Markus Hohl - Academia.edu (original) (raw)

Papers by Markus Hohl

Research paper thumbnail of High Spatial Resolution Time-of-Flight Secondary Ion Mass Spectrometry for the Masses: A Novel Orthogonal ToF FIB-SIMS Instrument with In Situ AFM

Advances in Materials Science and Engineering, 2012

We describe the design and performance of an orthogonal time-of-flight (TOF) secondary ion mass s... more We describe the design and performance of an orthogonal time-of-flight (TOF) secondary ion mass spectrometer that can be retrofitted to existing focused ion beam (FIB) instruments. In particular, a simple interface has been developed for FIB/SEM instruments from the manufacturer Tescan. Orthogonal extraction to the mass analyser obviates the need to pulse the primary ion beam and does not require the use of monoisotopic gallium to preserve mass resolution. The high-duty cycle and reasonable collection efficiency of the new instrument combined with the high spatial resolution of a gallium liquid metal ion source allow chemical observation of features smaller than 50 nm. We have also demonstrated the integration of a scanning probe microscope (SPM) operated as an atomic force microscope (AFM) within the FIB/SEM-SIMS chamber. This provides roughness information, and will also allow true three dimensional chemical images to be reconstructed from SIMS measurements.

Research paper thumbnail of Analysis of thin and thick Films

Lee/Mass Spectrometry Handbook, 2012

This work is dedicated to our colleague and friend Richard Payling -Dick to his friends -who was ... more This work is dedicated to our colleague and friend Richard Payling -Dick to his friends -who was not only a spectroscopist and glow discharge expert, but also a traveller discovering the world, sharing human values and building the bridges. We dedicate this work to his memory c) Acronyms

Research paper thumbnail of The concept of plasma cleaning in glow discharge spectrometry

Journal of Analytical Atomic Spectrometry, 2009

Research paper thumbnail of A comparison of non-pulsed radiofrequency and pulsed radiofrequency glow discharge orthogonal time-of-flight mass spectrometry for analytical purposes

Journal of Analytical Atomic Spectrometry, 2009

The analytical potential of a radiofrequency glow discharge orthogonal time-of-flight mass spectr... more The analytical potential of a radiofrequency glow discharge orthogonal time-of-flight mass spectrometer (RFGD-TOFMS) has been evaluated in both pulsed and non-pulsed modes. A certified reference steel was selected for this study. The operating conditions of the GD ...

Research paper thumbnail of A comparison of non-pulsed radiofrequency and pulsed radiofrequency glow discharge orthogonal time-of-flight mass spectrometry for analytical purposes

Journal of Analytical Atomic Spectrometry, 2009

The analytical potential of a radiofrequency glow discharge orthogonal time-of-flight mass spectr... more The analytical potential of a radiofrequency glow discharge orthogonal time-of-flight mass spectrometer (RFGD-TOFMS) has been evaluated in both pulsed and non-pulsed modes. A certified reference steel was selected for this study. The operating conditions of the GD ...

Research paper thumbnail of Prototype of a high sensitive Reflectron Time-of-Flight Mass Spectrometer for the ROSETTA comet rendezvous mission

Research paper thumbnail of Tests and calibrations of the PLASTIC Entrance System: design verification for flight models on the STEREO spacecraft

Research paper thumbnail of Analysis of thin and thick Films

Lee/Mass Spectrometry Handbook, 2012

This work is dedicated to our colleague and friend Richard Payling -Dick to his friends -who was ... more This work is dedicated to our colleague and friend Richard Payling -Dick to his friends -who was not only a spectroscopist and glow discharge expert, but also a traveller discovering the world, sharing human values and building the bridges. We dedicate this work to his memory c) Acronyms

Research paper thumbnail of Compact electron cyclotron resonance ion source for calibration of space plasma instrumentation

Electroencephalography and Clinical Neurophysiology/electromyography and Motor Control, 2001

