Reduction Of Dislocation Density Research Articles

Growth and characterization of micro-LED based on GaN substrate

As the diminution of micro-LED pixels advances, the pivotal role of dislocation phenomena becomes increasingly pronounced. This study provides insight into the key characteristics and dominant mechanisms of GaN-based micro-LEDs by comparing the homoepitaxial and heteroepitaxial configurations. Our findings reveal that variability in V-shaped pits distribution markedly influences the performance and uniformity of micro-LED chips. While the homoepitaxial micro-LEDs, alongside significantly reduced dislocation density and residual stress, effectively preclude the formation of them and thus ensuring superior uniformity both within and among micro-LED chips. Notably, the external quantum efficiency (EQE) peak of homoepitaxial micro-LEDs surpasses that of heteroepitaxial variants by 40%. Motivated by the realization that the reduced MQW thickness at the sidewalls of V-shaped pit aids carrier injection, a great enhancement in EQE from 7.9% to 14.8% (@ 10 A/cm2) was achieved by the optimization of homoepitaxial structure. Therefore, the growth of micro-LED with lower dislocation density, lower residual stress, and epi-structure of low-energy-barrier MQWs demonstrated the profound impact on advancing micro-LED technology to obtain the performance of high uniformity, high brightness, and low power consumption.

Development of photovoltaic and photodetection characteristics in CdS/P3HT devices through Al-doping

CdS thin films were deposited by chemical bath deposition onto FTO substrates with Al concentrations of 0, 1, 3, 5 and 6 %. X-ray diffraction revealed introduction of 1 % Al-doping reduced dislocation density and enhanced the crystal quality of CdS. Scanning electron microscopy confirmed a reduction in grain size in Al-doped CdS films compared to CdS. N3 and P3HT layers were spin-coated onto the prepared substrates, respectively. The fabrication of the solar cells was completed using Ag silver paste for the top contact. The lowest photoluminescence peak intensity was achieved for CdS (3 %Al):P3HT solar cell, indicating efficient exciton dissociation. 3 % Al-doped CdS-based device exhibited the highest efficiency at 0.210 %, nearly seven times that of reference device. CdS (3 %Al):P3HT device demonstrated the best photodetection characteristics, with a responsivity of 2.2 × 10-2 A/W, detectivity of 3.3 × 108 Jones, response time of 13 ms, and recovery time of 12 ms at zero bias voltage.

Recrystallization behavior and strengthening mechanism of friction stir welded T-joint of Ti80 titanium alloy

In this study, Ti80 titanium alloy T-joints were produced by friction stir welding (FSW), and the joint temperature and residual stress distribution of the joints were analyzed by numerical simulation based on the ABAQUS platform, and the correlation between microstructure and performance of FSWed T-joint was investigated. The results show that the SZ is lamellar α grains due to the fact that the peak temperature of all joints exceeds β phase transus. The deformation and dynamic recrystallization behavior take place in the β phase region. During the subsequent cooling stage, the acicular α/α' phase is precipitated from refined prior β phase. The non-uniform heating and cooling results in the significant microstructure differences in the weld thickness direction. The top and middle of the SZ are composed of basketweave structure, while the bottom of the SZ shows a bimodal structure. The microhardness distribution along the skin shows a higher value in the weld area, and the weakest area is located in the HAZ due to recovery, resulting in a significant reduction in dislocation density of the weld. The tensile specimen breaks in the HAZ when it is stretched along the skin direction, while it breaks in a direction parallel to the skin when it is stretched along the stringer. The fracture mechanism of the joint changes from a hybrid mode of ductile and brittle fracture to ductile fracture as the rotation speed increases from 600 rpm to 750 rpm.

