Etching Technique Research Articles

Minimal Damage and Tunable Fabrication of Atomic‐Scale Ultrathin YBa2Cu3O7‐δ Nanowires with High Uniformity

The growing demand for deep‐space optical communication and remote sensing has highlighted the need for high‐temperature superconducting nanowire single photon detectors (SNSPDs). However, fabricating ultrathin and ultranarrow high‐temperature superconducting nanowires remains significant challenges due to the extreme instability of their films. Herein, an effective approach is presented for fabricating high‐quality YBa2Cu3O7−δ (YBCO) nanowires by utilizing in situ protective layers that shield ultrathin films from environmental and processing‐induced degradation, coupled with low‐temperature etching techniques to achieve precise, and tunable etching while minimizing damage. Thus, YBCO nanowires are successfully fabricated with a minimum width of 68 nm, an atomic‐scale thickness of 5 nm, and lateral damage limited to ≈15 nm. These nanowires exhibit robust I–V hysteresis and a minimum switching current (Is) of about 120 μA. The coefficient of variation for the Is less than 6% and for the critical temperature (Tc0) is below 1%, confirming the exceptional uniformity of the nanowires. Electrical transport measurements reveal that voltage switching in these nanowires is governed by phase slip and hotspot effects. These advancements open new avenues for YBCO‐based high‐temperature SNSPDs, addressing a key challenge in the broader deployment of high‐temperature superconducting devices, including SNSPDs, superconducting quantum interference devices, and superconducting diodes.

Tolerable patterning in nanoimprint lithography by one-pass breakthrough etching of residual layer and spin-on-glass

Abstract In nanoimprint lithography (NIL), a residual layer inherently exists under the NIL resist features and must be removed in later etching steps. The subsequent etching process, known as breakthrough etching, leads to variations in the device pattern sizes and disrupts process integration because of NIL resist pattern loss. It was reported previously that the residual layer thickness (RLT) should be less than half the feature height (FH) for subsequent high-precision etching. In this work, we develop a one-pass etching process using an atomic-scale cycle stepped etching technique that passes through the residual layer to the spin-on-glass and demonstrate that the process can maintain the pattern width, regardless of RLT variations within the 12–32 nm thickness range. Even in the case of a 32-nm-thick RLT corresponding to 76% of the feature height (0.76 FH), good electrical performances were obtained without electrical failures in the half-pitch 26 nm line-and-space W-damascene interconnect patterns.

Grain size characterization of nickel alloy 718 with optimized metallographic sample preparation route followed by a novel etching technique

Abstract A suitable etching technique can distinguish the appearance of microscopic features such as grain boundaries (GBs), annealing twins (TBs), and precipitates, unlike nonmetallic inclusions, voids, and microcracks, which are visible in as-polished conditions. The difficulties arise when a semi-automatic or automatic grain size (GS) analyzer detects the TBs in addition to GBs concurrently. This study introduces a novel etching technique that has selectively highlighted the GBs without or faintly emphasizing TBs in heat-treated additively manufactured (AM) and wrought nickel alloy 718, respectively. The authors then measured the GS using the comparison and intercept procedure (lineal and Abrams three-circle) according to ASTM E112-2013. Moreover, the comparative study identified the comparison procedure as the most effective approach based on accuracy, post-processing, and time consumption. However, it had limitations in terms of precision and applicability. In contrast, the intercept procedure emerged as the preferred choice for higher accuracy demands.

Manipulating Heterogeneous Surface/Interface Reconstruction of Nickel Molybdate Nanofiber by In Situ Prussian Blue Analogs Etching Strategy for Oxygen Evolution

Bimetallic oxides are promising electrocatalysts due to their rich composition, facile synthesis, and favorable stability under oxidizing conditions. This paper innovatively proposes a strategy aimed at constructing a one‐dimensional heterostructure (Fe–NiO/NiMoO4 nanoparticles/nanofibers). The strategy commences with the meticulous treatment of NiMoO4 nanofibers, utilizing in situ etching techniques to induce the formation of Prussian Blue Analog compounds. In this process, [Fe(CN)6]3− anions react with the NiMoO4 host layer to form a steady NiFe PBA. Subsequently, the surface/interface reconstituted NiMoO4 nanofibers undergo direct oxidation, leading to a reconfiguration of the surface structure and the formation of a unique Fe–NiO/NiMoO4 one‐dimensional heterostructure. The catalyst showed markedly enhanced electrocatalytic performance for the oxygen evolution reaction. Density functional theory results reveal that the incorporation of Fe as a dopant dramatically reduces the Gibbs free energy associated with the rate‐determining step in the oxygen evolution reaction pathway. This pivotal transformation directly lowers the activation energy barrier, thereby significantly enhancing electron transfer efficiency.

