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We report on femtosecond (130 femto second) laser pulse removal and modification in Copper Boron Oxide thin films (CuBO2) deposited on silicon substrate. The samples were irradiated with 100 to 500 number of laser pulses at room temperature. Micro-size constructions on the surface of exposed CuBO2 thin films were produced and was observed using Scanning Electron Microscope (SEM). Self-prepared shapes like wrinkles, cellular erections, group of spots and cracks are observed by SEM studies. The small particles produced at initial laser pulses agglomerate into microspheres of Copper Boron Oxide. The optical properties show the high transmission value in (CuBO2) thin films when the number of laser pulses is increased. The optical band gap energy also decreases as compared to as deposited film up to 300 number of pulses and then increases up to 500 number of pulses. The results show that femtosecond laser irradiation considerably modifies the optical properties and surface morphology of (CuBO2) thin films.

In this contribution, we show CH3NH3PbI3–xClx perovskite solar cells (PSCs) processed in ambient air from a solution containing the diketone, acetylacetone (AA) solvent as an additive. PSCs with the AA additive show enhanced photovoltaic properties. The optimized PSC with 10 vol % AA additive shows an average open-circuit voltage (VOC) of about 1.02 V, short-circuit current density (Jsc) of around 18.7 mA/cm2, fill factor of about 76%, and power conversion efficiency of around 14.5%. Atomic force microscopy topographic imaging depicts that the addition of AA into the MAPbI3–xClx solution enhances the crystal growth with comparable improvement in the surface smoothness. Electrochemical impedance spectroscopy and intensity modulated photovoltage spectroscopy investigations show that incorporation of AA resulted in the improvement of charge carrier dynamics in the bulk and across interfaces, and reduction of recombination pathways. Moreover, MAPbI3–xClx films with the AA additive exhibit stronger photoluminescence compared to the pristine MAPbI3–xClx films. This appears to confirm that the AA solvent additive plays a vital role to reduce the trap states and recombination conduits across the film, which boosts the enhancement of radiative recombination pathways. We believe that this additive is highly practical and a viable option to fabricate and optimize large-area, stable, thin film PSCs in ambient environment.

Laser-induced breakdown spectroscopy (LIBS) is a rapidly developing technique for chemical materials analysis. LIBS is applied for fundamental investigations, e.g., the laser plasma matter interaction, for element, molecule, and isotope analysis, and for various technical applications, e.g., minimal destructive materials inspection, the monitoring of production processes, and remote analysis of materials in hostile environment. In this review, we focus on the element analysis of industrial materials and the in-line chemical sensing in industrial production. After a brief introduction we discuss the optical emission of chemical elements in laser-induced plasma and the capability of LIBS for multi-element detection. An overview of the various classes of industrial materials analyzed by LIBS is given. This includes so-called Technology materials that are essential for the functionality of modern high-tech devices (smartphones, computers, cars, etc.). The LIBS technique enables unique applications for rapid element analysis under harsh conditions where other techniques are not available. We present several examples of LIBS-based sensors that are applied in-line and at-line of industrial production processes.

We investigate femtosecond laser-induced breakdown spectroscopy (fs-LIBS) for the spectrochemical imaging of thin films with high spatial resolution. Chemical images are obtained by recording LIBS spectra at each site of 2D raster-scans across the samples employing one fs-laser pulse per site. The diffraction images of the Echelle spectrometer are binned to reduce the read-out time of the intensified CCD detector and to increase the stability of the emission signals against peak drifts in the echellograms. For copper thin films on glass the intensities of Cu I emission lines and the size of ablation craters vary non-monotonously with the film thickness h Cu = 5–500 nm. The emission efficiency, defined as the Cu I line intensity per ablated volume, strongly decreases for films thicker than the optical penetration depth. The Na I line intensity from glass increases exponentially with decreasing Cu film thickness. For yttrium barium copper oxide (YBCO) thin films on MgO various atomic and molecular emission lines of the laser-induced plasma are measured (film thickness h YBCO = 200–1000 nm). The obtained element (Y, Ba, Cu, Mg) and molecular (Y-O) fs-LIBS images match the structure of the micro-patterned YBCO films very well. The achieved lateral resolution δr = 6 μm is among the best values reported for spectrochemical LIBS imaging.

Laser-induced breakdown spectroscopy (LIBS) for composition analysis of polymer materials results in optical spectra containing atomic and ionic emission lines as well as molecular emission bands. In the present work, the molecular bands are analyzed to obtain spectroscopic information about the plasma state in an effort to quantify the content of different elements in the polymers. Polyethylene (PE) and a rubber material from tire production are investigated employing 157 nm F2 laser and 532 nm Nd:YAG laser ablation in nitrogen and argon gas background or in air. The optical detection reaches from ultraviolet (UV) over the visible (VIS) to the near infrared (NIR) spectral range. In the UV/VIS range, intense molecular emissions, C2 Swan and CN violet bands, are measured with an Echelle spectrometer equipped with an intensified CCD camera. The measured molecular emission spectra can be fitted by vibrational-rotational transitions by open access programs and data sets with good agreement between measured and fitted spectra. The fits allow determining vibrational-rotational temperatures. A comparison to electronic temperatures Te derived earlier from atomic carbon vacuum-UV (VUV) emission lines show differences, which can be related to different locations of the atomic and molecular species in the expanding plasma plume. In the NIR spectral region, we also observe the CN red bands with a conventional CDD Czerny Turner spectrometer. The emission of the three strong atomic sulfur lines between 920 and 925 nm is overlapped by these bands. Fitting of the CN red bands allows a separation of both spectral contributions. This makes a quantitative evaluation of sulfur contents in the start material in the order of 1 wt% feasible.

