ArF Excimer Laser Research Articles

Ablation effects and mechanism of sintered silicon carbide ceramics by an ArF excimer laser

The ablation of sintered silicon carbide ceramics by an ArF excimer laser was studied. Three zones are generated: the ablation zone that presented molten morphology and was composed by the Si and C phase; the condensation zone formed by vaporized SiC; and the oxidation zone that showed the characteristics of thermal oxidation. The ablation depth and oxidation range increase linearly with fluence and pulses within 0.5–4 J/cm2, but the normalized ablation efficiency is constant (3.60 ± 0.60 μm·mm2/J). The theoretical photochemical ablation depth supplies 25% of the total depth at 1 J/cm2 but decreases to 16% at 4 J/cm2. The ablation is dominated by the photothermal effect and conforms to the thermal evaporation mechanism.

Corrosion behaviors of the copper alloy electrodes in ArF excimer laser operation process

The corrosion behaviors of the ArF excimer laser copper alloy electrodes were studied. The morphology, composition and impurities were characterized by optical microscope, scanning electron microscopy, electron microprobe and glow discharge mass spectrometer methods. The anode produces the reef, the corrosion pits, the hole layer and the $1{-}10~\unicode[STIX]{x03BC}\text{m}$ level flake impurity. The cathode produces the particles, the sputtering pits, the element reduce layer and the $1~\unicode[STIX]{x03BC}\text{m}$ level particle impurity. Besides the Cu element, other elements in the alloy participate in the corrosion: Al element in the reef is over 1.5 times of the anode, Zn element in the particles is 1.3 times of the cathode, many trace elements congregate on the copper surface several and even hundreds of times. These elements are responsible to a great degree for the impurities and the rapid energy decline of the long-time idled laser.

CARS and Fluorescent study of ignition of H2/O2 mixtures upon photodissociation of O2 molecular

The research is devoted to gas mixtures ignition by UV laser radiation. The dissociation of O2 molecules by a pulse of excimer ArF laser radiation at 193-nm wavelength with formation of the chemically active oxygen atoms initiating chain reactions which cause ignition of H2/O2 mixture was employed. The experimental test bench was created with CARS and fluorescent techniques for experimental investigation of some peculiarities of mixture ignition and combustion caused by such photo-dissociation, at conditions typical for combustion chamber. Two-dimensional numerical modeling of combustion process in model combustion chamber, based on kinetic mechanism of H2 oxidation including atom O(1P) and radicals OH(A2Σ+), was performed.

Insight on agglomerates of gold nanoparticles in glass based on surface plasmon resonance spectrum: study by multi-spheres T-matrix method

The formation of a localized surface plasmon resonance (SPR) spectrum of randomly distributed gold nanoparticles in the surface layer of silicate float glass, generated and implanted by UV ArF-excimer laser irradiation of a thin gold layer sputter-coated on the glass surface, was studied by the T-matrix method, which enables particle agglomeration to be taken into account. The experimental technique used is promising for the production of submicron patterns of plasmonic nanoparticles (given by laser masks or gratings) without damage to the glass surface. Analysis of the applicability of the multi-spheres T-matrix (MSTM) method to the studied material was performed through calculations of SPR characteristics for differently arranged and structured gold nanoparticles (gold nanoparticles in solution, particles pairs, and core–shell silver–gold nanoparticles) for which either experimental data or results of the modeling by other methods are available. For the studied gold nanoparticles in glass, it was revealed that the theoretical description of their SPR spectrum requires consideration of the plasmon coupling between particles, which can be done effectively by MSTM calculations. The obtained statistical distributions over particle sizes and over interparticle distances demonstrated the saturation behavior with respect to the number of particles under consideration, which enabled us to determine the effective aggregate of particles, sufficient to form the SPR spectrum. The suggested technique for the fitting of an experimental SPR spectrum of gold nanoparticles in glass by varying the geometrical parameters of the particles aggregate in the recurring calculations of spectrum by MSTM method enabled us to determine statistical characteristics of the aggregate: the average distance between particles, average size, and size distribution of the particles. The fitting strategy of the SPR spectrum presented here can be applied to nanoparticles of any nature and in various substances, and, in principle, can be extended for particles with non-spherical shapes, like ellipsoids, rod-like and other T-matrix-solvable shapes.