(Invited) Scalable 2-Step Fabrication of Core-Shell GaN Micropillars

Group III-Nitride three-dimensional structures have gained substantial interest for application in optoelectronic, energy, and sensor devices with non-planar geometries [1-4]. The benefits of 3D structures, such as GaN-based nano-/micro-rods, compared to planar films include large surface area, high structural quality, non-polar-surface utilization, small footprint, mechanical flexibility, and enhanced light absorption/extraction efficiency. To advance the technology of non-planar III-Nitride semiconductors, it is necessary to optimize and scale up the fabrication of such structures with controlled geometries and desired electronic and optical properties. Here, we report the fabrication of wafer-scale periodic arrays of vertically aligned GaN core-shell micropillars using a combination of top-down etch and epitaxial overgrowth.The two-step process consists of inductively coupled plasma (ICP) etching of lithographically patterned GaN-on-Si substrate to produce an array of micropillars followed by selective growth of GaN shells over these pillars using Hydride Vapor Phase Epitaxy (HVPE). The most significant aspect of the study is the demonstration of the sidewall facet control in the shells, ranging from truncated hexagonal pyramids with the (1-101) semi-polar sidewalls to hexagonal prisms with the (1-100) non-polar sidewalls, by employing a post-ICP wet chemical etch and by tuning the HVPE growth temperature. Optimization of both ICP etching and epitaxial overgrowth reduced dislocation density in the GaN shells, thus enhancing the transport and optical characteristics of these device platforms. Photo- and cathodoluminescence showed a substantial reduction of parasitic yellow luminescence as well as strain-relaxation in the core-shell structures, supported by Raman scattering, electron-backscatter-diffraction (EBSD), and X-ray-diffraction measurements. Transmission electron microscopy revealed improved crystal quality with reduced dislocation density in the epitaxially grown shells. This work demonstrates the feasibility of selective epitaxy on micro/nano-engineered 3D templates for realizing high-quality GaN-on-Si devices such as LEDs and p-i-n photodetectors.

(Invited) Ultrahigh Efficiency Excitonic Micro-LEDs

To date, it has remained challenging to achieve high efficiency micro-LEDs, which are desired for next generation displays and virtual/augmented reality. The performance degradation with reducing dimensions for conventional LEDs has been largely attributed to the plasma damage induced on the mesa sidewalls. Here, we show such a fundamental challenge can be overcome by developing nanowire excitonic LEDs. In this study, InGaN/GaN nanowire LED heterostructures were grown on N-polar GaN-on-sapphire substrates utilizing selective area epitaxy. Studies have shown that the exciton binding energy in strain-relaxed InGaN nanostructures can be dramatically enhanced. Due to the strong Coulombic interaction between electrons and holes, the impact of nonradiative SRH recombination on the performance of an excitonic LED is significantly reduced. By exploiting the large exciton oscillator strength of quantum-confined nanostructures, we have achieved an external quantum efficiency (EQE) exceeding 25% for a green-emitting device with lateral dimensions less than 1 micrometer, which is the highest value reported for any LEDs of this size to the best of our knowledge. It is further observed that the EQE and output power of the excitonic LED show a significantly faster rising trend with current injection, compared to conventional devices. We have identified several important factors for achieving high efficiency excitonic LEDs, including the epitaxy of nanostructures to achieve strain relaxation and reduced dislocation densities and the formation of three-dimensional quantum-confinement to enhance electron-hole wavefunction overlap. We have further investigated the effect of Mg incorporation in p-GaN layer on the device performance. We found out that an optimized Mg dopant incorporation in nanowire structures can contribute significantly to the efficiency of micro-LEDs. We have measured significantly enhanced performance by optimizing Mg dopant incorporation, which leads to reduced leakage current and improved EQE. For example, for a red-emitting micro-LED, a peak external quantum efficiency of >8% was measured for a device with a lateral dimension less than one micrometer by optimizing Mg-dopant incorporation. Through these studies, we show that by harnessing the exciton oscillator strength of nearly dislocation-free nanostructures, together with a careful optimization of p-doping in the contact layer, the efficiency bottleneck of micro-LEDs can be addressed.Conflict of interest: Some IP related to this work has been licensed to NS Nanotech, Inc., which was co-founded by Z. Mi. The University of Michigan and Mi have a financial interest in the company.

