Eero Rauhala | University of Helsinki (original) (raw)

Papers by Eero Rauhala

Research paper thumbnail of Absolute thick-target gamma-ray yields for the light elements induced by 12C, 14N and 16O ions

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 1998

Thick-target gamma-ray yields for elements with Z=3–30 (excluding elements Z=10, 18, 21) at 12C i... more Thick-target gamma-ray yields for elements with Z=3–30 (excluding elements Z=10, 18, 21) at 12C ion energies of 22 and 28 MeV, for elements with Z=3–9 at 14N ion energy of 28 MeV and at 16O ion energies of 28 and 33 MeV have been determined. Tables of the most suitable gamma-ray lines for elemental analysis are given. The general applicability

Research paper thumbnail of Alpha–proton elastic scattering cross sections for ERDA in the resonance region

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2004

ABSTRACT We have investigated alpha–proton elastic scattering for He-ERDA. The broad maximum of t... more ABSTRACT We have investigated alpha–proton elastic scattering for He-ERDA. The broad maximum of the elastic scattering resonance around EHe=8.8 MeV is most important for hydrogen profiling with good sensitivity, since the cross section is more than hundredfold enhanced relative to Rutherford at the peak of the resonance. We present measurements covering the resonant energy region from 1.2 to 5.2 MeV of the inverse proton backscattering reaction at a laboratory backscattering angle of 129°. The present data and previous literature values found around the resonance were analysed by using the R-matrix theory. Comparison between the analysis of this work and an earlier work by Dodder et al. [Phys. Rev. C 15 (1977) 518] indicate the need of modified R-matrix parameters responsible for the shape of the resonance. Cross sections lower by 10–15% at the peak of the resonance and a new parameter set for calculating the cross sections for ERDA are suggested.

Research paper thumbnail of One-step electrodeposition of Cu{sub 2{minus}x}Se and CuInSe{sub 2} thin films by the induced co-deposition mechanism

Journal of The Electrochemical Society

The induced co-deposition mechanism in one-step electrodeposition of Cu{sub 2{minus}x}Se and CuIn... more The induced co-deposition mechanism in one-step electrodeposition of Cu{sub 2{minus}x}Se and CuInSe{sub 2} thin films was investigated. Cu{sub 2{minus}x}Se and CuInSe{sub 2} thin films were deposited potentiostatically on Mo substrates by a one-step process from an acidic electrolyte containing SCN{sup {minus}} ions as complexing agents. The films were examined by scanning electron microscopy, energy dispersive X-ray spectrometry. X-ray diffraction, and ion beam analysis methods. Good control of stoichiometry was achieved over a wide potential range, thus indicating that the film composition may indeed be controlled by the induced co-deposition mechanism. The effects of the thiocyanate ions on the reduction potentials of Cu{sup +}, In{sup 3+}, and Se{sup 4+} ions were examined by cyclic voltammetry. In order to improve their crystallinity, the CuInSe{sub 2} films were annealed under a N{sub 2} atmosphere after deposition.

Research paper thumbnail of Surface-driven incorporation of Ga into self-organized InAs islands

Research paper thumbnail of Rapid thermal annealing of Cu/WNx/Si structures

Research paper thumbnail of Effects of sample preparation on the stopping powers of Havar for protons and α particles

Physical Review B, 1994

ABSTRACT

Research paper thumbnail of The tailoring of the composition of Ag–As–S amorphous films using photo-induced solid state reaction between Ag and As30S70 films

Solid State Ionics, 2001

Kinetics of optically induced reaction between silver and As30S70 films was measured by monitorin... more Kinetics of optically induced reaction between silver and As30S70 films was measured by monitoring the change in thickness of the undoped chalcogenide using a modified computer-controlled reflectivity technique. Silver concentration profiles during optically induced solid state reaction (OSSR) were traced by means of Rutherford backscattering spectroscopy (RBS). The composition of the As–S films was chosen to be As30S70, which is