The properties of natural and synthetic rubber critically depend on the concentration of the vulcanizing system, among others. Sulfur and zinc oxide are typically used as cross-linking and activating agents for the vulcanization reaction (0-3 wt %). We present an advanced spectroscopic method to chemically analyze the vulcanizing system in rubber under ambient conditions, and we demonstrate a novel application to measure the elements in-line of industrial rubber production. The laser-induced breakdown spectroscopy (LIBS) technique is optimized to ablate material from the surface of produced rubber sheets and to measure the optical emission of S and Zn from the rubber plasma in air. The sulfur lines in the near-infrared range are masked by molecular emission bands of the C-N radical and spectrally interfered by atomic lines of O. Plasma excitation in collinear double-pulse geometry and detection of plasma emission with time-gated detectors suppresses the spectroscopic overlays and enables to resolve the sulfur lines. For the determination of ZnO the weak Zn lines in the ultraviolet range are measured due to their superior intensity stability compared to the much stronger lines in the deeper UV. S and ZnO are quantified in three different rubber materials prepared from the most important polymers used in rubber production. The mean error of prediction of concentrations RMSEP is ≤0.07 wt % for S and ≤0.33 wt % for ZnO for all polymer types. Our results demonstrate that the vulcanizing system of rubber can be quantified under ambient conditions with LIBS. Other chemical elements could be analyzed also and the rubber production could be controlled employing this multielement detection technique as process analytical sensor.

Slag from secondary metallurgy in industrial steel production is analyzed by laser-induced breakdown spectroscopy (LIBS). The major oxides CaO, Al2O3, MgO, SiO2, FeO, MnO, and TiO2 are determined by calibration-free LIBS (CF-LIBS) method. For the minor oxide P2O5 calibration curves are established and the limits of detection (LOD) and the root-mean squared errors of prediction (RMSEP) are determined. The optical emission of the laser-induced plasma is measured for different detection geometries and varying sample position relative to the focal plane of the laser beam. LIBS spectra, plasma parameters, and analytical results are very similar for light collection with optical fibres close to the plasma (“direct detection”) and at remote position (“collinear detection”). With collinear detection, the CF-LIBS calculated oxide concentrations are insensitive to sample position along the optical axis over wide range. The detection limits and the prediction errors of minor P2O5 depend on the major slag element used for signal normalization. With Mg and Si as internal reference elements the LOD values are 0.31 wt% and 0.07 wt%, respectively. The RMSEP values are lowest for signal normalization to Si. Calculations of the optical emission of ideal plasma support the experimental preference for Si as reference element in the phosphorous calibration.

Aluminum doped ZnO (AZO) and pure ZnO thin films are grown on polymer substrates by pulsed-laser deposition and the optical, electrical, and structural film properties are investigated. Laser fluence, substrate temperature, and oxygen pressure are varied to obtain transparent, conductive, and stoichiometric AZO layers on polyethylene terephthalate (PET) that are free of cracks. At low fluence (1 J/cm2) and low pressure (10− 3 mbar), AZO/PET samples of high optical transmission in the visible range, low electrical sheet resistance, and high figure of merit (FOM) are produced. AZO films on fluorinated ethylene propylene have low FOM. The AZO films on PET substrates are used as electron transport layer in inverted organic solar cell devices employing P3HT:PCBM as photovoltaic polymer-fullerene bulk heterojunction.

The halogen chlorine is hard to detect in laser-induced breakdown spectroscopy (LIBS) mainly due to its high excited state energies of 9.2 and 10.4 eV for the most intense emission lines at 134.72 nm and 837.59 nm, respectively. We report on sensitive detection of Cl in industrial iron oxide Fe 2 O 3 powder by single-pulse (SP) and dual-pulse (DP) LIBS measurements in the near infrared range in air. In compacted powder measured by SP excitation (Nd:YAG laser, 532 nm) Cl was detected with limit of detection LOD = 440 ppm and limit of quantitation LOQ = 720 ppm. Orthogonal DP LIBS was studied on pressed Fe 2 O 3 pellets and Fe 3 O 4 ceramics. The transmission of laser-induced plasma for orthogonal Nd:YAG 1064 nm and ArF 193 nm laser pulses showed a significant dependence on interpulse delay time (ipd) and laser wavelength (λ L ). The UV pulses (λ L = 193 nm) were moderately absorbed in the plasma and the Cl I emission line intensity was enhanced while IR pulses (λ L = 1064 nm) were not absorbed and Cl signals were not enhanced at ipd = 3 μs. The UV laser enhancement of Cl signals is attributed to the much higher signal/background ratio for orthogonal DP excitation compared to SP excitation and to the increased plasma temperature and electron number density. This enabled measurement at a very short delay time of t d ≥ 0.1 μs with respect to the re-excitation pulse and detection of the very rapidly decaying Cl emission with higher efficiency.

We report on measurements of the magnetoresistance and of the critical current in thin films of the high-temperature superconductor YBa 2 Cu 3 O 7 - δ (YBCO). A square array of regions with suppressed superconducting order parameter has been created in these films by introducing point defects via irradiation with He + ions through a silicon stencil mask. In such a structure distinct peaks of the critical current can be observed at commensurate arrangements of magnetic flux quanta with the artificial defect lattice. Concurrently, the magnetoresistance shows pronounced minima. Both observations demonstrate that the strong intrinsic pinning in YBCO can be overcome by a periodic array of ion-damage columns with 300 nm spacing.

