Ultraviolet Nanosecond Research Articles

Experimental study of flexible sensors based on ultraviolet nanosecond laser induced graphene

Current laser-induced graphene (LIG) methods encounter challenges such as subpar graphene quality and intricate manufacturing of electronic devices using graphene. In order to tackle these issues, this paper proposes a method of using an ultraviolet nanosecond pulse laser to stimulate the formation of graphene. Polyimide (PI) is subjected to laser irradiation in a single step to produce high-quality porous graphene. Subsequently, low-cost flexible pressure and strain sensors are manufactured using graphene. The Raman spectroscopy results demonstrate that the graphene generated has excellent quality (ID/IG = 0.14, I2D/IG = 0.37). Scanning electron microscopy shows that the LIG surface has a uniform porous morphology, with a patterning precision of 100 μm and a sheet resistance of 9.29 Ω/sq. The performance of the flexible pressure sensor was evaluated, demonstrating precise sensitivity (0.75 KPa−1 within 2.5 KPa range), a broad detection range (0–160 KPa), and a minimal detection limit of 20 Pa. The strain sensor exhibited a high level of sensitivity to strain (GF factor of 139), a broad linear range of strain (0–35 %), a low limit of detection (capable of detecting strains as low as 0.6 %), and outstanding durability (no signal distortion was observed even after subjecting it to over 2500 cycles of stretching). Flexible sensors can be worn as electronic skin on fingers, the neck, and the surface of robotic claws. The research results show that ultraviolet nanosecond pulsed lasers, using the LIG process, can produce graphene of higher known quality. The flexible pressure and strain sensors fabricated from this graphene exhibit outstanding performance.

Facile fabrication of foldable electrospun nanofiber electrodes for electrodes for electronic biosensing

This study presents a rapid, sensitive and selective sensor based on electrospun nanofibers on laser-patterned electrodes, in which the laser micromachining process can directly fabricate the graphene electrode device for the electronical detection of glucose molecule. The layer of graphene film was formed on the glass substrate by a screen printing technique, and then the graphene electrodes can be fabricated by the ultraviolet (UV) nanosecond laser process with the wavelength of 355 nm. Based on the controlled the laser fluence and pulses, the electrode gap of 60 μm within the device can be fabricated. The polyvinyl alcohol (PVA) and glucose oxidase (GOD) composite nanofiber with weight percentage of 8% can be used by the electrospun process with used Glutaraldehyde(GA) steam for cross linking process. After that, it is blended with the conductivity of poly(3,4-ethylenedioxythiophene): poly (styrene sulfonate) (PEDOT:PSS), and the foldable nanofiber structures was made by electrospun process on the graphene electrode device. Finally, the electrical detection of graphene electrode device with the nanofibers at different concentrations of glucose can be measured, resulting in the linear variation is detecting the glucose concentration ranging form 0.01 to 3.12 mM. This work indicated that the low concentration and highly sensitive can be used for electronic biosensors

Ultraviolet laser-induced fragmentation of hydrocarbon fuel droplets

The present study aims to understand droplet fragmentation due to instabilities from the radiative heating process. We focus on the plasma-induced breakup mechanism of iso-octane and n-hexane droplets from the nucleation of holes through sheets and instabilities. The plasma generation inside the droplets leads to an intense explosion followed by fragmentation of the droplets. A droplet is suspended in the air using an acoustic levitator and exposed to ultraviolet nanosecond laser pulses. The droplet sizes used are in the range of 0.5–2 mm in diameter, and laser energies are 10–20 mJ per pulse. Initially, plasma formation followed by shock wave emission is observed during the impact of the laser pulse. Afterward, the droplet opens at one side and is stretched vertically to form a liquid sheet. The hole formation and its rapid growth result in the breaking of the thin liquid sheet. Small droplets and ligaments emerge from the circular edge of the sheet, which follows the well-known ligament distribution. This study reveals the detailed analysis of expansion dynamics, evolution of single and multiple holes, and instabilities associated with the liquid sheet. The results observed are categorized into four different mechanisms: (1) plasma formation followed by shock wave propagation, (2) droplet deformation, (3) sheet breakup through nucleation of holes followed by rapid growth, and (4) complete atomization.

