Single Breakdown Research Articles

Single Event Effects in 3.3 kV 4H-SiC MOSFETs due to MeV Ion Impact

In this work, MeV alpha particles generated from an accelerator are used to study single event breakdown (SEB) in 4H-SiC MOSFET samples, rated at 3.3 kV. The samples are exposed to bursts of alpha particles under reverse bias conditions to investigate the SEB sensitivity to ion energy and reverse bias. The energies of alpha particles are chosen to reach different depths in the drift region of the MOSFET devices, and also to penetrate the whole drift region. Forward and reverse characteristics are measured after each exposure, as long as no failures occur, to ensure that the device performance is maintained. The measurements show that no significant effects are observed on the drain-source leakage current, while minor effects on gate behavior can be seen as a function of accumulated fluence. Furthermore, SEB can only be triggered with a reverse bias larger than, or equal to 3 kV. A standard MOSFET cell with a similar rated voltage is also simulated in Sentaurus TCAD to study these effects, using two different models for the incident ion-induced ionization: the Alpha Particle and the Heavy Ion model. Simulations show that the Alpha Particle model cannot induce any device failures even with a 3.5 kV reverse bias, while it is possible to trigger a failure by the Heavy Ion model, where the ionization can be selected. Carrier plasma and internal electric field distributions of the two models are plotted and compared, showing that device failures triggered by a heavy ion are related to the hole injection at epi-substrate interface, in which linear energy transfer (LET) of the particle plays an important role.

Analysis of Kidney Stones Using Single Pulse Laser-Induced Breakdown Spectroscopy (SP-LIBS) to Determine the Concentrations of Elements

Analysis of Kidney Stones Using Single Pulse Laser-Induced Breakdown Spectroscopy (SP-LIBS) to Determine the Concentrations of Elements

Effect of single and double pulse laser-induced breakdown spectroscopy towards steel alloy in different gaseous media

In recent years, laser-induced breakdown spectroscopy (LIBS) technique showed its promising for material analysis, quality control, forensic science, and environmental safety monitoring. Besides, due to its rapid measurement capability and minimal sample-preparation requirements, it is a widely recognized elemental analysis approach used in a variety of study domains. The current work compares spatially resolved single (SP) and double pulse (DP), especially orthogonal DP, setups for LIBS to examine and enhance the limit of detection (LOD) in duplex stainless steels alloy. Using the Boltzmann plot method and the Stark broadening mechanism, the electron temperature and density of local arc plasma are highlighted due to single pulse and orthogonal pre-pulse double pulse configurations. With delay time, the circumstances of arc plasma's local thermodynamic equilibrium (LTE) of emission spectral lines are investigated. The experimental results show that there are significant increases in the spectral intensities of the Fe lines in double pulse LIBS under Ar-gas compared to those under He-gas. Internal standardization was used to create calibration curves for the spectral lines of Cr, Cu, and Mn in the alloy sample for the both studied media. It demonstrated that argon outperforms helium in determining the elemental composition of steel alloys. Furthermore, LOD for SP-LIBS and DP-LIBS in both media were calculated, which showed a higher detection LOD for DP-LIBS in the presence of Ar-gas compared to that in He-gas.

Dynamic Events in the Flexible Job-Shop Scheduling Problem: Rescheduling with a Hybrid Metaheuristic Algorithm

In the real world of manufacturing systems, production planning is crucial for organizing and optimizing various manufacturing process components. The objective of this paper is to present a methodology for both static scheduling and dynamic scheduling. In the proposed method, a hybrid algorithm is utilized to optimize the static flexible job-shop scheduling problem (FJSP) and dynamic flexible job-shop scheduling problem (DFJSP). This algorithm integrates the genetic algorithm (GA) as a global optimization technique with a simulated annealing (SA) algorithm serving as a local search optimization approach to accelerate convergence and prevent getting stuck in local minima. Additionally, variable neighborhood search (VNS) is utilized for efficient neighborhood search within this hybrid algorithm framework. For the FJSP, the proposed hybrid algorithm is simulated on a 40-benchmark dataset to evaluate its performance. Comparisons among the proposed hybrid algorithm and other algorithms are provided to show the effectiveness of the proposed algorithm, ensuring that the proposed hybrid algorithm can efficiently solve the FJSP, with 38 out of 40 instances demonstrating better results. The primary objective of this study is to perform dynamic scheduling on two datasets, including both single-purpose machine and multi-purpose machine datasets, using the proposed hybrid algorithm with a rescheduling strategy. By observing the results of the DFJSP, dynamic events such as a single machine breakdown, a single job arrival, multiple machine breakdowns, and multiple job arrivals demonstrate that the proposed hybrid algorithm with the rescheduling strategy achieves significant improvement and the proposed method obtains the best new solution, resulting in a significant decrease in makespan.

