The mechanical strength of sintered nanoparticles (NPs) limits their application in advanced electronics packaging. In this study, we explore the anisotropy in the microstructure and mechanical properties of sintered copper (Cu) NPs by combining experimental techniques with molecular dynamics (MD) simulations. We establish a clear relationship between processing conditions, microstructural evolution, and resulting properties in pressure-assisted sintering of Cu NPs. Our findings reveal that pressure-assisted sintering induces significant anisotropy in the microstructure, as evidenced by variations in areal relative density and the orientation distribution of necks formed during sintering. Specifically, along the direction of applied pressure, the microstructure exhibits reduced variation in areal relative density and a higher prevalence of necks with favorable orientations. The resulting anisotropic mechanical properties, with significantly higher strength along the pressure direction compared to other directions, are demonstrated through micro-cantilever bending tests and tensile simulations. This anisotropy is further explained by the combined effects of strain localization (influenced by areal relative density) and the failure modes of necks (determined by their orientation relative to the loading direction). This work provides valuable insights into the analysis of sintered NPs microstructures and offers guidance for optimizing the sintering process.

Van der Waals heterojunctions (vdWHs) have garnered significant attention for their promising applications in optoelectronics, attributed to their exceptional physical attributes. In this study, we present a straightforward approach to fabricating high-performance vdWHs photodetectors. Specifically, we prepared WSO_x/WS₂ vdWH photodetectors through the ozone oxidation of a WS₂ thin films at 100 °C. To characterize the morphology and optical properties of both the WS₂ and WSO_x/WS₂ thin films, we utilized atomic force microscopy (AFM) and Raman spectroscopy. Additionally, X-ray photoelectron spectroscopy (XPS) was employed to delve into the structural evolution by scrutinizing the bonding states of W, O, and S in the WS₂ before and after the ozone oxidation process. The resultant WSO_x/WS₂ vdWH photodetectors exhibited impressive photoelectric performance at wavelengths of 475 nm and 532 nm. It demonstrated a high responsivity of 230.7 A/W, a remarkable specific detectivity of 1.794 × 10¹¹ Jones, and a swift response speed of 60 ms at 475 nm. Furthermore, first-principles calculations based on density functional theory (DFT) were conducted to validate the oxidation kinetics of monolayer WS₂, the type II energy band alignment, and the interlayer charge transfer within the WSO_x/WS₂ vdWH. This research contributes novel insights into the synthesis of two-dimensional transition metal oxides (TMOs)-transition metal dichalcogenides (TMDCs) heterostructures for photodetector applications.

This Letter presents a combined analytical and experimental method to effectively decouple the radial and tangential residual stress fields induced by Berkovich nanoindentation in single-crystalline 4H-SiC using micro-Raman spectroscopy. By integrating the Raman stress characterization model with Yoffe’s expanding cavity model, precise extraction of individual residual stress components around the indentation region is realized. Through the vertical backscattering micro-Raman mapping of the E2 phonon mode, we systematically investigate the residual stress distribution near the indentation. The results highlight significant anisotropy in nanoindentation-induced stress fields, strongly dependent on the crystal orientation of 4H-SiC, predominantly featuring radial tensile stress gradients. This comprehensive theoretical–experimental approach offers a robust optical framework for residual stress characterization in 4H-SiC and provides foundational insights for extending Raman spectroscopy-based stress characterization to other crystalline materials and related device structures.

With the miniaturization and high-power requirements of microelectronic devices, the current density carried by interconnects in packaging structures continually increases and reaches the threshold of electromigration (EM) failure. In this study, we investigated the microstructure evolution and void formation in aluminum (Al) interconnects during EM at three different current densities (1/3/5 MA/cm ²) and proposed a method coupling the fully coupled theory with an optimized atomic flux divergence method. The results show as follows. First, for the interconnects in integrated circuits, current density is the main factor affecting the EM lifetime of the interconnects in a certain temperature range. With the gradual increase of current density, the contribution of thermal transfer on EM cannot be ignored. The atomic concentration gradient and stress gradient can inhibit EM failure. Second, the increase of length and the decrease of width of interconnect will lead to the increase of atomic flux inside the structure, resulting in the accumulation of voids and atoms. Third, the structure is dynamically reconstructed after deleting the atoms below the failure threshold and the simulation results agree well with the experimental results. Compared with the traditional atomic flux divergence method, the improved atomic flux divergence method based on the fully coupled theory can better fit the change trend of atomic concentration after interconnect failure, and the failure time error is reduced by about 10%.

