Laser-ablated Material Research Articles

Space weathering by simulated micrometeorite bombardment on natural olivine and pyroxene: A coordinated IR and TEM study

We studied space-weathering effects caused by micrometeorite bombardment simulated by pulsed intense infrared laser, generating ∼15 mJ per pulse in high vacuum. For our investigation, we selected a natural olivine (San Carlos olivine (Fo91)) and a natural pyroxene (Bamble orthopyroxene (En87)) as important rock forming minerals of the Earth upper mantle as well as key planetary minerals. Irradiated areas of powdered pressed samples were examined by optical reflection spectroscopy in a broad optical and infrared wavelength range (visible-, near-, and mid-infrared) and transmission electron microscopy to identify changes due to micrometeorite impacts. The present study aims to investigate especially the effects of micrometeorite bombardment on reflectance spectra in the mid-IR in preparation for future space missions, as well as for the MERTIS experiment onboard the BepiColombo mission.For both irradiated samples, we found a reduction in albedo and in the reflectance of characteristic Reststrahlen bands and an increase of the transparency feature. VIS and NIR spectra of both minerals show the typical darkening and reddening as described for other space-weathered samples. TEM studies revealed that space-weathered layers in olivine and pyroxene differ in their respective thickness, ∼450 nm in olivine, 100-250 nm in pyroxene, as well as in developed “nanostratigraphy” of laser-ablated material, like nanophase iron (npFe).In conclusion, our spectral and structural findings were compared to samples in which space weathering was caused by different processes. A comparison with these data demonstrates that there is no difference in optical reflectance spectroscopy, but a significant difference in the microstructure of minerals due to the weathering source in space, as there are solar wind and solar flares cause other structural and chemical changes as the bombardment with micrometeorites.

Study of Spark Discharge Assisted to Enhancement of Laser-Induced Breakdown Spectroscopic Detection for Metal Materials

In this work, laser triggered spark discharge was combined with laser-ablation under Air and Ar gases to investigate the characteristics of laser-ablated plasma emission. The experimental results show that the optical emission intensity is significantly enhanced by electric discharge compared to without discharge and the spectral emission time of plasma is much longer than that without discharge. The enhancement effect is more apparent in the presence of Ar ambient. In addition, the plasma temperature and electron density as well as limits of detections (LOD) have been determined. The better LOD can be attributed to the improvement of plasma. The higher plasma temperature and electron density indicate that the enhanced mechanism in emission intensity is predominated by the further excitation/ionization of the laser-ablated material by the spark discharge due to the energy deposition in the plasma.

Transmission geometry laser ablation into a non-contact liquid vortex capture probe for mass spectrometry imaging.

Capture of material from a laser ablation plume into a continuous flow stream of solvent provides the means for uninterrupted sampling, transport and ionization of collected material for coupling with mass spectral analysis. Reported here is the use of vertically aligned transmission geometry laser ablation in combination with a new non-contact liquid vortex capture probe coupled with electrospray ionization for spot sampling and chemical imaging with mass spectrometry. A vertically aligned continuous flow liquid vortex capture probe was positioned directly underneath a sample surface in a transmission geometry laser ablation (355 nm, 10 Hz, 7 ns pulse width) set up to capture into solution the ablated material. The outlet of the vortex probe was coupled to the Turbo V™ ion source of an AB SCIEX TripleTOF 5600+ mass spectrometer. System operation and performance metrics were tested using inked patterns and thin tissue sections. Glass slides and slides designed especially for laser capture microdissection, viz., DIRECTOR(®) slides and PEN 1.0 (polyethylene naphthalate) membrane slides, were used as sample substrates. The estimated capture efficiency of laser-ablated material was 24%, which was enabled by the use of a probe with large liquid surface area (~2.8 mm(2) ) and with gravity to help direct ablated material vertically down towards the probe. The swirling vortex action of the liquid surface potentially enhanced capture and dissolution not only of particulates, but also of gaseous products of the laser ablation. The use of DIRECTOR(®) slides and PEN 1.0 (polyethylene naphthalate) membrane slides as sample substrates enabled effective ablation of a wide range of sample types (basic blue 7, polypropylene glycol, insulin and cyctochrome c) without photodamage using a UV laser. Imaging resolution of about 6 µm was demonstrated for stamped ink on DIRECTOR(®) slides based on the ability to distinguish features present both in the optical and in the chemical image. This imaging resolution was 20 times better than the previous best reported results with laser ablation/liquid sample capture mass spectrometry imaging. Using thin sections of brain tissue the chemical image of a selected lipid was obtained with an estimated imaging resolution of about 50 µm. A vertically aligned, transmission geometry laser ablation liquid vortex capture probe, electrospray ionization mass spectrometry system provides an effective means for spatially resolved spot sampling and imaging with mass spectrometry.