Comparison of single and double pulse laser-induced breakdown spectroscopy for the detection of biomolecules tagged with photon-upconversion nanoparticles

BackgroundLaser-induced breakdown spectroscopy (LIBS) is a well-recognized analytical technique used for elemental analysis. This method is gaining considerable attention also in biological applications thanks to its ability for spatial mapping and elemental imaging. The implementation of LIBS in the biomedical field is based on the detection of metals or other elements that either naturally occur in the samples or are present artificially. The artificial implementation of nanoparticle labels (Tag-LIBS) enables the use of LIBS as a readout technique for immunochemical assays. However, one of the biggest challenges for LIBS to meet immunoassay readout standards is its sensitivity. ResultsThis paper focuses on the improvement of LIBS sensitivity for the readout of nanoparticle-based immunoassays. First, the LIBS setup was optimized on photon-upconversion nanoparticle (UCNP) droplets deposited on the microtiter plate wells. Two collection optics systems were compared, with single pulse (SP) and collinear double pulse (DP) LIBS arrangements. By deploying the second laser pulse, the sensitivity was improved up to 30 times. The optimized SP and DP setups were then employed for the indirect detection of human serum albumin based on immunoassay with UCNP-based labels. Compared to our previous LIBS study, the detection limit was enhanced by two orders of magnitude, from 10 ng mL−1 to 0.29 ng mL−1. In addition, two other immunochemical methods were used for reference, based on the readout of upconversion luminescence of UCNPs and absorbance measurement with enzyme labels. Finally, the selectivity of the assay was tested and the practical potential of Tag-LIBS was demonstrated by the successful analysis of urine samples. Significance and noveltyIn this work, we improved the sensitivity of the Tag-LIBS method by combining new labels based on UCNPs with the improved collection optics and collinear DP configuration. In the instrumental setup optimization, the DP LIBS showed better sensitivity and signal-to-noise ratio than SP. The optimizations allowed the LIBS readout to surpass the sensitivity of enzyme immunoassay, approaching the qualities of upconversion luminescence readout, which is nowadays a state-of-the-art readout technique.

The Influence of Gadolinium Oxide Nanoparticles Concentration on the Chemical and Physical Processes Intensity during Laser-Induced Breakdown of Aqueous Solutions

The paper investigates the physicochemical processes that occur during laser-induced breakdown in colloids of gadolinium oxide nanoparticles of different concentrations. A monotonic change in the number of optical breakdowns, the average distance between the nearest breakdowns in the track of a single laser pulse, the average plasma size of a single optical breakdown, the integral luminosity of an optical breakdown plasma flash, the intensity of acoustic signals, and the rate of formation of dissociation products—O2, H2, OH•, and H2O2—is demonstrated. It is shown that the rate of formation of chemical products of the decomposition of H2O molecules under the action of breakdown when using nanoparticles of rare earth metals, in particular, gadolinium oxide, is the highest compared to other materials. Based on one laser pulse, the rates of formation of chemical products formed during the dissociation of water during laser-induced breakdown of a colloid of gadolinium oxide nanoparticles are 13.13 nmol/pulse for H2, 5.41 nmol/pulse for O2, and 6.98 nmol/pulse for hydrogen peroxide.

Rock breaking mechanism of electrode bit in heterogeneous granite formation and its optimization

