Search Results (91)

Aluminum nitride (AlN), a III-V wide-bandgap semiconductor, has attracted significant attention for high-temperature and high-power applications. However, achieving p-type doping in AlN remains challenging. In this study, p-type AlN thin films were fabricated via magnetron sputtering using Mg-Al alloy targets with varying Mg concentrations (0.01 at.%, 0.02 at.%, and 0.5 at.%), followed by ex situ high-temperature annealing to facilitate Mg diffusion and electrical activation. The structural, morphological, and electrical properties of the films were systematically characterized using X-ray diffraction (XRD), white light interferometry (WLI), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and Hall effect measurements. The results demonstrate that at a Mg doping concentration of 0.02 at.%, the films exhibit optimal crystallinity, uniform Mg distribution, and a favorable balance between carrier concentration and mobility, resulting in effective p-type conductivity. Increasing Mg doping leads to higher surface roughness and the formation of columnar and conical grain structures. While high Mg doping (0.5 at.%) significantly increases carrier concentration and decreases resistivity, it also reduces mobility due to enhanced impurity and carrier–carrier scattering, negatively impacting hole transport. XPS and EDS analyses confirm Mg incorporation and the formation of Mg-N and Al-Mg bonds. Overall, this study indicates that controlled Mg doping combined with high-temperature annealing can achieve p-type AlN films to a certain extent, though mobility and carrier activation remain limited, providing guidance for the development of high-performance AlN-based bipolar devices. Full article

Silicon carbide (SiC) is widely utilized in semiconductors, microelectronics, optoelectronics, and other advanced technologies. However, its inherent characteristics, such as its hardness, brittleness, and high chemical stability, limit the processing efficiency and application of SiC wafers. This study explores the use of plasma etching as a pre-treatment step before chemical mechanical polishing (CMP) to enhance the material removal rate and improve CMP efficiency. Experiments were designed based on the Taguchi method to investigate the etching rate of plasma under various processing parameters, including applied power, nozzle-to-substrate distance, and etching time. The experimental results indicate that the etching rate is directly proportional to the applied power and increases with nozzle-to-substrate distance within 3–5 mm, while it is independent of etching time. A maximum etching rate of 5.99 μm/min is achieved under optimal conditions. And the etching mechanism and microstructural changes in SiC during plasma etching were analyzed using X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), white light interferometry, and ultra-depth-of-field microscopy. XPS confirmed the formation of a softened SiO₂ layer, which reduces hardness and enhances CMP efficiency; SEM revealed that etching pits form in relation to distance; and white light interferometry demonstrated that etching causes a smooth surface to become rough. Additionally, surface defects resulting from the etching process were analyzed to reveal the underlying reaction mechanism. Full article

White-light interferometry is essential for surface topography measurement in precision manufacturing, yet existing algorithms face challenges in accuracy, speed, and robustness. Motivated by the application of deep learning in optical metrology, this study presents a novel simulation-driven, end-to-end deep learning approach that significantly advances white-light interference topography reconstruction. Validation with 200 simulated interferograms shows strong agreement with reference measurements. The neural network processes interferograms in <0.4 s with <0.3% calculation error, demonstrating real-time capability and noise robustness. Using simulated and experimental data from trapezoidal gratings, the method achieves a reconstruction error of 47.12 nm (<λ/8, λ ≈ 550 nm), outperforming traditional techniques by 9.0%. These results confirm the method’s superior accuracy, speed, and reliability for industrial metrology applications. Full article

Mesoporous silicon dioxide films have been shown to be well suited as adhesion-promoting interlayers for generating high-strength polymer–metal interfaces. These films can be fabricated via microwave plasma-enhanced chemical vapor deposition using the precursor hexamethyldisiloxane and oxygen as working gas. The resulting mesoporous structures enable polymer infiltration during overmolding, which leads to a nanoscale form-locking mechanism after solidification. This mechanism allows for efficient stress transfer across the interface and makes the resulting adhesion highly dependent on the morphology of the deposited film. To gain a deeper understanding of the underlying deposition mechanisms and improve process stability, this work investigates the growth behavior of mesoporous silica films using a multiple regression analysis approach. The seven process parameters coating time, distance, chamber pressure, substrate temperature, flow rate, plasma pulse duration, and pause-to-pulse ratio were systematically varied within a Design of Experiments framework. The resulting films were characterized by their free surface area, mean agglomerate diameter, and film thickness using digital image analysis, white light interferometry, and atomic force microscopy. The deposited films exhibit a wide range of morphological appearances, ranging from quasi-dense to dust-like structures. As part of this research, the free surface area varied from 15 to 55 percent, the mean agglomerate diameter from 17 to 126 nm, and the film thickness from 35 to 1600 nm. The derived growth model describes the deposition process with high statistical accuracy. Furthermore, all coatings were overmolded via injection molding and subjected to mechanical testing, allowing a direct correlation between film morphology and their performance as adhesion-promoting interlayers. Full article