This study demonstrates a breakdown analysis of the dynamics of a liquid crystal elastomer (LCE) including quality check, geometric measurement, thermal characterization, and comparison of heat- and light-induced contractions. A blue light-responsive acrylate side chain LCE with 1% azobenzene dye was characterized. From a classical viewpoint, photo-thermal contraction is considered a dominating effect, while direct photo-mechanical deformation can be neglected due to a low dye percentage. However, the findings of this research suggest that a low percentage of azobenzene dye does not necessarily lead to heat-dominating dynamics of LCE. This phenomenon has not yet been quantitatively studied before. The approach reported in this Letter can potentially be used to extract the data to improve the dynamics models of light-driven LCEs.

This work addresses a novel technique for selecting the best process parameters for the 4H–SiC epitaxial layer in a horizontal hot-wall chemical vapor reactor using a transient multi-physical (thermal-fluid-chemical) simulation model and combined with a machine-learning model. An experiment was performed to validate the feasibility of the numerical model. Secondly, a single-factor analysis was conducted to investigate the effects of process parameters, including the deposition temperature, inlet-flow volume, rotational speed of the susceptor, and cavity pressure, on the quality of the 4H–SiC epitaxial layer. Finally, a machine learning algorithm, the ant colony optimization-back propagation neural network (ACO–BPNN), was employed to develop the input/output model and optimize process parameters for obtaining a high-quality epitaxial layer and reducing the optimization cycle and costs. Notably, the optimized process was validated by real experiments, where the error between calculation and experiment is 4.03 % for deposition rate and 0.49 % for coefficient of variation, respectively. The results highlight the model as reliable and lay the foundation for the CVD growth of the 4H–SiC epitaxial layer.

The power semiconductor joining technology through sintering of copper nanoparticles is well-suited for die attachment in wide bandgap (WBG) semiconductors, offering high electrical, thermal, and mechanical performances. However, sintered nanocopper will be prone to degradation resulting from corrosion in sulfur-containing corrosive environments such as offshore areas. In this study, experiments, including aging test and corrosion characterization, and simulations based on density functional theory (DFT) studies were conducted to explore the corrosion behavior and mechanism of elemental sulfur (S₈) and hydrogen sulfide (H₂S) on sintered nanocopper. The experimental results indicated that loose corrosion products were observed on the sintered nanocopper during the ageing process involving S₈, and compact layered corrosion products formed during the ageing process involving H₂S. Furthermore, similar corrosion product compositions (Cu₂O, Cu₂S, CuO, CuS, and potentially Cu₂SO₄ or CuSO₄) were observed in both the S₈- and H₂S-ageing processes. However, the S₈-ageing process exhibited more noticeable corrosion penetration. This was explained in simulations results: the unsaturated Cu sites on the oxide layer [Cu₂O(1 1 1)] of the sintered nanocopper could adsorb both H₂S and S₈, while the saturated Cu sites only exhibited the potential to adsorb S₈.

During operation in environments containing hydrogen sulfide (H₂S), such as in offshore and coastal environments, sintered nanoCu in power electronics is susceptible to degradation caused by corrosion. In this study, experimental and molecular dynamics (MD) simulation analyses were conducted to investigate the evolution and mechanism of H₂S-induced corrosion of sintered nanoCu, and bulk Cu was used as the reference. The following results are obtained: (1) Both sintered nanoCu and bulk Cu reacted with O₂ prior to reacting with H₂S, forming Cu₂O, Cu₂S, CuO, and CuS. In addition, sintered nanoCu exhibited more severe corrosion. (2) For both sintered nanoCu and bulk Cu, H₂S-induced corrosion resulted in the deterioration of electrical, thermal, and mechanical properties, and sintered nanoCu experienced a greater extent of deterioration. (3) As was ascertained through Reactive Force Field (ReaxFF) MD simulations, the penetration of H₂S and O₂ combined with the upward migration of Cu resulted in the formation of a corrosion film. In addition, compared to bulk Cu, the H₂S and O₂ penetration in the sintered nanoCu structure was observed to occur to a greater depth, accounting for the more pronounced performance degradation.