High-performance negative differential resistance characteristics in homoepitaxial AlN/GaN double-barrier resonant tunneling diodes

In this work, high-performance negative differential resistance (NDR) characteristics are demonstrated in homoepitaxial AlN/GaN double-barrier resonant tunneling diodes (RTDs). The devices are grown by plasma-assisted MBE on bulk GaN substrates and exhibit robust and repeatable NDR at RT. A high peak current density of 183 kA cm−2 is simultaneously demonstrated with a large peak-to-valley current ratio of 2.07, mainly benefiting from the significantly reduced dislocation density and improved hyper-abrupt heterointerfaces in the active region, which boosts the electron quantum transport in the resonant tunneling cavity. The achievement shows the promising potential to enhance the oscillation frequency and output power of GaN-based RTD oscillators, imperative for next-generation high-power solid-state compact terahertz oscillators application.

Geometrically Controlled Microscale Patterning and Epitaxial Lateral Overgrowth of Nitrogen-Polar GaN.

In this Letter, we report on a novel two-step epitaxial growth technique that enables a significant improvement of the crystal quality of nitrogen-polar GaN. The starting material is grown on 4° vicinal sapphire substrates by metal-organic vapor-phase epitaxy, with an initial high-temperature sapphire nitridation to control polarity. The material is then converted to a regular array of hexagonal pyramids by wet-etching in a KOH solution and subsequently regrown to coalesce the pyramids back into a smooth layer of improved crystal quality. The key points that enable this technique are the control of the array geometry, obtained by exploiting the anisotropic behavior of the wet-etch step, and the use of regrowth conditions that preserve the orientation of the pyramids' sidewalls. In contrast, growth conditions that cause an excessive expansion of the residual (0001̅) facets on the pyramids' tops cause the onset of a very rough surface morphology upon full coalescence. An X-ray diffraction study confirms the reduction of the threading dislocation density as the regrowth step develops. The analysis of the relative position of the 0002̅ GaN peak, with respect to the 0006 sapphire peak, reveals a macroscopic tilt of the pyramids, probably induced by the large off-axis substrate orientation. This tilt correlates very well with an anomalous broadening of the 0002̅ diffraction peaks at the beginning of the regrowth step.

Microstructural and material property changes in severely deformed Eurofer-97

Severe plastic deformation changes the microstructure and properties of steels, which may be favourable for their use in structural components of nuclear reactors. In this study, high-pressure torsion (HPT) was used to refine the grain structure of Eurofer-97, a ferritic/martensitic steel. Electron microscopy and X-ray diffraction were used to characterise the microstructural changes. Following HPT at room temperature to a maximum shear strain of 230, the average grain size reduced by a factor of ∼30, with a marked increase in high-angle grain boundaries. Dislocation density also increased by more than one order of magnitude. The thermal stability of the deformed material was investigated via in-situ annealing during synchrotron X-ray diffraction. This revealed substantial recovery between 450 K – 800 K. Irradiation with 20 MeV Fe-ions to ∼0.1 dpa caused a 20% reduction in dislocation density compared to the as-deformed material. However, HPT deformation prior to irradiation only had a minor effect in mitigating the irradiation-induced reductions in thermal diffusivity and surface acoustic wave velocity of the material. Microstructural and material property changes are dominated by deformation compared to irradiation. In light of this, the benefits of using HPT to improve the irradiation resistance of Eurofer-97 are limited. These results provide a multi-faceted view of the changes in ferritic/martensitic steels due to severe plastic deformation, and how these changes can be used to alter material properties.