Strong subbandgap photoconductivity in GaP implanted with Ti

AbstractPhotovoltaic solar cells based on the intermediate band (IB) concept could greatly enhance the efficiency of future devices. We have analyzed the electrical and photoconductivity properties of GaP supersaturated with Ti to assess its suitability for IB solar cells. GaP:Ti was obtained by ion implantation followed by pulsed‐laser melting (PLM) using an ArF excimer laser. It was found that PLM energy densities between 0.35 and 0.55 J/cm2 produced a good recovery of the crystalline structure of GaP (both unimplanted and implanted with Ti), as evidenced by high mobility measured values (close to the reference GaP). Outside this energy density window, the PLM failed to recover the crystalline structure producing a low mobility layer that is electrically isolated from the substrate. Spectral photoconductivity measurements were performed by using the van der Pauw set up. For GaP:Ti a significant enhancement of the conductivity was observed when illuminating the sample with photon energies below 2.26 eV, suggesting that this photoconductivity is related to the presence of Ti in a concentration high enough to form an IB within the GaP bandgap. The position of the IB was estimated to be around 1.1 eV from the conduction band or the valence band of GaP, which would lead to maximum theoretical efficiencies of 25% to 35% for a selective absorption coefficients scenario and higher for an overlapping scenario.

Comparative Study of Refractive Index Sensing Based on Three Different Long-Period Grating Configurations by Pulsed ArF Excimer Laser

Comparative Study of Refractive Index Sensing Based on Three Different Long-Period Grating Configurations by Pulsed ArF Excimer Laser

Separation of samarium, europium and gadolinium in high purity using photochemical reduction-extraction chromatography

An effective method was studied for the separation of high-purity individual rare earths from middle rare earth concentrate. The method combines photochemical reduction and extraction chromatography and consists of two steps: first, injecting a middle rare earth feed solution to a column packed with extraction resin while photochemically reducing Eu3+ to Eu2+ in the feed solution, followed by separating the reduced Eu2+ which has not been adsorbed on the extraction resin by washing; and, second, separating Sm3+ and Gd3+ adsorbed on the extraction resin by elution. This study was carried out with a 193nm ArF excimer laser source, a column packed with HEH[EHP] resin, isopropanol as scavenger of hydroxyl radical formed in the photolysis of water, deionized water as washing solution and HCl solution as eluent. With the aim of obtaining high yields of high-purity products, parameters such as concentrations of isopropanol and Eu2O3 in the feed solution, acidity and flow rate of the feed solution and acidity and flow rate of the eluent were evaluated with synthetic solutions. Based on the obtained results, the method was applied to separate individual rare earths from a commercial solution. Finally, the yields of Sm2O3, Eu2O3 and Gd2O3 products were 82.5%, 93.7% and 78.1% respectively, with purities of 99.99%.

Formation and implantation of gold nanoparticles by ArF-excimer laser irradiation of gold-coated float glass

To develop a technique for the production of submicron line patterns and directed arrays of plasmonic nanoparticles, the generation and implantation of gold nanoparticles into float glass surfaces was studied by means of ArF-excimer laser irradiation (193 nm) below the ablation threshold of the glass which was sputter coated with a gold layer with a thickness of 70 nm. The formation of gold particles was confirmed by the characteristic surface plasmon resonance (SPR) peak at ∼550 nm. The intensity of the SPR peak of gold particles embedded in the glass matrix increases with the number of applied laser pulses, indicating a different degree of implantation of the gold nanoparticles into the glass surface. It was revealed that the laser implantation of the generated gold particles into the glass is supported on the tin-bath side by the enhanced absorption of tin ions. The dependences of SPR parameters upon the number of laser pulses at different fluences were obtained. Using the methods of X-ray diffraction and extended X-ray absorption fine structure, the mean size of implanted gold particles was estimated at 15–20 nm. This particle size was confirmed by analytical (scanning) transmission electron microscopy, but a small fraction of single particles with a size of ∼50 nm have also been observed. The particles arrangement was further examined by the fitting of experimental optical extinction spectra, varying the particles sizes and interparticle distances within the direct calculations of spectra by the multi-spheres T-matrix method, considering the possible agglomerations of particles. The applied experimental technique provides the creation of arrays of gold nanoparticles in the near-surface region of the glass, which can be used as the substrates or nuclei in the glass for producing bimetallic nanoparticles with gold as the core and SPR characteristics varied in a wide range of visual wavelengths.