Characterization of ZnWO4, MgWO4, and CaWO4 Ceramics Synthesized in the Field of a Powerful Radiation Flux

This paper presents the results of a study on the morphology, structure, and luminescent properties of ceramics synthesized in the radiation field of MeWO4 compositions (where Me is Mg, Ca, and Zn). The synthesis of ceramics was carried out by the direct action of the electron flux on an initial mixture of powders of the given stoichiometric composition. WO3, ZnO, MgO, and CaO powders with particle sizes in the range of 1–50 microns were used for the synthesis of the samples. It was found that the yield of the radiation synthesis reaction (the ratio of the mass of the sample and the charge used), when treated with an electron flux with an energy of 1.4 MeV and a flux power density of 15–18 kW/cm2, was in the range of 75–99%. The synthesis of all compositions was carried out under the same radiation treatment modes, although the melting temperatures of the starting materials varied significantly and ranged from 1473 °C (WO3) to 2825 °C (MgO). The study of the ceramic structure showed that under the radiation effect of powerful radiation fluxes on the charge, a crystalline phase of the appropriate composition formed, regardless of the synthesis modes. The results of XRD studies show that during the radiation treatment of the charge, ceramics are formed mainly with the crystalline phases ZnWO4, MgWO4, and CaWO4. These resulting MeWO4 ceramics can be used for the same purposes as crystals. Photoluminescence (PL) and cathodoluminescence (CL) were studied under excitation using stationary ultraviolet radiation and nanosecond pulses of electron flux. In general, the PL and CL of synthesized ceramic samples ZnWO4, MgWO4, and CaWO4 showed that their luminescent properties are similar to those of luminescence in corresponding crystalline materials. This indicates the formation of a crystalline phase in synthesized ceramic samples.

Laser‐Annealed SiO2/Si1−xGex Scaffolds for Nanoscaled Devices, Synergy of Experiment, and Computation

Laser‐Annealed SiO₂/Si_1−<i>x</i>Ge_<i>x</i> Scaffolds for Nanoscaled Devices, Synergy of Experiment, and Computation

Alternate deposition and remelting microdroplets via single laser for printing low-defect and high-performance metal micropillars

Laser-induced forward transfer (LIFT) has emerged as a versatile technique for printing high-resolution metal microstructures. However, a common drawback of this method is the inadequate coalescence of the deposited metal microdroplets, which results in inferior electrical and mechanical properties. This paper proposes a novel approach for fabricating high-performance metal micropillars using a single-pulsed laser to alternately deposit and remelt metal microdroplets. Specifically, an ultraviolet nanosecond laser was used to induce the deposition of copper microdroplets, forming a patterned powder bed with high resolution. Subsequently, a laser pulse train was applied to fuse the patterned powder bed. The results showed that voids and microdroplet delamination were eliminated in the printed copper micropillars, whose yield strength and elastic modulus increased threefold, approaching 63% of those of the bulk metal. The remelting behavior of the deposited microdroplets was elucidated by modelling and analysing the thermal accumulation effects of a laser pulse train. A remelting map was proposed, including the non-melting, remelting, and vaporizing regimes. According to the depth of melt pool, the evolutions of morphology and microstructure in the depositing and remelting process were elucidated. Hence, this study advances the LIFT process for fabricating high-performance metal microstructures.

Gradient-Pattern Micro-Grooved Wicks Fabricated by the Ultraviolet Nanosecond Laser Method and Their Enhanced Capillary Performance.

Capillary-gradient wicks can achieve fast or directional liquid transport, but they face fabrication challenges by traditional methods in terms of precise patterns. Laser processing is a potential solution due to its high pattern accuracy, but there are a few studies on laser-processed capillary-gradient wicks. In this paper, capillary step-gradient micro-grooved wicks (CSMWs) were fabricated by an ultraviolet nanosecond pulsed laser, and their capillary performance was studied experimentally. The CSMWs could be divided into three regions with a decreasing capillary radius. The equilibrium rising height of the CSMWs was enhanced by 124% compared to the non-gradient parallel wick. Different from the classical Lucas-Washburn model describing a uniform non-gradient wick, secondary capillary acceleration was observed in the negative gradient direction of the CSMWs. With the increase in laser power and the decrease in scanning speed, the capillary performance was promoted, and the optimal laser processing parameters were 4 W-10 mm/s. The laser-enhanced capillary performance was attributed to the improved hydrophilicity and reduced capillary radius, which resulted from the increased surface roughness, protrusion morphology, and deep-narrow V-shaped grooves induced by the high energy density of the laser. Our study demonstrates that ultraviolet pulsed laser processing is a highly efficient and low-cost method for fabricating high-performance capillary gradient wicks.

