Over the last decade, lasers have been gradually employed for Si wafer dicing to replace blade dicing. Laser dicing has the potential to replace blade dicing as the future generation ultrathin wafer ...singulation method as it enables higher cutting speed, lower damage, and smaller kerf width but various technical challenges still remain to be resolved. In this article, laser ablation and dicing of Si wafers are reviewed in terms of the physics of laser-material interaction based on nanosecond, picosecond, and femtosecond pulse durations. The effects of various laser settings, dicing process parameters, and material factors on ablation rate, ablation precision and quality, and die fracture strength are discussed in detail. With the increasing usage of Cu stabilization layer on the backside of ultrathin Si wafers, we also review laser-material interaction in Cu and elaborate on recent findings on the effects of laser dicing through Si and Cu simultaneously on the microstructural and fracture strength properties of the die. Various approaches to improve the ablation rate, ablation quality, and die fracture strength are discussed.
•Laser dicing of thin Si wafers is gaining more importance in the semiconductor industry because of its cost-effectiveness compared to conventional blade dicing.•Understanding laser ablation mechanisms remains a huge challenge because of the complexity of the processes taking place, the variety of species involved, and the range of length and time scales covered.•Many challenges remain for laser dicing of Si wafers primarily in three critical areas, i.e., ablation rate, ablation precision and quality, and die fracture strength.•Optimization of the ablation rate, ablation quality, and die fracture strength will require thorough consideration of all the influencing laser and process parameters in order to meet the requirements of the end product applications.
The focused ion beam technique has become a standard tool for micro-mechanical sample preparation in the last decade due to its high precision and general applicability in material removal. Besides ...disadvantages such as possible ion damage and high operation costs especially the characteristically small removal rates represent a bottleneck for this application. In contrast, femtosecond lasers provide material removal rates orders of magnitude higher, with small or ideally without thermal impact on the surrounding material. Hence, a combination of these two methods offers an ideal tool for time-efficient, micrometer-sized sample preparation. A prototype implementing this idea is presented here in combination with a case study. Cantilevers with a length of several hundred micrometers were machined into 25 μm, 50 μm and 100 μm thick, cold rolled tungsten foils. Scanning electron microscopy analyses reveal the influence of laser parameters and different scanning routines on the resulting sample quality and the effect of the laser pulse length (femtoseconds versus nanoseconds) on the ultra-fine grained microstructure. Finally, the performance for unprecedented rapid sample preparation is demonstrated with a sample array consisting of 100 cantilevers with a dimension of 420×60×25 μm3 processed in only half an hour, opening completely new testing possibilities.
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•A prototype device combining a focused ion beam and a femtosecond laser is presented.•A case study of fabricating cantilevers for micro-mechanical tests into cold rolled tungsten foils was performed.•No coarsening of the ultra-fine grained microstructure was found after femtosecond laser ablation.•A sample array consisting of 100 cantilevers with a dimension of 420×60×25 μm3 was processed in only half an hour.
Here, we report on ZnO nanoparticles (NPs) generated by nanosecond pulsed laser (Nd:YAG, 1064 nm) through ablation of metallic Zn target in water and air and their comparative analysis as potential ...nanomaterials for biomedical applications. The prepared nanomaterials were carefully characterized in terms of their structure, composition, morphology and defects. It was found that in addition to the main wurtzite ZnO phase, which is conventionally prepared and reported by others, the sample laser generated in air also contained some amount of monoclinic zinc hydroxynitrate. Both nanomaterials were then used to modify model wound dressings based on biodegradable poly l-lactic acid. The as-prepared model dressings were tested as biomedical materials with bactericidal properties towards
and
strains. The advantages of the NPs prepared in air over their counterparts generated in water found in this work are discussed.
This review describes promising laser-based approaches to produce silicon nanostructures, including laser ablation of solid Si targets in residual gases and liquids and laser pyrolysis of silane. ...These methods are different from, and complementary to, widely used porous silicon technology and alternative synthesis routes. One can use these methods to make stable colloidal dispersions of silicon nanoparticles in both organic and aqueous media, which are suitable for a multitude of applications across the important fields of energy and healthcare. Size tailoring allows production of Si quantum dots with efficient photoluminescence that can be tuned across a broad spectral range from the visible to near-IR by varying particle size and surface functionalization. These nanoparticles can also be integrated with other nanomaterials to make multifunctional composites incorporating magnetic and/or plasmonic components. In the energy domain, this review highlights applications to photovoltaics and photodetectors, nanostructured silicon anodes for lithium ion batteries, and hydrogen generation from water. Application to nanobiophotonics and nanomedicine profits from the excellent biocompatibility and biodegradability of nanosilicon. These applications encompass several types of bioimaging and various therapies, including photodynamic therapy, RF thermal therapy, and radiotherapy. The review concludes with a discussion of challenges and opportunities in the applications of laser-processed nanosilicon.