We report on laser-induced breakdown spectroscopy (LIBS) of chlorine containing waste polymers in-line of an industrial materials sorting plant. Material from municipal waste plastic collection containing different types of plastic pieces and impurities is measured without pre-treatment directly on the conveyor belt (conveyor speed 2 m/s). The encapsulated LIBS system mounted to the conveyor comprises a fast Nd:YAG laser and spectrometer with charge-coupled device (CCD) detector, a distance sensor, and a software for quasi real-time evaluation of measured LIBS spectra. Approximately 800,000 spectra are collected during the in-line measurement series using one laser pulse per spectrum. The optical plasma emission of Cl I at 837.6 nm is detected to identify waste polymers with high Cl content such as polyvinylchloride (PVC). The LIBS spectra are evaluated employing a fast linear correlation algorithm. The correlation histogram for more than 20,000 spectra shows three distinct peaks that are associated to different materials containing high amount of Chlorine (>20 wt %), Titanium, and low amount of Cl (

The present work deals with the formation of nanostructures and tuning of optical band gap of ZnO thin films by high energy electron bombardment. In first step, Zinc Oxide (ZnO) thin films were deposited on silicon (1 0 0) substrates by pulsed laser deposition (PLD) technique using KrF Excimer laser. In second step, ZnO thin films were irradiated by electron beam of energy 6, 9, 12 and 15 MeV at constant dose. The surface morphology was studied by Atomic Force Microscope (AFM), whereas the optical properties were determined by Spectroscopic Ellipsometry (SE). Atomic force micrographs showed the formation of nanoscale structures on the surface of ZnO thin film. The nanostructures grew in size and reached its maximum size at 12 MeV electron energy. SE analysis revealed the increase in refractive index, appearance of broad absorption peak in visible region, and increase in optical band gap energy of ZnO thin film by 12 MeV electron bombardment. From the results, it can be concluded that the size of nanostructures and the optical band gap energy of ZnO thin films can be tuned by electron irradiation at various energies.

Aluminum and gallium doped zinc oxide thin films with negative dielectric permittivity in the near infrared spectral range are grown by pulsed laser deposition. Composite ceramics comprising ZnO and secondary phase Al2O3 or Ga2O3 are employed as targets for laser ablation. Films deposited on glass from dense and small-grained ceramic targets show optical transmission larger than 70 % in the visible and reveal an onset of metallic reflectivity in the near infrared at 1100 nm and a crossover to a negative real part of the permittivity at approximately 1500 nm. In comparison to noble metals, doped ZnO shows substantially smaller losses in the near infrared.

Laser-induced breakdown spectroscopy (LIBS) is a promising method for fast and quantitative element analysis of complex materials. We report on LIBS measurements of multi-component oxide materials and the compositional analysis of materials by a calibration-free (CF) method. This CF-LIBS method relies on modeling of the optical emission of laser-induced plasma assuming local thermodynamic equilibrium. Various materials are investigated and the calculated concentration values (CCF) of oxides CaO, Al2O3, MgO, SiO2, FeO, and MnO are in agreement with nominal concentration values (CN) from reference analysis. The relative error in oxide concentration er=|CCF−CN|/CN decreases with increasing concentration. The quantification is limited to major oxides (CN≥1 wt%). Slag samples from industrial steel production are analyzed on site by means of a mobile measurement system. LIBS measurements are performed at different sample temperatures. The results obtained show that CF-LIBS is applicable to fast compositional analysis of complex materials in harsh environments.

Double-pulse laser-induced breakdown spectroscopy (LIBS) is an emerging technique for accurate compositional analysis of many different materials. We present results of collinear double-pulse LIBS for analysis of the trace elements aluminum, phosphorus and boron in sintered iron oxide targets. The samples were ablated in air by double-pulse Nd:YAG laser radiation (6 ns pulse duration, laser wavelength of 532 nm) and spectra were recorded with an Echelle spectrometer equipped either with a CCD (charge coupled device) or an ICCD (intensified charge coupled device) camera. For the trace elements aluminum and phosphorus, the use of the CCD detector system resulted in considerable higher signal-to-noise ratios and/or better limits of detection compared to the results achieved with the ICCD detector. The use of CCD double-pulse LIBS enables to detect low concentrations of phosphorus with a limit of detection of 10 ppm by evaluating the UV line at 214.91 nm, which overlaps with a Fe I line. Compared to the ICCD system, the CCD system requires the accumulation of a higher number of laser double-pulses to achieve acceptable signal quality. This can be disadvantageous for elements showing pronounced depletion effects as for the trace element boron in sintered iron oxide targets.

Double-pulse laser-induced breakdown spectroscopy (LIBS) is an emerging technique for accurate compositional analysis of many different materials. We present a systematic study of collinear double-pulse LIBS for analysis of the trace and side elements boron, manganese, copper, aluminum, titanium, silicon, chromium, nickel, potassium, and calcium in sintered iron oxide targets. The samples were ablated in air by single-pulse and double-pulse Nd:YAG laser radiation (6 ns pulse duration, laser wavelength of 532 nm) and spectra were recorded with an Echelle spectrometer equipped with an ICCD camera. We investigated the evolution of atomic and ionic line emission intensities for different interpulse delay times between the laser pulses (from 100 ns to 50 μs) and gate delays after the second laser pulse. We also varied the energy partition between the first and second laser pulse and the size of the irradiated spot at the sample surface. For the trace and side elements, we observed double-pulse LIBS signals that were enhanced as compared to single-pulse measurements depending on the interpulse delay time, the energy partition between the pulses, and the spot size. For the elements boron, copper, aluminum, titanium, chromium, potassium, and calcium limits of detection below 10 ppm were achieved.