Nano-metal materials have received considerable attention because of their promising performance in wide bandgap semiconductor packaging. In this study, molecular dynamics (MD) simulation was performed to simulate the nano-Cu sintering mechanism and the subsequent mechanical behaviors. Hybrid sintering, comprising nanosphere (NS) and nanoflake (NF), was performed at temperatures from 500 to 650 K. Furthermore, shear and tensile simulations were conducted with constant strain rates on the sintered structure at multiple temperatures. Subsequently, the extracted mechanical properties were correlated with the sintering behavior. The results revealed that the mechanical properties of the nano-Cu sintered structure could be improved by tuning material composition and increasing the sintering temperature. We established a relationship between the sintered microstructure and mechanical response. The shear modulus and shear strength of the sintered structure with NF particles increased to 41.20 and 3.51 GPa respectively. Furthermore, the elastic modulus increased to 55.60, and the tensile strength increased to 4.88 GPa. This result provides insights into the preparation phase of nano-Cu paste for sintering technology.

MAlSiN₃:Eu²⁺ (M = Ca, Sr) is commonly used in high-power phosphor-converted white-light-emitting diodes and laser diodes to promote their color-rendering index. However, the wide application of this phosphor is limited by the degradation of its luminescent properties in high-temperature, high-humidity, and high-sulfur-content environment. Here, the degradation mechanism of the (Sr,Ca)AlSiN₃:Eu²⁺ (SCASN) red phosphor under thermal-moisture-sulfur coupling conditions is investigated. Furthermore, by performing first-principles calculations, the hydrolysis mechanism on an atomic scale is assessed. The adsorption energy (E_ads) and charge transfer (ΔQ) results showed that H₂O chemically adsorbed on the (0 1 0), (3 1 0), and (0 0 1) surfaces of the CaAlSiN₃ (CASN) host lattice. The energy barrier for H₂O dissociation is only 29.73 kJ mol⁻¹ on the CASN (0 1 0) surface, indicating a high dissociation probability. The formation of NH₃, Ca(OH)₂, and CaAl₂Si₂O₈ is confirmed by H⁺ tended to combine with surface N atoms, while OH⁻ combined with the surface Al/Si or Ca atoms. Moreover, ab initio molecular dynamics simulations were performed to further understand the hydrolysis process. This work offers a guidance on the design and applications of luminescent materials in LED packages with higher reliability and stability requirements in harsh environment.

Corrosion protection is one of the most important issues when copper is applied in power electronics packaging as bonding wire, die attachment, interconnection, and DBC substrate. Covering a layer of corrosion-resistant encapsulation material is a worthy consideration to protect copper. In this paper, the corrosion-resistant effects of two organic encapsulation materials, polydimethylsiloxane (PDMS) and hexamethyldisiloxane (HMDSO), on the copper surface were performed by molecular dynamics simulations. Firstly, the Cu-coating bilayer models were constructed, and the binding performances of the encapsulation material/copper interface were evaluated through calculating their interaction energy, proving that the organic coatings can form interconnection on copper surface. Then, the diffusion processes of corrosive gas molecules (H₂S, H₂O and O₂) into the copper layer under different coating conditions were simulated, and both coatings exhibited good corrosion protection performances. The above results indicate that both PDMS and HMDSO have promising potential for copper corrosion protection in power electronics packaging. This may provide some guidance for corrosion protection of copper material used in power electronics packaging.

Sintered nanocopper (nanoCu) paste, exhibiting excellent electrical, thermal, and mechanical performances, offers promise for interconnections in wide bandgap (WBG) semiconductors operating at higher temperatures. However, sintered nanoCu is prone to severe corrosion in environments containing H2S, with on-site characterization methods for the composition of corrosion products currently lacking. In this study, a novel method was proposed for the rapid characterization of corrosion products during the corrosion process based on hyperspectral imaging (HSI) technology. Sintered nanoCu samples were subjected to 336 h H2S gas corrosion tests with bulk Cu as the reference, followed by correlating the corrosion element content with hyperspectral characteristic parameters. Then, the morphology and composition of corrosion products were researched using focused ion beam scanning electron microscope (FIB-SEM) and transmission electron microscope (TEM) analysis. The results showed that (1) during the corrosion process, a linear relationship was established between the Cu, O elemental atomic contents on the sample surfaces and their hyperspectral characteristic parameters. (2) The elemental atomic content of S exhibited an exponential relationship with the characteristic parameter. (3) The change rate in the spectral characteristic parameters during the corrosion process reflected the severity of corrosion, which was confirmed by comparing the thickness of the corrosion products of the sintered nanoCu and bulk Cu. This study offers a foundation for the further investigation of rapid on-site characterization of sintered nanoCu corrosion involving H2S.