Electro-pulse-boring (EPB) technology is one of the most potential and nearly industrialized new rock breaking methods in geothermal drilling. However, the mechanism of EPB is not clear, and the structural parameters of EPB electrode bit are not well matched with the corresponding strata parameters and voltage parameters, which seriously hindered the commercialization process of this technology. Based on the dynamic electrical breakdown model (DEBM), a single electric breakdown of rock is realized by coupling the circuit field, the current field and the breakdown field. At the same time, considering the heterogeneity of rock, the three-dimensional numerical simulation of full-bit electrical breakdown using five kinds of electrode bits with different structures is conducted. From these five kinds of electrode bits, an electrode bit suitable for EPB is selected. Finally, the adaptability between the structural parameters and voltage parameters of the selected electrode bit is studied. The results show that the initiation and development of electrical breakdown are affected by the mineral composition, mineral quantity and mineral position of the rock. The petal-structural electrode bits with the same clearance between the high voltage electrode and all ground electrodes are more suitable for EPB drilling due to their higher chip removal function. Moreover, the minimum initial output pulse peak voltage, i.e., the adaptive voltage, of petal-structural electrode bit under different structural parameters is calculated by fitting, which is the best rock breaking voltage parameter. This research can provide reliable help for the design of EPB electrode bit, the optimization of structural parameters and voltage parameters of electrode bit to increase geothermal resources.

Emission Properties and Dielectric Strength of a Nanostructured Tungsten Field-Emissive Cathode

Research of the tungsten “fuzz” emission properties and dielectric strength was carried out. A “fuzzy” sample was made through He+ ion exposure of an initially polished tungsten surface using an inductively coupled plasma (ICP) facility. The eventual He+ ion fluence was <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim 1.7\times 10^{25}\,\,\text{m}^{-2}$ </tex-math></inline-formula> . The induced nanostructured layer thickness was estimated to be <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim 1~\mu \text{m}$ </tex-math></inline-formula> . The measurements were performed with an automated experimental setup developed. The setup was operated under the control of the programmable DAC/ADC module “LCard E20-10.” As a result, the untypical behavior of a nanostructured cathode in comparison with an ordinary field emissive cathode was registered. Instability of the W “fuzz” emission properties was demonstrated. Typical values of the electric field enhancement factor were found to be in the range of ~120–200 both before a single breakdown and after it. These values are in agreement with the estimations of the enhancement factor performed with taking into account the geometry of protrude cathode structures. Stabilization of the emission properties after the breakdown was observed. The conditioning effect of the nanostructured cathode was found to take place after approximately five breakdowns. After conditioning, an asymptotic value of a breakdown electric field strength was <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim 8.5\times 10^{7}$ </tex-math></inline-formula> V/m, which is in agreement with the one for an ordinary tungsten cathode. The conditioning effect and the emission current stabilization are believed to be due to the destruction of the nanostructure under the impact of the breakdowns.

Direct determination of Cu, Cr, and Ni in river sediments using double pulse laser-induced breakdown spectroscopy: Ecological risk and pollution level assessment.

Double pulse laser-induced breakdown spectroscopy (DP LIBS) has attracted much attention for analyzing trace elements due to its higher sensitivity when compared to single pulse laser-induced breakdown spectroscopy (SP LIBS). However, the development of quantitative methods in LIBS for the analysis of complex samples, such as sediments, is a great challenge due to the matrix effects that are very accentuated in this technique. In this study, different spectral treatments and calibration strategies were investigated to obtain calibration models that allow determinations with satisfactory accuracy and precision of Cr, Cu, and Ni in river sediments from different hydrographic basins. The best model developed for Cr was using MMC without spectral normalization and for Cu and Ni it was using MMC with spectral normalization, and using inverse regression, an increase in the accuracy of the determinations of all analytes was obtained. These models showed limit of quantification (LOQ) of 7.87 mg kg-1, 1.62 mg kg-1, and 2.21 mg kg-1 and root mean square error of prediction (RMSEP) of 7.54 mg kg-1, 14.53 mg kg-1, and 8.29 mg kg-1 for Cr, Cu, and Ni, respectively. Therefore, the models have adequate sensitivity and precision for the quantification of the potentially toxic elements (PTEs) evaluated, since, according to Brazilian legislation, the lower concentration of threshold effect level (TEL) for Cr, Cu, and Ni is <37.3 mg kg-1, <35.7 mg kg-1, and <18 mg kg-1, respectively. The concentrations of Cr, Cu, and Ni determined by DP LIBS allowed to obtain a partial ecological risk assessment of the studied sediments. Also, the chemometric tool Kohonen self-organizing map (KSOM) were used for data interpretation.

Laser-Induced Plasmonic Nanobubbles and Microbubbles in Gold Nanorod Colloidal Solution.