Optimizing laser-induced deep etching technique for micromachining of NXT glass.

Recent advancements in display technology have led to the development and diversification of complex glass materials. Among them, Corning's Lotus NXT glass offers excellent optical properties, high thermal stability, and dimensional accuracy, which are crucial for display applications. However, these characteristics make it difficult to apply pre-existing machining techniques developed for conventional glass materials directly to NXT glass. In this study, we used the laser-induced deep etching (LIDE) technique to fabricate micro holes in NXT glass. Various laser, chemical, and mechanical parameters were subjected to experimental analysis and optimization to achieve higher etching speed and aspect ratio. In this study, successful etching of Corning's Lotus NXT glass was achieved by optimizing laser parameters, including a wavelength of 1030 nm, a pulse energy of 45 µJ, a pulse count of 2 × 104, and a repetition rate of 40 kHz, combined with a chemical composition consisting of a 1:5 molar ratio of HF to HCl. This resulted in a high aspect ratio of ∼23:1 and an impressive etching speed of 1200 µm/h.

Interfacial Elemental Analysis of Slanted Edge-Contacted Monolayer MoS2 Transistors via Directionally Angled Etching.

Edge contacts offer a significant advantage for enhancing the performance of semiconducting transition metal dichalcogenide (TMDC) devices by interfacing with the metallic contacts on the lateral side, which allows the encapsulation of all of the channel material. However, despite intense research, the fabrication of feasible electrical edge contacts to TMDCs to improve device performance remains a great challenge, as interfacial chemical characterization via conventional methods is lacking. A major bottleneck in explicitly understanding the chemical and electronic properties of the edge contact at the metal-two-dimensional (2D) semiconductor interface is the small cross section when characterizing nominally one-dimensional edge contacts. Here, we demonstrate a directional angled etching technique that enables the characterization of the interfacial chemistry at the metal-MoS2 junction when in an edge-contact configuration. The slanted edge structure provides a substantial cross section for elemental analysis of the edge contact by conventional X-ray photoemission spectroscopy, in which a simple chemical environment and sharp interface were revealed. Facilitated by the well-characterized contact interface, we realized slanted edge-contacted monolayer MoS2 transistors encapsulated by hexagonal boron nitride. The transport characteristics and photoluminescence of these transistors allowed us to attribute the efficient carrier injection to direct and Fowler-Nordheim tunneling, validating the distinct Au-MoS2 interface. The established method represents a viable approach to fabricating edge contacts with encapsulated 2D material devices, which is crucial for both the fundamental study of 2D materials and high-performance electronic applications.

Fabrication and simulation of silicon nanogaps pH sensor as preliminary study for Retinol Binding Protein 4 (RBP4) detection

In this research, a silicon nanogap biosensor has the potential to play a significant role in the field of biosensors for detecting Retinol Binding Protein 4 (RBP4) molecules due to its unique nanostructure morphology, biocompatibility features, and electrical capabilities. Additionally, as preliminary research for RBP4, a silicon nanogap biosensor with unique molecular gate control for pH measurement was developed. Firstly, using conventional lithography followed by the Reactive-ion etching (RIE) technique, a nanofabrication approach was utilized to produce silicon nanogaps from silicon-on-insulator (SOI) wafers. The critical aspects contributing to the process and size reduction procedures were highlighted to achieve nanometer-scale size. The resulting silicon nanogaps, ranging from 100 nm to 200 nm, were fabricated precisely on the device. Secondly, pH level detection was performed using several types of standard aqueous pH buffer solutions (pH 6, pH 7, pH 12) to test the electrical response of the device. The sensitivity of the silicon nanogap pH sensor was 7.66 pS/pH (R² = 0.97), indicating that the device has a wide range of pH detecting capacity. This also includes the silicon nanogap biosensor validated by simulation, with the sensitivity obtained being 3.24 μA/e.cm² (R² = 0.98). The simulation of the sensitivity is based on the interface charge (Qf) that represents the concentration of RBP4. The results reveal that the silicon nanogap biosensor has excellent characteristics for detecting pH levels and RBP4 with outstanding sensitivity performance. In conclusion, this silicon nanogap biosensor can be used as a new electrical RBP4 biosensor for biomedical diagnostic applications in the future.

