Search Results (142)

Erosion detection in materials exposed to plasma-generated species, such as those used for space propulsion systems, is critical for ensuring their reliability and longevity. This study introduces an efficient image processing technique to monitor the evolution of the erosion depth in boron nitride (BN) subjected to multiple cycles of iodine plasma exposure. Utilising atomic force microscopy (AFM) images from both untreated and treated BN samples, the technique uses a modified semi-automated image registration method that accurately aligns surface profiles—even after substantial erosion—and overcomes challenges related to changes in the eroded surface features. The registered images are then processed through frequency-domain subtraction to visualise and quantify erosion depth. Our technique tracks changes across the BN surface at multiple spatial locations and generates erosion maps at exposure durations of 24, 48, 72 and 84 min using both one-stage and multi-stage registration methods. These maps not only reveal localised material loss (up to 5.5 μm after 84 min) and assess its uniformity but also indicate potential re-deposition of etched material and redistribution across the surface through mechanisms such as diffusion. By analysing areas with higher elevations and observing plasma-treated samples over time, we notice that these elevated regions—initially the most affected—gradually decrease in size and height, while overall erosion depth increases. Progressive surface smoothing is observed with increasing iodine plasma exposure, as quantified by AFM-based erosion mapping. Notably, up to 89.3% of surface heights were concentrated near the mean after 72–84 min of plasma treatment, indicating a more even distribution of surface features compared to the untreated surface. Iodine plasma was compared to argon plasma to distinguish material loss during degradation between these two mechanisms. Iodine plasma causes more aggressive and spatially selective erosion, strongly influenced by initial surface morphology, whereas argon plasma results in milder and more uniform surface changes. Additional scale-dependent slope and curvature analyses confirm that iodine rapidly smooths fine features, whereas argon better preserves surface sharpness over time. Tracking such sharpness is critical for maintaining the fine structures essential to the fabrication of modern semiconductor components. Overall, this image processing tool offers a powerful and adaptable method for accurately assessing surface degradation and morphological changes in materials used in plasma-facing and space propulsion environments. Full article

This paper presents a novel Spiral Slot Planar Inverted-F Antenna (SSPIFA) specifically designed for telemedicine and healthcare applications, featuring compact size, biocompatible safety, and high integration suitability. By replacing the conventional top metal patch of a Planar Inverted-F Antenna (PIFA) with a slot spiral radiator whose geometry is precisely matched to the ground plane, the proposed antenna achieves a significant size reduction, making it ideal for encapsulation in miniaturized medical devices—a critical requirement for implantation scenarios. Tailored for the ISM 915 MHz band, the antenna is fabricated with a four-turn slot spiral etched on a 30 mm-diameter dielectric substrate, achieving an overall height of 22 mm and an electrically small profile of approximately 0.09λ × 0.06λ (λ: free-space wavelength at the center frequency). Simulation and measurement results demonstrate a −16 dB impedance matching (S11 parameter) at the target frequency, accompanied by a narrow fractional bandwidth of 1% and stable right-hand circular polarization (RHCP). When implanted in a layered biological tissue model (skin, fat, muscle), the antenna exhibits a near-omni directional radiation pattern in the azimuthal plane, with a peak gain of 2.94 dBi and consistent performance across the target band. These characteristics highlight the SSPIFA’s potential for reliable wireless communication in implantable medical systems, balancing miniaturization, radiation efficiency, and biocompatible design. Full article

A low-profile reflectarray has been designed in the Ka-band to efficiently generate wideband orbital angular momentum (OAM) vortex beams. The proposed design employs a reflective phase-shifting patch etched onto a dielectric substrate, featuring a three-square loop structure intersected by two transverse dipoles. This unit cell achieves a 440° phase shift at 30 GHz with a minimal magnitude loss of (−0.25 dB), enabling high-efficiency reflectarray performance. The OAM vortex beam supports high-order phase distributions ($l=+1,+2,+3,+4$) modes, though fabrication and experimental validation focused on the $+1$ mode. Measurements confirm that the reflectarray produces a high-purity OAM vortex beam for +1 mode, covering the operational frequency range from 27 to 39 GHz, and achieving a 40% bandwidth with a peak gain of 23.39 dBi at 33 GHz and an aperture efficiency of 17.38%. These results demonstrate the ability of the reflectarray to produce broadband directive OAM beams with robust performance, making it ideal for Ka-band communication systems. Full article