Laser-induced breakdown spectroscopy method is modified using an external radiofrequency (RF) plasma jet that overlaps spatially with the laser-induced plasma. Short UV laser pulses (wavelength 193 nm) are employed to ablate iron oxide ceramics, zinc oxide ceramics and polyethylene pressed pellets in ambient air background. An RF generator (frequency 13.56 MHz, power ≤1 kW) and a gas nozzle system are employed to generate a continuous jet of argon and nitrogen plasma expanding into air. The optical emission of the overlapped plasma is analyzed using an Echelle spectrometer equipped with an intensified CCD camera. The time dependence of optical emission intensities and of plasma parameters is investigated by varying the spectrometer delay time with respect to the laser pulse. The emission intensities of major (Fe, Zn) and minor (Mn, Al) elements are moderately increased with the RF plasma jet (≤2×). The intensities of atomic lines and molecular bands from ablated polymer material are increased also.

Laser induced breakdown spectroscopy (LIBS) is an emerging technique for fast and accurate compositional analysis of many different materials. We present a systematic study of collinear double-pulse LIBS on different technical polymers such as polyamide, polyvinyl chloride, polyethylene etc. Polymer samples were ablated in air by single-pulse and double-pulse Nd:YAG laser radiation (8 ns pulse duration) and spectra were recorded with an Echelle spectrometer equipped with an ICCD camera. We investigated the evolution of atomic and ionic line emission intensities for different delay times between the laser pulses (from 20 ns to 500 μs) at a laser wavelength of 532 nm. We observed double-pulse LIBS signals that were enhanced as compared to single-pulse measurements depending on the delay time and the type of polymer material investigated. LIBS signals of polymer materials that are enhanced by double-pulse excitation may be useful for monitoring the concentration of heavy metals in polymer materials.

The quantitative determination of oxide concentration by laser-induced breakdown spectroscopy is relevant in various fields of applications (e.g.: analysis of ores, concrete, slag). Calibration free laser-induced breakdown spectroscopy and the multivariate calibration are among the methods employed for quantitative concentration analysis of complex materials. We measured the intensity of neutral and ionized atomic emission lines of oxide materials by laser-induced breakdown spectroscopy and we modified the calibration free laser-induced breakdown spectroscopy method to increase the accuracy. The concentration of oxides was obtained by using stoichiometric relations. Sample materials were prepared from oxide powder (Fe 2 O 3 , MgO, CaO) by mixing and pressing. The concentration was 9.8–33.3 wt.% Fe 2 O 3 , 7.6–33.3 wt.% MgO and 33.3–81.2 wt.% CaO for different samples. Nd:YAG laser (wavelength 1064 nm, pulse duration ≈ 6 ns) ablation was performed in air. The laser-induced plasma emission was measured by an Echelle spectrometer equipped with a sensitivity calibrated ICCD camera. The numerical calibration free laser-induced breakdown spectroscopy algorithm included the fast deconvolution of instrumental function, and the correction of self-absorption effects. The oxide concentration C CF calculated from calibration free laser-induced breakdown spectroscopy results and the nominal concentration C N were very close for all samples investigated. The relative error in concentration, | C CF – C N |/ C N , was 2 O 3 , MgO, and CaO, respectively. The results indicate that this method can be employed for the analysis of major elements in multi-component technical materials.

Aluminum doped Zinc Oxide (AZO) and Lithium doped Zinc Oxide (LZO) thin films are obtained by Pulsed Laser Deposition (PLD) method. These films are characterized by using Spectroscopic Ellipsometry (SE), X-ray Diffraction (XRD) and Photoluminescence (PL). By modeling the ellipsometry spectra we get the dielectric functions, the optical band gap Eg, and the electrical properties. Our results show the influence of the processing parameters on the optical and structural properties of doped ZnO thin films. The post-annealing treatment applied to AZO thin films, changes strongly the optical properties, by lowering the resistivity and red-shifting the band gap.

Laser-induced breakdown spectroscopy (LIBS) in the vacuum ultraviolet range (VUV, λ < 200 nm) is employed for the detection of trace elements in polyethylene (PE) that are difficult to detect in the UV/VIS range. For effective laser ablation of PE, we use a F2 laser (wavelength λ = 157 nm) with a laser pulse length of 20 ns, a pulse energy up to 50 mJ, and pulse repetition rate of 10 Hz. The optical radiation of the laser-induced plasma is measured by a VUV spectrometer with detection range down to λ = 115 nm. A gated photon-counting system is used to acquire time-resolved spectra. From LIBS measurements of certified polymer reference materials, we obtained a limit of detection (LOD) of 50 µg/g for sulphur and 215 µg/g for zinc, respectively. The VUV LIBS spectra of PE are dominated by strong emission lines of neutral and ionized carbon atoms. From time-resolved measurements of the carbon line intensities, we determine the temporal evolution of the electronic plasma temperature, Te. For this, we use Saha–Boltzmann plots with the electron density in the plasma, Ne, derived from the broadening of the hydrogen H-α line. With the parameters Te and Ne, we calculate the intensity ratio of the atomic sulphur and carbon lines at 180.7 nm and at 175.2 nm, respectively. The calculated intensity ratios are in good agreement with the experimentally measured results.

Time-resolved photography was employed to study plasma dynamics and particle ejection of laser-irradiated iron oxide materials. Nano-particle powder, pressed powder pellets and sintered ceramics were ablated in air and Ar gas background by means of short laser pulses (Nd:YAG laser wavelength λ = 1064 nm and pulse duration τ L ≈ 6 ns; KrF laser λ = 248 nm and τ L ≈ 20 ns). Plasma plume dynamics significantly depended on sample morphology. The ejection of non-luminous particles up to several hundreds of microseconds after the laser pulse was observed for powder and pressed powder target materials. Laser-induced breakdown spectroscopy (LIBS) was employed for element analysis of iron oxide powders, pressed pellets and sintered ceramics. LIBS spectra of the different targets were comparable to each other and qualitatively independent of target morphology.