Efficacy of different adhesive systems in bonding direct resin composite restorations: a systematic review and meta-analysis.

This study aimed to identify and evaluate scholarly research on the efficacy, durability, and long-term stability of various adhesive systems used for bonding direct resin composite restorations and to identify factors influencing bonding performance, such as adhesive composition, application protocol, substrate type, and etching technique. An all-inclusive electronic database search for peer-reviewed scholarly journal articles was conducted using PubMed, ScienceDirect, Google Scholar, Dimensions, and the Cochrane Library for research articles investigating the effectiveness of different adhesive systems in direct resin composite restorations, excluding reviews, meta-analyses, opinion pieces, and case reports. The risk of bias was assessed using the Cochrane tool (Robvis 2.0). Data were extracted and thematically analyzed, and quantitative data were statistically analyzed using Review Manager software. Dichotomous data were evaluated using the Mantel-Haenszel method, applying a random effects model and 95% confidence interval. The database search yielded 1632 potential articles, of which 14 were included in this study. Several adhesive systems exhibit excellent tensile bond strength. In addition, the type of resin composite, adhesive system, and artificial aging significantly influenced the bonding performance of resin composite restorations. However, the failure rates were low in the different adhesive systems, showing comparable results between the two-step etch-and-rinse and one-step self-etch adhesive systems (p = 0.71). The results showed an overall trend of high bonding effectiveness with a low incidence of adverse events, such as postoperative sensitivity, adhesive failure, and fractures. The study results emphasize the importance of selecting appropriate adhesive systems based on clinical case requirements, restoration characteristics, and patient factors to enhance bonding efficacy, durability, and long-term stability.

Ultra-short stripe microlasers fabricated with a focused ion beam etching technique.

Fabry-Perot (FP) lasers with a cavity length shorten down to 50 µm were investigated. One or two laser mirrors were formed by focused ion beam etching. InGaAs quantum dots of high density were used as the laser active region. The lasers operate in a pulsed regime up to at least 105°С. A comparison with lasers formed by the facet cleaving method (minimum length is 100 µm) reveals the similarity of the emission wavelength and the threshold current depending on the cavity length. This allows us to conclude that the etched facets do not significantly affect the non-radiative recombination rate and provide a reflection coefficient close to that of the cleaved facet. The maximum modal gain was estimated to be not less than 240 cm-1. No evidence of the excited-state lasing was found.

Research on the photoelectrical properties of TiO2-doped V2O5/FTO nanocomposite thin films under thermal and electrical excitation

The TiO2-doped V2O5/FTO nanocomposite thin films were prepared on the FTO substrates by sol-gel method and post-annealing process, and the MSM structural devices based on the prepared films were fabricated by sputtering, photolithography and etching techniques. SEM, XRD, and XPS were respectively used to study the morphology, structure and composition of the film, and the electrical and optical regulations of the device were measured by using spectrophotometry and semiconductor parameter analyzer. In the temperature range of 20℃-360℃, the maximum modulation amplitude of the TiO2-doped V2O5/FTO film in the 400-1600nm band was 18.282% and the modulation of the V2O5/FTO film was increased by 9.663% after TiO2-doping. The resistance of the FTO/V2O5-TiO2/FTO device reduced by 3-4 orders of magnitude by comparing with the FTO/V2O5/FTO device. The FTO/V2O5-TiO2/FTO device underwent semiconductor-metal state transition (SMT) around 259.91℃. Under the applied voltage of 0-5V, the maximum transmittance variations could reach 8.821%, 7.174% and 11.540% in 400-1600nm band at the temperature of 20℃, 40℃ and 80℃, respectively. The outstanding optical and electrical regulation properties and the favorable cycling stability make the nanocomposite film expected to be applied in the field of optoelectronic devices.