In this work, we studied the initiated plasmonic nanobubbles and the follow-up microbubble in gold nanorod (GNR) colloidal solution induced by a pulsed laser. Owing to the surface plasmon resonance (SPR)-enhanced photothermal effect of GNR, several nanobubbles are initiated at the beginning of illumination and then to trigger the optical breakdown of water at the focal spot of a laser beam. Consequently, microbubble generation is facilitated; the threshold of pulsed laser energy is significantly reduced for the generation of microbubbles in water with the aid of GNRs. We used a probing He-Ne laser with a photodetector and an ultrasonic transducer to measure and investigate the dynamic formations of nanobubbles and the follow-up microbubble in GNR colloids. Two wavelengths (700 nm and 980 nm) of pulsed laser beams are used to irradiate two kinds of dilute GNR colloids with different longitudinal SPRs (718 nm and 966 nm). By characterizing the optical and photoacoustic signals, three types of microbubbles are identified: a single microbubble, a coalesced microbubble of multiple microbubbles, and a splitting microbubble. The former is caused by a single breakdown, whereas the latter two are caused by discrete and series-connected multiple breakdowns, respectively. We found that the thresholds of pulsed energy to induce different types of microbubbles are reduced as the concentration of GNRs increases, particularly when the wavelength of the laser is in the near-infrared (NIR) region and close to the SPR of GNRs. This advantage of a dilute GNR colloid facilitating the laser-induced microbubble in the NIR range of the bio-optical window could make biomedical applications available. Our study may provide an insight into the relationship between plasmonic nanobubbles and the triggered microbubbles.

Accuracy improvement of single-sample calibration laser-induced breakdown spectroscopy with self-absorption correction.

The single sample calibration laser-induced breakdown spectroscopy (SSC-LIBS) is quite suitable for the fields where the standard sample is hard to obtain, including space exploration, geology, archaeology, and jewelry identification. But in practice, the self-absorption effect of plasma destroys the linear relationship of spectral intensity and element concentration based on the Lomakin-Scherbe formula which is the guarantee of the high accuracy of the SSC-LIBS. Thus, the self-absorption effect limits the quantitative accuracy of SSC-LIBS greatly. In this work, an improved SSC-LIBS with self-absorption correction (SSC-LIBS with SAC) is proposed for the promotion of quantitative accuracy of SSC-LIBS. The SSC-LIBS with SAC can correct the intensity ratio of spectral lines in the calculation of SSC-LIBS through relative self-absorption coefficient K without complicated preparatory information. The alloy samples and pressed ore samples were used to verify the effect of the SSC-LIBS with SAC. Compared with SSC-LIBS, for alloy samples, the average RMSEP and average ARE of SSC-LIBS with SAC decreased from 0.83 wt.% and 13.75% to 0.40 wt.% and 4.06%, respectively. For the pressed ore samples, the average RMSEP and average ARE of SSC-LIBS with SAC decreased from 4.77wt.% and 90.48% to 2.34 wt.% and 14.60%. The experimental result indicates that SSC-LIBS with SAC has a great improvement of quantitative accuracy and better universality compared with traditional SSC-LIBS, which is a mighty promotion of the wide application of SSC-LIBS.

Double pulse laser-induced breakdown spectroscopy for the analysis of plasma-facing components

Laser-induced breakdown spectroscopy is applied successfully for plasma-wall interaction studies in several fusion devices and post-mortem analyses of plasma-facing materials. However, the quantitative as well as qualitative analysis of low hydrogen isotope contents in tungsten plasma-facing components is still challenging. A promising approach to increase the optical signal in laser-induced breakdown spectroscopy is to apply a second laser pulse to the laser-produced plasma. We present two setups for post mortem plasma-facing component analyses using different laser pulse properties and different excitation geometries. The enhancement factors and changes in spectral line shapes for double pulse compared to single pulse laser-induced breakdown spectroscopy are presented.

Impact of electrical grounding conditions on plasma\u2013liquid interactions using Thomson scattering on a pulsed argon jet

The interaction between an argon plasma jet excited using microsecond duration voltage pulses and a liquid target was examined using Thomson scattering to quantify the temporal evolution of the electron density and temperature. The electrical resistance between a liquid target and the electrical ground was varied from 1 to 680, text {k}Omega to mimic different conductivity liquids while the influence of the varying electrical properties on the electron dynamics within the plasma were examined. It was demonstrated that the interaction between the plasma jet and a liquid target grounded via a high resistance resulted in typical dielectric barrier discharge behaviour, with two discharge events per applied voltage pulse. Under such conditions, the electron density and temperature reached a peak of 1cdot 10^{15}, text {cm}^{-3} and 3.4 eV, respectively; with both rapidly decaying over several hundreds of nanoseconds. For liquid targets grounded via a low resistance, the jet behaviour transitioned to a DC-like discharge, with a single breakdown event being observed and sustained throughout the duration of each applied voltage pulse. Under such conditions, electron densities of 2{-}3 cdot 10^{15}, text {cm}^{-3} were detected for several microseconds. The results demonstrate that the electron dynamics in a pulsed argon plasma jet are extremely sensitive to the electrical characteristics of the target, which in the case of water, can evolve during exposure to the plasma.

