UV Laser Ablation Research Articles

Selective gold film removal from multi-layer substrates with nanosecond UV pulsed laser ablation

Pulsed UV laser ablation was explored as a means of removing thin (200 nm) gold films from one side of a transparent, thin (50 μm) quartz substrate. Single-pulse laser ablation (KrF excimer laser, 248 nm) was used to remove a top gold film without damaging the pre-patterned gold electrode deposited on the opposite side of the quartz substrate. Scanning electron microscope images were taken to evaluate the quality and consistency of the metal removal. It was found that the ablation threshold is 160 mJ/cm2 for 5 ns pulses. The highest-quality single-pulse ablation was observed with 200 mJ/cm2 for 5 ns pulses, and significant shielding was observed for fluences up to six times the ablation threshold for both 5 and 15 ns pulse durations. Further, the impact of increasing pulse energies upon the bottom electrode was measured, and a progression from pinhole formation to simultaneous removal of both gold films as a function of pulse intensity was determined.

Fabrication of contact holes by rear side laser ablation of polyimide foils for CIGS solar modules

Laser technology is of increasing interest for the improvement of photovoltaic generators also for mass production. Copper–indium–gallium–diselenide (CIGS) thin film solar cells on flexible polyimide (PI) foil have great potential for specific applications requiring mechanical flexibility. To reduce the dead area of solar modules especially that of the serial interconnection shingling of the solar cells is one encouraging approach. The former developed back side opening process is utilized for via preparation to realize the serial interconnection at the rear side of the solar cells. Arrays of square vias that were fabricated into the polyimide foil by UV laser ablation were filled with a silver-based conductive adhesive for realizing the electrical and mechanical interconnection. Contact resistance of the silver-based adhesive to the solar cell back contact of less than 0.2Ωmm2 has been measured. Shingled CIGS modules with a size of 100 cm2 having an open circuit voltage of 2.3V and a short circuit current of more than 500mA demonstrate the great potential of this interconnection approach for flexible electronic applications.

Medieval glass from the Cathedral in Paderborn: a comparative study using X-ray absorption spectroscopy, X-ray fluorescence, and inductively coupled laser ablation mass spectrometry

We have investigated four stained glass samples recovered from an archaeological excavation at the Cathedral in Paderborn (Germany) between 1978 and 1980. On two of the samples there are parts of paintings. Concentrations of major elements were determined using two independent techniques: LA–ICP–MS (a UV laser ablation microsampler combined with an inductively coupled plasma mass spectrometer) and synchrotron radiation X-ray excited X-ray fluorescence (SR-XRF). The SR-XRF data were quantified by using the program package PyMCA developed by the software group of the ESRF in Grenoble. Significant differences were found between the concentrations determined by the two techniques that can be explained by concentration gradients near the surface of the glasses caused, for example, by corrosion/leaching processes and the different surface sensitivities of the applied techniques. For several of the elements that were detected in the glass and in the colour pigments used for the paintings X-ray absorption near edge structure (XANES) spectra were recorded in order to determine the chemical speciation of the elements of interest. As was expected, most elements in the glass were found as oxides in their most stable form. Two notable exceptions were observed: titanium was not found as rutile—the most stable form of TiO2—but in the form of anatase, and lead was not found in one defined chemical state but as a complex mixture of oxide, sulphate, and other compounds.

Micron and Sub-Micron Gratings on Glass by UV Laser Ablation

Abstract ArF excimer laser ablation is applied for the generation of surface relief gratings on various glass materials. At the laser wavelength of 193 nm even highly transparent borosilicate glasses exhibit sufficient absorption for the fabrication of precise, crack free ablation patterns. Gratings with periods down to 3 μm are created in a line by line process by projecting a laser illuminated slit onto the glass surface. Micron- and sub-micron-periodic gratings are made by projecting a transmission grating using a Schwarzschild objective. Such gratings can be applied for surface functionalization or diffractive marking.

UV-laser Ablation of Fibre Reinforced Composites with Ns-Pulses

Within this work the ablation behaviour of both carbon and glass fibre reinforced epoxy resin was assessed when ablated by a nanosecond-pulsed laser source emitting radiation in the ultra-violet spectrum. The investigation focussed on the influences of pulse overlap, focus spot diameter and resulting fluence on process quality and machining time.Results showed that ns-pulsed UV-lasers are capable of machining both types of fibre reinforced composites, while achieving good quality surfaces without burn marks or otherwise heat-damaged areas.

