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Si-based group III-V material enables a multitude of applications and functionalities of the novel optoelectronic integration chips (OEICs) owing to their excellent optoelectronic properties and compatibility with the mature Si CMOS process technology. To achieve high performance OEICs, the crystal quality of the group III-V epitaxial layer plays an extremely vital role. However, there are several challenges for high quality group III-V material growth on Si, such as a large lattice mismatch, highly thermal expansion coefficient difference, and huge dissimilarity between group III-V material and Si, which inevitably leads to the formation of high threading dislocation densities (TDDs) and anti-phase boundaries (APBs). In view of the above-mentioned growth problems, this review details the defects formation and defects suppression methods to grow III-V materials on Si substrate (such as GaAs and InP), so as to give readers a full understanding on the group III-V hetero-epitaxial growth on Si substrates. Based on the previous literature investigation, two main concepts (global growth and selective epitaxial growth (SEG)) were proposed. Besides, we highlight the advanced technologies, such as the miscut substrate, multi-type buffer layer, strain superlattice (SLs), and epitaxial lateral overgrowth (ELO), to decrease the TDDs and APBs. To achieve high performance OEICs, the growth strategy and development trend for group III-V material on Si platform were also emphasized.

Crystallographic defects in noble metal nanocrystals are recognized as highly active catalytic sites, significantly enhancing activities in many important reactions. Despite their importance, synthesizing noble metal nanocrystals with a high density of defects poses a considerable synthetic challenge. Here, we present a novel lattice mismatch-induced formation mechanism to create high-density defects in noble metal nanocrystals. This approach takes advantage of lattice mismatch to enable non-epitaxial nucleation and growth of a noble metal on a foreign metal substrate, forming abundant noble metal crystallites with random lattice orientations not dictated by the substrate lattice. As these crystallites grow extensively, they merge, forming numerous grain boundaries and yielding defect-rich noble metal nanocrystals. Defect-rich alloy nanocrystals can also be synthesized through a subsequent vacancy-diffusion alloying process. We take defective PdCu alloy nanocages as an example and demonstrate the effectiveness of crystallographic defects in enhancing catalytic performance of noble metal nanocrystals. The nanocages exhibit superior activity in the electrocatalytic formic acid oxidation reaction, which is 1.6 times greater than their defect-free counterparts. Our strategy offers a new avenue for creating defect-rich noble metal nanocrystals as highly efficient catalysts for a wide array of catalytic applications.

Phase engineering of nanomaterials opens a promising gateway to the construction of noble metal hierarchical heterostructures in a well‐defined manner. Here, by using zero‐dimensional (0D) Pd nanoparticles with hexagonal close‐packed (hcp, 2H type) phase, denoted as 2H‐Pd, as seeds, we report a facet‐selective epitaxial growth method to prepare two‐dimensional (2D)/0D Pd@Rh hierarchical heterostructures, in which two parallel triangular Rh nanoplates selectively grow on two opposite (002)h facets of 2H‐Pd due to the confined growth of Rh along h direction. Systematic characterizations demonstrate that a phase transformation from 2H phase to 2H/face‐centered cubic (fcc) heterophase occurs during the formation of such 2D/0D hierarchical heterostructure with the continuous growth of Rh nanoplates. The obtained 2D/0D Pd@Rh hierarchical heterostructures with a Pd/Rh atomic ratio of ∼39/61, denoted as Pd39@Rh61, exhibit excellent performance toward electrochemical hydrogen evolution reaction (HER) in acid electrolyte. To reach the current density of 10 mA cm–2, the overpotential of only 21.3 mV is required for the 2D/0D Pd39@Rh61, which is comparable to commercial Pt/C and also among the best Rh‐based HER catalysts reported until now. Key Points The rational synthesis of novel 2D/0D Pd@Rh hierarchical heterostructures via the facet‐selective epitaxial growth of Rh nanoplates on Pd nanoparticles with an unconventional 2H phase is realized. Two parallel triangular Rh nanoplates selectively grow on two opposite (002)h facets of 2H‐Pd due to the confined growth of Rh along h direction. 2D/0D Pd@Rh hierarchical heterostructures exhibit excellent performance toward electrochemical hydrogen evolution reaction in acid electrolyte. 2D/0D Pd@Rh hierarchical heterostructures have been prepared via the facet‐selective epitaxial growth of two parallel triangular Rh nanoplates on two opposite (002)h facets of unconventional 2H‐Pd nanoparticles. Such hierarchical heterostructures exhibit excellent performance toward electrochemical hydrogen evolution reaction in acid electrolyte.

