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Selected
papers from the latest issue:
Selective ablation of Copper-Indium-Diselenide (CIS) solar cells monitored by laser-induced breakdown spectroscopy and classification methods
09 July 2013,
11:15:37
Publication date: Available online 5 July
2013
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
Author(s): David Diego-Vallejo , David Ashkenasi , Andreas Lemke , Hans-Joachim Eichler
Laser-induced breakdown spectroscopy (LIBS) and two classification methods, i.e. linear correlation and artificial neural networks (ANN), are used to monitor P1, P2 and P3 scribing steps of Copper-Indium-Diselenide (CIS) solar cells. Narrow channels featuring complete removal of desired layers with minimum damage on the underlying film are expected to enhance efficiency of solar cells. The monitoring technique is intended to determine that enough material has been removed to reach the desired layer based on the analysis of plasma emission acquired during multiple pass laser scribing. When successful selective scribing is achieved, a high degree of similarity between test and reference spectra has to be identified by classification methods in order to stop the scribing procedure and avoid damaging the bottom layer. Performance of linear correlation and artificial neural networks is compared and evaluated for two spectral bandwidths. By using experimentally determined combinations of classifier and analyzed spectral band for each step, classification performance achieves errors of 7, 1 and 4 % for steps P1, P2 and P3, respectively. The feasibility of using plasma emission for the supervision of processing steps of solar cell manufacturing is demonstrated. This method has the potential to be implemented as an online monitoring procedure assisting the production of solar cells.
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
Author(s): David Diego-Vallejo , David Ashkenasi , Andreas Lemke , Hans-Joachim Eichler
Laser-induced breakdown spectroscopy (LIBS) and two classification methods, i.e. linear correlation and artificial neural networks (ANN), are used to monitor P1, P2 and P3 scribing steps of Copper-Indium-Diselenide (CIS) solar cells. Narrow channels featuring complete removal of desired layers with minimum damage on the underlying film are expected to enhance efficiency of solar cells. The monitoring technique is intended to determine that enough material has been removed to reach the desired layer based on the analysis of plasma emission acquired during multiple pass laser scribing. When successful selective scribing is achieved, a high degree of similarity between test and reference spectra has to be identified by classification methods in order to stop the scribing procedure and avoid damaging the bottom layer. Performance of linear correlation and artificial neural networks is compared and evaluated for two spectral bandwidths. By using experimentally determined combinations of classifier and analyzed spectral band for each step, classification performance achieves errors of 7, 1 and 4 % for steps P1, P2 and P3, respectively. The feasibility of using plasma emission for the supervision of processing steps of solar cell manufacturing is demonstrated. This method has the potential to be implemented as an online monitoring procedure assisting the production of solar cells.
Consideration on excitation mechanisms in a high-power two-jet plasma
09 July 2013,
11:15:37
Publication date: Available online 5 July
2013
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
Author(s): Natalia P. Zaksas , Vladimir A. Gerasimov
The study of excitation mechanisms in the region before the jet confluence of a high-power two-jet plasma used for analysis of different powders has been undertaken. Distribution of excited levels of Fe atoms and ions according to the Boltzmann population was found. Measuring Fe atomic and ionic excitation temperatures showed their considerable difference (≈ 2000 – 2500K). The effect of argon on line intensities of a wide range of elements was investigated by the experiment with argon covering. A negligible effect of argon covering on line intensities of atoms with ionization energy<8eV allows one to assume their predominant excitation by electron impact. The argon participation in excitation of atoms having ionization energy>8eV was revealed. This is likely to be due to Penning ionization by metastable argon followed by ion recombination with an electron and stepwise de-excitations. A more pronounced effect of argon covering was observed for ionic lines of investigated elements with total excitation energy ranging from 11 to 21eV. Penning ionization followed by electron impact is believed to be a probable mechanism for ion excitation. The contribution of metastable argon to excitation processes results in departure from local thermodynamic equilibrium and different atomic and ionic excitation temperatures.