1 W solid-state 193 nm coherent light by sum-frequency generation

We report a 1.02 W coherent light at 193 nm and a 2.15 W coherent light at 221 nm generated by sum-frequency generation in CLBO crystals. The conversion efficiency from 221 nm to 193 nm was about 47%. To the best of our knowledge, this is the highest average power of 193 nm and 221 nm coherent light generated by SFG, respectively. These two DUV coherent lights could be used in many applications such as laser machining for their high photon energy features as well as the high power. The 193 nm coherent light also meets the requirements of injection-seeding hybrid ArF excimer laser.

Off-axis ultraviolet-written thin-core fiber Bragg grating for directional bending measurements

A directional bending sensor based on thin-core fiber Bragg grating is proposed and demonstrated experimentally. It is inscribed by off-center technique and exposed by 193 nm ArF excimer laser through a phase mask. A series of cladding modes are excited and their intensities are enhanced to about 10 dB. The formation mechanism of those cladding modes is discussed and analyzed. The intensities of these cladding mode resonances is detected for bending and direction with maximum sensitivity 1.93 dB/m1 at 0° to −1.95 dB/m1 at 180°under the curvature varied from 0 m−1to 2.5 m−1. The sensitivity of surrounding temperature is 11.3pm/°C ranging from 25 °C to 60 °C. This all-fiber structure has a great advantage for fiber orientation identification sensor with more convenient manufacture and needless de-localize FBGs.

Synthesis, conformation, and photochemistry of difluoroacetyl isocyanate CF2HC(O)NCO and isothiocyanate CF2HC(O)NCS

Two carbonyl pseudohalogen compounds CF2HC(O)NCO and CF2HC(O)NCS have been synthesized and fully characterized by IR (gas-phase, matrix-isolation), Raman (liquid), UV–vis (gas-phase), and NMR (19F, 13C, 1H) spectroscopy. The conformational properties and photochemistry of both species have been studied by combining matrix-isolation IR spectroscopy and quantum chemical calculations with the B3LYP, MPW1PW91, CBS-QB3 methods. Two conformers (syn and anti), depending on the configuration between the CO and pseudohalogen ligands (NCO and NCS), have been unambiguously identified in both gas phase and solid noble gas matrices (Ar and Ne). Consistent with the theoretical calculations, the syn conformation is energetically more favorable. Upon irradiation with an ArF excimer laser (193 nm), CF2HC(O)NCO and CF2HC(O)NCS in cryogenic matrices eliminate CO and yield CF2HNCO and CF2HNCS, respectively. The underlying mechanism for the photochemistry of CF2HC(O)NCO is rationalized by the elimination of the carbonyl rather than the isocyanato CO moiety.

Magma Mixing as a Trigger for Sulphide Saturation in the UG2 Chromitite (Bushveld): Evidence from the Silicate and Sulphide Melt Inclusions in Chromite

AbstractIt is of great importance to understand the origin of UG2 chromitite reefs and reasons why some chromitite reefs contain relatively high contents of platinum group elements (PGEs: Os, Ir, Ru, Rh, Pt, Pd) or highly siderophile elements (HSEs: Au, Re, PGE). This paper documents sulphide‐silicate assemblages enclosed in chromite grains from the UG2 chromitite. These are formed as a result of crystallisation of sulphide and silicate melts that are trapped during chromite crystallisation. The inclusions display negative crystal shapes ranging from several micrometres to 100 μm in size. Interstitial sulphide assemblages lack pyrrhotite and consist of chalcopyrite, pentlandite and some pyrite. The electron microprobe data of these sulphides show that the pentlandite grains present in some of the sulphide inclusions have a significantly higher iron (Fe) and lower nickel (Ni) content than the pentlandite in the rock matrix. Pyrite and chalcopyrite show no difference. The contrast in composition between inter‐cumulus plagioclase (An68) and plagioclase enclosed in chromite (An13), as well as the presence of quartz, is consistent with the existence of a felsic melt at the time of chromite saturation. Detailed studies of HSE distribution in the sulphides and chromite were conducted by LA‐ICP‐MS (laser ablation‐inductively coupled plasma‐mass spectrometry), which showed the following. (I) Chromite contained no detectable HSE in solid solution. (II) HSE distribution in sulphide assemblages interstitial to chromite was variable. In general, Pd, Rh, Ru and Ir occurred dominantly in pentlandite, whereas Os, Pt and Au were detected only in matrix sulphide grains and were clearly associated with Bi and Te. (III) In the sulphide inclusions, (a) pyrrhotite did not contain any significant amount of HSE, (b) chalcopyrite contained only some Rh compared to the other sulphides, (c) pentlandite was the main host for Pd, (d) pyrite contained most of the Ru, Os, Ir and Re, (e) Pt and Rh were closely associated with Bi forming a continuous rim between pyrite and pentlandite and (f) no Au was detected. These results show that the use of ArF excimer laser to produce high‐resolution trace element maps provides information that cannot be obtained by conventional (spot) LA‐ICP‐MS analysis or trace element maps that use relatively large beam diameters.