Two‐dimensional/three‐dimensional (2D/3D) halide perovskite heterojunctions are widely used to improve the efficiency and stability of perovskite solar cells. However, interfacial defects between the 2D and 3D perovskites and the poor coverage of the 2D capping layer still hinder long‐term stability and homogeneous charge extraction. Herein, a surface planarization strategy on 3D perovskite is developed that enables an epitaxial growth of uniform 2D/3D perovskite heterojunction via a vapor‐assisted process. The homogeneous charge extraction and suppression of interfacial nonradiative recombination is achieved by forming a uniform 2D/3D interface. As a result, a stabilized power output efficiency of 25.97% is achieved by using a 3D perovskite composition with a bandgap of 1.55 eV. To demonstrate the universality of the strategy applied for different perovskites, the champion device based on a 1.57 eV bandgap 3D perovskite results in an efficiency of 25.31% with a record fill factor of 87.6%. Additionally, perovskite solar modules achieve a designated area (24.04 cm2) certified efficiency of 20.75% with a high fill factor of 80.0%. Importantly, the encapsulated uniform 2D/3D modules retain 96.9% of the initial efficiency after 1246 h operational tracking under 65 °C (ISOS‐L‐3 protocol) and 91.1% after 862 h under the ISOS‐O‐1 protocol. By employing a surface planarization strategy, a uniform and dense p‐i‐n 2D/3D heterojunction is successfully developed. This approach has enabled planarized 2D/3D PSCs and modules to achieve remarkable efficiencies of 26.02% for a 0.1 cm2 area and 23.06% for a 22.8 cm2 area, primarily by suppressing interface nonradiative recombination. Additionally, these devices exhibit exceptional operational stability under accelerated testing protocols.

This paper aims to investigate the unique substructure and grain growth of 316L stainless steel processed by selective laser melting (SLM) and clarify the mechanism. Results showed that the grain orientation on the x-z plane parallel to the build direction was the same type as the y-z plane, which all grow along the heat flow direction to form elongated columnar grains passing through the multi-layer fusion line. The epitaxial growth direction of grains changed abruptly with the vary of temperature gradient direction. Moreover, to expound the substructure formation based on solidification theory, a finite element model was established to obtain the distribution map of cooling rate G × R and solidified morphology G/R.

HighlightsA facile and effective epitaxial-like growth strategy is applied to fabricate the NiSe2/Ni(OH)2 heterojunction composite.The assembled asymmetric supercapacitor based on the heterojunction composite surpasses most of the reported results. It is the first time that the powdered electrode materials can have such large capacity, high rate, and extreme long cycle life.Constructing heterojunction is a promising way to improve the charge transfer efficiency and can thus promote the electrochemical properties. Herein, a facile and effective epitaxial-like growth strategy is applied to NiSe2 nano-octahedra to fabricate the NiSe2-(100)/Ni(OH)2-(110) heterojunction. The heterojunction composite and Ni(OH)2 (performing high electrochemical activity) is ideal high-rate battery-type supercapacitor electrode. The NiSe2/Ni(OH)2 electrode exhibits a high specific capacity of 909 C g−1 at 1 A g−1 and 597 C g−1 at 20 A g−1. The assembled asymmetric supercapacitor composed of the NiSe2/Ni(OH)2 cathode and p-phenylenediamine-functional reduced graphene oxide anode achieves an ultrahigh specific capacity of 303 C g−1 at 1 A g−1 and a superior energy density of 76.1 Wh kg−1 at 906 W kg−1, as well as an outstanding cycling stability of 82% retention for 8000 cycles at 10 A g−1. To the best of our knowledge, this is the first example of NiSe2/Ni(OH)2 heterojunction exhibiting such remarkable supercapacitor performance. This work not only provides a promising candidate for next-generation energy storage device but also offers a possible universal strategy to fabricate metal selenides/metal hydroxides heterojunctions.

This study provides experimental evidence regarding the mechanism of gallium nitride (GaN) selective-area growth (SAG) on a polished plateau-patterned sapphire substrate (PP-PSS), on which aluminum nitride (AlN) buffer layers are deposited under the same deposition conditions. The SAG of GaN was only observed on the plateau region of the PP-PSS, irrespective of the number of growth cycles. Indirect samples deposited on the bare c-plane substrate were prepared to determine the difference between the AlN buffer layers in the plateau region and silicon oxide (SiO2). The AlN buffer layer in the plateau region exhibited a higher surface energy, and its crystal orientation is indicated by AlN [001]. In contrast, regions other than the plateau region did not exhibit crystallinity and presented lower surface energies. The direct analysis results of PP-PSS using transmission electron microscopy (TEM) and electron backscattered diffraction (EBSD) are similar to the results of the indirect samples. Therefore, under the same conditions, the GaN SAG of the deposited layer is related to crystallinity, crystal orientation, and surface energy.