Bandwidth enhancement of resonating absorber using a lossy dielectric layer for RCS reduction in X-band

Abstract In this paper, a resonating absorber is proposed for radar cross section reduction in the X-band, with the inclusion of a high loss dielectric layer. The absorber consists of a pair of co-centered resonating Jerusalem cross printed on a FR4 substrate cascaded with a high-loss dielectric layer and a metallic back plane. The designed absorber offers 90 % absorption from 7.8–12 GHz with a fractional bandwidth of 42.42 %. The designed absorber is 0.106λ L thick with a compact square unit cell of size 0.076λ L (wavelength at the lowest frequency). An equivalent circuit model is developed to analyze the proposed absorber. The absorber is angularly stable for varying angle of incidences up to 40°–60° for TE and TM polarizations respectively. The planar as well as the conformal structure of the proposed absorber offer a minimum 10 dB radar cross section reduction in the X-band. The conventional approach which involves complex fabrication process of soldering thousands of lumped resistors to increase the bandwidth, whereas the proposed absorber is realized to offer wide absorption using simple PCB etching technique. To validate the design prototype is fabricated and the measurement is carried out.

Etching and isolation technique for synthesis of CNTs-encapsulated NiSe2/CoSe2 for supercapacitor applications

Etching and isolation technique for synthesis of CNTs-encapsulated NiSe2/CoSe2 for supercapacitor applications

Cerium oxide anchored free-standing silicon nanowires as potential anode materials for electrochemical supercapacitor

Cerium oxide anchored free-standing silicon nanowires as potential anode materials for electrochemical supercapacitor

Design and fabrication of photonic devices and a microfluidic channel with a femtosecond laser

This article presents the modeling and fabrication of photonic devices such as a Mach-Zehnder waveguide interferometer (MZWI) and a 1 × 4 optical power splitter (OPS) with a microfluidic channel. The photonic structures were designed using CAD software and BeamPROPTM to have an s-shaped waveguide bend geometry and a total length of 8000 μm, and the devices were then integrated with a 6000 μm microfluidic channel to form configurations based on conical spirals and helices with femtosecond laser radiation. The entire writing process was performed in a single step with a 20X microscope objective to achieve greater accuracy in the manufacturing process. A chemical etching step was performed using the shape-controlled with femtosecond laser irradiation followed by chemical etching (SC-FLICE) technique, forming a uniform cross-section in the central part of the microfluidic channel. The energy doses and translation speeds of the system were varied, resulting in a longer microfluidic channel. However, this work was limited to the design and development of the prototype due to the project objectives and limited resources. In this research, we introduce an optofluidic system which integrates the principles of optics and microfluidics, is suitable for biosensing applications. The compatibility of this system with biosensing applications paves the way for significant progress in various sectors, including medical diagnostics, environmental surveillance, and biochemical studies. The originality and value of this work lie in its unique design and potential for broad application. The present work, it was demonstrated that using ultrafast laser writing, we can fabricate photonic devices and a consistent microfluidic channel on a single step.

Optimized Interface between the High-Temperature Proton Exchange Membrane and the Catalytic Layer Using the Plasma Etching Technique

Optimized Interface between the High-Temperature Proton Exchange Membrane and the Catalytic Layer Using the Plasma Etching Technique

Open-layered MBenes: Comparisons of Different Wet Etching Techniques and Electrochemical Detection of Heavy Metal Ions with High Sensitivity & Selectivity

Open-layered MBenes: Comparisons of Different Wet Etching Techniques and Electrochemical Detection of Heavy Metal Ions with High Sensitivity & Selectivity

Selective molecular gas phase etching in layered high aspect-ratio nanostructures for semiconductor processing. I. Modeling framework and simulation