Quantitative analysis of microstructural evolution in cold-sprayed CuCrZr: Understanding heat transfer mechanisms from room temperature to 600°C

Cold-sprayed CuCrZr coating offers interesting multifunctional properties with a combination of high mechanical property, good thermal stability and substantial deposition thickness. Despite these advantages, the incorporation of solid solution elements and the deposit’s unique microstructure often result in suboptimal heat transfer capabilities. This study delved into the thermal conductivity of cold-sprayed CuCrZr coatings over a temperature range from room temperature to 600 °C. Furthermore, it quantitatively analyzed their microstructural evolution post-thermal testing and its correlation with thermal properties, employing techniques such as FESEM, EBSD, TEM, and XRD. Findings indicate the CuCrZr coating exhibits significant thermal sensitivity, with conductivity increasing from 65.83±1.79 W/(m∙K) at 25 °C to 198.42±0.63 W/(m∙K) at 600 °C. The annealing effect during thermal testing significantly enhances the coatings’ room temperature thermal properties, chiefly through the enhancement of interparticle metallurgical bonding, grain enlargement, solid solution precipitation, and a reduction in dislocation density. The thermal conduction across the coating/substrate interface is intricately influenced by the interplay between electrons and phonons, with impediments at the interface becoming markedly pronounced beyond 300 °C. The investigation pinpointed interparticle interfaces as the predominant barriers to heat transfer, contributing to 73.77 % of the total resistance. Meanwhile, the effects of solid solution elements, grain boundaries, and dislocations on thermal conductivity were comparatively minor, contributing 9.36 %, 1.04 %, and 0.44 %, respectively. However, it is also noted that the annealing effect can induce the coalescence of microcracks into pores and promote the precipitation or oxidation of Cr at the interfaces, which, in turn, limits the potential for further enhancements in thermal conductivity.

Characterization of the p-NiO/n-GaN heterojunction and development of ultraviolet photodiode

Nickel oxide semiconductor is a good p-type material for fabricating a p-n-heterojunction with n-type GaN semiconductor. The p-NiO/n-GaN heterojunction, which produces a type II band bias, has significant prospects for creating photosensitive devices. Herein, it is shown that a selective ultraviolet photodetector can be created based on this heterojunction. p-NiO films were formed using magnetron sputtering onto n-doped GaN epitaxial layers grown by plasma assisted molecular beam epitaxy. The structural, optical, and electronic properties of the formed nickel oxide films were studied. A mechanism for reducing dislocation density and conductivity and increasing transparency due to film annealing is proposed. It has been established that the current–voltage characteristics of the p-NiO/n-GaN heterojunction are typical for diode structures and show selective sensitivity to ultraviolet radiation. The band model and sensitivity of the fabricated ultraviolet photodiode were evaluated. The photosensitivity at zero voltage was 3.11 mA/W, the quantum yield was 0.011, and the detection ability was 8.69 × 109 Jones. The work shows the potential of using the p-NiO/n-GaN heterojunction to create ultraviolet photodetectors.

High bonding strength of Ti /steel clad plates prepared by a developed electromagnetic induction heating followed by rolling

Titanium/steel clad plates exhibit significant potential for industrial applications, such as petrochemical and aerospace, due to their combined advantages of two components. In the conventional hot rolling process, the formation of brittle intermetallic compounds (IMCs) had a detrimental effect on the mechanical properties of Ti/steel clad plates. Therefore, the present study proposed an electromagnetic induction heating rolling (EIHR) technique for efficiently fabricating Ti/steel clad plates with high bonding strength at a relatively low temperature, while avoiding the formation of brittle IMCs. Additionally, a pure iron DT4 interlayer with good fluidity was introduced between Ti and steel, which can further enhance both the interface bonding strength and elongation of the clad plates. Based on the electron backscattered diffraction characterization results of the interface, it was found that the addition a DT4 interlayer facilitated dynamic recrystallization of steel side and led to a reduction in dislocation density. Moreover, a pronounced {100}〈011〉 rotational cube texture was evident on the (100) pole figures as a result of substantial plastic deformation during the rolling process. Finally, the relationship between interface microstructure and mechanical performance was established.