Summary form only given. To test and calibrate instruments for space research applications, espec... more Summary form only given. To test and calibrate instruments for space research applications, especially for experiments investigating the composition of heliospheric plasma, we have developed an electron cyclotron resonance ion source (ECRIS), which operates at 2.45 GHz using only permanent magnets to contain the plasma. The solar wind plasma flow typically contains elements with solar composition with the more abundant species having atomic masses from 1 amu (hydrogen) to 56 amu (iron). The most abundant species, up to Mg, are mostly stripped to the K-shell in the solar wind (e.g. oxygen occurs as O6+) and iron quite frequently appears in the form of Fe16+. The ECRIS contains an autonomous six-port reflectometer and impedance matching system, controlling the microwave heating process used for electron heating. The system provides important information on the characteristic impedance of the microwave load. In order to better understand the performance of our ECR ion source and to car...

Research paper thumbnail of Pulsed r.f.-glow-discharge time-of-flight mass spectrometry for fast surface and interface analysis of conductive and non-conductive materials

Surface and Interface Analysis, 2006

ABSTRACT Glow discharge (GD) is a highly specialised source that especially meets the requirement... more ABSTRACT Glow discharge (GD) is a highly specialised source that especially meets the requirements for accuracy, simplicity and speed for content depth profiling and bulk analysis in both optical emission (OES) and mass spectrometry (MS). The pulsed radio frequency GD source has the potential for both elemental and molecular analysis of conductive and non-conductive materials. To exploit the information delivered by pulsed radio frequency (r.f.)-GD sources, fast sampling is required, and is available only through time-of-flight mass spectrometry (ToF-MS). Compared to optical glow discharge (GD-OES) instrumentation, a GD-ToF-MS system shows much simpler spectra, lower background signals and lower detection limits. The presented new r.f.-GD-ToF-MS system is a successful combination of a commercial high-end glow discharge instrument and an extremely fast and high-resolution time-of-flight mass spectrometer. This new instrument was applied to analyse conductive and non-conductive materials like anodic thin films. We could resolve 2-nm Cr makers in aluminium oxide layers and measure trace elements in ultra thin titanium oxide films. Furthermore, we show the potential of the pulsed mode to separate analyte species from elements originating from residual gas. Copyright © 2006 John Wiley & Sons, Ltd.

Research paper thumbnail of DESIGN AND PERFORMANCE OF TWO ORTHOGONAL EXTRACTION TIME-OF-FLIGHT SECONDARY ION MASS SPECTROMETERS FOR FOCUSED ION BEAM INSTRUMENTS

Instrumentation Science & Technology, 2014

Research paper thumbnail of A radiofrequency glow-discharge-time-of-flight mass spectrometer for direct analysis of glasses

Analytical and Bioanalytical Chemistry, 2004

A radiofrequency (rf) glow-discharge (GD) ion source coupled to a commercial on-axis time-of-flig... more A radiofrequency (rf) glow-discharge (GD) ion source coupled to a commercial on-axis time-of-flight mass spectrometer (TOFMS) has been developed for the direct analysis of non-conducting samples. Different instrumental configurations of the rf-GD source, including the optional use of a sampler cone and the possibility of allowing electrical floating of the discharge, were evaluated first with a conducting sample. Higher ion signals were obtained when the GD was electrically floating and no sampler cone was used. A homogeneous glass was then analyzed using two different rf-GD configurations-with a sampler cone and discarding the use of the sampler cone. The atomic mass spectra obtained with the TOFMS using both configurations were compared. Analyte signals were systematically higher for the latest mode which avoids the sampler cone. The analytical capability of the proposed rf-GD-TOFMS system for the analysis of thick glasses, up to 6 mm, has been investigated in terms of sensitivity, isotopic ratio accuracy, and mass-resolving power. Different homogeneous glasses (including glasses as thick as 6 mm) have been analyzed and major and minor elements were detected. Isotope ratio accuracies of about ±1% and mass resolving powers of about 700 were observed.