Fiber Metal Laminates (FMLs), a class of hybrid materials combining the benefits of metals and composites, have emerged as promising lightweight structural materials. Consequently, research interest in FML production technologies is growing. According to a thorough analysis of the state of the art, the effectiveness of surface treatments in influencing the bond strength, formability, and durability of components during FML manufacturing still needs to be better understood. This paper compares several functionalization strategies to optimize the surface characteristics that lead to superior FML quality: burnishing, laser texturing, sandblasting, and chemical etching. Each method will be appropriately set up to alter the surface’s initial characteristics and, consequently, the adhesion performance for the subsequent stages. Moreover, sustainability considerations are also considered during surface functionalization processes. This study aims to assess and optimize these techniques for reduced environmental impact, considering energy efficiency and waste reduction. By integrating sustainable practices into FML manufacturing, this research seeks to enhance the overall environmental profile of these advanced materials. Full article

The electrodes of thin film transistors (TFTs) have evolved from conventional single Cu layers to multi-layered structures formed by Cu and other metals or alloys. Different etching rates of various metals and galvanic corrosion between distinct metals may cause etching defects such as rough or uneven cross-sectional surfaces of stacked electrodes. Therefore, the etching of stacked electrodes faces new challenges. CD Bias and profile angle (PA) are two main performance indicators for the wet etching of TFT electrodes. Adjusting CD Bias and PAs quantitatively and evaluating their stability accurately is crucial to ensure the performance and yield of TFTs. In this work, the bilayer MoNb/Cu-stacked electrodes with different MoNb thicknesses and the MoNb/Cu/MTD triple-layered electrodes were prepared, and the influence of MoNb thickness and stacked structure on the CD Bias and PAs was investigated. It is found that in the H₂O₂-based etchant, the order of corrosion potential is E_MTD < E_MoNb < E_Cu; both MoNb/Cu and Cu/MTD will form a primary cell with MoNb or MTD as the anodes. The CD Bias and PAs of the MoNb/Cu bilayer structure also increase with MoNb thickness, but those of the MoNb/Cu/MTD triple-layered structure decrease with the introduction of the top MTD film. Finally, regression equations between CD Bias or PA and etching parameters were established based on the results of uniform experiments, and the 95% confidence intervals for CD Bias and PA were proposed after the Monte Carlo simulation. These obtained results provide a basis for quantitative adjustment of CD Bias and PA and precise control of etching stability. Full article

In this paper, we report the growth of high-quality ${\mathrm{In}}_{0.59}{\mathrm{Ga}}_{0.41}\mathrm{As}/{\mathrm{In}}_{0.37}{\mathrm{Al}}_{0.63}\mathrm{As}$ strain-balanced quantum cascade lasers (QCLs) in the low-pressure MOCVD production type multi-wafer planetary reactor addressing, in particular, quality and scaled manufacturing issues. Special attention was given to achieving the sharp interfaces (IFs), by optimizing the growth interruptions time and time of exposure of InAlAs layer to oxygen contamination in the reactor, which all result in extremely narrow IFs width, below 0.5 nm. The lasers were designed for emission at $7.7\mu$m. The active region was based on diagonal two-phonon resonance design with 40 cascade stages. For epitaxial process control, the High Resolution X-Ray Diffraction (HR XRD) and Transmission Electron Microscopy (TEM) were used to characterize the structural quality of the QCL samples. The grown structures were processed into mesa Fabry-Perot lasers using dry etching RIE ICP processing technology. The basic electro-optical characterization of the lasers is provided. We also present results of Green’s function modeling of QCLs and demonstrate the capability of non-equilibrium Green’s function (NEGF) approach for sophisticated, but still computationally effective simulation of laser’s characteristics. The sharpness of the grown IFs was confirmed by direct measurements of their chemical profiles and as well as the agreement between experimental and calculated wavelength obtained for the bandstructure with ideally abrupt (non-graded) IFs. Full article

This study presents a novel methodology for designing a planar broadband wide-scanning dual-polarized array using tightly-coupled dipoles and wide-angle impedance matching. By etching the S-shaped gaps between the dipoles and incorporating shorting vias with defected ground structures, we demonstrated that all radiation elements can be arranged on a single-layer substrate. Additionally, we introduced a thin printed circuit board (PCB) layer with two-dimensional periodic structures for impedance matching at wide scan angles. Leveraging high permittivity and constrained electromagnetic waves, we realized zero-scan blindness within this band. The aperture consisted of only two PCB layers, with a total profile of approximately 0.091λ_low, where λ_low represented the free-space wavelength at 6 GHz. A 3 × 4 dual-polarized array was fabricated and measured to validate the proposed approach. The measured active voltage standing wave ratio for one embedded array element surpassed 2.2 over 6–18 GHz. By enabling the orthogonal dipoles at the edge of the array to be mutually coupled using an additional metal patch, the active S₁₁ for the edge cells exceeded −8.8 dB over 6.9–18 GHz. The measured patterns were in good agreement with simulations over 6–18 GHz, with the array exhibiting good radiation performance over ±60° in the E- and H-planes. Full article