Driven by the increasing demand for high-power systems, ceramic substrates have received more attention for handling higher power density. Warpage in active metal brazed (AMB) ceramic substrate becomes a critical issue as it can deteriorate the reliability performance. This study comprises three phases, including investigation of the cause of the warpage, validation of the proposed model, and optimization for effective warpage management. At first, the coefficient of thermal expansion (CTE) and yield strength of the copper (Cu) layer in AMB were characterized and adopted in a two-dimensional (2D) finite element model. The evolution of simulated strain and moments revealed the cause of the warpage during the manufacturing processes. Furthermore, the 2D model was extended to a three-dimensional (3D) model. The finite element method (FEM) and experiments were conducted on different heat treatment conditions for 3D model validation. The validated 3D model was applied to carry out a design of experiments (DoEs) for design optimization to reduce the warpage. Consequently, the factor analysis in DoEs was demonstrated by different pattern designs using subtractive milling techniques.

Silicon carbide (SiC) devices have shown definite advantages over Si counterparts in high-temperature, high-voltage, and high-frequency applications. To fully exploit the potentiality of SiC devices in high temperatures, die-attach materials that can withstand high temperatures for a long time are required in the power electronics packaging. In this article, the high-temperature die-attach materials, such as high-temperature solders and transient liquid-phase bonding materials, were reviewed first. Then, metallic (mainly Ag and Cu) nanoparticles (NPs) sintering technologies were thoroughly overviewed. The metallic NPs sintering materials, metallic NPs sintering process, and interface and reliability were analyzed, respectively. Finally, the challenges and outlook of promising Cu NPs sintering technology were discussed.

4H-SiC is widely used in power electronics owing to its superior physical properties. However, temperature-induced stresses compromise the reliability of 4H-SiC power devices in high-temperature applications, warranting precise, and nondestructive stress characterization responsive to temperature variations. Herein, a temperature-dependent predictive model is proposed for analyzing the Raman shift–stress in 4H-SiC. The 4H-SiC epitaxial samples prepared via chemical vapor deposition are characterized using in situ variable-temperature Raman spectroscopy, resulting in a temperature correction factor of approximately −0.021 cm−1 K−1, which is integrated into the conventional Raman shift–stress relationship to assess stress variations induced by temperature variations. The elastic modulus tensor of 4H-SiC at various temperatures determined using molecular dynamics simulations indicates a linear reduction in modulus with increasing temperature. This variable temperature modulus is incorporated into the Raman shift–stress relationship. Furthermore, a finite element method is used for model simplification to perform stress calculations in three axial directions. The experimental results confirm the consistency between calculated and experimental values with a 10% error range under the uniaxial stress condition. The study findings provide valuable insights into assessing stress evolution in 4H-SiC under temperature variations based on Raman spectroscopy, thereby advancing the application of spectroscopic techniques in material stress detection.

In the domain of power electronics, especially for applications requiring high power, high temperature, and high frequency, Silicon Carbide Metal Oxide Semiconductor Field-Effect Transistors (SiC MOSFETs) stand out due to their excellent properties such as high thermal conductivity, elevated breakdown electric field, and minimal power loss. These devices are pivotal in the reliability and safety of electric vehicles, where avalanche-induced failures represent a significant risk within automotive uses. This study extensively explores the avalanche ruggedness of both planar and trench SiC MOSFET configurations through a combination of Unclamped Inductive Switching (UIS) testing in single and multiple pulse scenarios, and Technology Computer-Aided Design (TCAD) simulations. Initial UIS experiments revealed the primary failure mechanisms and their origins in SiC MOSFETs. Following empirical analysis, TCAD simulations were employed to develop comprehensive models of these devices., enhancing the understanding of failure dynamics during UIS conditions. The integration of empirical and simulation data supports the creation of advanced strategies to reduce the risk of avalanche failures, thereby enhancing the durability and reliability of Wide Bandgap Semiconductor devices.