Research paper thumbnail of Mass selective blanking in a compact multiple reflection time-of-flight mass spectrometer

International Journal of Mass Spectrometry, 1999

ABSTRACT In a time-of-flight mass spectrometer with a reflectron (RTOF), an additional small ion ... more ABSTRACT In a time-of-flight mass spectrometer with a reflectron (RTOF), an additional small ion mirror, named Hardmirror, is used to increase the mass resolution and to efficiently blank out selected mass lines. Since the mass resolution of a RTOF spectrometer mainly depends on the effective ion driftpath, an increase in mass resolution is achieved by enlarging the driftpath, either by expanding the distance between the ion source and the reflectron or by using multiple reflections. The overall dimension of the instrument was severely constrained so that an elongation of the driftpath was not an option. Using multiple reflections, facilitated by the Hardmirror, we found a way to double the flight path without doubling the distance between the source and the reflectron. In addition with this design we were able to blank out selected mass lines by reducing its intensities by a factor of more than 1000. Blanking out mass lines is performed with an electrical pulse temporarily added to the potential of the Hardmirror’s backplane electrode. The effect of this blank pulse is to geometrically defocus ions so they do not reach the detector.

Research paper thumbnail of Global plasma simulation of charge state distribution inside a 2.45 GHz ECR plasma with experimental verification

Plasma Sources Science & Technology, 2010

For the first time, the charge state distribution inside the MEsskammer für FlugzeitInStrumente u... more For the first time, the charge state distribution inside the MEsskammer für FlugzeitInStrumente und Time-Of-Flight (MEFISTO) electron cyclotron resonance (ECR) plasma and in the extracted ion beam was successfully simulated. A self-consistent ECR plasma ionization model (Hohl M 2002 MEFISTO II: Design, setup, characterization and operation of an improved calibration facility for solar plasma instrumentation PhD Thesis University of Bern) was further developed, recomputing the ion confinement time for every ion species and in every time step based on the actual plasma potential rather than using a prescribed constant ion confinement time. The simulation starts with a user defined set of initial conditions and develops the problem in time space by an adaptive step length fourth order Runge-Kutta (RK4) solver, considering particle densities based on ionization rates, recombination rates, ion confinement times and plasma potential. At the simulation end, a steady-state ion charge state distribution is reached, which is in excellent agreement with the measured ion beam charge state distribution of the MEFISTO ion source for Ar 1+ to Ar 5+ and in good agreement for Ar 6+ .

Research paper thumbnail of Investigation of the density and temperature of electrons in a compact 2.45 GHz electron cyclotron resonance ion source plasma by x-ray measurements

Plasma Sources Science & Technology, 2005

X-ray measurements of the plasma of a compact 2.45 GHz electron cyclotron resonance ion source (E... more X-ray measurements of the plasma of a compact 2.45 GHz electron cyclotron resonance ion source (ECRIS) are performed to determine the temperature and density of the electrons heated resonantly in the ECRIS. The x-ray detector used to investigate the plasma consists of a small silicon (Si-PIN) photodiode to detect photons in the energy range of 1-100 keV. The detector has an energy resolution of 180 eV at 5.9 keV that allows us to record detailed x-ray spectra. Assuming two temperature electron populations, both Maxwellian distributed, the analysis of the x-ray spectra shows a temperature of about 2 keV for the hot electron fraction in addition to the population of cold electrons at less than 2 eV. The fraction of the hot electrons amounts to 1-10%. We present a description of the x-ray detector set-up as well as x-ray spectra and calculations for the temperature and density of the electrons in the ECRIS plasma.

Research paper thumbnail of A comparison of non-pulsed radiofrequency and pulsed radiofrequency glow discharge orthogonal time-of-flight mass spectrometry for analytical purposes

Journal of Analytical Atomic Spectrometry, 2009

The analytical potential of a radiofrequency glow discharge orthogonal time-of-flight mass spectr... more The analytical potential of a radiofrequency glow discharge orthogonal time-of-flight mass spectrometer (RFGD-TOFMS) has been evaluated in both pulsed and non-pulsed modes. A certified reference steel was selected for this study. The operating conditions of the GD ...