Thin films of complex oxides have been obtained by pulsed-laser deposition (PLD) from glass targets belonging to the system Li 2 O–Al 2 O 3 –P 2 O 5 –(RE) 2 O 3 , with RE = Nd, Pr, Er. The films were deposited on quartz, silicon and ITO/glass substrates using a F 2 laser ( λ = 157 nm, ι ≈ 20 ns) for ablation in vacuum. The structural, morphological and optical properties of the oxide films were investigated through IR and UV–VIS spectroscopy, Atomic Force Microscopy (AFM), Scanning Electron Microscopy, Energy Dispersive X-ray Spectroscopy (SEM-EDX) and Spectroscopic Ellipsometry. The laser wavelength was found to be the key parameter to obtain thin films with very smooth surface. In this way new possibilities are opened to grow multilayer structures for photonic applications.

Multi-component oxide ceramics and epitaxial oxide thin films are analyzed by laser-induced breakdown spectroscopy (LIBS). Furthermore, pulsed-laser deposition (PLD) of thin films is investigated by long-term monitoring of the optical plasma emission. Both nano-composite high-temperature superconductors (HTS) consisting of YBa2Cu3O7 − δ bulk and Y2Ba4MCuOx (M-2411, M = Ag, Nb) nano-particles, and semiconducting ZnO doped with Aluminum and Lithium are ablated by nano-second laser pulses. The plasma emission is recorded using grating spectrometers with intensified gated detectors. The LIBS signals of nano-particles correlate with the nominal content of the M-2411 phase (0–15 mol%) and reveal a strong signal of Ytterbium impurity (3–35 ppm). In situ monitoring of the PLD process shows element signals that are stable for more than 10,000 laser pulses for both HTS and ZnO ceramics. The relative concentration of elements in thin films and ceramics as determined by LIBS is almost the same.

We present studies of the relaxation of persistent photoconductivity in 60-K YB2C3Ox. By using thin films grown on vicinal SrTiO3 substrates, measurements of the in-plane (a–b plane) conductivity and of the out-of-plane (c-axis) conductivity were performed. The photo-induced enhancements of both conductivities showed the well-known stretched-exponential relaxation. We observed a small anisotropy of the relaxation rates of the two conductivity components. The relaxation of the c-axis conductivity appeared somewhat delayed compared to the a–b plane conductivity. In a simple thermal relaxation picture this finding implies different energy barriers for the c-axis and a–b plane relaxations, which is not consistent with generally accepted models of persistent photoconductivity in YB2C3Ox. We interpret the observed anisotropy as a consequence of the structural modifications of the copper-oxide chains that are induced by light illumination. Structural changes such as the re-ordering of the oxygen ions are slow processes compared to electronic excitations. Hence, the c-axis conductivity, which is more influenced by (small) structural modifications of the chain layer, needs a longer time to return to the equilibrium state after the cessation of the illumination.

Piezoelectric gallium orthophosphate (GaPO4) thickness – shear mode resonators were patterned by F2-laser ablation and employed for gas sensing. The thickness of GaPO4 crystals was reduced from ∼215 μm to ∼115 μm by laser ablation and the piezoelectric fundamental resonance frequency in the thinned region increased thereby from ∼6 MHz to ∼12 MHz. The Q values of laser-thinned and pristine resonators in air were Q≈7000 and Q≈95000, respectively. The GaPO4 crystals were coated by thin polyimide layers that served as receptor for water vapour. The resonance frequency of coated crystals decreased linearly with increasing level of relative humidity (RH) and the sensitivity for laser-patterned 12 MHz GaPO4 resonators, SRH≈-98 Hz/% RH, was much larger than for the pristine 6 MHz GaPO4 resonators.

Pulsed-laser ablation and micro-patterning of gallium orthophosphate (GaPO4) single crystals and ceramics by 157 nm F2-laser radiation is reported. Micron-sized holes with sharp edges and smooth walls are obtained by employing projection-mask techniques. The threshold fluence of ablation is around Φth ≈ 180 mJ/cm2 and ablation rates of WA ≤ 90 nm/pulse are achieved at fluence levels of Φ ≤ 2 J/cm2 for both material types.

The impact of long-term light excitation on YBa 2 Cu 3 O x (YBCO) ( x ≈6.4) thin films grown on “wedged” SrTiO 3 substrates was studied at several temperatures between 50 and 275 K. From the anisotropic resistance of the films, the in-plane ( ρ ab ) and the out-of-plane ( ρ c ) resistivities were calculated. The electrical anisotropy ρ c / ρ ab increased substantially during the light excitation at all studied temperatures. At 50 K, an increase of more than a factor of two was observed, whereas at higher temperatures the increases were smaller. At 275 K, ρ c / ρ ab showed a slightly falling tendency after about 1 h of illumination indicating oxygen ordering. The results strongly support our previously proposed two-mechanism picture of persistent photoconductivity in YBCO.

In this paper we discuss some fundamentals on uniform target ablation and present some new results on thin films of high-temperature superconductors, ferroelectrics, and polymers.