Surface Treatment of Polyimide Film by Pulsed UV Laser Ablation and Its Effect on the Electrochemical Characteristics

Polyimide (PI) possess outstanding proper-ties, such as thermo-oxidative stability, high mechanicalstrength, excellent electrical properties and thermal/chemi-cal stability. Polyimide plays an important role in flexibleprinted circuit board, flexible display, and flexible electrode.Most of the applications of UV laser ablation of PI focusedon the micropatternings,

Metamorphic rocks seek meaningful cooling rate: Interpreting 40Ar/39Ar ages in an exhumed ultra-high pressure terrane

40Ar/39Ar dating of metamorphic white mica is commonly used to elucidate the timing of cooling and/or exhumation of metamorphic terranes. In theory, so long as the dated mineral originally crystallised above its closure temperature, the yielded 40Ar/39Ar ages should not vary significantly within or between samples, and should vary only due to grain size (~3Ma variation depending on the estimated cooling rate). Infra-red laser single grain fusion and ultra-violet laser spot muscovite and/or phengite data from mafic eclogite bodies and their host gneisses in the Nordfjord region of the Western Gneiss Complex (WGC), Norway, show that the ages yielded both within and between white micas from the same mafic eclogite sample vary by up to 284Ma. Ages yielded within the same pelitic gneiss sample vary by up to 28Ma. Overall the 40Ar/39Ar phengite dates from mafic eclogites range from ~750 to 440Ma and are significantly older than the previously reported 405–400Ma U–Pb zircon age constraining peak metamorphism in the Nordfjord WGC. The felsic host gneiss samples, which recrystalised during a post-peak, exhumation-related, amphibolite-facies overprint, yield single grain fusion and laser spot 40Ar/39Ar white mica dates spanning ~420 to 385Ma, encompassing previous estimates of the timing of the entire metamorphic cycle. These data suggest that Ar is heterogeneously distributed both within grains and between grains on the cm to sub-mm scale in all samples, and imply restricted Ar transport and inefficient removal during the metamorphic cycle. Open system (zero grain boundary Ar concentration) behaviour is an inherent assumption in the commonly applied closure temperature formulation, but unless this can be demonstrated, linking 40Ar/39Ar ages to temperature is no longer trivial. The high spatial and chronological precision afforded by UV laser ablation mean that intra-grain Ar concentration distributions may be used to assess open vs. closed system behaviour. The data presented here suggest that open system behaviour cannot be assumed in metamorphic systems, even those in which the pressure, temperature and time conditions in theory allow for efficient diffusion during the metamorphic cycle. High spatial resolution 40Ar/39Ar data and robust comparison with numerical models of open system behaviour provide the greatest future potential for unravelling the complexities of metamorphic exhumation timescales.

355 nm UV 레이저 어블레이션을 이용한 마이크로-나노 구조의 액적 분리용 박막 필터 쾌속 제작

Recently micro-nano structures has widely been reported to improve the performance of waterproof, heat isolation, sound and light absorption in various fields of electric devices such as mobiles, battery, display and solar panels. A lot of micro-sized holes on the surface of thin film provide excellent sound, or heat, or light transmission efficiency more than solid film and simultaneously nano-sized protrusions around micro hole increase the hydrophobicity of the surface of thin film because of lotus leaf effects as generally known previously. In this paper new rapid fabrication process with 355 nm UV laser ablation was proposed to get micro-nano structures on the surface of thin film, which have only been observed at higher laser fluence. Developed thin micro-nano structured film was also investigated the hydrophobic property by measuring the contact angle and demonstrated the possibility to apply to water droplet separation.

Physically stable proton exchange membrane with ordered electrolyte for elevated temperature PEM fuel cell

Dimensional change and humidity-induced stress of the proton exchange membrane were demonstrated to be main reasons for membrane physical failure during the long-term fuel cell operation. In this work, UV laser ablation was proposed to prepare physically stable polyimide supports to reduce the dimensional swelling and humidity-induced stress of the proton exchange membrane under variable humidities. Long-range ordered straight holes with definable open pattern and diameter of 50–200 μm were formed through the polyimide support. Composite proton exchange membrane prepared from the straight-hole polyimide support presented desirable performance and high durability in fuel cells. When Nafion fraction in the composite membrane increased to 48.67%, the proton conductivities of the composite membranes were equal to or greater than that of the conventional Nafion membrane with activation energies lower than that of the Nafion 211 membrane. The dimensions of the composite membranes are very stable in both low and elevated temperature conditions. The proportion of humidity-induced stress to the yield strength for the composite membrane is 0.20%–0.21%, much lower than that of the conventional Nafion membrane (24.77%). As a result, the composite proton exchange membrane prepared from the straight-hole polyimide presented high durability in the fuel cell operation. In the open circuit voltage accelerated test under in situ accelerating RH cyclic test, the irreversible OCV reduction rate of the composite membranes was 2.41–2.72 × 10−5 V/cycle, 37.1%–41.8% lower than that of the conventional Nafion 211 membrane.