Tailoring the microstructure and mechanical properties of laser directed energy deposited Inconel 718 alloy via thermostatic substrate heating

The effects of different thermostatic substrate heating (TSH) temperatures on the stress state, microstructures, and mechanical properties of laser directed energy deposited (LDEDed) Inconel 718 alloy were systematically investigated. The results showed that the optimized TSH temperature (200 °C) transformed the original tensile residual stresses into compressive residual stresses, improved microstructure uniformity, and enhanced the comprehensive mechanical properties of the LDEDed Inconel 718 alloy. When the TSH temperature was 200 °C, the ultimate tensile strength (UTS) and yield strength (YS) of the specimen perpendicular to the building direction (0°) did not change significantly, while the elongation (EL) value was improved by 35.2 %. It was attributed to reduced dislocation density in conjunction with the relaxation of residual stresses. In contrast, the UTS and YS in the specimen parallel to the building direction (90°) increased by 20.4 % and 34.9 %, respectively, whereas the EL values decreased slightly. It was due to the combined effects of the massively precipitated finer and more homogeneous γ'' phase and grain refinement. Finally, the strengthening mechanism of TSH on the microstructures and mechanical properties of the LDEDed Inconel 718 alloy were systematically revealed.

Influence of Mo carbides and two-stage tempering methodology on the susceptibility of medium carbon martensitic steel to hydrogen embrittlement

The objective of the present study was to enhance the hydrogen embrittlement (HE) resistance of the quenched and tempered martensitic steel via the interplay of heat treatment variance and precipitation of nanosized carbides. For this purpose, one-stage tempering and two-stage tempering methodologies were implemented, and steel was alloyed with Mo to instigate the precipitation of Mo carbides. The results revealed that two-stage tempered steel exhibited superior resistance to HE, as a result of reduced dislocation density and higher quantity of Mo2C. To discern the role and trapping behaviour of Mo2C carbides, Thermal Desorption Spectroscopy (TDS) combined with electrochemical hydrogen charging was utilized. Precipitated nanosized Mo2C exhibited the ability to trap hydrogen. On the contrary, an increase of dislocations and higher diffusible hydrogen content in one-stage tempered steel promoted deterioration of mechanical properties which was investigated by Slow Strain Rate Test (SSRT) and fracture surface morphology analysis. In addition, the effective diffusion coefficient for one-stage tempered steel was lower, as dislocations served as additional trap sites.

Experimental Observation of a New Attenuation Mechanism in hcp‐Metals That May Operate in the Earth's Inner Core

AbstractSeismic observations show the Earth's inner core has significant and unexplained variation in seismic attenuation with position, depth and direction. Interpreting these observations is difficult without knowledge of the visco‐ or anelastic dissipation processes active in iron under inner core conditions. Here, a previously unconsidered attenuation mechanism is observed in zinc, a low pressure analog of hcp‐iron, during small strain sinusoidal deformation experiments. The experiments were performed in a deformation‐DIA combined with X‐radiography, at seismic frequencies (∼0.003–0.1 Hz), high pressure and temperatures up to ∼80% of melting temperature. Significant dissipation (0.077 ≤ Q−1(ω) ≤ 0.488) is observed along with frequency dependent softening of zinc's Young's modulus and an extremely small activation energy for creep (⩽7 kJ mol−1). In addition, during sinusoidal deformation the original microstructure is replaced by one with a reduced dislocation density and small, uniform, grain size. This combination of behavior collectively reflects a mode of deformation called “internal stress superplasticity”; this deformation mechanism is unique to anisotropic materials and activated by cyclic loading generating large internal stresses. Here we observe a new form of internal stress superplasticity, which we name as “elastic strain mismatch superplasticity.” In it the large stresses are caused by the compressional anisotropy. If this mechanism is also active in hcp‐iron and the Earth's inner‐core it will be a contributor to inner‐core observed seismic attenuation and constrain the maximum inner‐core grain‐size to ≲10 km.