AI-based modeling and multi-objective optimization of ultraviolet nanosecond laser-machined sapphire

AI-based modeling and multi-objective optimization of ultraviolet nanosecond laser-machined sapphire

355 nm Nanosecond Ultraviolet Pulsed Laser Annealing Effects on Amorphous In-Ga-ZnO Thin Film Transistors.

Bottom-gate thin-film transistors (TFTs) with n-type amorphous indium-gallium-zinc oxide (a-IGZO) active channels and indium-tin oxide (ITO) source/drain electrodes were fabricated. Then, an ultraviolet (UV) nanosecond pulsed laser with a wavelength of 355 nm was scanned to locally anneal the active channel at various laser powers. After laser annealing, negative shifts in the threshold voltages and enhanced on-currents were observed at laser powers ranging from 54 to 120 mW. The energy band gap and work function of a-IGZO extracted from the transmittance and ultraviolet photoelectron spectroscopy (UPS) measurement data confirm that different energy band structures for the ITO electrode/a-IGZO channel were established depending on the laser annealing conditions. Based on these observations, the electron injection mechanism from ITO electrodes to a-IGZO channels was analyzed. The results show that the selective laser annealing process can improve the electrical performance of the a-IGZO TFTs without any thermal damage to the substrate.

Monte Carlo simulation for KDP crystals induced by ultraviolet nanosecond laser irradiation

Potassium dihydrogen phosphate and its deuteride (KDP/DKDP) are the only tripled frequency crystals used for inertial confinement fusion. The photonic behavior of KDP under laser irradiation is unknown. In this study, the ultraviolet photon transport behavior of KDP with different growth environments has been simulated based on the Monte Carlo method. By comparison, it is shown that the linear absorption of filtered grown crystal is obviously weaker, and the relaxation time is much longer. Moreover, the concentration of defects inside KDP is the critical cause of linear absorption and relaxation time. Finally, the influence of multi-photon absorption on the damage of KDP is discussed.

Eliciting calcium transients with UV nanosecond laser stimulation in adult patient-derived glioblastoma brain cancer cells in vitro

Objective. Glioblastoma (GBM) is the most common and lethal type of high-grade adult brain cancer. The World Health Organization have classed GBM as an incurable disease because standard treatments have yielded little improvement with life-expectancy being 6–15 months after diagnosis. Different approaches are now crucial to discover new knowledge about GBM communication/function in order to establish alternative therapies for such an aggressive adult brain cancer. Calcium (Ca2+) is a fundamental cell molecular messenger employed in GBM being involved in a wide dynamic range of cellular processes. Understanding how the movement of Ca2+ behaves and modulates activity in GBM at the single-cell level is relatively unexplored but holds the potential to yield opportunities for new therapeutic strategies and approaches for cancer treatment. Approach. In this article we establish a spatially and temporally precise method for stimulating Ca2+ transients in three patient-derived GBM cell-lines (FPW1, RN1, and RKI1) such that Ca2+ communication can be studied from single-cell to larger network scales. We demonstrate that this is possible by administering a single optimized ultra-violet (UV) nanosecond laser pulse to trigger GBM Ca2+ transients. Main results. We determine that 1.58 µJ µm−2 is the optimal UV nanosecond laser pulse energy density necessary to elicit a single Ca2+ transient in the GBM cell-lines whilst maintaining viability, functionality, the ability to be stimulated many times in an experiment, and to trigger further Ca2+ communication in a larger network of GBM cells. Significance. Using adult patient-derived mesenchymal GBM brain cancer cell-lines, the most aggressive form of GBM cancer, this work is the first of its kind as it provides a new effective modality of which to stimulate GBM cells at the single-cell level in an accurate, repeatable, and reliable manner; and is a first step toward Ca2+ communication in GBM brain cancer cells and their networks being more effectively studied.