Ferroelectric SrBi2Ta2O9 (SBT) films were grown by pulsed-laser deposition (PLD) at different substrate temperatures and fluences. A correlation between film structure and ferroelectric properties is established. The dielectric function e′ of thin SBT films shows a Curie–Weiss behavior well below the peak temperature Tmax and relaxor-like behavior in the vicinity of Tmax. Domain walls have a strong influence on the dielectric and ferroelectric properties and on the polarization fatigue of SBT films below 100 °C. The formation of ferroelectric phases is favored at lower substrate temperatures by incorporating Bi2O3 template layers into the structure.

Long-term photoexcitation experiments were performed on oxygen depleted YBa 2 Cu 3 O x ( x ≈6.6) thin films, prepared by pulsed laser ablation on tilted SrTiO 3 substrates. From the anisotropic resistivity of these films, the in-plane ( σ ab ) and out-of-plane ( σ c ) conductivities were calculated. White-light photoexcitation at various temperatures from 70 to 305 K yielded strongly temperature dependent increases of both σ ab and σ c . The photoinduced changes of the anisotropy σ ab / σ c strongly depended on the temperature at which the experiment was performed. At 70 K, the anisotropy increased monotonically during 24 h of illumination, whereas, at higher temperatures, a short increase at the very beginning of the illumination was followed by a long-term decrease. Additionally, spectroscopic investigations at the above temperatures were performed to determine the influence of different excitation energies.

Long-term photoexcitation experiments were performed on Y Ba 2 Cu 3 O x (x≈6.6) thin films, prepared by pulsed-laser deposition on “tilted” SrTiO3 substrates. From the anisotropic resistance of the samples, the in-plane and the out-of-plane resistivities were calculated. Photoexcitation was carried out with a He-Ne laser at various temperatures from 70 K to 305 K. We observed that the electrical anisotropy ρc/ρab increased at low temperatures, but decreased at high temperatures. This unusual behavior resembles that of the in-plane Hall mobility in a previous study. Possible interpretations according to the models for the photodoping effect in YBa 2 Cu 3 O x are discussed.

We investigate the photoluminescence properties of Er-doped SiO2 and glass films fabricated by pulsed-laser deposition (PLD) for different deposition parameters and erbium host materials. The luminescence yield of SiO2 : Er films increases strongly with increasing oxygen background pressure during laser ablation. We compare SiO2 and soda-lime glass as host materials for erbium ions. Under identical growth conditions and the same erbium concentrations in both targets, films deposited from the soda-lime glass show a much higher luminescence yield. This enhancement is attributed to a higher concentration of optically active erbium in the multicomponent glass environment.

Laser-induced breakdown spectroscopy (LIBS) is an upcoming technique for element analysis of solid, liquid, and gaseous material. We give a brief introduction to LIBS, estimate the optical emission for most chemical elements in laser-induced plasma, and discuss the achievable limits of detection. An overview of industrial materials analyzed by LIBS is given. Secondary raw materials are a relevant resource in production and can be measured by LIBS sensors under harsh conditions. We present LIBS analysis of waste polymers, metal oxide powder, and metallurgical slags from steel production. Heavy metals in polymers and impurities in powders are detected with ppm sensitivity. Slags are analyzed by a calibration-free method.

Laser melting of rough metal surfaces, in particular in those containing parallel scratch lines of micron and submicron size, differs from melting of smooth planar surfaces. It is associated with the reach of the spectra of self-organized structures, which consist of vortex filaments as basic entities. Self-organized structures of vortex filaments on rough metal surfaces were generated by short laser pulses and studied by optical and scanning electron microscopy. Their formation starts with melting of the surface that generates a shear layer with radially oriented flow in the laser spot. Parallel scratch lines represent the flow perturbation which is spanwise, streamwise or oblique in different zones of the spot giving rise to the self-organized flow structures. The flow structures are permanently frozen by ultra-fast cooling after laser pulse termination, thus enabling a posteriori analysis. Long vortex filaments organized into very complex structures ranging from parallel Kelvin-Helmholtz rolle...

We report on the deposition of Al doped ZnO (AZO) thin films on unheated polyethylene terephthalate (PET) substrates by pulsed laser deposition technique using a UV excimer laser and Al 2 O 3 :ZnO ceramic targets (1.5 and 2 wt% Al 2 O 3 ). The deposited AZO films have been investigated by atomic force microscopy, scanning electron microscopy, X-ray diffraction, and optical spectrophotometry. Films present excellent optical and electrical properties (transmission in the visible range T > 85%; resistivity at room temperature ρ = 1.3 × 10 −3 Ω cm) as electrodes for plastic solar cells. A good correlation was found between deposition conditions (laser fluence) and structural, morphological, optical and electrical properties.

Calibration-free laser-induced breakdown spectroscopy (CF-LIBS) method is employed for quantitative determination of oxide concentrations in multi-component materials. Industrial oxide materials from steel industry are laser ablated in air, and the optical plasma emission is collected by spectrometers and gated detectors. The temperature and electron number density of laser-induced plasma are determined from measured LIBS spectra. Emission lines of aluminium (Al), calcium (Ca), iron (Fe), manganese (Mn), magnesium (Mg), silicon (Si), titanium (Ti), and chromium (Cr) of low self-absorption are selected, and the concentration of oxides CaO, Al2O3, MgO, SiO2, FeO, MnO, TiO2, and Cr2O3 is calculated by CF-LIBS analysis. For all sample materials investigated, we find good match of calculated concentration values (C CF) with nominal concentration values (C N). The relative error in oxide concentration, e r = |C CF − C N|/C N, decreases with increasing concentration and it is e r ≤ 100% for concentration C N ≥ 1 wt.%. The CF-LIBS results are stable against fluctuations of experimental parameters. The variation of laser pulse energy over a large range changes the error by less than 10% for major oxides (C N ≥ 10 wt.%). The results indicate that CF-LIBS method can be employed for fast and stable quantitative compositional analysis of multi-component materials.