Predicting the wear of disc cutters in Tunnel Boring Machines (TBMs) is a complex challenge due to the large scale of the machinery and the numerous operational variables involved. Laboratory-scale tests offer a controlled approach to isolating and analyzing specific wear mechanisms. However, the extremely low wear rates observed in such simulations pose challenges for conventional characterization methods, as gravimetric and profilometric techniques often lack the precision and accuracy needed to measure low wear patterns with an uneven morphology. To address this, this study revisited a methodology for quantifying low wear rates in a reciprocating wear test using AISI H13 tool steel disc cutters. This approach integrates spherical indentation marks as reference points with 3D white-light interferometry, enabling high-precision material loss measurements. Eighteen disc samples were subjected to wear testing, with 3 indentations analyzed per sample, for a total of 54 indentations. The statistical validation confirmed the method’s reproducibility and reliability. The proposed approach provides a robust alternative to existing techniques, addressing a critical gap regarding the accurate quantification of low wear rates in controlled laboratory settings. Full article

Titanium nitride (TiN) is a widely used industrial hard coating material, known for its excellent hardness and chemical stability. However, its relatively high coefficient of friction (COF) often leads to interfacial heat accumulation and adhesive wear during service, limiting its applicability in high-temperature tribological environments. To enhance its tribological performance, a TiN–WS₂ soft–hard composite coating was fabricated on cemented carbide substrates using reactive co-sputtering magnetron deposition. By adjusting the sputtering parameters and target power ratio, a synergistic deposition of the hard (TiN) and lubricating (WS₂) phases was achieved and compared with a pure TiN coating. The results revealed that the incorporation of WS₂ significantly reduced the COF at both room temperature (25 °C) and an elevated temperature (200 °C), with the average values decreasing from 0.61 to 0.39 at 25 °C and from 0.53 to 0.36 at 200 °C. A white light interferometry analysis showed that the TiN–WS₂ coating exhibited narrower wear tracks and less surface damage than TiN at elevated temperatures, demonstrating superior friction-reducing and wear-resistant capabilities. In terms of mechanical properties, the composite coating showed a reduction in the hardness, the reduced elastic modulus (Er), and the adhesion strength by 27.3%, 19.8%, and 9.5%, respectively, compared to pure TiN. These findings indicate that the introduction of a quantitatively controlled lubricating WS₂ phase allows for a balance between nanoscale hardness and wear resistance, offering promising potential for engineering applications under complex working conditions. Full article

Fiber-optic Fabry–Pérot (F–P) sensors offer significant potential for non-invasive hemodynamic monitoring, but existing sensing systems face limitations in multi-channel measurement capabilities and dynamic demodulation accuracy. This study introduces a sparse-frequency-scanning white-light interferometry (SFS-WLI) system with an adaptive mode-locked cross-correlation (MLCC) algorithm to address these challenges. The system leverages telecom-grade semiconductor lasers (191.2–196.15 THz sweep range, 50 GHz step) and a Fibonacci-optimized MLCC algorithm to achieve real-time cavity length demodulation at 5 kHz. Compared to normal MLCC algorithm, the Fibonacci-optimized algorithm reduces the number of computational iterations by 57 times while maintaining sub-nanometer resolution under dynamic perturbations. Experimental validation demonstrated a carotid–radial pulse wave velocity of 5.12 m/s in a healthy male volunteer. This work provides a scalable and cost-effective solution for cardiovascular monitoring with potential applications in point-of-care testing (POCT) and telemedicine. Full article