Fully automated laser ablation liquid capture surface analysis using nanoelectrospray ionization mass spectrometry.

Laser ablation provides for the possibility of sampling a large variety of surfaces with high spatial resolution. This type of sampling when employed in conjunction with liquid capture followed by nanoelectrospray ionization provides the opportunity for sensitive and prolonged interrogation of samples by mass spectrometry as well as the ability to analyze surfaces not amenable to direct liquid extraction. A fully automated, reflection geometry, laser ablation liquid capture spot sampling system was achieved by incorporating appropriate laser fiber optics and a focusing lens into a commercially available, liquid extraction surface analysis (LESA(®))-ready Advion TriVersa NanoMate system. Under optimized conditions about 10% of laser-ablated material could be captured in a droplet positioned vertically over the ablation region using the NanoMate robot-controlled pipette. The sampling spot size area with this laser ablation liquid capture surface analysis (LA/LCSA) mode of operation (typically about 120 µm × 160 µm) was approximately 50 times smaller than that achievable by direct liquid extraction using LESA(®) (ca 1 mm diameter liquid extraction spot). The setup was successfully applied for the analysis of ink on glass and paper as well as the endogenous components in Alstroemeria Yellow King flower petals. In a second mode of operation with a comparable sampling spot size, termed laser ablation/LESA(®), the laser system was used to drill through, penetrate, or otherwise expose material beneath a solvent resistant surface. Once drilled, LESA(®) was effective in sampling soluble material exposed at that location on the surface. Incorporating the capability for different laser ablation liquid capture spot sampling modes of operation into a LESA(®)-ready Advion TriVersa NanoMate enhanced the spot sampling spatial resolution of this device and broadened the surface types amenable to analysis to include absorbent and solvent-resistant materials.

Laser microdissection and atmospheric pressure chemical ionization mass spectrometry coupled for multimodal imaging

Improvement in spatial resolution of atmospheric pressure molecular chemical imaging is required to resolve distinct surface features in the low micrometer and sub-micrometer scale. Laser capture microdissection systems have the capability to focus laser light to a few micrometers. This type of system, when employed for laser ablation (LA) mass spectrometry (MS)-based chemical imaging, has the potential to achieve high spatial resolution with multimodal optical and chemical imaging capability. A commercially available laser capture microdissection system was coupled to a modified ion source of a mass spectrometer. This design allowed for sampling of laser-ablated material via a transfer tube directly into the ionization region. Ionization of the ablated material was accomplished using atmospheric pressure chemical ionization (APCI). Rhodamine 6G dye of red permanent marker ink in a laser etched pattern as well as cholesterol and phosphatidylcholine in a cerebellum mouse brain thin tissue section were identified and imaged from the mass spectral data. Employing a spot diameter of 8 µm using the 10× microscope cutting objective and lateral oversampling resulted in a pixel size of about 3.7 µm in the same dimension. Distinguishing between features approximately 13 µm apart in a cerebellum mouse brain thin tissue section was demonstrated in a multimodal fashion co-registering optical and mass spectral images. A LA/APCI-MS system was developed that comprised a commercially available laser microdissection instrument for transmission geometry LA and a modestly modified ion source for secondary ionization of the ablated material. The set-up was successfully applied for multimodal imaging using the ability to co-register bright field, fluorescence and mass spectral chemical images on one platform.