Design and operation of smart hybrid microgrid

Abstract Renewable energy resources based hybrid microgrid has emerged as a significant component of the power system. Nevertheless, the control and management of power, voltage and frequency under transition between grid-connected mode (GCM) and islanded mode (IM) is a major concern. This paper proposes a self-sustained and flexible novel cooperative control strategy (CCS) for smart hybrid microgrid (SHMG) under GCM and IM mode operations. In islanded operation of SHMG, conventional droop offers ease of control but its execution with seamless transition between operating modes poses poor voltage regulation and frequency deviation. For this purpose, an intelligent cooperative controller is proposed. It consists of a modified P/f-Q/V droop control (MDC) algorithm along with soft computing based VF-controller unit (VFCU). The proposed control scheme is implemented to regulate voltage and frequency. It also enhances the power quality with unbalanced non-linear load and source intermittencies. The absence of a communication link reduces cost and also eliminates the risk of single point breakdown. The SHMG has been simulated in MATLAB and implemented in real-time. The obtained experimental results demonstrate the competency and high robustness of the proposed scheme.

Unusual parallel laser irradiation for suppressing self-absorption in single pulse laser-induced breakdown spectroscopy.

This study demonstrates a new approach for suppressing the self-absorption effect in single-pulse laser-induced breakdown spectroscopy (LIBS) using unusual parallel laser irradiation. A nanosecond Nd:YAG laser with a wavelength of 1064 nm was fired parallel to and focused at a very close distance of 1 mm to the sample surface. The experiment was carried out in air at atmospheric pressure. In this configuration, the sample was ablated by a shockwave generated from the air breakdown plasma formed near the sample surface. Under this condition, we successfully obtained spectra of the resonance emission line for high concentration K (K I 766.4 nm and K I 769.9 nm) that are free from self-reversal and weakly affected by the self-absorption. Furthermore, the quantitative analysis results for the element K showed that a linear calibration curve over a wide concentration range could be achieved, which indicates the effectiveness of this technique in reducing the self-absorption effect and improving the analytical performance of ordinary single-pulse LIBS.

Multi-elemental analysis of landfill leachates by single and double pulse laser-induced breakdown spectroscopy

In this work, the potential of single and double-pulse laser induced breakdown spectroscopy (SP and DP LIBS) has been investigated for multi-elemental analysis of the elements manganese, zinc, arsenic and lead in landfill leachates. Instrumental parameters such as detection delay and interpulse delay times were investigated in order to find the optimal operating values for multi-elemental analysis. The following emission lines were used: Mn II: 257.61; 259.37 and 260.56 nm; Zn II: 206.20 nm and Zn I: 213.85 nm; As I: 228.81; 234.98 nm and Pb I: 405.78 nm. All elements showed a strong enhancement factor (2.5) of DP LIBS signal intensities compared to SP LIBS. Analyses were performed using a background correction and the sum of the areas below each element emission lines. The limits of detection (LODs) achieved by SP LIBS were: 21.3, 77.5, 89.3, 38.9 mgkg−1 and for DP LIBS: 7.1, 13.4, 11.9 and 7.3 mgkg−1 respectively for Mn, Zn, As and Pb. The LOD values achieved by DP LIBS were improved by factors of 3, 6, 7.5 and 5 times respectively for Mn, Zn, As and Pb, with respect to SP LIBS. The average quantification errors were 7.5, 19.6, 38.2 and 28% for SP LIBS and 9.2, 21.3, 12.9 and 14.4% for DP LIBS respectively for Mn, Zn, As and Pb. The LIBS approach was demonstrated to be suitable for quantitative analysis of toxic elements and sufficiently fast for real time continuous monitoring of landfill leachates.