Pre-softening HIP treatment enabled crack-healing and superior mechanical properties for René 142 superalloy fabricated via laser powder bed fusion

The generation of defects, such as cracks and pores, presents significant challenges for high-strength metals and alloys fabricated by the quick-emerging additive manufacturing technology, and subsequent post-processing treatments are often necessary before their practical applications. In this work, a novel heat treatment approach, involving a pre-softening treatment before hot isostatic pressing (HIP), is developed to facilitate the crack-healing in René 142 superalloy produced through laser powder bed fusion. Results demonstrate that René 142 alloy exhibits a propensity for severe cracking across a wide range of printing parameters, primarily in the form of solidification cracks and liquation cracks. These cracks are formed mainly due to a wide solidification range, the presence of a liquid film, and the concentration of residual stress. The pre-softening solution heat treatment significantly reduces dislocation density and residual stress levels, and the subsequent HIP together leads to a defect-free, dense structure for René 142 superalloy. Consequently, the René 142 alloy processed by the pre-softening HIP treatment achieves an excellent combination of yield strength (850 MPa), ultimate tensile strength (1227 MPa), and elongation (13.7 %), with pseudo-equiaxed grains (120–150 μm) and square γ′ precipitates (approximately 540 nm). These findings provide valuable insights for exploring crack elimination methods in other nickel-based superalloys fabricated through additive manufacturing.

Microstructural analysis of cold-drawn medium-carbon low-alloy martensite: effect of deformation and tempering temperature

Microstructure of cold-drawn (≈ 0.9 effective deformation) medium-carbon steel containing Cr and Mo, was investigated in samples tempered at 923 K (tempering at high temperature [HTT]) and 723 K (tempering at intermediate temperature [ITT]) using transmission electron microscopy, X-ray diffraction and microhardness. The study revealed distinct features in lath martensite. HTT samples showed reduced dislocation density and larger precipitates compared to ITT samples. After cold drawing, ITT samples exhibited lamellar dislocation cells and cell blocks, while HTT specimens primarily showed cell block structures. Analysis of precipitates revealed changes in orientation after drawing, as well as alterations in both inter- and intragranular precipitate density. ITT samples also displayed higher post-tempering hardness. This analysis provides quantitative insights into the microstructural evolution and mechanical behaviour after tempering and cold-drawing, which can help optimise processes for achieving ultrafine-grained structures.

Optimizing misfit dislocation glide kinetics for enhanced threading dislocation density reduction in Si1−xGex/Si(001) layers through dynamic growth rate control

Relaxed Si1−xGex layers on Si(001) serve as virtual substrates for strained Si or Ge layers. However, plastically relaxed layers inevitably contain misfit and threading dislocations, negatively affecting devices. Deposition of a SiGe layer on the backside of the substrate introduces a dislocation reservoir at the wafer edge that can reduce the threading dislocation density (TDD) of Si0.98Ge0.02/Si layers, as these preexisting dislocations start gliding toward the wafer center upon reaching the critical thickness. Here, we show that this low-strain system can be used effectively to study dislocation glide kinetics. In agreement with the literature, dislocation glide is a thermally activated process with an activation energy of 2.12–2.16 eV. Near the critical thickness, relaxation is sluggish and inefficient due to the linear dependence of the glide velocity on excess stress. At lower growth rates, dislocations from the edge reservoir are activated in a lower density due to the increase in the critical thickness through partial strain relaxation by already activated dislocations. Contrary to common models, here, the lowest possible growth rate is not essential for minimizing the TDD. Instead, a careful balance between low and high growth rates is beneficial. Overcoming the initial sluggish and inefficient relaxation phase is critical while also avoiding accumulation of strain energy, and, therefore, the activation of dislocation sources. Only in a later stage of buffer growth, the growth rate should be reduced to a minimum. With this method, the TDD of strain relaxed Si0.84Ge0.16 layers is reduced to 7 × 104 cm−2.