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
Author(s): Natalia P. Zaksas , Vladimir A. Gerasimov
The study of excitation mechanisms in the region before the jet confluence of a high-power two-jet plasma used for analysis of different powders has been undertaken. Distribution of excited levels of Fe atoms and ions according to the Boltzmann population was found. Measuring Fe atomic and ionic excitation temperatures showed their considerable difference (≈ 2000 – 2500K). The effect of argon on line intensities of a wide range of elements was investigated by the experiment with argon covering. A negligible effect of argon covering on line intensities of atoms with ionization energy<8eV allows one to assume their predominant excitation by electron impact. The argon participation in excitation of atoms having ionization energy>8eV was revealed. This is likely to be due to Penning ionization by metastable argon followed by ion recombination with an electron and stepwise de-excitations. A more pronounced effect of argon covering was observed for ionic lines of investigated elements with total excitation energy ranging from 11 to 21eV. Penning ionization followed by electron impact is believed to be a probable mechanism for ion excitation. The contribution of metastable argon to excitation processes results in departure from local thermodynamic equilibrium and different atomic and ionic excitation temperatures.
Plasma-cavity ringdown spectroscopy for analytical measurement: Progress and prospectives
09 July 2013,
11:15:37
Publication date: 1 July
2013
Source:Spectrochimica Acta Part B: Atomic Spectroscopy, Volume 85
Author(s): Sida Zhang , Wei Liu , Xiaohe Zhang , Yixiang Duan
Plasma-cavity ringdown spectroscopy is a powerful absorption technique for analytical measurement. It combines the inherent advantages of high sensitivity, absolute measurement, and relative insensitivity to light source intensity fluctuations of the cavity ringdown technique with use of plasma as an atomization/ionization source. In this review, we briefly describe the background and principles of plasma-cavity ringdown spectroscopy(CRDS) technology, the instrumental components, and various applications. The significant developments of the plasma sources, lasers, and cavity optics are illustrated. Analytical applications of plasma-CRDS for elemental detection and isotopic measurement in atomic spectrometry are outlined in this review. Plasma-CRDS is shown to have a promising future for various analytical applications, while some further efforts are still needed in fields such as cavity design, plasma source design, instrumental improvement and integration, as well as potential applications in radical and molecular measurements.
Source:Spectrochimica Acta Part B: Atomic Spectroscopy, Volume 85
Author(s): Sida Zhang , Wei Liu , Xiaohe Zhang , Yixiang Duan
Plasma-cavity ringdown spectroscopy is a powerful absorption technique for analytical measurement. It combines the inherent advantages of high sensitivity, absolute measurement, and relative insensitivity to light source intensity fluctuations of the cavity ringdown technique with use of plasma as an atomization/ionization source. In this review, we briefly describe the background and principles of plasma-cavity ringdown spectroscopy(CRDS) technology, the instrumental components, and various applications. The significant developments of the plasma sources, lasers, and cavity optics are illustrated. Analytical applications of plasma-CRDS for elemental detection and isotopic measurement in atomic spectrometry are outlined in this review. Plasma-CRDS is shown to have a promising future for various analytical applications, while some further efforts are still needed in fields such as cavity design, plasma source design, instrumental improvement and integration, as well as potential applications in radical and molecular measurements.
Study on distribution of elements in deep-sea Pacific polymetallic nodules via two-dimensional mapping laser ionization orthogonal time-of-flight mass spectrometry
09 July 2013,
11:15:37
Publication date: 1 July
2013
Source:Spectrochimica Acta Part B: Atomic Spectroscopy, Volume 85
Author(s): Bochao Zhang , Dongxuan Zou , Rongfu Huang , Guangshan Liu , Zhenbin Gong , Wei Hang , Benli Huang
A newly developed two-dimensional mapping high irradiance laser ionization orthogonal time-of-flight mass spectrometer (LI-O-TOFMS) has been applied for the elemental mapping of polymetallic nodules. Two polymetallic nodule standards were used to demonstrate the efficacy of LI-O-TOFMS for the standardless semiquantitative analysis and the spatial distribution of elements in a deep-sea Pacific polymetallic nodule was mapped. It was found that the two groups of elements, Mn–Ni–Cu–Fe and Co–Si–Al, show clear element-dependent spatial relationships. It is hypothesized that these spatial distributions reflect the environmental and physico-chemical conditions during the nodule formation. LI-O-TOFMS is shown to be a powerful tool in elemental analysis of polymetallic nodules, with the detection limits down to 10−7 g/g and a dynamic range of 7 orders of magnitude. Based on the images acquired, the contents of elements and their relationships can be revealed visually.