Origins of a damage-induced green photoluminescence band in fused silica revealed by time-resolved photoluminescence spectroscopy

With combined lifetime and intensity spectra in time-resolved photoluminescence (PL) spectroscopy, the origins of a green PL band consisting of a 2.39eV-band with lifetime ~10μs and a 2.25eV-band with lifetime ~50μs, of high-purity fused silica under ArF excimer laser (6.4eV) excitation were revealed. The 2.39eV PL defects from the surface were annealed due to the deoxidation of the dioxasilyrane group ( = SiO2). The 2.25eV PL defects from bulk showed a UV induced growth. Mechanical and laser damage induced growth of the 2.25eV PL band confirmed that it was due to physical disorder from bending of Si-O-Si bonds. Theoretical calculations further assigned the 2.25eV PL band to silanone groups ( = Si = O), which can be created by relaxation process of strained Si-O bonds in SiO2 network.

Visualization of fiber Bragg gratings of type II induced by radiation of an ArF excimer laser in an anisotropic single-mode optical fiber with an elliptical stress cladding

results in visualization of fiber Bragg gratings of type II recorded in birefringent single-mode optical fibers with an elliptical stress cladding with a high concentration of germanium dioxide are shown. Periodic structures of the induced refractive index are inscribed by a single pulse of an excimer laser with a working- gas mixture of ArF using the phase mask. Fiber Bragg gratings into anisotropic optical fiber were investigated by optical and scanning-probe microscopes. It is shown that single-pulse recording by ArF excimer laser creates in the fiber, both inside and on the surface of the quartz cladding, periodic structures, the spatial period of which corresponds to the period of the phase mask, optimized for the +1/–1 diffraction order.

Formation of periodic microswelling structures on silicone rubber surface using ArF excimer laser to realize superhydrophobic property

Periodic microswelling structures were photochemically induced on a silicone rubber surface using a 193 nm ArF excimer laser. Microspheres made of silica glass (SiO2) of 2.5 µm diameter were aligned on the silicone rubber surface during laser irradiation; the laser beam was focused on the silicone surface underneath each microsphere. The height and diameter of the formed microswelling structures were found to be controllable by changing the Ar gas flow rate, single-pulse laser fluence, and laser irradiation time. The chemical bonding of the laser-irradiated sample did not change and thus remained to be a silicone, as analyzed by X-ray photoelectron spectroscopy. As a result, microswelling structures of approximately 1.3 µm height and 1.3 µm diameter were successfully obtained. The contact angles of water on the microstructured silicone were measured to be 150° and larger, clearly indicating superhydrophobicity. The mechanism by which the microswellings form their shape was discussed on the basis of the changes in the focal point and spot size during laser irradiation through the SiO2 microsphere.