We present the first comprehensive P-T-deformation-time and kinematic constraints for HP/UHP eclogite, blueschist and greenschist-facies metavolcano-sedimentary rocks cropping out in the Chinese ...SW-Tianshan metamorphic complex (within the ~30 km wide N-S Akeyazi-Kebuerte area). We reappraise this HP/UHP “mélange”, which should be divided into three main tectonic units, from north to south, according to their discrepant lithologies and P-T-time-deformation histories. These three units crop out in a tectonic window beneath greenschist-facies metavolcanics. P-T estimates point to 1) UHP-LT conditions around 2.6–2.9 GPa at ~520 °C for the metavolcano-sedimentary rocks of the northern HP/UHP unit, 2) HP-LT conditions of 1.8–2.1 GPa and ~500 °C for the central blueschist horizon and 3) lower-blueschist facies conditions of 1.0–1.5 GPa at ~485 °C for the southern ultramafic-mafic unit. In situ laser probe Ar-Ar age constraints (with textural control) on recrystallized phengites from the HP/UHP unit cluster within 315 to 325 Ma. Phengite ages from the central blueschist horizon are 10–15 Ma older, at ~325–345 Ma. Laser-ICP-MS U-Pb dating on zircon from the south ultramafic-mafic unit yield ages around ~360 Ma for metamorphic overgrowths. In contrast, step-heating Ar-Ar phengite age constraints for the greenschist-facies metavolcano-sediments fall within 280–300 Ma. These new field and P-T-time data disclose an episodic exhumation of three main tectonic slices, respectively from ~85 km, ~65 km and ~45 km depths, and a progressive change of metamorphic gradients from ~12 to ~6–7 °C/km, which could reflect a cooling of the subduction system with time. Final juxtaposition at ~20 km was probably achieved around 300 Ma, prior to collision.
•The HP/UHP mélange should be subdivided into several coherent, km-scale, metavolcanoclastic tectonic units bearing with P-T-t-D histories•4 sub-units identified: the UH (~2.8GPa, 520˚C), EB (~2.1, 505), MU (~1.5, 485) and GT units (>~0.7 - 1.0, 470 - 520) experienced subduction and were buried to depths of ~85, 65, 45 and 30km respectively•In situ laser probe 40Ar-39Ar radiometric dating of phengite and zircon U-Pb dating yield peak burial ages of 320 ± 4, 332 ± 6, 359 ± 2 and ~280 - 310Ma, respectively, for the UH, EB, MU and GS facies units•The progressive change of metamorphic gradients from ~12 to 6-7˚C /km could reflect a cooling of the subduction system with time•Juxtaposition & exhumation of the diverse sub-units to mid-crustal was accomplished around 290-300 Ma, at rates on the order of 1-3 mm/yr
Laser ablation coupled to a multi-collector inductively coupled mass spectrometer (LA-MC-ICP-MS) is a promising tool for in situ analysis of metal and metalloid stable isotope ratios. Potential ...isotopic fractionation associated with laser ablation may, however, cause biased sampling of the substrate, posing a major challenge for precise and accurate isotope ratio measurements. To better characterize the nature of laser ablation induced isotopic fractionation, this study compared particle morphologies, sizes, and size-dependent Fe isotope fractionations produced by ablation of a suite of semi-conductive samples, including natural Fe oxide, sulfide, and carbonate minerals, under various conditions using a 193nm ArF nanosecond (ns) laser and a 266nm Ti:sapphire femtosecond (fs) laser. Ablation-produced particles were sorted based on aerodynamic size using a cascade impactor, and Fe isotope compositions of size-sorted particles were then measured offline using conventional solution nebulization ICP-MS to quantify isotopic fractionation produced by the laser ablation. Particle morphology and size distributions produced by ns-laser ablation are more substrate and fluence dependent as compared to fs-laser ablation, resulting from the thermal nature of ns-laser ablation. Often, a higher proportion of the ablated Fe mass resides in particles with large aerodynamic sizes during ns-laser ablation as compared to fs-laser ablation, posing a potential difficulty for LA-ICP-MS analysis due to the increased possibility of incomplete ionization of large particles. Significant size-dependent Fe isotope fractionations of up to several per mil can occur during both ns- and fs-laser ablation, highlighting the importance of quantitative transport of particles to the ICP-MS for accurate Fe isotope analysis. Size-dependent Fe isotope fractionation observed for fs-laser ablation of all Fe minerals can be explained by particle formation through a condensation model, but multiple processes need to be considered to explain the observed Fe isotope fractionation during ns-laser ablation. Mass-balance calculations suggest that ns-laser ablation does not sample magnetite stoichiometrically for Fe isotope compositions at low fluence (1J/cm2), but does at higher fluences for all minerals. In contrast, fs-laser ablation always provides stoichiometric sampling for Fe isotopes regardless of fluence. Results of this study demonstrate that ns-laser ablation is substrate- and fluence-dependent, resulting in variable particle size distributions and Fe isotope fractionations, and possible non-stoichiometric sampling of semi-conductive samples for Fe isotope analysis. Instead, fs-laser ablation largely minimizes the substrate and fluence dependence, providing more consistent ablation.
