MoSe2) domains on a Au(111) substrate. In contrast, surface steps, particularly their step height, are mainly responsible for the integrity and thickness of MoS2/MoSe2films. In detail, it is found that the lateral growth of monolayer thick MoS2/MoSe2domains only proceeds across mono-Au-atom high surface steps (∼2.4 Å), but fail for higher ones (bi-Au atom step and higher) during the growth. Our cross-sectional STEM study also confirms the existence of considerable compressive residual strain that reaches ∼3.0% for ML-MoS2/MoSe2domains on Au(111). The present study aims to understand the growth mechanism of 2D TMD wafers.

Efficient large-scale nondestructive quality assessment of graphene on Pt is essential to the in-depth growth research and practical applications of graphene. Here, we present a very simple method for directly observing the domains and defects in graphene on Pt using an ordinary optical microscope. This was achieved by modifying graphene on Pt using methylene blue (MB). Because the chemical activities of graphene and Pt surface differ significantly, the adsorption and reaction of MB on graphene and platinum surface differ. We can determine the distribution of graphene crystal domains and defects by comparing the colors in the optical images. In addition, this characterization method causes no obvious damage to the Pt substrate and graphene. Moreover, it does not affect the recycling of the substrate or the subsequent characterization or application of graphene. Our study provides a nondestructive method for measuring the quality of graphene on Pt on a large scale, as well as a reference for the characterization and doping of other two-dimensional materials.

Reconfigurable intelligent surface (RIS) is more likely to develop into extremely large-scale RIS (XL-RIS) to efficiently boost the system capacity for future 6G communications. Beam training is an effective way to acquire channel state information (CSI) for XL-RIS. Existing beam training schemes rely on the far-field codebook. However, due to the large aperture of XL-RIS, the scatters are more likely to be in the near-field region of XL-RIS. The far-field codebook mismatches the near-field channel model. Thus, the existing far-field beam training scheme will cause severe performance loss in the XL-RIS assisted near-field communications. To solve this problem, we propose the efficient near-field beam training schemes by designing the near-field codebook to match the near-field channel model. Specifically, we firstly design the near-field codebook by considering the near-field cascaded array steering vector of XL-RIS. Then, the optimal codeword for XL-RIS is obtained by the exhausted training procedure. To reduce the beam training overhead, we further design a hierarchical near-field codebook and propose the corresponding hierarchical near-field beam training scheme, where different levels of sub-codebooks are searched in turn with reduced codebook size. Simulation results show the proposed near-field beam training schemes outperform the existing far-field beam training scheme.

Growing graphene on metal thin films, especially Cu or CuNi thin films, has become an efficient way to obtain large single-crystal graphene. Most studies focus on the epitaxial growth of graphene, but the effects of defects, such as wrinkles and point defects, on graphene stability are rarely explored. In this work, we mainly focus on the distribution of wrinkles and point defects to study the stability of graphene growth on CuNi thin films. It is found that graphene grown on a CuNi thin film shows the same peripheral etching phenomena other than central etching holes or wrinkle stripes whether it is cooled or not. Raman and TEM studies show that the graphene has high quality. We believe that graphene grown on a CuNi thin film has few wrinkles and point defects. Thus, the results show that graphene grown on a CuNi thin film is more stable than graphene grown on a Cu foil in a high-temperature hydrogen and air environment.

Despite extensive study, geochemical modeling often fails to accurately predict lead (Pb) immobilization in environmental samples. This study employs the Charge Distribution MUlti-SIte Complexation (CD-MUSIC) model, X-ray absorption fine structure (XAFS), and density functional theory (DFT) to investigate mechanisms of phosphate (PO4) induced Pb immobilization on metal (hydr)oxides. The results reveal that PO4mainly enhances bidentate-adsorbed Pb on goethite via electrostatic synergy at low PO4concentrations. At relatively low pH (below 5.5) and elevated PO4concentrations, the formation of the monodentate-O-sharing Pb-PO4ternary structure on goethite becomes important. Precipitation of hydropyromorphite (Pb5(PO4)3OH) occurs at high pH and high concentrations of Pb and PO4, with an optimized log Kspvalue of −82.02. The adjustment of log Kspcompared to that in the bulk solution allows for quantification of the overall Pb-PO4precipitation enhanced by goethite. The CD-MUSIC model parameters for both the bidentate Pb complex and the monodentate-O-sharing Pb-PO4ternary complex were optimized. The modeling results and parameters are further validated and specified with XAFS analysis and DFT calculations. This study provides quantitative molecular-level insights into the contributions of electrostatic enhancement, ternary complexation, and precipitation to phosphate-induced Pb immobilization on oxides, which will be helpful in resolving controversies regarding Pb distribution in environmental samples.