Laser ablation of polyetheretherketone films for reversible wafer bonding

A reversible wafer bonding method has been developed that enables high-temperature processing of thinned silicon wafers. The silicon wafers are bonded to Pyrex carriers using a polyetheretherketone (PEEK) film, which melts at 343 °C, and provides a very strong bond. Debonding is accomplished by UV laser ablation through the Pyrex carrier and can be facilitated by coating the Pyrex wafer with Teflon. Most of the PEEK film remains on the silicon wafer after debonding and is removed with solvents. Precoating the silicon with germanium/tetraethyl orthosilicate (TEOS) might enable PEEK removal without solvents. This germanium/TEOS layer lifts off with the PEEK film during laser ablation.

Conical Structures on Acrylic Intraocular Lens (IOLs) Materials after 193-nm Excimer Laser Ablation

Intraocular lens (IOLs) implants are synthetic lenses used to replace the natural lens of the eye and obtain optical reha- bilitation. The materials and methods of IOLs fabrication have been correlated with postoperative complications such as diffractive aberrations, capsular opacification or discoloration. Thus, several new materials and patterns are studied for the formation and etching of intraocular lenses (IOLs). In our work, we studied the use of UV laser as an alternative method to conventional surface shaping techniques for IOLs etching. Ablation experiments were conducted on hydrophobic acrylic IOLs by a commercial excimer laser system used in photorefractive surgery. The morphology of the irradiated area was observed by scanning electron microscopy (SEM) and a mathematical algorithm was used for SEM image processing. The effect of IOLs exposure to UV light before excimer laser irradiation was also examined, since natural ageing and cross-linking of IOLs material were reported. Conical structures were revealed after UV laser ablation and their population was increased with the number of laser pulses. Period distribution of cones was measured with the combination of image processing and a scanning algorithm which was developed for this reason. According to the graphs, the mean period and the distribution of the cones was depending of the number of irradiation pulses and the exposure to UV lamp before laser irradiation. Although a photochemical and a theoretically smooth-surface ablation mechanism is considered for the UV excimer laser interaction with polymers, surface conical-like abnormalities and thermal degradation of the lenses materials was observed.

Influence of organic solvent on optical and structural properties of ultra-small silicon dots synthesized by UV laser ablation in liquid

Ultra small silicon nanoparticles (Si-NPs) with narrow size distribution are prepared in a one step process by UV picosecond laser ablation of silicon bulk in liquid. Characterization by electron microscopy and absorption spectroscopy proves Si-NPs generation with an average size of 2 nm resulting from an in situ photofragmentation effect. In this context, the current work aims to explore the liquid medium (water and toluene) effect on the Si-NPs structure and on the optical properties of the colloidal solution. Si-NPs with high pressure structure (s.g. Fm3m) and diamond-like structure (s.g. Fd3m), in water, and SiC moissanite 3C phase (s.g. F4[combining macron]3m) in toluene are revealed by the means of High-Resolution TEM and HAADF-STEM measurements. Optical investigations show that water-synthesized Si-NPs have blue-green photoluminescence emission characterized by signal modulation at a frequency of 673 cm(-1) related to electron-phonon coupling. The synthesis in toluene leads to generation of Si-NPs embedded in the graphitic carbon-polymer composite which has intrinsic optical properties at the origin of the optical absorption and luminescence of the obtained colloidal solution.

Self-Diffusion of Lithium in LiAlSi2O6 Glasses Studied Using Mass Spectrometry

In order to improve our understanding of the transport mechanisms of lithium in glasses, we have performed diffusion and ionic conductivity studies on spodumene composition (LiAlSi(2)O(6)) glasses. In diffusion couple experiments pairs of chemically identical glasses with different lithium isotopy (natural Li vs pure (7)Li) were processed at temperatures between 482 and 732 K. Profiles of lithium isotopes were measured after the diffusion runs innovatively applying femtosecond UV laser ablation combined with inductively coupled plasma mass spectrometry (LA ICP-MS). Self-diffusion coefficients of lithium in the glasses were determined by fitting the isotope profiles. During some of the diffusion experiments the electrical conductivity of the samples was intermittently measured by impedance spectrometry. Combining ionic conductivity and self-diffusivity yields a temperature-independent correlation factor of ~0.50, indicating that motions of Li ions are strongly correlated in this type of glasses. Lithium self-diffusivity in LiAlSi(2)O(6) glass was found to be very similar to that in lithium silicate glasses although Raman spectroscopy demonstrates structural differences between these glasses; that is, the aluminosilicate is completely polymerized while the lithium silicate glasses contain large fractions of nonbridging oxygen.