•The first offline comparison of ns- and fs-laser for Fe isotope analysis.•Ablation produced particle size distribution and morphology were studied.•Laser ablation induced isotopic fractionation was quantified and investigated.•Isotopically non-stoichiometric sampling was found for ns-laser ablation.•Ablation is largely independent of samples and laser conditions for fs-laser.
Homogeneity, mass fractions of about forty trace elements and Sr isotope composition of Ca carbonate reference materials (RMs) between original and nano‐powdered pellets are compared. Our results ...using nanosecond and femtosecond LA‐(MC)‐ICP‐MS show that the nano‐pellets of the RMs MACS‐3NP, JCp‐1NP and JCt‐1NP are about a factor of 2–3 more homogeneous than the original samples MACS‐3, JCp‐1 and JCt‐1, and are therefore much more suitable for microanalytical purposes. With the exception of Si, the mass fractions of the synthetic RM MACS‐3 agree with its fine‐grained analogue MACS‐3NP. Very small, but significant, differences between original and nano‐pellets are observed in the RMs JCp‐1 and JCt‐1 for some trace elements with very low contents, indicating the need for re‐certification. Strontium mass fractions in the analysed RMs are high (1500–7000 mg kg−1), and their isotope compositions determined by LA‐MC‐ICP‐MS in the original and the nano‐pellets agree within uncertainty limits.
key points
Investigations of carbonate reference materials using fs‐ and ns‐ LA‐ICP‐MS.
Nanopowdered pellets are a factor 2 –3 more homogenous than original samples.
New reference values for MACS‐3 are provided.
Paired U/Pb and (U-Th-Sm)/He dating of individual detrital apatite crystals has potential as a valuable tool for constraining the high- and low-temperature thermal evolution of sediment source ...terrains. Here we present the results of exploratory applications of the laser ablation double-dating (LADD) method – originally developed for detrital zircon research – to the widely available Durango fluorapatite standard in order to evaluate the practicality of the method. Sixty-two laser-ablation analyses of a single large crystal of Durango fluorapatite yielded an inverse-variance weighted mean 206Pb/238U date of 31.46 ± 0.48 Ma and an inverse-variance weighted mean (U-Th-Sm)/He date of 31.75 ± 0.60 Ma, both of which are in good agreement with previously published conventional dates. While these results are encouraging, several factors suggest that LADD may be less useful for detrital apatites than for detrital zircons given widely available analytical instrumentation. These principally reflect the propensity for apatites to have comparatively lower U + Th concentrations, and thus lower radiogenic He and Pb concentrations, as well as high concentrations of common Pb. These factors contribute to substantially higher analytical imprecision for most LADD U/Pb dates for apatite, occasionally too high for the dates to be geologically useful. Reasonably precise laser ablation (U-Th-Sm)/He dating of detrital apatites requires relatively large crystal sizes (≥ 100 μm in the shortest dimension), with the minimum useful size increasing with decreasing (U-Th-Sm)/He apparent age. In contrast to the geological interpretation of LADD datasets for detrital zircons, the interpretation of datasets for detrital apatites is less straightforward. In particular, researchers should consider carefully the possibility that (U-Th-Sm)/He apparent age distributions are biased by the need to analyze only larger apatites.
Laser ablation from a solid target assists the synthesis of nanoparticles (NPs) as an alternative physical process. This work is attempt to investigate the morphological properties of silver ...nanoparticles (AgNPs) synthesized by femtosecond pulsed laser ablation in different liquid medium; Double Distilled Water (DDW), Deionized Water (DIW), Tetrahydrofuran (THF), and Dimethylformamide (DMF). XRD diffraction peaks that corresponds to (111), (200), (220) and (311) planes confirm the synthesized of AgNPs. The absorption spectra confirm the existence surface plasmon resonance (SPR) peak of AgNPs. The direct optical energy band gap (Eg) values have been calculated according to Tauc's equation and equal to 3.97, 3.82, 3.86, and 3.88 eV for synthesized AgNPs by Fs PLAL at different medium; DDW, DIW, THF, and DMF, respectively. Also, the influence of different liquid medium on the antibacterial efficiency was studied. In vitro Antibacterial activity of synthesized AgNPs was carried out against four types of bacteria employing agar plate technique. The experiments demonstrated that ablation efficiency, stability, and antibacterial efficiency of AgNPs in DIW medium are higher than those prepared in DDW, THF, and DMF medium.
•The synthesis of silver nanoparticles by Femtosecond laser ablation process was performed.•The morphological characterization of the synthesized AgNPs by Fs PLAL at different were discussed.•XRD diffraction peaks confirm the synthesized of AgNPs in all the prepared samples.•The absorption spectra confirm the existence surface plasmon resonance (SPR) peak of AgNPs.•AgNPs synthesized by Fs PLAL in DIW possess a potential antibacterial activity against the given bacteria.
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