This paper presents the design and characterization of a coplanar waveguide (CPW) fed, low-profile, and flexible arrow-shaped filtenna for ISM band applications at 2.45 GHz. The antenna design involves an innovative approach incorporating etching slots to achieve miniaturization by 34%, contrasting with a traditional quadrilateral-shaped antenna. After the attainment of desired miniaturization, the unwanted harmonics are also mitigated by deploying simple filtering methodology. A perpendicular rectangular stub is strategically introduced to the feedline, effectively minimizing harmonics across a broad frequency range of 3.3–11.0 GHz. Through simulations and measurements, the results indicate that the antenna’s operational band spans from 2.276 to 2.75 GHz, encompassing the entire ISM band (2.4–2.5 GHz). Notably, the antenna demonstrates promising radiation characteristics, including omnidirectional gain of approximately 2.2 dBi and a radiation efficiency exceeding 95%. With a compact overall size of 0.24λ × 0.20λ × 0.0005λ (where λ is the free-space wavelength at 2.45 GHz), coupled with wide harmonic rejection property, the proposed arrow-shaped flitenna emerges as a compelling candidate for ISM band applications. Full article

We examined how controlling variables in a pre-metallization Ar sputter-etching process for in situ contact-hole cleaning affects the contact-hole profile, etching rate, and substrate damage. By adjusting process parameters, we confirmed that increasing plasma power lowered the DC bias but enhanced the etching rate of SiO₂, while increasing RF power raised both, with RF power having a more pronounced effect. Higher Ar flow rate reduced etching uniformity and slightly lowered the DC bias. There was no significant difference in the amount of etching between the oxide film types, but the nitride/oxide selectivity ratio was about 1:2. Physical damage during Ar sputter-etching was closely linked to DC bias. finally, Finally, etching of the Si and CoSi₂ sublayers was performed on the device contact hole model. At this time, Si losses of up to about 31.7 Å/s occurred, and the etch speed was strongly affected by the DC bias. By optimizing the RF power and plasma power, we achieved a Si/CoSi₂ etch selectivity ratio of about 1:2. Full article

Wire Electrical Discharge Machining (WEDM) technology represents an unconventional but vital manufacturing technology in many different industrial branches. The automotive industry and its many significant requirements bring the need to manufacture inserts and mould segments for plastic injections from Albromet W130 material, with a required roughness, Ra, from 4.5 to 5 µm so that subsequent profile etching can be eliminated. A planned experiment of 60 rounds was carried out to discover the optimal machining parameters, namely, the pulse-off time, gap voltage, discharge current, pulse-on time, and wire speed in order for the thickness of 10 to 100 mm (after 10 mm) to demonstrate the required roughness. The goal was to evaluate the surface roughness, maximise the cutting speed, and manufacture it without surface or subsurface defects. The evaluation of the planned experiment led to the establishment of optimised WEDM machining parameters with which thicknesses of 10–100 mm will always be produced with the required roughness, Ra, from 4.5 to 5 µm and with the highest possible cutting speed. It was also proven that the machining does not lead to surface or subsurface defects, and thus, the service life of the manufactured parts will not be affected. Full article

This paper presents a detailed physical model for a novel method of two- and three-dimensional microstructure formation: dry electron beam etching of the resist (DEBER). This method is based on the electron-beam induced thermal depolymerization of positive resist, and its advantages include high throughput and relative simplicity compared to other microstructuring techniques. However, the exact mechanism of profile formation in DEBER has been unclear until now, hindering the optimization of this technique for certain applications. The developed model takes into account the major DEBER phenomena: e-beam scattering in resist and substrate, e-beam induced main-chain scissions of resist molecules, thermal depolymerization of resist, monomer diffusion, and resist reflow. Based on the developed model, a simulation algorithm was implemented, which allowed simulation of the profile obtained in resist by DEBER. Experimental verification of the DEBER model was carried out, which demonstrated the reliability of the model and its applicability for theoretical study of this method. The ultimate DEBER characteristics were estimated by simulation. The minimum line width and the maximum profile slope that could be obtained by DEBER were approximately 300 nm and 70°, respectively. Full article