Research paper thumbnail of Characterisation of a pulsed rf-glow discharge in view of its use in OES

Journal of Analytical Atomic Spectrometry, 2006

ABSTRACT Pulsed radiofrequency glow discharges are studied in view of their possible advantages f... more ABSTRACT Pulsed radiofrequency glow discharges are studied in view of their possible advantages for optical emission spectroscopy (GD-OES). The excitation characteristics of a pulsed radiofrequency Grimm-type glow discharge are studied. The effects of a pulsed power supply on the sputtering are investigated and the effect on the emission yield for resonant and non-resonant emission lines is described. The enhancement of the emission yield through rf-power pulsing in the 10 μs range is attributed to a temporal reduction of the self-absorption. The possibility of analysing heat-sensitive non-conductive materials and layers through pulsed rf-GDOES is demonstrated. The work opens several subjects and questions for further research on understanding the plasma processes linked to analytical rf-GD-OES.

Research paper thumbnail of Potential analytical applications of negative ions from a pulsed radiofrequency glow discharge in argon

Journal of Analytical Atomic Spectrometry, 2009

ABSTRACT Detection of negative ions from a conventional analytical glow discharge source using ar... more ABSTRACT Detection of negative ions from a conventional analytical glow discharge source using argon as the working gas is reported. The negative ions are recorded using a pulsed discharge source coupled with a time-of-flight mass spectrometer. A considerable enhancement in the “afterglow” region of the negative ion signal for halogens and halogenated molecules and reduction in background is observed. This is the first time when negative ions have been reported for halogen containing materials and we illustrate our findings with results from the polytetrafluoroethene polymer (PTFE).

Research paper thumbnail of The concept of plasma cleaning in glow discharge spectrometry

Journal of Analytical Atomic Spectrometry, 2009

Research paper thumbnail of High Spatial Resolution Time-of-Flight Secondary Ion Mass Spectrometry for the Masses: A Novel Orthogonal ToF FIB-SIMS Instrument with In Situ AFM

Advances in Materials Science and Engineering, 2012

We describe the design and performance of an orthogonal time-of-flight (TOF) secondary ion mass s... more We describe the design and performance of an orthogonal time-of-flight (TOF) secondary ion mass spectrometer that can be retrofitted to existing focused ion beam (FIB) instruments. In particular, a simple interface has been developed for FIB/SEM instruments from the manufacturer Tescan. Orthogonal extraction to the mass analyser obviates the need to pulse the primary ion beam and does not require the use of monoisotopic gallium to preserve mass resolution. The high-duty cycle and reasonable collection efficiency of the new instrument combined with the high spatial resolution of a gallium liquid metal ion source allow chemical observation of features smaller than 50 nm. We have also demonstrated the integration of a scanning probe microscope (SPM) operated as an atomic force microscope (AFM) within the FIB/SEM-SIMS chamber. This provides roughness information, and will also allow true three dimensional chemical images to be reconstructed from SIMS measurements.

Research paper thumbnail of Analysis of thin and thick Films

Lee/Mass Spectrometry Handbook, 2012

This work is dedicated to our colleague and friend Richard Payling -Dick to his friends -who was ... more This work is dedicated to our colleague and friend Richard Payling -Dick to his friends -who was not only a spectroscopist and glow discharge expert, but also a traveller discovering the world, sharing human values and building the bridges. We dedicate this work to his memory c) Acronyms

Research paper thumbnail of The concept of plasma cleaning in glow discharge spectrometry

Journal of Analytical Atomic Spectrometry, 2009

Research paper thumbnail of A comparison of non-pulsed radiofrequency and pulsed radiofrequency glow discharge orthogonal time-of-flight mass spectrometry for analytical purposes

Journal of Analytical Atomic Spectrometry, 2009

The analytical potential of a radiofrequency glow discharge orthogonal time-of-flight mass spectr... more The analytical potential of a radiofrequency glow discharge orthogonal time-of-flight mass spectrometer (RFGD-TOFMS) has been evaluated in both pulsed and non-pulsed modes. A certified reference steel was selected for this study. The operating conditions of the GD ...