Core IdeasThe spatial arrangements of soil MOAs are highly heterogeneous.The processes of carbon binding in different soil types are different.Combination of SR‐FTIR mapping and 2DCOS could in situ characterize the sequences of MOAs. Direct characterization of spatial distribution and binding environments of soil mineral‐organic associations (MOAs) are imperative for understanding the mechanism of C storage. Here, we propose a new strategy of synchrotron‐radiation‐based Fourier transform‐infrared (SR‐FTIR) technology and two‐dimensional FTIR correlation spectroscopy (2DCOS) analysis to simultaneously characterize the MOAs extracted from two types of soil, which one is classiðed as Ferralic Cambisol and another is Typic Hapludoll. This study successfully showed the spatial heterogeneity by SR‐FTIR mapping, which illustrated that the different soil types had different spatial arrangements at the microscale scale. Moreover, the overlapped one‐dimensional (1D) SR‐FTIR spectra and various sequence orders in two types of soil were demonstrated by 2DCOS analysis. The results showed that the intra hydrogen bonds in clay‐OH minerals and Si‐O‐metal bonds were more highly reactive in the Ferralic Cambisol soils than that in the Typic Hapludoll soils, which was critical for understanding the binding processes in soil micro‐environments.

The undesired segregation of inactive secondary phase that randomly distributed across the perovskite film is detrimental to charge-carrier transport dynamics and light stability. However, in-depth studies for understanding the underlying chemical reaction mechanism and the relationship between phase structural configuration and physical properties are still lacking. Herein, the segregation behavior of the inactive secondary phase and the underlying microcosmic mechanism regarding ionic chemical replacement reaction and lattice reconfiguration process are systematically elaborated. A high-quality perovskite-PbI2heterojunction film is constructed via converting the three-dimensional PbI2photoactive phase into a two-dimensional inactive phase, alleviating the energetic disorder of carrier dynamics and photochemical dissociation. The resultant perovskite solar cells achieve an efficiency of 24.23% with excellent light-resistance. The dissociation energetics of phase dimensional structure is theoretically analyzed. This work provides new insights into crystal structure design for constructing high-quality perovskite heterojunction devices.

Core IdeasOrganic fertilization increased the oxalate extractable iron oxides.Oxalate extractable iron oxides contributed to soil organic carbon sequestration.Soil organic carbon from 20 to 40 cm was more labile than that from 0 to 20 cm.Oxalate extractable iron oxides preferentially preserved aromatic compounds. Carbon sequestration in paddy soils through organic fertilization is of great importance for soil quality improvement in subtropical Asia. This study explored the effect of oxalate extractable iron oxides (Feo) on soil organic carbon (SOC) sequestration in response to different fertilization treatments. Soil samples were collected from 0‐ to 10‐cm, 10‐ to 20‐cm, and 20‐ to 40‐cm depth intervals in June 2016 after a wheat (Triticum aestivumL.) harvest. This study involved five treatments: control with no fertilizer (CK), chemical fertilizer (NPK), 50% chemical fertilizer plus manure (NPKM), 100% chemical fertilizer plus straw (NPKS), and 30% chemical fertilizer plus manure organic‐inorganic compound fertilizer (NPKMOI). Organic fertilization significantly (P< 0.05) increased the SOC content and the Feo concentration compared with chemical fertilization alone. The specific C mineralization rate (SCMR, rate per unit SOC) increased with increasing soil depths, suggesting that SOC at the 20‐ to 40‐cm depth was more labile than that from 0 to 20 cm. The percentage of SOC present as microbial biomass carbon (MBC) was significantly (P< 0.001) positively correlated with SCMR, indicating that soil microorganisms influenced the potential SOC mineralization. Furthermore, the alternation of drying and wetting in paddy soils drives the biogeochemical cycles of iron and SOC, during which organic fertilization promotes the accumulation of Feo possibly by forming organo‐iron complexes as indicated by the higher Feo content in NPKM than in NPK. The Feo was significantly (P< 0.001) positively correlated with SOC and the percentage of aromatic C, indicating that Feo may play an important role in preserving SOC, especially the aromatic compounds. Therefore, the enhancement of Feo by organic fertilization, especially organic manure that is enriched in aromatic compounds, improved the SOC sequestration potential in the rice (Oryza sativa)–wheat rotation system.