Novel droop integrated technique for regulation of islanded and grid connected hybrid microgrid

Hybrid microgrid comprising of distributed generation is evolved as most proficient solution for environmental and energy crisis problem especially in remote areas. In this paper, the performance of proposed hybrid microgrid interlinked with fuzzy logic-based voltage-frequency controller is tested under islanding and grid connected mode. The novel distributed droop control scheme is implemented to sustain voltage and frequency in seamless transition among these two modes. The power management strategy with a re-synchronising circuit is also employed in this study. This control technique enhances the power quality without the need of any communication link. This leads to considerable reduction in cost and also conquers the hitch of single point breakdown. The results derived from SPS tool demonstrate the efficacy and high robustness of proposed control strategy.

Effects of metal fluoride/sulfide microparticles generated by consecutive high-pulse-power breakdowns on the insulating performance in compressed SF6

Spark gas switches (SGS) are widely used in various pulsed power applications where sulfur hexafluoride (SF6) is still dominant because of its excellent insulating performance. However, particle contamination generated by SF6 possesses some special properties that can greatly reduce the effectiveness of the gas switches. The objective of this paper is to study the effects of particles generated spontaneously by consecutive breakdowns of high-pulse-power SGS on the insulating performance in compressed SF6. A double electrode/double pulse method, coupled with laser scattering and laser shadow photography, is adopted to detect the particles and examine their specific roles in the breakdown process. Many large particles in SF6, of approximately 150 μm in diameter, are observed at about 80 milliseconds after a single breakdown. Furthermore, numerous particles gradually suspend and accumulate in the gap after consecutive breakdowns. Particles generated by SF6 can reach tens of micrometers in size. They have rough microtopography covered by abundant floccules, and contain rich electronegative elements: fluorine and sulfur. Moreover, particle-involved abnormal breakdowns in SF6 usually occur with nearly equal threshold and probability in spite of the increasing consecutive breakdowns, and conversely, the abnormal breakdowns in N2 appear more frequently and unsteadily with a high dispersibility. The analysis of field enhancement caused by these large metal-fluoride/sulfide particles shows that they can directly cause significant field emission (FE) due to their properties of surface-field enhancement and causticity. Such FE further triggers micro-discharge. Subsequently, this behavior eventually leads to abnormal breakdowns at a lower threshold.

Suppression of self-absorption in laser-induced breakdown spectroscopy using a double pulse orthogonal configuration to create vacuum-like conditions in atmospheric air pressure

Self-absorption, which is known to severely disturb identification of the emission peak intensity in emission-based spectroscopy, was first studied using ordinary single pulse laser-induced breakdown spectroscopy (LIBS). It was found that severe self-absorption, with an evident self-reversal, occurs in the resonance emission lines of high concentration Na, K, and Al, and thus it is impossible to obtain the linear calibration curve required for quantitative analysis. To overcome this problem, we introduce a double pulse orthogonal technique in which the first laser is fired in a parallel orientation at a varied distance of 2–6 mm from the sample surface. It is well known that the strong shock wave generated by this laser irradiation temporarily creates a vacuum-like condition immediately in front of the sample surface. This action is followed by a second laser irradiation oriented perpendicular to the sample surface. The sample ablated by the second laser irradiation expands following the shockwave excitation process in the vacuum-like air atmosphere created by the first laser. The obtained spectra of the resonance emission lines of high concentration Na, K, and Al are free from the self-reversal and weakly affected by the self-absorption effect. A linear calibration curve that intercepts near zero point for K element over a wide concentration range is also demonstrated in this study. This simple modification is considered notably helpful in overcoming the self-absorption that occurs in ordinary single pulse atmospheric pressure LIBS.

Electrical breakdown spots in metal-aluminum oxide-metal structures

Metal-aluminum oxide-metal structures are prepared by evaporation in vacuum on silicon wafers using Au, Cu or Pd on top and Al as bottom electrode. The aluminum oxide layer is deposited by electron beam evaporation with a thickness of 200 nm. The diameter of the top electrode is varied between 0.1 and 1.9 mm. Capacitance measurements reveal a relaxational dielectric permittivity as expected for aluminum oxide. Applying ramp voltages results in single breakdown spots on the electrode before the structure finally becomes conductive. The breakdown spots, as characterized with an AFM, are in the form a crater, reaching 500 nm into the silicon. However, for the smallest electrode, the calculated electrostatic energy stored in the capacitance is not high enough to form the craters.