Source:Spectrochimica Acta Part B: Atomic Spectroscopy, Volume 85
Author(s): Bochao Zhang , Dongxuan Zou , Rongfu Huang , Guangshan Liu , Zhenbin Gong , Wei Hang , Benli Huang
A newly developed two-dimensional mapping high irradiance laser ionization orthogonal time-of-flight mass spectrometer (LI-O-TOFMS) has been applied for the elemental mapping of polymetallic nodules. Two polymetallic nodule standards were used to demonstrate the efficacy of LI-O-TOFMS for the standardless semiquantitative analysis and the spatial distribution of elements in a deep-sea Pacific polymetallic nodule was mapped. It was found that the two groups of elements, Mn–Ni–Cu–Fe and Co–Si–Al, show clear element-dependent spatial relationships. It is hypothesized that these spatial distributions reflect the environmental and physico-chemical conditions during the nodule formation. LI-O-TOFMS is shown to be a powerful tool in elemental analysis of polymetallic nodules, with the detection limits down to 10−7 g/g and a dynamic range of 7 orders of magnitude. Based on the images acquired, the contents of elements and their relationships can be revealed visually.
Stark broadening of Mg I and Mg II spectral lines and Debye shielding effect in laser induced plasma
09 July 2013,
11:15:37
Publication date: 1 July
2013
Source:Spectrochimica Acta Part B: Atomic Spectroscopy, Volume 85
Author(s): M. Cvejić , M.R. Gavrilović , S. Jovićević , N. Konjević
We report Stark broadening parameters for three Mg I lines and one Mg II line in the electron number density range (0.67–1.09)·1017 cm−3 and electron temperature interval (6200–6500) K. The electron density is determined from the half width of hydrogen impurity line, the Hα, while the electron temperature is measured from relative intensities of Mg I or Al II lines using Boltzmann plot technique. The plasma source was induced by Nd:YAG laser radiation at 1.06μm having pulse width 15ns and pulse energy 50mJ. Laser induced plasma is generated in front of a solid state surface. High speed photography is used to determine time of plasma decay with good homogeneity and then applied line self-absorption test and Abel inversion procedure. The details of data acquisition and data processing are described and illustrated with typical examples. The experimental results are compared with two sets of semiclassical calculations and the results of this comparison for Mg I lines are not unambiguous while for Mg II 448.1nm line, the results of Dimitrijević and Sahal-Bréchot calculations agree well with our and other experimental results in the temperature range (5000–12,000) K and these theoretical results are recommended for plasma diagnostic purposes. The study of line shapes within Mg I 383.53nm multiplet shows that the use of Debye shielding correction improves the agreement between theoretical and experimental Stark broadening parameters.
Source:Spectrochimica Acta Part B: Atomic Spectroscopy, Volume 85
Author(s): M. Cvejić , M.R. Gavrilović , S. Jovićević , N. Konjević
We report Stark broadening parameters for three Mg I lines and one Mg II line in the electron number density range (0.67–1.09)·1017 cm−3 and electron temperature interval (6200–6500) K. The electron density is determined from the half width of hydrogen impurity line, the Hα, while the electron temperature is measured from relative intensities of Mg I or Al II lines using Boltzmann plot technique. The plasma source was induced by Nd:YAG laser radiation at 1.06μm having pulse width 15ns and pulse energy 50mJ. Laser induced plasma is generated in front of a solid state surface. High speed photography is used to determine time of plasma decay with good homogeneity and then applied line self-absorption test and Abel inversion procedure. The details of data acquisition and data processing are described and illustrated with typical examples. The experimental results are compared with two sets of semiclassical calculations and the results of this comparison for Mg I lines are not unambiguous while for Mg II 448.1nm line, the results of Dimitrijević and Sahal-Bréchot calculations agree well with our and other experimental results in the temperature range (5000–12,000) K and these theoretical results are recommended for plasma diagnostic purposes. The study of line shapes within Mg I 383.53nm multiplet shows that the use of Debye shielding correction improves the agreement between theoretical and experimental Stark broadening parameters.