Research paper thumbnail of A comparison of non-pulsed radiofrequency and pulsed radiofrequency glow discharge orthogonal time-of-flight mass spectrometry for analytical purposes

Journal of Analytical Atomic Spectrometry, 2009

The analytical potential of a radiofrequency glow discharge orthogonal time-of-flight mass spectr... more The analytical potential of a radiofrequency glow discharge orthogonal time-of-flight mass spectrometer (RFGD-TOFMS) has been evaluated in both pulsed and non-pulsed modes. A certified reference steel was selected for this study. The operating conditions of the GD ...

Research paper thumbnail of Prototype of a high sensitive Reflectron Time-of-Flight Mass Spectrometer for the ROSETTA comet rendezvous mission

Research paper thumbnail of Tests and calibrations of the PLASTIC Entrance System: design verification for flight models on the STEREO spacecraft

Research paper thumbnail of Analysis of thin and thick Films

Lee/Mass Spectrometry Handbook, 2012

This work is dedicated to our colleague and friend Richard Payling -Dick to his friends -who was ... more This work is dedicated to our colleague and friend Richard Payling -Dick to his friends -who was not only a spectroscopist and glow discharge expert, but also a traveller discovering the world, sharing human values and building the bridges. We dedicate this work to his memory c) Acronyms

Research paper thumbnail of Compact electron cyclotron resonance ion source for calibration of space plasma instrumentation

Electroencephalography and Clinical Neurophysiology/electromyography and Motor Control, 2001

Summary form only given. To test and calibrate instruments for space research applications, espec... more Summary form only given. To test and calibrate instruments for space research applications, especially for experiments investigating the composition of heliospheric plasma, we have developed an electron cyclotron resonance ion source (ECRIS), which operates at 2.45 GHz using only permanent magnets to contain the plasma. The solar wind plasma flow typically contains elements with solar composition with the more abundant species having atomic masses from 1 amu (hydrogen) to 56 amu (iron). The most abundant species, up to Mg, are mostly stripped to the K-shell in the solar wind (e.g. oxygen occurs as O6+) and iron quite frequently appears in the form of Fe16+. The ECRIS contains an autonomous six-port reflectometer and impedance matching system, controlling the microwave heating process used for electron heating. The system provides important information on the characteristic impedance of the microwave load. In order to better understand the performance of our ECR ion source and to car...

Research paper thumbnail of Pulsed r.f.-glow-discharge time-of-flight mass spectrometry for fast surface and interface analysis of conductive and non-conductive materials

Surface and Interface Analysis, 2006

ABSTRACT Glow discharge (GD) is a highly specialised source that especially meets the requirement... more ABSTRACT Glow discharge (GD) is a highly specialised source that especially meets the requirements for accuracy, simplicity and speed for content depth profiling and bulk analysis in both optical emission (OES) and mass spectrometry (MS). The pulsed radio frequency GD source has the potential for both elemental and molecular analysis of conductive and non-conductive materials. To exploit the information delivered by pulsed radio frequency (r.f.)-GD sources, fast sampling is required, and is available only through time-of-flight mass spectrometry (ToF-MS). Compared to optical glow discharge (GD-OES) instrumentation, a GD-ToF-MS system shows much simpler spectra, lower background signals and lower detection limits. The presented new r.f.-GD-ToF-MS system is a successful combination of a commercial high-end glow discharge instrument and an extremely fast and high-resolution time-of-flight mass spectrometer. This new instrument was applied to analyse conductive and non-conductive materials like anodic thin films. We could resolve 2-nm Cr makers in aluminium oxide layers and measure trace elements in ultra thin titanium oxide films. Furthermore, we show the potential of the pulsed mode to separate analyte species from elements originating from residual gas. Copyright © 2006 John Wiley & Sons, Ltd.