Efficiency of Bragg grating inscription by ArF excimer laser radiation depending on orientation of birefrin-gence axis of anisotropic optical fiber

Efficiency of Bragg grating inscription by ArF excimer laser radiation depending on orientation of birefrin-gence axis of anisotropic optical fiber

Luminescence of α-quartz crystal and silica glass under excitation of excimer lasers ArF (193 nm), KrF (248 nm)

Luminescence of crystalline α-quartz and silica glass was studied under focused laser excitation. It was found that in crystalline α-quartz the luminescence of self-trapped exciton (STE) is excited in two-photon regime with ArF (193nm) excimer laser. In the case of KrF (248nm) laser excitation mainly luminescence related to near surface area is seen even without laser beam focusing. The near surface luminescence has an emission band similar to that of STE in bulk. Temperature quenching is also similar, therefore this luminescence is attributed to STE created in the area of surface. Luminescence decay kinetic of surface STE is longer than bulk STE decay (tens of ms compared to 1ms at 80K). Electron or/and hole self-trapping near the surface is assumed. Their recombination could provide longer duration of surface STE luminescence. Similar surface luminescence was not excited with ArF (193nm) excimer laser. The nature of absorption for laser 248nm photons at surface is not yet clear.Luminescence of silica glass of III type excited with focused beam of KrF (248nm) laser resembles that of previously studied luminescence of STE in silica.

Formation of ArF laser-induced self-assembled macrostructures on poly methyl methacrylate and CR-39 polymers

ArF excimer laser at λ = 193 nm induces the regular macrostructures on poly methyl methacrylate (PMMA) and CR-39 with the periodicity Λ under the proper UV doses. The periodic self-organizing pattern lucidly appears on the polymeric surface, creating the grooves parallel along with the direction of the focal line of the cylindrical lens. The spatial period Λ is enlarged in terms of the focal length f varying tens of microns, much larger than the laser wavelength (22–145 μm, Λ ≫ λ). The interspacing also alters in terms of the incident angle θ by the expression 1/ cos θ, however it remains nearly invariant against the laser fluence F ranging several hundreds of mJ/cm2. Finally, the crisscross macroripples are created by situating a couple of cylindrical lenses in the orthogonal configuration. The formation of the gridiron patterns on PMMA and CR-39 attests that the linear superposition holds accordingly.

Conversion of p to n-type reduced graphene oxide by laser annealing at room temperature and pressure

Physical properties of reduced graphene oxide (rGO) are strongly dependent on the ratio of sp2 to sp3 hybridized carbon atoms and the presence of different functional groups in its structural framework. This research for the very first time illustrates successful wafer scale integration of graphene-related materials by a pulsed laser deposition technique, and controlled conversion of p to n-type 2D rGO by pulsed laser annealing using a nanosecond ArF excimer laser. Reduced graphene oxide is grown onto c-sapphire by employing pulsed laser deposition in a laser MBE chamber and is intrinsically p-type in nature. Subsequent laser annealing converts p into n-type rGO. The XRD, SEM, and Raman spectroscopy indicate the presence of large-area rGO onto c-sapphire having Raman-active vibrational modes: D, G, and 2D. High-resolution SEM and AFM reveal the morphology due to interfacial instability and formation of n-type rGO. Temperature-dependent resistance data of rGO thin films follow the Efros-Shklovskii variable-range-hopping model in the low-temperature region and Arrhenius conduction in the high-temperature regime. The photoluminescence spectra also reveal less intense and broader blue fluorescence spectra, indicating the presence of miniature sized sp2 domains in the vicinity of π* electronic states, which favor the VRH transport phenomena. The XPS results reveal a reduction of the rGO network after laser annealing with the C/O ratio measuring as high as 23% after laser-assisted reduction. The p to n-type conversion is due to the reduction of the rGO framework which also decreases the ratio of the intensity of the D peak to that of the G peak as it is evident from the Raman spectra. This wafer scale integration of rGO with c-sapphire and p to n-type conversion employing a laser annealing technique at room temperature and pressure will be useful for large-area electronic devices and will open a new frontier for further extensive research in graphene-based functionalized 2D materials.

1030 nm Yb^3+ distributed feedback short cavity silica-based fiber laser

A narrow line distributed feedback (DFB) fiber laser based on a 16 mm long Bragg grating, inscribed in a purpose-made strongly activated and highly photosensitive silica fiber, was fabricated and tested. A fiber preform synthesized by means of surface-plasma chemical vapor deposition (SPCVD), and a standard Bragg grating writing technology using an ArF excimer laser and a π-shifted phase mask, were applied to fiber drawing and grating writing, respectively. A single-mode generation regime of the DFB laser core-pumped at a wavelength of 976 nm was obtained, the measured linewidth being less than 8 kHz.