Picosecond laser ablation of poly-L-lactide: Effect of crystallinity on the material response

The picosecond laser ablation of poly-L-lactide (PLLA) as a function of laser fluence and degree of crystallinity was examined. The ablation parameters and the surface modifications were analyzed under various irradiation conditions using laser wavelengths ranging from the ultraviolet through the visible. When processing the amorphous PLLA, both energy threshold and topography varied considerably depending on laser wavelength. Laser irradiation showed a reduction in the energy ablation threshold as the degree of crystallinity increased, probably related to photomechanical effects involved in laser ablation with ultra-short pulses and the lower stress accommodation behavior of semicrystalline polymers. In particular, cooperative chain motions are impeded by the higher degree of crystallinity, showing fragile mechanical behavior and lower energy dissipation. The experimental results on ablation rate versus laser energy showed that UV laser ablation on semicrystalline PLLA was more efficient than the visible ablation, i.e., it exhibits higher etch rates over a wide range of pulse energy conditions. These results were interpreted in terms of photo-thermal and photo-chemical response of polymers as a function of material micro-structure and incident laser wavelength. High quality micro-grooves were produced in amorphous PLLA, reveling the potential of ultra-fast laser processing technique in the field of micro-structuring biocompatible and biodegradable polymers for biomedical applications.

Experimental Investigation on the Scribing of Sapphire Using UV Laser

Sapphire is an important wide bandgap semiconductor material for developing UV/blue optoelectronic devices, however because of its high hardness and chemical stability; it is mechanically and chemically difficult machine. In this paper, the scribing of sapphire by UV laser pulses is investigated under various conditions of pulse energies, scanning speed and repetition rate. The quality and morphology of the laser ablation of sapphire surface are evaluated by scanning electron microscopy. The mechanism of UV laser ablation of sapphire is discussed. The formation of grooves with high aspect ratio and good surface quality is achieved by selecting appropriate laser parameters. Scribing by pulsed UV laser therefore provide a new approach in the development of sapphire-based devices.

Novel Technology Options for Multilayer-Based Ceramic Microsystems

Ceramic multilayer technologies as LTCC (Low Temperature Cofired Ceramics) or HTCC (High Temperature Cofired Ceramics) are applied for the fabrication of highly integrated ceramic microelectronic packages. Furthermore ceramic multilayer technologies offer the possibility of the additional integration of 3-D-structures for multilayer-based microsystems. The paper presents a new machine for tape/ multilayer structuring combining micro punching tools and micro UV-laser ablation/ cutting. The application for the production of different multilayer based components is described (e.g. LTCC-based PEM fuel cell system, LTCC-based pressure sensors). Aerosol printing is a new technology e.g. for rapid prototyping for LTCC multilayer and 3-D-deposition of functional layers on LTCC. Advantages and limitations of the technology are discussed.

Early plume and shock wave dynamics in atmospheric-pressure ultraviolet-laser ablation of different matrix-assisted laser ablation matrices

Pulsed laser ablation of molecular solids is important for identification and quantification in (bio-)organic mass spectrometry, for example using matrix-assisted laser desorption/ionization (MALDI). Recently, there has been a major shift to using MALDI and related laser ablation/post-ionization methods at atmospheric pressure. However, the underlying laser ablation processes, in particular early plume formation and expansion, are still poorly understood. Here, we present a study of the early ablation processes on the ns-time scale in atmospheric pressure UV-laser ablation of anthracene as well as of different common MALDI matrices such as 2,5-dihydroxybenzoic acid (2,5-DHB), α-cyano-4-hydroxycinnamic acid and sinapinic acid. Material release as well as the formation and expansion of hemi-spherical shock waves were studied by shadowgraphy with high temporal resolution (∼5 ns). The applicability of the classical Taylor-Sedov model for expansion of strong shock waves (“point-blast model”), as well as the drag force model, were evaluated to mathematically describe the observed shock wave propagation. The time- and energy-dependent expansion of the shock waves could be described using a Taylor-Sedov scaling law of the form R ∝ tq, when a q-exponent of ∼0.5 instead of the theoretical value of q = 0.4 was found, indicating a faster expansion than expected. The deviations from the ideal value of q were attributed to the non-negligible influence of ambient pressure, a weak versus strong shock regime, and additional acceleration processes present in laser ablation that surpass the limit of the point-blast model. The onset of shock wave formation at a fluence of ∼15–30 mJ/cm2 for the compounds investigated coincides with the onset of bulk material release, whereas, pure desorption below this fluence threshold did not lead to features visible in shadowgraphy.