This study presents a novel method to control the site‐selective growth of Au nanostars on CuS nanodisc substrate, it indicates that the surfactant ligands play a key role in the architecture control, only CTAC and homologous series with appropriate affinity to CuS can direct the annular‐epitaxial growth of Au nanoparticles on the CuS, which demonstrates superior peroxidase (POD)‐mimic and SERS activity. Mechanistic studies indicate that plasmon‐enhanced catalytic and SERS activity can be attributed to the spatially separated CuS‐Au heterostructure, which supports the light‐triggered hot electron‐hole pairs production and localized surface plasmon resonance hotspots. For practical biosensing, the CuS‐Au heterostructures assembled lateral flow assay (LFA) was used for SERS/catalytic colorimetric/photothermal three‐mode detection of Streptococcus pneumoniae and Klebsiella pneumoniae, with visually colorimetric mode at 103 CFU/mL and quantitative SERS/photothermal modes at 2–102 CFU/mL within 15 min, 15 clinical samples were used to validate the assay, the result was 100% concordant to the results of quantitative real‐time PCR. This study provides a unique avenue to controllably produce plasmon‐enhanced nanozyme, which can provide multi‐mode signals for LFA application and meet the requirements of different scenarios. CuS‐Au heterostructures were synthesized via ligand‐regulated annular‐epitaxial growth strategy, biotin‐Concanavalin A (ConA) was modified on the CuS‐Au heterostructures for universal bacterial‐labelling, assembled with strip, Streptococcus pneumoniae and Klebsiella pneumoniae can be sensitively recognized by SERS/colorimetric/temperature three‐mode signals within 20 min simultaneously.

In this manuscript, a novel dual-step selective epitaxy growth (SEG) of Ge was proposed to significantly decrease the defect density and to create fully strained relaxed Ge on a Si substrate. With the single-step SEG of Ge, the threading defect density (TDD) was successfully decreased from 2.9 × 107 cm−2 in a globally grown Ge layer to 3.2 × 105 cm−2 for a single-step SEG and to 2.84 × 105 cm−2 for the dual-step SEG of the Ge layer. This means that by introducing a single SEG step, the defect density could be reduced by two orders of magnitude, but this reduction could be further decreased by only 11.3% by introducing the second SEG step. The final root mean square (RMS) of the surface roughness was 0.64 nm. The strain has also been modulated along the cross-section of the sample. Tensile strain appears in the first global Ge layer, compressive strain in the single-step Ge layer and fully strain relaxation in the dual-step Ge layer. The material characterization was locally performed at different points by high resolution transmission electron microscopy, while it was globally performed by high resolution X-ray diffraction and photoluminescence.

Highlights A versatile selective epitaxial growth strategy was developed for fabricating perovskite single-crystal heterojunction arrays, enabling precise control over pixel size, arrangement angle, and crystal orientation. The self-powered photodetector arrays based on the single-crystal heterojunction exhibited high sensitivity with a weak-light detection limit of 9 nW cm −2 , long-term operational stability, and clear imaging capability under zero bias. Perovskite single-crystal heterojunction arrays exhibit significant application potential in advanced optoelectronics, however, achieving comprehensive control over crystallographic and spatial properties of the array remains challenging. Here, we report a selective epitaxial growth strategy for fabricating single-crystal MAPbCl 3 /MAPbBr 3 and MAPbBr 3 /MAPbI 3 heterojunction arrays. This method employs patterned polymer templates to define the pixel dimension and arrangement, while the underlying single-crystal substrate guides the crystal orientation of the heterojunction array, enabling precise control over the pixel size, pixel arrangement angle and crystal plane. The self-powered photodetector arrays were fabricated based on these heterojunctions, showing a specific detectivity of 6.0 × 10 11 Jones, a weak-light detection limit of 9 nW cm −2 and long-term operation stability under zero bias. Furthermore, the light pattern with different illumination intensities could be clearly imaged by the device array in the self-powered mode. This work establishes a robust method of fabricating the single-crystal heterojunction arrays for advanced optoelectronic applications.