Objectives: This study evaluates the effectiveness of laser surface texturing (LST) using a Surface Transition Machine (STM) on pre-sintered zirconia, comparing its impact on surface characteristics and shear bond strength (SBS) with resin cement to conventional sandblasting techniques. Methods: Zirconia specimens were treated with either STM or sandblasting, followed by surface analysis through scanning electron microscopy (SEM) and White Light Interferometry (WLI), wettability assessment via contact angle measurements, and SBS testing with resin cement and a 10-MDP-containing primer. Results: SEM and WLI revealed significant surface alterations in STM-treated zirconia, producing microscale textures. STM-treated surfaces exhibited significantly lower contact angles (28.4 ± 10.0°) compared to untreated (78.2 ± 8.0°) and sandblasted (79.2 ± 5.7°) surfaces, indicating enhanced wettability (p < 0.05). SBS was highest in the STM with primer group (46.3 ± 8.3 MPa) and STM without primer (43.4 ± 4.3 MPa), both of which significantly outperformed sandblasting with primer (30.06 ± 3.09 MPa) and sandblasting alone (9.8 ± 3.7 MPa) (p < 0.05). Conclusions: These findings suggest that STM-based LST is a more effective method for improving zirconia surface characteristics and adhesion in dental restorations, simplifying bonding procedures, and potentially offering better clinical outcomes than conventional sandblasting. Full article

Titanium alloys are widely used in the aerospace, automotive, chemical, and biomedical industries due to their excellent corrosion resistance, mechanical properties, and biocompatibility. However, the surface properties of titanium alloys are often insufficient to meet the increasingly complex requirements of certain applications. Therefore, enhancing the surface performance of titanium alloys in physiological environments has become a key focus of research. In this study, a porous oxide layer was generated on the surface of a titanium substrate through micro-arc oxidation (MAO). This layer served as an intermediate layer for a subsequently deposited polyurethane (PU) coating, providing a strong foundation for adhesion. The high porosity of the MAO layer not only facilitated the adhesion of the PU coating but also protected the titanium alloy, further enhancing its corrosion resistance. The surface microstructure after MAO treatment and the morphological changes after application of the PU coating were characterized using scanning electron microscopy. The PU layer uniformly covered the surface of the MAO layer, significantly improving the smoothness and uniformity of the surface. The increase in surface smoothness due to the PU coating on top of the MAO layer was verified through white light interferometry. Additionally, surface hydrophobicity was assessed through water contact angle measurements. The PU layer over the MAO coating significantly enhanced the hydrophobicity of the titanium alloy’s surface, which is crucial for reducing biofouling and improving the effectiveness of biomedical implants. Finally, electrochemical analysis was conducted to study the corrosion resistance of the titanium alloy after MAO and PU treatment. The titanium alloy with an MAO–PU composite coating exhibited the highest corrosion resistance. The findings revealed that the combination of the MAO layer and PU coating provides an excellent multifunctional protective layer for titanium alloys, not only enhancing their durability but also their ability to adapt to physiological and harsh environments. Full article

Fiber-optic tip sensors offer significant potential in biomedical applications due to their high sensitivity, compact size, and resistance to electromagnetic interference. This study focuses on advancing phase demodulation techniques for ultra-short Fabry–Pérot cavities within limited spectral bandwidths to enhance their application in biomedicine and diagnostics. We propose a novel sparse-sampled white-light interferometry system for respiratory monitoring, utilizing a monolithic integrated semiconductor tunable laser for quasi-continuous frequency scanning across 191.2–196.15 THz at a sampling rate of 5 kHz. A four-step phase-shifting algorithm (PSA) ensures precise phase demodulation, enabling high sensitivity for short-cavity fiber-optic sensors under constrained spectral bandwidth conditions. Humidity sensors fabricated via a self-growing polymerization process further enhance the system’s functionality. The experimental results demonstrate the system’s capability to accurately capture diverse breathing patterns—including normal, rapid, and deep states—with fast response and recovery times. These findings establish the system’s potential for real-time respiratory monitoring in clinical and point-of-care settings. Full article