Regulating the microstructure and strength of the advancing side interface zone in AZ31 friction stir welded joint via localized selective remelting

Friction stir welding (FSW) is a solid-state welding technique widely used for various series of magnesium (Mg) alloys. However, in the process of transverse loading for FSW joints in Mg alloys, the ultimate fracture often occurs near the advancing side (AS) interface zone. To enhance the AS interface strength and overall joint strength, this research employed tungsten inert gas welding (TIG) arc to locally remelt the AS interface zone in the FSW-AZ31 joint. The microstructure characterization after remelting showed that two TIG melting zones were formed in the interface area between the AS and nugget zone (NZ). Within these zones, the grains exhibited significant coarsening and the texture intensity noticeably decreased. Conversely, the interface between the retreating side (RS) and NZ, being far from the TIG melting zone, experienced minimal changes in texture and grain size. Mechanical testing conducted at room temperature indicated that the joint ultimately fractured at the RS, resulting in an interface strength difference of ∼16 MPa between the AS and RS. The enhanced strength of the AS interface was attributed to the low Schmid factor of basal slip, reduced dislocation density, and pronounced twinning behavior.

Development of Nanopillar Arrays Nanopatterning Without Lift‐Off for Transferable GaN‐Based µLEDs

AbstractThe mass production of µLEDs requires an upscaling approach on 200 mm wafers, which implies the deployment of a technology that achieves zero defectivity without liftoff. In this report, Nanoimprint lithography (NIL) processing is successfully optimized for nanostructuring GaN‐based Silicon‐On‐Insulator (SOI) substrates. The etching of SiO2/GaN/AlN/Si/SiO2 layers using different plasmas is conducted and multi‐layer nanopillars 100–200 mm in diameter are fabricated. This approach generates zero‐defect arrays of pillars, which is particularly advantageous for the growth process. In addition, the SiO2 at the bottom of the pillar allows it to twist during the subsequent GaN regrowth, as this layer becomes soft at the growth temperature >1000 °C. This ability to deform enables a coalescence of pillars into layers with reduced dislocation density. As a result, high‐quality GaN microplatelets and µLEDs are grown via a bottom‐up approach based on pendeoepitaxy using metal–organic vapor phase epitaxy (MOVPE). The fabricated µLEDs have a very smooth surface with a roughness of 0.6 nm which facilitated the implementation of an easy and simple transfer protocol. Adhesive tape and metalmetal bonding, are used to bond the µLEDs onto a metal‐coated silicon substrate. The reported findings offer exciting new insights into the development of high‐performance displays.

Effect of Annealing Temperature on Microstructure and Properties of Solid Solution Extruded Mg–2.0Zn–1.0Y–0.5Zr Alloys

In this investigation, the effects of different annealing temperatures (180, 200, 220, 240, 260, and 280 °C) on the microstructure evolution and properties of an extruded Mg–2.0Zn–1.0Y–0.5Zr (wt%) magnesium alloys were determined. Optical microscopy (OM), scanning electron microscopy (SEM), immersion corrosion, electrochemical corrosion experiments, and tensile testing were performed. Research has found that combining hot extrusion with subsequent low-temperature annealing significantly improves the strength, plasticity, and corrosion resistance of alloys due to grain refinement and a reduced dislocation density. The alloy was completely recrystallized at an annealing temperature of 240 °C for 4 h after solid solution extrusion, and the grains were fine and uniform, demonstrating the best comprehensive properties. Its corrosion rate, ultimate tensile strength, yield strength, and elongation were 0.454 ± 0.023 mm/y, 346.7 ± 8.9 MPa, 292.4 ± 6.9 MPa, and 19.0 ± 0.4%, respectively. The corrosion mechanism of the specimens under extruded and annealed conditions was analyzed. After annealing at 240 °C for 4 h, the dislocation and bimodal grain structure of the samples were almost eliminated, resulting in uniform and fine grains, which were conducive to the formation of a more uniform and denser oxide film, thus improving the corrosion resistance of the alloy.