Pulsed-laser deposition (PLD) and laser-induced breakdown spectroscopy (LIBS) techniques are reviewed and new results on PLD and LIBS of functional oxide materials are reported. Nano-composite high-T c superconducting (HTS) films with enhanced critical current density are produced by laser ablation of novel ceramic targets. The transport properties of HTS thin films are modified by light-ion irradiation. Nano-patterning of HTS films is achieved by masked ion beam irradiation. Optically transparent epitaxial ZnO layers are grown by PLD and acoustic resonances in the GHz range are excited by piezoelectric actuation. LIBS is employed to analyze impurity trace elements in industrial oxide powder. For quantitative analysis of major and minor elements the calibration-free LIBS method is refined. This CFLIBS method is employed to the analysis of multi-element materials and very good match with nominal concentration of oxides is achieved (relative error less than 20 %).

Waste polymer materials were analyzed by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The concentrations of 35 elements were determined by using different types of external standards, namely glass and polyethylene (PE) based. Prior to the LA-ICP-MS analysis of determined elements, Na and/or Zn were used as internal standards. The investigations concentrated mainly on the detection of Cr, As, Cd, Sn, Sb, Hg, and Pb. Using PE-based calibration standards, the measured concentrations in the waste polymers were within 49% of the wet chemical data. The determined deviation was up to 102% when using the glass standards. Trace concentration of As and Hg (and also of S) could be determined with a concentration below 1 mg/kg. However, Hg provided very low intensity with a high relative standard deviation (RSD) and was therefore not further evaluated. Cryomilling of polymers was applied to reduce the particle size of the material and improved the precision and accuracy of LA-ICP-MS analysis. On average, the LA-ICP-MS results showed a deviation from the wet chemical reference analysis of 38% and an RSD of 56% for pressed polymer powder samples prepared by cryomilling. In general, waste pellets without sample preparation (i.e., use of pellets as delivered) are too heterogeneous, not suitable for micro-beam techniques, and showed a strong matrix dependence. With homogeneous pellets that appear similar to each other agreement in the determined concentrations was found for some elements.

New results of the Linz group on pulsed—laser deposition (PLD) of oxide thin films and on laser—induced breakdown spectroscopy (LIBS) of multi‐element materials are reported. High‐Tc superconducting (HTS) films with enhanced critical current density Jc are produced by laser ablation of novel nano‐composite ceramic targets. The targets contain insulating nano‐particles that are embedded into the YBa2Cu3O7 matrix. Epitaxial double‐layers of lithium‐doped and aluminum‐doped ZnO are deposited on r‐cut sapphire substrates. Acoustic over‐modes in the GHz range are excited by piezoelectric actuation of layers. Smooth films of rare‐earth doped glass are produced by F2—laser ablation. The transport properties of HTS thin films are modified by light—ion irradiation. Thin film nano—patterning is achieved by masked ion beam irradiation. LIBS is employed to analyze trace elements in industrial iron oxide powder and reference polymer materials. Various trace elements of ppm concentration are measured in the UV/VIS and vacuum‐UV spectral range. Quantitative LIBS analysis of major components in oxide materials is performed by calibration‐free methods.

Pulsed-laser deposition (PLD) is an excellent technique to grow thin films and multi-layers of complex oxide materials. We present our recent results on deposition, characterization and nano-patterning of novel oxide high-temperature superconductors (HTS) and piezoelectric materials. HTS thin films of improved superconducting properties are fabricated from ceramic targets consisting of Y 2 Ba 4 CuMO y (M = metal) nano-particles embedded in YBa 2 CU 3 O 7 (YBCO) matrix. The nano-composite ceramics are UV-laser ablated and the optical plasma emission is monitored by laser - induced breakdown spectroscopy. The HTS films reveal superconducting critical current densities that depend on target composition and are strongly enhanced as compared to phase pure YBCO films. Application of HTS layers in future nano-electronic devices requires novel techniques for nano-patterning. Masked ion-beam structuring enables the nano-patterning of YBCO thin films in a direct and single-step process. Gallium orthophosphate (GaPO 4 ) thin films and piezoelectric ZnO multi-layers are reported also. GaPO 4 is an outstanding piezoelectric material with very high transition temperature (∼ 970 °C). Epitaxial GaPO 4 films are fabricated on quartz substrates by PLD and thermal post-annealing. Long-term annealing at high temperature does not degrade the GaPO 4 films. Multi-layers of Al and Li doped ZnO are pulsed-laser deposited on various substrates and investigated for applications in thin film sensors.

Cu3O7-δ films have been patterned by means of an arrangement employed in scanning near-field optical microscopy (SNOM). Standard SNOM probes were modified to achieve high transmission for direct writing by oxygen depletion in N2 atmosphere. The written lines are about 1.5 μm wide and show a semiconductor-like resistivity behavior (δ≥0.5). The morphology of illuminated regions is about the same as that of the YBCO films.