Parametric optimization of hole taper control in ultraviolet nanosecond laser micro-drilling of copper foil

While hole taper is inevitably formed in the laser micro-drilling of through micro-holes, the formation propensity is largely determined by the interaction between laser processing parameters. In the present work, we perform numerical simulations and experiments to investigate the ultraviolet nanosecond laser micro-drilling of 1 mm diameter through micro-holes on copper foil with a thickness of 280 μm, with an emphasis on the coupled influence of laser processing parameters on both the hole taper and circularity. Firstly, the characteristics of formed micro-hole quality are experimentally characterized, and the formation mechanisms of hole taper are further revealed by finite element simulations of multi-pulse laser ablation. Then, the relational degree of individual laser processing parameters in determining the hole taper and circularity is discovered by experimental investigation based on the gray relational analysis model. Finally, the coupled effect between significant parameters of laser power and repeat scanning number on the hole taper and circularity is further investigated by utilizing the response surface methodology, which derives the optimum laser processing parameters for manufacturing 1 mm diameter through micro-hole with a taper degree of 2.556° and a circularity of 0.992 on the copper foil.

Study on the ultraviolet nanosecond laser ablation and heat-affected zone of polydimethylsiloxane films based on comprehensive surface analysis

Study on the ultraviolet nanosecond laser ablation and heat-affected zone of polydimethylsiloxane films based on comprehensive surface analysis

Electroconvective instability at the surface of one-dimensionally patterned ion exchange membranes

The development of an electroconvective vortex explains the induction of overlimiting current in high voltage applications. However, an in-depth understanding of the dynamics remains challenging because the electrohydrodynamic behavior is unstable. Here, we show how the vortex develops and actively control this using a one-dimensional (1D) grid-patterned ion exchange membrane (IEM). We employed ultraviolet nanosecond laser ablation to fabricate micro-scale (100 μm) non-conductive 1D grid patterns on a commercial IEM. Vortex growth and the electrical responses were simultaneously monitored to derive correlations between the vortex dynamics and ion transport. The rate of electric potential fall increased rapidly during vortex development but decreased more gradually on transverse merging of the vortices. When shear flow was present, the modified scaling law was redefined via dimensionless number analysis of the electroconvective flow by the length of the impermeable 1D grid pattern and the applied voltage. The overlimiting currents and the desalination performances of 1D grid-patterned IEMs were successfully demonstrated. Based on these insights into the electroconvective vortex, we show that the electrical heterogeneity of the IEM actively controls the vortex and enhances desalination performance.

Numerical simulation study of ultraviolet nanosecond laser ablation of Cu-Al2O3 dispersion strengthened alloys

Numerical simulation study of ultraviolet nanosecond laser ablation of Cu-Al2O3 dispersion strengthened alloys

Characterization of graphene oxide by pulsed UV nanosecond laser irradiation for flexible electrodes

This article focused on the fabrication of a thin film of rGO through pulsed Ultraviolet nanosecond laser irradiation. With the influence of laser power energy, the thickness of the fabricated thin film decreased, the contents of Carbon increased, Oxygen contents decreased, electrical resistance decreased, and a normalized specific surface area increased. When the thin film of GO was exposed to laser-irradiation, leads to the reduction of oxygen and the restoration of sp2 hybridization, resulting in a material with reduced electrical resistance and improved specific surface area. As a result, at 125 mW of laser power energy and 200 mm/s scanning speed of pulsed UV nanosecond laser, the contents of Carbon increased up to 81.6%, Oxygen contents decreased to 11.3%, and normalized specific surface area of 0.97 m2/g with good electrical conductivity was obtained. Therefore, its good electrical properties offer prospects for fabricating flexible electrodes and the practical application of pulsed laser-irradiated rGO substrate films for flexible electronics applications.