Optical interferometry has emerged as a cornerstone technology for high-precision length measurement, offering unparalleled accuracy in various scientific and industrial applications. This review provides a comprehensive overview of the latest advancements in optical interferometry, with a focus on grating and laser interferometries. For grating interferometry, systems configurations ranging from single-degree- to multi-degree-of-freedom are introduced. For laser interferometry, different measurement methods are presented and compared according to their respective characteristics, including homodyne, heterodyne, white light interferometry, etc. With the rise of the optical frequency comb, its unique spectral properties have greatly expanded the length measurement capabilities of laser interferometry, achieving an unprecedented leap in both measurement range and accuracy. With regard to discussion on enhancement of measurement precision, special attention is given to periodic nonlinear errors and phase demodulation methods. This review offers insights into current challenges and potential future directions for improving interferometric measurement systems, and also emphasizes the role of innovative technologies in advancing precision metrology technology. Full article

In the fabrication of optical polymer-based components, such as diffractive gratings and waveguides, high throughput and high precision are required. The non-destructive evaluation of these complex polymer-based structures is a significant challenge. Different measurement techniques can measure the structure geometry directly or via its functionality indirectly. This study investigates various measurement techniques aimed at assessing these structures from 200 nm up to 20 µm. Environmental scanning electron microscopy (ESEM), white light interferometry (WLI), atomic force microscopy (AFM), micro computed tomography (µCT), optical coherence tomography (OCT), phase contrast microscopy (PCM), and Mueller matrix ellipsometry (MME) are investigated for their practical limits of lateral resolution and aspect ratio. The impact of the specimens’ complexity factors, including structure width and aspect ratio, on measurement quality is discussed. A particular focus of this study is on the suitability of different measurement systems for evaluating undercuts and enclosed structures while considering structure size, slant angle, and cover thickness. The aim is to discuss the specific advantages of the individual measurement systems and their application areas in order to be able to quickly select suitable measurement systems for a non-destructive evaluation of polymer-based micro and nanostructures. Full article

The topography measurement accuracy of coherence scanning interferometry (CSI) suffers from the local characteristic of micro-structured surfaces, such as local surface slopes. A cylindrical reference artefact made of single-mode fiber with high roundness and low roughness has been proposed in this manuscript to traceably investigate the surface tilting induced measurement deviations using coherence scanning interferometry with high NA objectives. A feed-forward neural network (FF-NN) is designed and trained to model and thereafter compensate the systematic measurement deviations due to local surface tilting. Experimental results have verified that the FF-NN approach can well enhance the accuracy of the CSI for radius measurement of cylindrical samples up to 0.3%. Further development of the FF-NN for modelling of the measurement errors in CSI due to the optical properties of surfaces including areal roughness is outlined. Full article

Cu pillars serve as interconnecting structures for 3D chip stacking in heterogeneous integration, whose height uniformity directly impacts chip yield. Compared to typical methods such as white-light interferometry and confocal microscopy for measuring Cu pillars, microscopic fringe projection profilometry (MFPP) offers obvious advantages in throughput, which has great application value in on-line bump height measurement in wafer-level packages. However, Cu pillars with large curvature and smooth surfaces pose challenges for signal detection. To enable the MFPP system to measure both the top region of the Cu pillar and the substrate, which are necessary for bump height measurement, we utilized rigorous surface scattering theory to solve the bidirectional reflective distribution function of the Cu pillar surface. Subsequently, leveraging the scattering distribution properties, we propose a hybrid bright-dark-field MFPP system concept capable of detecting weakly scattered signals from the top of the Cu pillar and reflected signals from the substrate. Experimental results demonstrate that the proposed MFPP system can measure the height of Cu pillars with an effective field of view of 15.2 mm × 8.9 mm and a maximum measurement error of less than 0.65 μm. Full article

Membrane surface fouling has always been a critical issue for the long-term operation of polymeric membranes. Therefore, it is crucial to develop new approaches to prevent fouling. While developing new approaches, characterization methods are greatly important for understanding the distribution of fouling on the membrane surface. In this work, a cellulose acetate membrane was fouled by the filtration of artificial wastewater based on alginate. The surfaces of fouled membranes were characterized through scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM), atomic force microscopy (AFM), and white light interferometry (WLI). The results were then compared in terms of the resolution, accuracy, feasibility, and cost-efficiency. Full article