This study developed a fibre-optic laser Doppler velocimetry sensor for use in opaque, high-temperature, and high-pressure fluid flows by inserting the fibre perpendicular to the main flow. The tip of the optical fibre was obliquely polished and chemically etched using a buffered hydrofluoric acid solution, and a reflective mirror was deposited on the surface of the oblique fibre tip. Based on the results of the verification test using the rotating annular open channel, the fabrication conditions of the fibre tip were optimized for measuring the lubricating oil flow. The flow velocity profiles in the engine’s oil flow of the lubrication system during engine bench testing were measured. These velocity profiles were influenced by variations in the measurement position, oil temperature, and engine speed. The measurement accuracy of this sensor was compared with the volumetric flow rate obtained by cross-sectional area integration of the flow velocity profile, as measured using a Coriolis flowmeter, and the difference was within 1%. By combining computational simulation for flow and optical attenuation and particle scattering in light transmission through a working fluid, this fibre-optic sensor achieved a measurement volume of 200 microns in length and 200 microns in width at a distance of 900–1000 microns from the sensor. Full article

Our target USH reservoir in the D oilfield is characterized by “inverse rhythm” deposition with the noticeable features of “high porosity and low permeability”. The reservoir has been developed with waterflooding using horizontal wells. Due to the strong heterogeneity of the reservoir, water channeling is severe, and the water cut has reached 79%. Considering the high temperature and high salinity reservoir conditions, polymer microspheres (PMs) were selected to realize conformance control. In this study, characterization of the polymer microsphere suspension was achieved via morphology, size distribution, and viscosity measurement. Furthermore, a multi-scale visualization study of the reservoir development process, including waterflooding, polymer microsphere flooding, and subsequent waterflooding, was conducted using macro-scale coreflooding and calcite-etched micromodels. It was revealed that the polymer microspheres could swell in the high salinity brine (170,000 ppm) by 2.7 times if aged for 7 days, accompanied by a viscosity increase. This feature is beneficial for the injection at the wellbore while swelled to work as a profile control agent in the deep formation. The macro-scale coreflood with a 30 cm × 30 cm × 4.5 cm layer model with 108 electrodes installed enabled the oil distribution visualization from different perpendicular cross sections. In this way, the in situ conformance control ability of the polymer microsphere was revealed both qualitatively and quantitatively. Furthermore, building on the calcite-etched visible micro-model, the pore-scale variation of the residual oil when subjected to waterflooding, polymer microsphere waterflooding, and subsequent waterflooding was collected, which revealed the oil displacement efficiency increase by polymer microspheres directly. The pilot test in the field also proves the feasibility of conformance control by the polymer microspheres, i.e., more than 40,000 bbls of oil increase was observed in the produces, accompanied by an obvious water reduction. Full article

Increasing the bit density in 3D NAND flash memory involves reducing the pitch of ON (Oxide-Nitride) molds in the Z-direction. However, this reduction drastically increases Z-interference, adversely affecting cell distribution and accelerating degradation of reliability limits. Previous studies have shown that programming from the top word line (WL) to the bottom WL, instead of the traditional bottom-to-top approach, alleviates Z-interference. Nevertheless, detailed analysis of how Z-interference varies at each WL depending on the programming sequence remains insufficient. This paper investigates the causes of Z-interference variations at Top, Middle, and Bottom WLs through TCAD analysis. It was found that as more electrons are programmed into WLs within the string, Z-interference variations increase due to increased resistance in the poly-Si channel. These variations are exacerbated by tapered vertical channel profiles resulting from high aspect ratio etching. To address these issues, a method is proposed to adjust bitline biases during verification operations of each WL. This method has been validated to enhance the performance and reliability of 3D NAND flash memory. Full article

Black GaAs nanotip arrays (NTs) with 3300 nm lengths were fabricated via self-masked plasma etching. We show, both experimentally and numerically, that these NTs, with three gradient refractive index layers, effectively suppress Fresnel reflections at the air–GaAs interface over a broad range of wavelengths. These NTs exhibit exceptional UV-Vis light absorption (up to 99%) and maintain high NIR absorption (33–60%) compared to bare GaAs. Moreover, possessing a graded layer with a low refractive index (n = 1.01 to 1.12), they achieve angular and polarization-independent antireflection properties exceeding 80° at 632.8 nm, aligning with perfect antireflective coating theory predictions. This approach is anticipated to enhance the performance of optoelectronic devices across a wide range of applications. Full article