Combinatorial pulsed laser deposition of Fe/MgO granular multilayers

Combinatorial pulsed laser deposition (PLD) makes use of the angular spread of laser-ablated material to prepare thin films with lateral compositional gradient. In this paper we have used combinatorial PLD to grow discontinuous Fe/MgO multilayers by alternate ablation from two separate Fe and MgO targets. Films of composition [Fe(tFe)/MgO(tMgO)]15 were deposited on glass substrates. The thickness of Fe and MgO were varied in the vicinity of critical values determined in previous studies to maximize the tunneling magnetoresistance (TMR) in the current-in-plane configuration. Optimized multilayers show a substantial improvement of both TMR and field sensitivity at room temperature.

Application of pulsed laser deposition and laser-induced ion implantation for formation of semiconductor nano-crystallites

This work describes the application of laser ion source (LIS) for fabrication of semiconductor nanostructures, as well as relevant equipment completed and tested in the IPPLM for the EU STREP “SEMINANO” project and the obtained experimental results. A repetitive pulse laser system of parameters: energy of ∼0.8 J in a 3.5 ns-pulse, wavelength of 1.06 μm, repetition rate of up to 10 Hz and intensity on the target of up to 1011 W/cm2, has been employed to produce Ge ions intended for ion implantation into SiO2 substrate. Simultaneously, laser-ablated material (atoms clusters debris) was deposited on the substrate surface. The parameters of the Ge ion streams (energy and angular distributions, charge states, and ion current densities) were measured with the use of several ion collectors and an electrostatic ion energy analyzer. The SiO2 films of thickness from 20–400 nm prepared on substrates of a single Si crystal were deposited and implanted with the use of laser-produced germanium of different properties. The modified SiO2 layers and sample surface properties were characterized with the use of different methods: X-ray photoelectron and Auger electron spectroscopy (XPS+AES), Raman scattering spectroscopy (RSS) and scanning electron microscopy (SEM). The production of the Ge nano-crystallites has been demonstrated for annealed samples prepared in different experimental conditions.

Ablative Laser Propulsion: Specific Impulse and Thrust Derived from Force Measurements

Specie c impulse, thrust, and other dynamic characteristics of solid elemental propellants for ablative laser propulsion are studied experimentally with the aid of a piezoelectric force sensor. This sensor allows direct measurements of applied thrust. Experimental results show that the highest specie c impulse, » 4:0 ££ 10 3 s, occurs for carbonand aluminum, whereasthehighestcoupling coefe cient (8dyne/W)wasobserved forleadtargets.Theablation time,derived from independenttime-of-e ight (TOF)experimentsand used forthecalculation of impulses, was » 1.5 πs for the majority of the elements studied. These new measurements cone rm a decrease of specie c impulse and an increase in thrust with increasing atomic mass of the propellant; the major trend previously determined from TOF experiments. The plasma image analysis also cone rms the previously reported angular independence of ion velocity, established after the e rst 100 ns of plasma life. In previously reported TOF studies, all observations were based on the ionic component ejected from a laser-ablated material. An almost e vefold reduction in the absolute values of the specie c impulse was observed in the current effort. This result is attributed to “ dilution” of the high specie c impulse values for ions by slower atomic neutrals and larger fragments. Among all of the tested elements, aluminum is found to provide the optimum tradeoff for Isp and thrust values.

Investigations of single-wall carbon nanotube growth by time-restricted laser vaporization

The growth times of single-wall carbon nanotubes (SWNT's) within a high-temperature laser-vaporization (LV) reactor were measured and adjusted through in situ imaging of the plume of laser-ablated material using Rayleigh-scattered light induced by time-delayed, 308-nm laser pulses. Short SWNT's were synthesized by restricting the growth time to less than 20 ms for ambient growth temperatures of 760--1100 \ifmmode^\circ\else\textdegree\fi{}C. Statistical analysis of transmission electron microscope photographs indicated most-probable lengths of 35--77 nm for these conditions. Raman spectra ${(E}_{\mathrm{ex}}=1.96$ and 2.41 eV) of the short nanotubes indicate that they are well-formed SWNT's. The temperature of the particles in the vortex-ring-shaped plume during its thermalization to the oven temperature was estimated by collecting its blackbody emission spectra at different spatial positions inside the oven and fitting them to Planck's law. These data, along with detailed oven temperature profiles, were used to deduce a complete picture of the time spent by the plume at high growth temperatures (760--1100 \ifmmode^\circ\else\textdegree\fi{}C). The upper and lower limits of the growth rates of SWNT's were estimated as 0.6 and 5.1 \ensuremath{\mu}m/s for the typical nanosecond Nd:YAG laser-vaporization conditions used in this study. These measurements permit the completion of a general picture of SWNT growth by LV based on imaging, spectroscopy, and pyrometry of ejected material at different times after ablation, which confirms our previous measurements that the majority of SWNT growth occurs at times greater than 20 ms after LV by the conversion of condensed phase carbon.