A method for direct, semi-quantitative analysis of gas phase samples using gas chromatography–inductively coupled plasma-mass spectrometry
09 July 2013,
11:15:37
Publication date: 1 July
2013
Source:Spectrochimica Acta Part B: Atomic Spectroscopy, Volume 85
Author(s): Kimberly E. Carter , Kirk Gerdes
A new and complete GC–ICP-MS method is described for direct analysis of trace metals in a gas phase process stream. The proposed method is derived from standard analytical procedures developed for ICP-MS, which are regularly exercised in standard ICP-MS laboratories. In order to implement the method, a series of empirical factors were generated to calibrate detector response with respect to a known concentration of an internal standard analyte. Calibrated responses are ultimately used to determine the concentration of metal analytes in a gas stream using a semi-quantitative algorithm. The method was verified using a traditional gas injection from a GC sampling valve and a standard gas mixture containing either a 1ppm Xe+Kr mix with helium balance or 100ppm Xe with helium balance. Data collected for Xe and Kr gas analytes revealed that agreement of 6–20% with the actual concentration can be expected for various experimental conditions. To demonstrate the method using a relevant “unknown” gas mixture, experiments were performed for continuous 4 and 7hour periods using a Hg-containing sample gas that was co-introduced into the GC sample loop with the xenon gas standard. System performance and detector response to the dilute concentration of the internal standard were pre-determined, which allowed semi-quantitative evaluation of the analyte. The calculated analyte concentrations varied during the course of the 4hour experiment, particularly during the first hour of the analysis where the actual Hg concentration was under predicted by up to 72%. Calculated concentration improved to within 30–60% for data collected after the first hour of the experiment. Similar results were seen during the 7hour test with the deviation from the actual concentration being 11–81% during the first hour and then decreasing for the remaining period. The method detection limit (MDL) was determined for the mercury by injecting the sample gas into the system following a period of equilibration. The MDL for Hg was calculated as 6.8μg·m−3. This work describes the first complete GC–ICP-MS method to directly analyze gas phase samples, and detailed sample calculations and comparisons to conventional ICP-MS methods are provided.
Source:Spectrochimica Acta Part B: Atomic Spectroscopy, Volume 85
Author(s): Kimberly E. Carter , Kirk Gerdes
A new and complete GC–ICP-MS method is described for direct analysis of trace metals in a gas phase process stream. The proposed method is derived from standard analytical procedures developed for ICP-MS, which are regularly exercised in standard ICP-MS laboratories. In order to implement the method, a series of empirical factors were generated to calibrate detector response with respect to a known concentration of an internal standard analyte. Calibrated responses are ultimately used to determine the concentration of metal analytes in a gas stream using a semi-quantitative algorithm. The method was verified using a traditional gas injection from a GC sampling valve and a standard gas mixture containing either a 1ppm Xe+Kr mix with helium balance or 100ppm Xe with helium balance. Data collected for Xe and Kr gas analytes revealed that agreement of 6–20% with the actual concentration can be expected for various experimental conditions. To demonstrate the method using a relevant “unknown” gas mixture, experiments were performed for continuous 4 and 7hour periods using a Hg-containing sample gas that was co-introduced into the GC sample loop with the xenon gas standard. System performance and detector response to the dilute concentration of the internal standard were pre-determined, which allowed semi-quantitative evaluation of the analyte. The calculated analyte concentrations varied during the course of the 4hour experiment, particularly during the first hour of the analysis where the actual Hg concentration was under predicted by up to 72%. Calculated concentration improved to within 30–60% for data collected after the first hour of the experiment. Similar results were seen during the 7hour test with the deviation from the actual concentration being 11–81% during the first hour and then decreasing for the remaining period. The method detection limit (MDL) was determined for the mercury by injecting the sample gas into the system following a period of equilibration. The MDL for Hg was calculated as 6.8μg·m−3. This work describes the first complete GC–ICP-MS method to directly analyze gas phase samples, and detailed sample calculations and comparisons to conventional ICP-MS methods are provided.