Advanced thin film materials with giant dielectric permittivities up to r ’ 10000 were produced by pulsed-laser deposition. Composite targets of barium titanate (BaTiO 3 ) and polytetrafluorethylene (PTFE) were ablated with 248 nm KrF-laser radiation in Ar atmosphere. The synthesized films have a complex microstructure and contain product species which are formed during the pulsed-laser ablation / deposition process. The dielectric permittivities of films exhibit pronounced dispersion for frequencies higher than 10 kHz. Strong dependencies of the film permittivity on target composition, layer thickness, ambient gas pressure and relative humidity are revealed. The large dielectric permittivity of these film materials may be attributed to space-charge polarization phenomena. Films deposited from the same targets in oxygen atmosphere have much lower dielectric permittivity ( r ’ 30). Keywords: Pulsed-laser deposition, PTFE polymer, ceramic / polymer composites, giant dielectric permittivity, space-charge / interfacial polarization

A comparison of the photoluminescence (PL) properties of Er-doped SiO/sub 2/, soda-lime glass, and ZBLAN glass films fabricated by pulsed-laser deposition (PLD) is given. The PL yield depends strongly on the host material. Under identical growth conditions and the same erbium concentrations in the targets, films deposited from the soda lime and ZBLAN glass show more than an order of magnitude higher luminescence yield. This enhancement is attributed to a higher concentration of optically active erbium in the multicomponent glass environment. Temperature quenching of the PL yield is observed for SiO/sub 2/:Er. The PL yield of soda-lime glass:Er and ZBLAN:Er increases with increasing temperature. A room temperature external quantum efficiency of 2/spl times/10/sup -4/ was obtained for Er-doped soda-lime glass.

The persistent photoconductivity (PPC) in oxygen-deficient YBa2Cu3Ox (YBCO) has many peculiar features. The illumination of YBCO with visible light or ultraviolet radiation leads to significant changes in the electronic properties: the free carrier concentration increases, the carrier mobility changes and, in metallic samples, the superconducting transition temperature Tc increases. Most intriguing is the persistence of the photo-induced effects up to surprisingly high temperatures. Below 250 K, PPC relaxation is practically unobservable and, at higher temperatures, the decay of the photo-induced changes takes hours or even days to complete. This temperature stability has stimulated the term photodoping for the photo-induced changes. Our studies have shown a pronounced dependence of the photodoping results on the temperature at which the experiment is performed. Hall effect studies demonstrated that the changes of the carrier concentration and of the mobility are completely different at high temperatures compared to lower temperatures. The photo-induced Tc increase was twice as large at high temperatures. Also, at high temperatures, our mobility data very clearly show the sign of a competition between two processes that contribute to the photodoping. We have identified one of the processes as photo-assisted oxygen ordering within the chain layer of YBCO. The investigation of the PPC effect was noticeably promoted by a new technique of growing YBCO thin films on so-called off-axis oriented substrates. From photodoping experiments on such films, the photo-induced changes of the in-plane ρab and of the out-of-plane ρc resistivities were derived. Both resistivity components decrease under illumination with light, but asynchronously, so the electronic anisotropy ρc/ρab gradually changes during the illumination. Our results are consistent with previously proposed models of the PPC based on the charge transfer from the copper-oxide planes to the copper-oxide chains. We obtained evidence that this process is accompanied by a re-arrangement of the oxygen atoms and/or oxygen vacancies in the chain layer. The latter process seems to be more pronounced at high temperatures, most likely because of the higher mobility of the oxygen atoms at those temperatures. Very recent results from the photo-excitation of ion-irradiated samples indicate that the observed photo-induced changes have a different origin than the PPC in oxygen-deficient YBCO.

Ion-beam irradiation of high-temperature superconductors creates different types of defects depending on ion mass, energy and dose. Computer simulations reveal the diversity of the ion-target interactions with YBa2Cu3O7 and are compared to previous experimental results from transmission electron microscopy and electrical transport properties. While protons have a very low efficiency to create defects in YBa2Cu3O7, significantly heavier ions produce defect clusters and inhomogeneous damage in the target material. The situation is exemplarily illustrated by a computer simulation study of the defect cascades produced by H+, He+, Ne+, and Pb+ ions of moderate energy. He+ ions with energy of about 75 keV were found useful for a systematic modification of the electrical properties of high-temperature superconductors, since they do not implant into 100-nm thick films of YBa2Cu3O7 but primarily create point defects by displacement of the oxygen atoms. Such defects are very small and distributed homogeneously in YBa2Cu3O7. The small lateral spread of the collision cascades allows for the patterning of nanostructures by directing a low-divergence beam of He+ ions onto a thin film of YBa2Cu3O7 through a mask. Simulations indicate that the resolution can be about 10 nm. An experimental test with a masked ion beam irradiation confirmed that features with about 200 nm size could be produced in a YBa2Cu3O7 thin film and observed by scanning electron microscopy.

Iron oxide Fe2O3 nano-particle powder is investigated by laser-induced breakdown spectroscopy (LIBS). Laser ablation of loose Fe2O3 powder (density 0.43 g cm−3) leads to the ejection of particles and generates a plasma channel along the laser beam path. LIBS spectra are obtained by spatially integrated and time-gated measurement in flushed N2 gas background. A simple powder delivery system allows for investigation of the nano-particle powder directly without any pre-treatment and fixation of the loose material. The Saha–Boltzmann analysis of spectra yields plasma temperature T = (10250 ± 200) K and electron density Ne = (11 ± 3) × 1016 cm−3 for the loose Fe2O3 powder and for pressed Fe2O3 powder pellets that are investigated for comparison. LIBS analysis of more than 20 different powder samples establishes calibration curves for Al, Si, Ni and Mn element impurities. The limits of detection derived from such curves are 8, 15, 66 and 860 ppm for Al, Si, Ni and Mn, respectively.

Thin epitaxial films of gallium orthophosphate (GaPO4) are grown on α-quartz (SiO2) substrates. Here, amorphous stoichiometric precursor layers fabricated by pulsed-laser deposition on (001) SiO2 substrates are transformed to crystalline GaPO4 by postannealing in air at 650–950°C. Epitaxial films with thicknesses up to 300nm exhibit strong in-plane and out-of-plane textures (angular widths