A top-gated graphene FET with an ultralow 1/fnoise level of 1.8 × 10–12μm2Hz1–(f= 10 Hz) has been fabricated. The noise has the least value at Dirac point, it then increases fast when the current deviates from that at Dirac point, the noise slightly decreases at large current. The phenomenon can be understood by the carrier-number-fluctuation induced low frequency noise, which caused by the trapping-detrapping processes of the carriers. Further analysis suggests that the effect trap density depends on the location of Fermi level in graphene channel. The study has provided guidance for suppressing the 1/fnoise in graphene-based applications.

In common wheat (Triticum aestivum L.) and its relative species, considerable progress has been made in understanding the structure and function of the high-molecular-weight glutenin subunit (HMW-GS). As a species closely related to wheat, Aegilops umbellulata is an important resource for wheat genetic improvement. In this paper, we report a novel HMW-GS 1Ux3.5 in Aegilops umbellulata Y361. The complete open reading frame (ORF) coding for 1Ux3.5 was cloned and sequenced. Analysis of the deduced amino acid sequence revealed that the primary structure of 1Ux3.5 was similar to those of previously published HMW-GSs. The 1Ux3.5 possessed an extra cysteine residue in the repetitive domain, indicating that the subunit may be related to excellent dough quality. Subsequently, the single proteins of 1Ux3.5 and 1Dx5 (used as positive control) were purified at a scale sufficient for incorporation into flour for a dough quality test. Both the SDS sedimentation volume and mixograph parameters demonstrated that 1Ux3.5 showed a greater contribution to the dough quality than 1Dx5. Therefore, the 1Ux3.5 subunit from Aegilops umbellulata may have potential value in improving the processing properties of hexaploid wheat varieties.

Graphene is a promising candidate in analog electronics with projected operation frequency well into the terahertz range. In contrast to the intrinsic cutoff frequency (fT) of 427 GHz, the maximum oscillation frequency (fmax) of graphene device still remains at low level, which severely limits its application in radio frequency amplifiers. Here, we develop a novel transfer method for chemical vapor deposition graphene, which can prevent graphene from organic contamination during the fabrication process of the devices. Using a self-aligned gate deposition process, the graphene transistor with 60 nm gate length exhibits a record high fmaxof 106 and 200 GHz before and after de-embedding, respectively. This work defines a unique pathway to large-scale fabrication of high-performance graphene transistors, and holds significant potential for future application of graphene-based devices in ultra high frequency circuits.

An array of high-density, vertically aligned GaN nanowires is fabricated through thermal evaporation of GaN powder with the assistance of HCl gas. All GaN nanowires with needlelike tips are well-aligned with the axis direction perpendicular to the substrate without the use of catalysts. A possible growth mechanism of the vertical GaN nanowires array is proposed. Furthermore, field emission measurement shows that the obtained GaN nanowires array has a lower turn-on field of 2.1 V/μm, and the current density is about 1 mA/cm(2) at a bias field of 4.5 V/μm, which means such GaN nanowires are good candidates for large area and uniform flat display applications.