Characterization of a Pulsed Glow Discharge Laser Ablation System Using Optical Emission

Investigations involving laser-based sampling of copper into an auxiliary pulsed glow discharge for ionization and excitation are presented. The interaction of the ablated copper with the auxiliary glow discharge was studied by monitoring the copper atom emission signal at 368.744 nm. Results demonstrate the ability to time ablation appropriately to access specific temporal regions of the pulsed plasma. More specifically, laser-ablated material was introduced into the glow discharge negative glow during the afterpeak. Ionization and excitation was accomplished by collisions with a metastable argon population produced by the glow discharge (Penning ionization) followed by recombination to yield excited-state Cu atoms. The work presented investigates parameters that affect the atomic emission signal intensity of the ablated material, including cathode-to-target distance, discharge gas pressure, and relative timing of discharge and ablation. Results demonstrate that decreasing the glow discharge working gas pressure increases the transport efficiency of laser-ablated material into the negative glow. These investigations are part of an ongoing series of studies on sample introduction schemes that utilize different ionization and excitation mechanisms found in pulsed glow discharge plasmas.

Possibility of rarefaction shock wave under short pulse laser ablation of solids.

Attention is drawn to a phenomenon that may give a radically different explanation for the recent observations of the system of dark rings above a solid surface vaporized by a short laser pulse. If a substance is heated to near-critical temperature, the existence of the compression shock wave becomes impossible, whereas the rarefaction wave takes a form of shock. The rarefaction shock can be considered as an interface in the expanding near-critical substance to form Newton rings in time-resolved optical microscopy experiments. The qualitative picture of the laser-ablated material expansion in vacuum with the generation of the rarefaction shock is discussed.

Theory and numerical modeling of the accelerated expansion of laser-ablated materials near a solid surface

A self-similar theory and numerical hydrodynamic modeling is developed to investigate the effects of dynamic source and partial ionization on the acceleration of the unsteady expansion of laser-ablated material near a solid target surface. The dynamic source effect accelerates the expansion in the direction perpendicular to the target surface, while the dynamic partial ionization effect accelerates the expansion in all directions. The vaporized material during laser ablation provides a nonadiabatic dynamic source at the target surface into the unsteady expanding fluid. For studying the dynamic source effect, the self-similar theory begins with an assumed profile of plume velocity, ${u=v/v}_{m}=\ensuremath{\alpha}+(1\ensuremath{-}\ensuremath{\alpha})\ensuremath{\xi},$ where ${v}_{m}$ is the maximum expansion velocity, $\ensuremath{\alpha}$ is a constant, and $\ensuremath{\xi}{=x/v}_{m}t.$ The resultant profiles of plume density and plume temperature are derived. The relations obtained from the conservations of mass, momentum, and energy, respectively, all show that the maximum expansion velocity is inversely proportional to $\ensuremath{\alpha},$ where $1\ensuremath{-}\ensuremath{\alpha}$ is the slope of plume velocity profile. The numerical hydrodynamic simulation is performed with the Rusanov method and the Newton Raphson method. The profiles and scalings obtained from numerical hydrodynamic modeling are in good agreement with the theory. The dynamic partial ionization requires ionization energy from the heat at the expansion front, and thus reduces the increase of front temperature. The reduction of thermal motion would increase the flow velocity to conserve the momentum. This dynamic partial ionization effect is studied with the numerical hydrodynamic simulation including the Saha equation. With these effects, $\ensuremath{\alpha}$ is reduced from its value of conventional free expansion. This reduction on $\ensuremath{\alpha}$ increases the flow velocity slope, decreases the flow velocity near the surface, and reduces the thermal motion of plume, such that the maximum expansion velocity is significantly increased over that found from conventional models. The result may provide an explanation for experimental observations of high-expansion front velocities even at low-laser fluence.