The need for precise control of nanoscale geometric features poses a challenge in manufacturing advanced gate-all-around nanotransistors. The high material selectivity required in fabricating these transistors makes thermal gas etching much more appealing in comparison to liquid phase and plasma-based etching techniques. The selective thermal etching by F2 of silicon–germanium (SiGe) stacks comprised of alternating layers of silicon (Si) and SiGe is explored in this context for semiconductor manufacturing applications. We propose and develop computer simulations as a tool to predict the etch profile evolution over time in such an etching process. The tool is based on a mathematical model that considers the transport processes and surface interactions involved in the gas phase etching process—which at the nanoscale is primarily Knudsen diffusion in the free molecular flow regime. Thus, the transport model is formulated as a boundary integral equation, which takes into account the direct flux of etchant molecules that any given point on the exposed surface receives from the bulk gas phase as well as the re-emission flux from other parts of the structure itself. We compared the applicability of two different surface reaction models—a model where the local etch rate is linear in the flux at a point and a Langmuir adsorption/reaction model—to connect the net flux received at a point on the surface to the local etch rate. This paper precedes Paper II of this series, which describes the experimental methods and comparison with model predictions of F2 etching in high aspect ratio Si–SiGe stacked nanostructures.

High-Performance Edge-Contact Monolayer Molybdenum Disulfide Transistors.

Edge contact is essential for achieving the ultimate device pitch scaling of stacked nanosheet transistors with monolayer 2-dimensional (2D) channels. However, due to large edge-contact resistance between 2D channels and contact metal, there is currently a lack of high-performance edge-contact device technology for 2D material channels. Here, we report high-performance edge-contact monolayer molybdenum disulfide (MoS2) field-effect transistors (FETs) utilizing well-controlled plasma etching techniques. Plasma etching with pure argon improves the edge dangling bonds and thus improves the edge-contact quality. Edge-contact monolayer MoS2 FET shows good ohmic contact even at cryogenic temperatures (20 K), achieving a record-low contact resistance (R c) of 1.25 kΩ·μm among all edge-contact MoS2 devices. The record-high on-state current of 436 μA/μm and transconductance of 123 μS/μm at V ds = 1 V are achieved on an edge-contact monolayer MoS2 FET with L ch = 120 nm. This work highlights the great potential of edge contacts for high-performance monolayer transition metal dichalcogenide (TMD) material electronics.

Broadband transparency in terahertz free-standing anapole metasurface

We report on an all-dielectric compound anapole metasurface featuring metaatoms based on concentric disks and rings arranged in a square lattice. In this free-standing metasurface, the radiating multipole components cancel each other out in the far field, regardless of the angle of incidence and the polarization of incoming radiation. To demonstrate experimentally a broadband transparency in the terahertz range, we fabricated a silicon metasurface with a total thickness of 60 μm using electron beam lithography and plasma deep etching techniques. Terahertz time-domain spectroscopy experiments revealed that the transmittance spectra measured at various incident angles and polarization states agree well with the respective modeling data. The proposed compound anapole approach has strong application potential for broadband terahertz photonics and sensing devices.

Performance of YBCO Step Edge Josephson Junctions for Different Film Thickness to Step Height Ratio

Step edge Josephson junction devices of YBa2Cu3O7‐x films on SrTiO3 substrates are fabricated, and the device performance is studied for different t/h (t: the thickness of the film, h: step height) ratios. After depositing YBCO films on the step etched substrates, photolithography, and ion beam etching techniques are used to fabricate three devices with t/h ratios of ≈0.4, 0.7, and 1.2. The critical temperatures (Tc) of the devices are ≈82, 85, and 88 K, respectively. The critical current (Ic) and normal state resistance (Rn) are observed to be t/h ratio dependent. The critical current values at 70 K for the devices with t/h ratios of 0.4, 0.7, and 1.2 are ≈425, 550, and 820 μA, respectively. The IcRn product at 70 K is ≈2.06, 2.76, and 0.43 mV for t/h ratios 0.4, 0.7, and 1.2, respectively, which indicates that the t/h ratio of 0.7 is optimum for the device performance. The current versus voltage curves at 68 K are fitted using the resistively shunted junction model using the Portable Superconducting Circuit Analyzer (PSCAN2) simulator, which suggests that there can be normal conducting links present across the microbridge, and it becomes effective for I > Ic, contributing to excess current.