Research paper thumbnail of DESIGN AND PERFORMANCE OF TWO ORTHOGONAL EXTRACTION TIME-OF-FLIGHT SECONDARY ION MASS SPECTROMETERS FOR FOCUSED ION BEAM INSTRUMENTS

Instrumentation Science & Technology, 2014

Research paper thumbnail of A radiofrequency glow-discharge-time-of-flight mass spectrometer for direct analysis of glasses

Analytical and Bioanalytical Chemistry, 2004

A radiofrequency (rf) glow-discharge (GD) ion source coupled to a commercial on-axis time-of-flig... more A radiofrequency (rf) glow-discharge (GD) ion source coupled to a commercial on-axis time-of-flight mass spectrometer (TOFMS) has been developed for the direct analysis of non-conducting samples. Different instrumental configurations of the rf-GD source, including the optional use of a sampler cone and the possibility of allowing electrical floating of the discharge, were evaluated first with a conducting sample. Higher ion signals were obtained when the GD was electrically floating and no sampler cone was used. A homogeneous glass was then analyzed using two different rf-GD configurations-with a sampler cone and discarding the use of the sampler cone. The atomic mass spectra obtained with the TOFMS using both configurations were compared. Analyte signals were systematically higher for the latest mode which avoids the sampler cone. The analytical capability of the proposed rf-GD-TOFMS system for the analysis of thick glasses, up to 6 mm, has been investigated in terms of sensitivity, isotopic ratio accuracy, and mass-resolving power. Different homogeneous glasses (including glasses as thick as 6 mm) have been analyzed and major and minor elements were detected. Isotope ratio accuracies of about ±1% and mass resolving powers of about 700 were observed.

Research paper thumbnail of Mass selective blanking in a compact multiple reflection time-of-flight mass spectrometer

International Journal of Mass Spectrometry, 1999

ABSTRACT In a time-of-flight mass spectrometer with a reflectron (RTOF), an additional small ion ... more ABSTRACT In a time-of-flight mass spectrometer with a reflectron (RTOF), an additional small ion mirror, named Hardmirror, is used to increase the mass resolution and to efficiently blank out selected mass lines. Since the mass resolution of a RTOF spectrometer mainly depends on the effective ion driftpath, an increase in mass resolution is achieved by enlarging the driftpath, either by expanding the distance between the ion source and the reflectron or by using multiple reflections. The overall dimension of the instrument was severely constrained so that an elongation of the driftpath was not an option. Using multiple reflections, facilitated by the Hardmirror, we found a way to double the flight path without doubling the distance between the source and the reflectron. In addition with this design we were able to blank out selected mass lines by reducing its intensities by a factor of more than 1000. Blanking out mass lines is performed with an electrical pulse temporarily added to the potential of the Hardmirror’s backplane electrode. The effect of this blank pulse is to geometrically defocus ions so they do not reach the detector.

Research paper thumbnail of Global plasma simulation of charge state distribution inside a 2.45 GHz ECR plasma with experimental verification

Plasma Sources Science & Technology, 2010

For the first time, the charge state distribution inside the MEsskammer für FlugzeitInStrumente u... more For the first time, the charge state distribution inside the MEsskammer für FlugzeitInStrumente und Time-Of-Flight (MEFISTO) electron cyclotron resonance (ECR) plasma and in the extracted ion beam was successfully simulated. A self-consistent ECR plasma ionization model (Hohl M 2002 MEFISTO II: Design, setup, characterization and operation of an improved calibration facility for solar plasma instrumentation PhD Thesis University of Bern) was further developed, recomputing the ion confinement time for every ion species and in every time step based on the actual plasma potential rather than using a prescribed constant ion confinement time. The simulation starts with a user defined set of initial conditions and develops the problem in time space by an adaptive step length fourth order Runge-Kutta (RK4) solver, considering particle densities based on ionization rates, recombination rates, ion confinement times and plasma potential. At the simulation end, a steady-state ion charge state distribution is reached, which is in excellent agreement with the measured ion beam charge state distribution of the MEFISTO ion source for Ar 1+ to Ar 5+ and in good agreement for Ar 6+ .