Biosynthesis/metabolism, perception/signaling, and transport are three essential aspects of the actions of phytohormones. Jasmonates (JAs), including jasmonic acid (JA) and related oxylipins, are implicated in the regulation of a range of ecological interactions, as well as developmental programs to integrate these interactions. Jasmonoyl-isoleucine (JA-Ile) is the most bioactive JAs, and perception of JA-Ile by its coreceptor, the Skp1-Cullin1-F-box-type (SCF) protein ubiquitin ligase complex SCFCOI1-JAZ, in the nucleus derepresses the transcriptional repression of target genes. The biosynthesis and metabolism of JAs occur in the plastid, peroxisome, cytosol, endoplasmic reticulum, and vacuole, whereas sensing of JA-Ile levels occurs in the nucleus. It is increasingly apparent that a number of transporters, particularly members of the jasmonates transporter (JAT) family, located at endomembranes as well as the plasma membrane, constitute a network for modulating and coordinating the metabolic flux and signaling of JAs. In this review, we discuss recent advances in the metabolism, signaling, and especially the transport of JAs, focusing on intracellular compartmentation of these processes. The roles of transporter-mediated cell-cell transport in driving long-distance transport and signaling of JAs are also discussed.

ABSTRACTMobile wound signals transmitted from local damaged to distal undamaged sites induce upsurge of jasmonic acid (JA) and activation of core JA signaling, priming the whole plant for broad-spectrum resistance/immunity against future challenges. We recently characterized two jasmonate importers AtJAT3 and AtJAT4 in Arabidopsis thalianajasmonate transporter (JAT) family that cooperatively regulate the transmission of JA from leaf-to-leaf in this wound-induced systemic response/resistance (WSR). As half-molecule ATP-binding cassette transporters, AtJAT3 and AtJAT4 need to form homodimers or/and heterodimer to function. Here we show interactions in AtJAT3-AtJAT3, AtJAT3-AtJAT4, and AtJAT4-AtJAT4 pairs by both yeast two-hybrid and bimolecular fluorescent complementation assays. Furthermore, we propose a model in which the homo-/hetero-dimers of AtJAT3/AtJAT4 mediated cell-cell transport of JA drives long-distance transmission of JA signal in a self-propagation mode and give perspectives on future works to reinforce this model.

High-quality thick gallium nitride (GaN) films were overgrown by hydride vapor phase epitaxy (HVPE) on a nanoporous GaN template which was prepared by inductively coupled plasma etching employing an anodized aluminum oxide mask. An obvious reduction of the dislocation density in the thick GaN layer was demonstrated by high-resolution X-ray diffraction, which exhibited the improved crystalline quality in GaN films overgrown on a nanopatterned surface. Moreover, the peak redshift in photoluminescence and micro-Raman spectroscopy indicates a significant strain relaxation in the HVPE-GaN layer. Compared with conventional overgrowth, such a deposition pathway is a more promising technique for the growth of thick GaN layers.

We report nanoepitaxy of thick GaN films by hydride vapor-phase epitaxy (HVPE) using a uniform array of SiO2nanomasks that were prepared by electron-beam evaporation and anodic aluminum oxide membranes. The controllable size and density of the SiO2nanoisland mask were about 65nmand 1010cm−2, respectively. Subsequent overgrowth takes place selectively on the exposed GaN surface without the SiO2masks to the formation of the continuous layer. High-resolution X-ray diffraction shows reduction of threading dislocations in the overgrown layers. Improved optical property and significant stress relaxation in the epilayer are demonstrated by photoluminescence and micro-Raman spectra. The deposition method is a more promising technique for obtaining freestanding GaN substrates with high-quality and uniform features.

High-quality thick gallium nitride (GaN) films were overgrown by hydride vapor phase epitaxy (HVPE) on a nanoporous GaN template which was prepared by inductively coupled plasma etching employing an anodized aluminum oxide mask. An obvious reduction of the dislocation density in the thick GaN layer was demonstrated by high-resolution X-ray diffraction, which exhibited the improved crystalline quality in GaN films overgrown on a nanopatterned surface. Moreover, the peak redshift in photoluminescence and micro-Raman spectroscopy indicates a significant strain relaxation in the HVPE-GaN layer. Compared with conventional overgrowth, such a deposition pathway is a more promising technique for the growth of thick GaN layers.

High-quality GaNfilms were deposited by hydride vapor phase epitaxy (HVPE) on metalorganic chemical vapor deposition GaNtemplates using an anodized aluminum oxide mask. High-resolution X-ray diffraction, scanning electron microscopy, and cathodoluminescence were used to highlight the excellent crystalline quality of the films, and the optical properties at different positions of the as-grown layers. The optical properties of the GaNfilms improved with increased film thickness. The PL peak position indicates stress relaxation by the AAO mask.