Spatial distribution of laser-ablated material by probing a plasma plume in three dimensions

A Pb0.2Bi1.8Sr2Ca1Cu2O{ce:italic}x{/ce:italic} target has been irradiated with 30 ns FWHM KrF excimer laser pulses having a wavelength of 248 nm and an energy density of ∼ 8 J/cm2. An intensified charge coupled device camera was used to measure the overall luminescence of the resulting plume in three dimensions as it moved from the target to the substrate. For small enough laser spots the plumes were found to have an ellipsoidal shape with {ce:italic}two{/ce:italic} distinct axes. On the other hand, for a large rectangular laser spot ({ce:inline-formula}3.0 × 1.2mm2{/ce:inline-formula} or {ce:inline-formula}2.4 × 1.0mm2{/ce:inline-formula}) the plumes were found to have an ellipsoidal shape with {ce:italic}three{/ce:italic} distinct axes. For example, at a time delay of 1000 ns the extensions were {ce:inline-formula}z = 34mm{/ce:inline-formula} (normal), {ce:inline-formula}y/2= 12mm{/ce:inline-formula}, and {ce:inline-formula}x/2= 8mm{/ce:inline-formula}, the lateral dimensions ({ce:inline-formula}x{/ce:inline-formula} and {ce:inline-formula}y{/ce:inline-formula} axes) being rotated at 90° with respect to the laser spot. The {ce:inline-formula}z{/ce:inline-formula} extension is sufficiently greater than those for {ce:inline-formula}x/2{/ce:inline-formula} and {ce:inline-formula}y/2{/ce:inline-formula}, and the {ce:inline-formula}z{/ce:inline-formula} expansion-front velocity is sufficiently high, that both {ce:italic}normal{/ce:italic} vaporization and {ce:italic}normal{/ce:italic} boiling can be excluded as the mechanisms of the laser sputtering. Subsurface explosion can be eliminated on the grounds that the analysis demonstrating its existence was wrong. It follows that either an electronic process or else phase explosion (also termed {ce:italic}explosive{/ce:italic} boiling) or else another still-to-be-defined but violent process may be involved. The results were finally compared with numerical solutions of the two-dimensional flow equations and a rotation effect was found essentially as observed. For example, it was largely absent at 200–700 ns, fully developed at 600–2000 ns, and, interestingly, starting to disappear at 3000–9000 ns.

Accelerated expansion of laser-ablated materials near a solid surface.

A dynamic source effect that accelerates the expansion of laser-ablated material in the direction perpendicular to the target is demonstrated. A self-similar theory shows that the maximum expansion velocity is proportional to {ital c}{sub {ital s}}/{alpha}, where 1{minus}{alpha} is the slope of the velocity profile and {ital c}{sub {ital s}} is the sound speed. Numerical hydrodynamic modeling is in good agreement with the theory. A dynamic partial ionization effect is also studied. With these effects, {alpha} is reduced and the maximum expansion velocity is significantly increased over that found from conventional models. {copyright} {ital 1995 The American Physical Society.}