Laser Ablation of Metal Substrates for Super-hydrophobic Effect

Pulsed UV laser ablation is applied to fabricate super-hydrophobic surfaces on metal substrates. The spike shape micro-structure arrays achieved by the laser ablation on the brass substrates increase the surface roughness (Ra) from ~ 400 nm to ~ 5 μm. Meanwhile, plenty of nano-structures (200 ~ 600 nm) are also formed and scattered on the surface of the micro-structures. It is found that the water contact angle of the brass substrate increases from 110° to 161°. Super-hydrophobic property of the metal surfaces with both the micro& nano-roughness is explained by water repellent model for double roughness structures. High speed camera imaging is used to analyze water droplet dynamics during its rolling down along the slanted super-hydrophobic brass surface. It shows that the pulsed laser ablation is a versatile approach to create large area super-hydrophobic surfaces for industrial applications.

Experimental study of the dynamics and macrostructure of laser-induced high-pressure dust gas-plasma flows

We propose and for the first time experimentally carry out a method of laser-induced generation of high-pressure dust gas-plasma flows with complex chemical and ionization composition under UV laser ablation of a polymer matrix containing the dust component. The method uses the difference in the spectral-energy threshold of laser ablation and optical properties of polymer materials and dust components in the short-wavelength region of the spectrum. We present the results of an experimental study of the dynamics and macrostructure of laser-induced high-pressure dust gas-plasma flows under UV (λ1 = 213 nm, λ2 = 266 nm, λ3 = 355 nm) laser ablation of condensed targets based on a (C2F4)n polymer matrix with a dust component (SiO2, Al2O3, CeO2). Using laser interferometry and shadowgraphy, we determined the spectral-energy thresholds and conditions for generating dust structures in ionized pairs of the target matrix and their spatiotemporal localization in a gas-dust flow up to spatial division of the evaporated substance of the target matrix and the dust-component cloud. We determine the lifetimes of heterophase flows as a function of the parameters of laser action on a condensed target and the charge of dust particles.

Quantification of transient signals in multiple collector inductively coupled plasma mass spectrometry: accurate lead isotope ratio determination by laser ablation of individual fluid inclusions

This work establishes the analytical protocol for accurate Pb isotopic analysis of fast transient signals by multiple-collector ICP-MS instruments. Individual synthetic fluid inclusions of known Pb and Tl isotopic compositions (dissolved SRM 981 with or without SRM 997 from NIST, enclosed in quartz by a hydrothermal crack annealing technique) were liberated by 193 nm UV laser ablation (LA). Data were recorded on Faraday detectors, for which correction schemes for bias in amplifier response (“tau correction”) are presented and evaluated. tau-Corrected Pb isotope data reveal LA-induced isotope fractionation amounting to ∼0.5% amu−1 for Pb isotopes over the course of an entire fluid inclusion ablation. Instrumental mass bias correction was effected within-run using Tl provided by the fluid inclusion itself or admixed to the ablation aerosol via desolvated nebulization. Isotope ratios derived from the transient signals were either based on individual readings or on bulk signal integration, of which the latter produces significantly more accurate data. The external precision achieved by ablating SRM 610 glass with a 60 µm beam is ±0.011% (2 SD, relative) for 208Pb/206Pb and 207Pb/206Pb ratios and ±0.032% for Pb isotope ratios normalized to mass 204 (n = 18). Inclusion-to-inclusion reproducibilities (n = 11; ∼0.1 ng Pb per inclusion) are ±0.05% (2 SD; 208Pb/206Pb and 207Pb/206Pb) and ±0.13% (20xPb/204Pb), respectively; inclusions containing as little as 0.005 ng Pb returned ±0.1% and ±0.8%. These results are accurate as demonstrated by analysis of synthetic fluid inclusions containing SRM 981 Pb. The analytical protocol presented here for measuring isotope ratios on minute analyte quantities by multiple-collector ICP-MS in fast transient signal mode has great potential for applications to geochemical, archaeological, environmental and possibly biochemical problems.