Effect of using reflective target materials on enhancing UV nanosecond laser machining of sapphire

The machining of sapphire, a hard and transparent material, is of significant interest in various industries due to its exceptional properties. Traditional machining methods for sapphire suffer from drawbacks such as low efficiency and poor processing quality. Laser machining, particularly using ultraviolet (UV) nanosecond lasers, has emerged as a promising alternative for machining sapphire. In this article, we explored the use of reflective target materials to enhance laser energy absorption during the machining of sapphire. The effect of different reflective target materials, including aluminum and silicon, on the laser machining process was examined. Parametric calculations and finite-difference time-domain (FDTD) simulation were performed to evaluate the laser intensity at the top surface of sapphire when a reflective target material was employed. The results demonstrated that the use of reflective target materials leads to increased laser intensity due to the interference of incident and reflected laser beams, thus improving material removal efficiency. Moreover, experimental observations confirmed the effectiveness of using reflective target materials in enhancing the machined depth of sapphire. For example, the machined depth of 21.6 µm with a power density of 1.7 × 108 W/cm2 increased to 23.3 µm and 26.5 µm by using silicon and aluminum target materials. It is found that using aluminum target led to higher machined depth than silicon owing to its higher reflectivity.

Laser debonding application in ultra-thin device processing.

Laser debonding offers several advantages such as precision, speed, minimal damage, and being noncontact. We investigated the feasibility of utilizing laser processing technology in producing high-performance ultra-thin wafer devices at a low cost. We successfully utilized the 355nm ultraviolet nanosecond laser to develop a compatible laser debonding process for domestic temporary bonding adhesives, which effectively performed the laser lift-off of 8-in (20.3 cm) silicon/temporary bonding adhesive/glass substrate samples at a power density of 250m J/c m 2. We designed and developed a line light source shaping system that was ultimately able to produce a line spot with a length exceeding 1cm and an energy distribution unevenness of less than 10%.

Impact of surface reflectivity on the ultra-fast laser melting of silicon-germanium alloys

Ultraviolet nanosecond laser annealing (LA) is a powerful tool where strongly confined heating and melting are desirable. In semiconductor technologies the importance of LA increases with the increasing complexity of the proposed integration schemes. Optimizing the LA process along with the experimental design is challenging, especially when complex 3D nanostructured systems with various shapes and phases are involved. Within this context, reliable simulations of laser melting are required for optimizing the process parameters while reducing the number of experimental tests. This gives rise to a virtual Design of Experiments (DoE). Si1−xGex alloys are nowadays used for their compatibility with silicon devices enabling to engineer properties such as strain, carrier mobilities and bandgap. In this work, the laser melting process of relaxed and strained Si1−xGex is simulated with a finite element method/phase field approach. Particularly, we calibrated the dielectric functions of the alloy for its crystalline and liquid phase using experimental data. We highlighted the importance of reproducing the exact reflectivity of the interface between air and the material in its different aggregation states, to correctly mimic the process. We indirectly discovered intriguing features on the optical behaviour of melt silicon-germanium.

Nanosecond laser annealing of pseudomorphic GeSn layers: Impact of Sn content

Interactions between nanosecond laser pulses and various Sn content pseudomorphic GeSn layers were investigated. The aim was to evaluate the suitability of Ultraviolet Nanosecond Laser Annealing (UV-NLA), with an excimer laser emitting at 308 nm and a pulse duration of 160 ns, for the fabrication of performant contacts in GeSn devices such as electrically pumped lasers. Atomic Force Microscopy (AFM) and X-Ray Diffraction (XRD) revealed similar melt regimes for GeSn on Ge and SiGe on Si. At the melt threshold, surface structures formed where small areas melted. We were then in the so-called surface melt regime. The surface structures’ shape changed with the Sn content. A similar trend was recently evidenced when submitting SiGe layers on Si to UV-NLA. The shape change was more drastic in GeSn than in SiGe. A larger built-in compressive strain because of a much larger size difference between Ge and Sn than Si and Ge might be the reason why. Time Resolved Reflectivity maps showed a more reflective plateau after the melt peak at an Energy Density (ED) of around 1.00 Jcm−2, stemming from the presence of a smooth Sn rich surface layer, as revealed by AFM images at the same ED. Stacked XRD maps outlined that this ED corresponded to the formation of rather high Sn content layers with Sn contents of up to 6.3%, i.e., concentrations significantly above the solid solubility limit, which is below 1%, at variance with conventional annealing processes at 450 °C. UV-NLA has thus opened a new processing window that might be useful for contact formation.