In situ Sr isotopic analysis by laser ablation

We demonstrate that the Sr isotopic compositions of geological materials can be measured in situ through laser ablation using an ICP multiple-collector double focusing magnetic sector mass spectrometer (MC-ICPMS). This provides rapid, texturally sensitive, high precision (0.004%) Sr isotopic analysis without the need for chemical preparation of samples. The system used employs a Q-switched Nd-YAG infrared laser. The laser-ablated material is carried by Ar flow to an ICP torch. The resulting ions are extracted from the plasma and focused with d.c. quadrupole lenses and an electrostatic analyzer prior to entering a magnetic sector analyzer and collection in an array of Faraday collectors. A feldspar megacryst, with independently known 87 Sr 86 Sr of 0.703117 ± 13, and a modern gastropod shell, with independently known 87 Sr 86 Sr of 0.709170 ± 10, were used evaluate the method. Both have ∼ 2000 ppm Sr. Laser power was adjusted to give an average 88Sr of 2 × 10 −11 amps during analysis to replicate the beam size during typical thermal ionization mass spectrometry (TIMS). Within-run precisions in 87 Sr 86 Sr of < ± 4 × 10 −5 compare favorably with the precision from TIMS. Thirteen analyses of the Cameroon feldspar megacryst yielded a weighted average 87 Sr 86 Sr of 0.703106 ± 22, in perfect agreement with the TIMS measurement. Similarly, 22 analyses of the modern gastropod shell gave a weighted average of 0.709182 ± 22, identical to the known value. No memory effect was observed when switching from the Cameroon feldspar sample (run for several hours) to the modern shell material. The power of this technique is illustrated with a preliminary study of systematic differences in 87 Sr 86 Sr of ∼ 0.0004 between two feldspar crystals of a Long Valley basalt. One feldspar has identical 87 Sr 86 Sr to the host basalt, confirming the lack of any matrix effect with this method.

Laser-Solid Interaction and Dynamics of the Laser-Ablated Materials

AbstractRapid transformations through the liquid and vapor phases induced by laser-solid interactions are described by our thermal model with the Clausius-Clapeyron equation to determine the vaporization temperature under different surface pressure condition. Hydrodynamic behavior of the vapor during and after ablation is described by gas dynamic equations. these two models are coupled. Modeling results show that lower background pressure results lower laser energy density threshold for vaporization. the ablation rate and the amount of materials removed are proportional to the laser energy density above its threshold. We also demonstrate a dynamic source effect that accelerates the unsteady expansion of laser-ablated material in the direction perpendicular to the solid. a dynamic partial ionization effect is studied as well. a self-similar theory shows that the maximum expansion velocity is proportional to cs/α, where 1 – α is the slope of the velocity profile. Numerical hydrodynamic modeling is in good agreement with the theory. With these effects, α. is reduced. therefore, the expansion front velocity is significantly higher than that from conventional models. the results are consistent with experiments. We further study the plume propagates in high background gas condition. Under appropriate conditions, the plume is slowed down, separates with the background, is backward moving, and hits the solid surface. then, it splits to be two parts when it rebounds from the surface. the results from the modeling will be compared with experimental observations where possible.

Schlieren and dye laser resonance absorption photographic investigations of KrF excimer laser-ablated atoms and molecules from polyimide, polyethyleneterephthalate, and aluminum

Hydrodynamic phenomena from KrF excimer laser ablation (10−3–20 J/cm2) of polyimide, polyethyleneterephthalate, and aluminum are diagnosed by schlieren photography, shadowgraphy, and dye laser resonance absorption photography (DLRAP). Experiments were performed both in vacuum and gaseous environments (10−5–760 Torr air, nitrogen, and argon). In vacuum, ablation plumes are observed to expand like a reflected rarefaction wave. As the background gas pressure is increased, shock waves and reduced-density ablation plumes become visible. Below 10 Torr, the ablation plume follows closely behind the shock wave. Between 20 and 100 Torr, the plume recedes behind the shock wave. Below 10 Torr and above about 200 Torr, both the plume and the shock expand with the same temporal power law dependence. Agreement is found between these power law dependences and those predicted by ideal blast wave theory. The DLRAP diagnostic clearly shows that the ablated material (CN molecule from polyimide and ground state neutral aluminum atoms from laser-ablated aluminum) resides in the ablation plume. CN molecules are detected in both argon and air environments proving that CN is generated as an ablation product and not by reaction with the background gas. As the background gas pressure and the time after ablation is increased, the film darkening due to the laser-ablated material begins to fade leaving only the nonresonant shadowgraphy component of the plume. The plume dynamics observed by DLRAP are discussed in terms of gas dynamics, plume chemical kinetics, material diffusion in the plume, and cluster/particulate formation.