Further insights into prepeak emission in pulsed radiofrequency glow discharge
09 July 2013,
11:15:37
Publication date: 1 July
2013
Source:Spectrochimica Acta Part B: Atomic Spectroscopy, Volume 85
Author(s): Rebeca Valledor , Paola Vega , Jorge Pisonero , Thomas Nelis , Nerea Bordel
Side-on optical emission measurements, with spatial and temporal resolution, have been carried out on a modified Grimm type pulsed rf glow discharge, using a copper sample and argon as discharge gas. In particular, the early ignition phase of the pulsed discharge, prepeak, and the beginning of the plateau have been electrically characterized and spectroscopically evaluated along the plasma plume for several argon and copper emission lines. Different pulse repetition frequencies have been used while keeping a constant duty cycle of 25%, covering a range from the μs to the ms pulsed GD. In all the cases a spatially extended discharge has been observed during the first 10–20μs of the pulse, when the dc bias voltage has not been fully established yet. During this early phase of the pulse, the species present in the chamber are excited following the amplitude of the voltage symmetrical oscillations, and argon and copper emission can be detected at all the distances evaluated along the plasma axis at delays as short as 4μs. After the first 20μs approximately, the discharge has contracted close to the sample surface, the dc bias voltage has been almost established and the sputtering process is taking place. Emission registered through side-on observation, at positions relatively far from the sample, decreases and then progressively increases to reach a plateau if the voltage pulse lasts long enough. Moreover, the further the detection position is from the sample surface, the later the increase of the copper and argon emission is observed. Therefore transport phenomena involving both argon and copper species are now evidently leading to an estimated average speed of 100m/s. Additionally, end-on optical emission measurements have been carried out to evaluate the prepeak emission from the negative glow region close to the sample surface, and then to compare this emission with that occurring at farther positions (side-on detection experiments). The results have shown that the basis of both prepeaks might be different as the prepeak signal measured using end-on detection peaks around 10μs later than that observed using side-on detection.
Source:Spectrochimica Acta Part B: Atomic Spectroscopy, Volume 85
Author(s): Rebeca Valledor , Paola Vega , Jorge Pisonero , Thomas Nelis , Nerea Bordel
Side-on optical emission measurements, with spatial and temporal resolution, have been carried out on a modified Grimm type pulsed rf glow discharge, using a copper sample and argon as discharge gas. In particular, the early ignition phase of the pulsed discharge, prepeak, and the beginning of the plateau have been electrically characterized and spectroscopically evaluated along the plasma plume for several argon and copper emission lines. Different pulse repetition frequencies have been used while keeping a constant duty cycle of 25%, covering a range from the μs to the ms pulsed GD. In all the cases a spatially extended discharge has been observed during the first 10–20μs of the pulse, when the dc bias voltage has not been fully established yet. During this early phase of the pulse, the species present in the chamber are excited following the amplitude of the voltage symmetrical oscillations, and argon and copper emission can be detected at all the distances evaluated along the plasma axis at delays as short as 4μs. After the first 20μs approximately, the discharge has contracted close to the sample surface, the dc bias voltage has been almost established and the sputtering process is taking place. Emission registered through side-on observation, at positions relatively far from the sample, decreases and then progressively increases to reach a plateau if the voltage pulse lasts long enough. Moreover, the further the detection position is from the sample surface, the later the increase of the copper and argon emission is observed. Therefore transport phenomena involving both argon and copper species are now evidently leading to an estimated average speed of 100m/s. Additionally, end-on optical emission measurements have been carried out to evaluate the prepeak emission from the negative glow region close to the sample surface, and then to compare this emission with that occurring at farther positions (side-on detection experiments). The results have shown that the basis of both prepeaks might be different as the prepeak signal measured using end-on detection peaks around 10μs later than that observed using side-on detection.
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