Research paper thumbnail of Investigation of the density and temperature of electrons in a compact 2.45 GHz electron cyclotron resonance ion source plasma by x-ray measurements

Plasma Sources Science & Technology, 2005

X-ray measurements of the plasma of a compact 2.45 GHz electron cyclotron resonance ion source (E... more X-ray measurements of the plasma of a compact 2.45 GHz electron cyclotron resonance ion source (ECRIS) are performed to determine the temperature and density of the electrons heated resonantly in the ECRIS. The x-ray detector used to investigate the plasma consists of a small silicon (Si-PIN) photodiode to detect photons in the energy range of 1-100 keV. The detector has an energy resolution of 180 eV at 5.9 keV that allows us to record detailed x-ray spectra. Assuming two temperature electron populations, both Maxwellian distributed, the analysis of the x-ray spectra shows a temperature of about 2 keV for the hot electron fraction in addition to the population of cold electrons at less than 2 eV. The fraction of the hot electrons amounts to 1-10%. We present a description of the x-ray detector set-up as well as x-ray spectra and calculations for the temperature and density of the electrons in the ECRIS plasma.

Research paper thumbnail of A comparison of non-pulsed radiofrequency and pulsed radiofrequency glow discharge orthogonal time-of-flight mass spectrometry for analytical purposes

Journal of Analytical Atomic Spectrometry, 2009

The analytical potential of a radiofrequency glow discharge orthogonal time-of-flight mass spectr... more The analytical potential of a radiofrequency glow discharge orthogonal time-of-flight mass spectrometer (RFGD-TOFMS) has been evaluated in both pulsed and non-pulsed modes. A certified reference steel was selected for this study. The operating conditions of the GD ...

Research paper thumbnail of Characterisation of a pulsed rf-glow discharge in view of its use in OES

Journal of Analytical Atomic Spectrometry, 2006

ABSTRACT Pulsed radiofrequency glow discharges are studied in view of their possible advantages f... more ABSTRACT Pulsed radiofrequency glow discharges are studied in view of their possible advantages for optical emission spectroscopy (GD-OES). The excitation characteristics of a pulsed radiofrequency Grimm-type glow discharge are studied. The effects of a pulsed power supply on the sputtering are investigated and the effect on the emission yield for resonant and non-resonant emission lines is described. The enhancement of the emission yield through rf-power pulsing in the 10 μs range is attributed to a temporal reduction of the self-absorption. The possibility of analysing heat-sensitive non-conductive materials and layers through pulsed rf-GDOES is demonstrated. The work opens several subjects and questions for further research on understanding the plasma processes linked to analytical rf-GD-OES.

Research paper thumbnail of Potential analytical applications of negative ions from a pulsed radiofrequency glow discharge in argon

Journal of Analytical Atomic Spectrometry, 2009

ABSTRACT Detection of negative ions from a conventional analytical glow discharge source using ar... more ABSTRACT Detection of negative ions from a conventional analytical glow discharge source using argon as the working gas is reported. The negative ions are recorded using a pulsed discharge source coupled with a time-of-flight mass spectrometer. A considerable enhancement in the “afterglow” region of the negative ion signal for halogens and halogenated molecules and reduction in background is observed. This is the first time when negative ions have been reported for halogen containing materials and we illustrate our findings with results from the polytetrafluoroethene polymer (PTFE).

Research paper thumbnail of The concept of plasma cleaning in glow discharge spectrometry

Journal of Analytical Atomic Spectrometry, 2009