This study presents a dual approach combining molecular dynamics simulations and experimental analysis to explore the sintering behavior of copper (Cu) nanoparticles. Our simulation model comprises 240 nanoparticles, through which we systematically examine the coalescence kinetics during the sintering process. The simulations provide a detailed view of the particle interactions, structural evolution, and the mechanisms driving nanoparticle fusion at the atomic level. Complementing the simulations, we conducted 3D reconstructions using Focused Ion Beam Scanning Electron Microscopy (FIB-SEM) to characterize the microstructure of the sintered nanoparticles. This hybrid approach not only deepens our understanding of the fundamental processes governing the sintering of Cu nanoparticles but also bridges the gap between theoretical predictions and experimental observations, offering insights into the optimization of sintering processes in practical applications.

Tungsten disulfide (WS2) has recently attracted considerable attention owing to its excellent physical, chemical, electronic, and optical properties, leading to increased research into its applications in electronic and optoelectronic devices. However, the oxidation of 2D material affects significantly its optical and electronic properties during storage or processing. This study employs density functional theory (DFT) to analyze the effects of natural and thermal oxidation on the optical and electronic properties of WS2 monolayer. First, the climbing-image nudged elastic band (cNEB) method is applied to analyze transitional states and the potential barriers of WS2 oxidation. It reveals that primarily involves the bonding of oxygen atoms with sulfur atoms, whereas thermal oxidation introduces both oxygen substitutions and generates oxygen vacancies. Second, the electron band structures after natural and thermal oxidation are comparably analyzed, which reveals that natural and thermal oxidation both can narrow the bandgap. Lastly, we investigate the optical properties of WS2 monolayer under different oxidation conditions. The results demonstrate that natural oxidation results in weakened light absorption and a blue shift relative to the pristine WS2, whereas thermal oxidation enhances absorption and induces a red shift. These findings underscore the importance of carefully managing oxidation conditions to effectively modulate the optoelectronic properties of WS2.

High-power white light-emitting diodes (LEDs) have demonstrated superior efficiency and reliability compared to traditional white light sources. However, ensuring maximum performance for a prolonged lifetime use presents a significant challenge for manufacturers and end users, especially in safety–critical applications. Thus, identifying functional anomalies and predicting the remaining useful lifetime (RUL) is of enormous importance in the operational longevity of the device. To address such challenges, this study proposes a combination of distance-based Mahalanobis distance (MD), entropy generation rate (EGR), and deep learning models for improved anomaly detection and RUL prediction accuracy. Unlike conventional health indicators based on luminous flux data that are challenging to monitor relevant optical performance, the MD and EGR methods are employed to extract in-situ monitored thermal and electrical data as new health indicators. Long short-term memory recurrent neural networks (LSTM-RNN) and convolutional neural networks (CNN) are established to detect anomalies and predict the RUL. The accelerated degradation tests of 3 W high-power white LED have been conducted, and the online and offline collected experimental data are deployed for model development and performance evaluation. The performance of the proposed methods is compared against the Illuminating Engineering Society of North America (IESNA) TM-21 method. The results indicate that LSTM-RNN, when combined with either MD or EGR, can detect anomalies with significantly fewer data (70 %) than is typically required. Furthermore, a significant improvement in prediction accuracy in RUL prediction based on MD and EGR-constructed time series health indicators and employed with the LSTM-RNN model demonstrates the effectiveness of the proposed methods.

The nano-copper particles are widely used in the sintering processes of packaging wide bandgap semiconductors. Despite the significant success in the industry, the mechanism bridging the sintering process to the mechanical properties of sintered nano-copper is not yet well-modeled. In this paper, the impacts of different sintering temperatures and initial porosities caused by different stacking patterns on the uniaxial tensile performance of the sintered layer were studied via a molecular dynamics approach. Two stacking patterns, simple cubic and face-centered cubic, were simulated, respectively. Evolution of their structure at temperatures of 300, 400, 500, and 600 K were simulated as the sintering process. Afterward, the sintered structures were subjected to uniaxial tensile with rates of 0.01 and 0.04 Å/ps at different temperatures to compare the mechanical properties. The results show that the sintering rate and density of the sintered structure increase with a higher temperature. However, the tensile strength of the sintered structure is less relevant to the difference in stacking pattern. This study proves that porosity has a greater effect on sintering quality.