Research paper thumbnail of Stopping powers of Al and Sn for 4 He, 7 Li, 11 B, 12 C, 14 N and 16 O ions in the energy range 0.5–2.6 MeV/amu

Radiation Effects and Defects in Solids, 1991

Stopping powers of aluminium and tin in the energy range 3?10 MeV for 4He ions, in the range 3?17... more Stopping powers of aluminium and tin in the energy range 3?10 MeV for 4He ions, in the range 3?17 MeV for 7Li, 8?20 MeV for 11B, 10?23 MeV for 12C, 9?22 MeV for 14N, and 11?25 MeV for 16O ions have been determined by using the transmission technique. The experimental stopping powers are compared with the predictions of semiempirical models.

Research paper thumbnail of Characteristics of PIXE channeling and its application to ZnSe thin films

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 1998

The characteristics of the PIXE-method in channeling measurements of epitaxially grown ZnSe were ... more The characteristics of the PIXE-method in channeling measurements of epitaxially grown ZnSe were studied and compared to RBS channeling. Especially the eect of the analysis depth and ion energy on the PIXE channeling minimum yield was focused on. The experimental minimum yields were compared to Monte Carlo simulations and the agreement was good. The PIXE minimum yield was found to increase signi®cantly as a function of the ZnSe ®lm thickness i.e. the analysis depth. A strong dependence of the channeling parameters on the beam angular divergence was also observed. According to our results, the PIXE minimum yield from ZnSe thin ®lms does not follow the conventional energy dependence of the RBS minimum yield.

Research paper thumbnail of An external beam method for ion backscattering

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 1985

ABSTRACT

Research paper thumbnail of Energy loss of 1.3–2.6 MeV 4He ions in Havar, nickel, Kapton and Mylar foils

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 1987

ABSTRACT

Research paper thumbnail of Cross sections for 170° backscattering of 0.8–2.7 MeV protons from magnesium and sulfur

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 1988

Scattering cross sections for 0.8-2.7 MeV proton backscattering from natural solid sulfur (ZnS) a... more Scattering cross sections for 0.8-2.7 MeV proton backscattering from natural solid sulfur (ZnS) and magnesium have been determined at laboratory scattering angles 170 o and also at 155 o for sulfur. Non-Rutherford scattering cross sections above 0.8 MeV for Mg and above 1.8 MeV for S were observed. Prominent resonances were found at 0.82, 1.48, 1.62 and 2.05 MeV for Mg, and at 1.90, 2.34 and 2.60 MeV for S. The smooth, slowly varying regions of the excitation cruves are well-suited for quantitative backscattering analysis. Enhanced or reduced yields at or near resonances may also be used for analytical purposes. The effects of inelastic proton and other competing nuclear reactions on the scattering yields are being investigated. The present experimental technique involves data reduction from both thick and thin target yields. Computer data analysis of proton backscattering from light elements has been studied.

Research paper thumbnail of Elastic scattering cross sections of protons by copper, molybdenum, silver and tin near the Coulomb barrier

Journal of Applied Physics, 1998

Cross sections for elastic scattering of protons by natural copper, molybdenum, silver and tin ha... more Cross sections for elastic scattering of protons by natural copper, molybdenum, silver and tin have been measured in the energy range of 2.3-6.5 MeV at typical Rutherford backscattering angles of 135° and 165°. The threshold energies have been determined above which the Rutherford cross sections become invalid. The threshold energies obtained are 3.5 and 3.4 MeV for copper, 5.1 and

Research paper thumbnail of Elastic scattering cross sections for the p+He system in the energy region of 1.4–24 MeV

Journal of Applied Physics, 1997

ABSTRACT The elastic scattering cross sections for proton scattering from 4He were determined in ... more ABSTRACT The elastic scattering cross sections for proton scattering from 4He were determined in the proton energy region of 1.4–6.0 MeV. The measurements were performed at laboratory angles of 110°–170° for proton energies of 1.4–2.7 MeV and at angles of 140° and 170° for proton energies of 2.7–6.0 MeV. The scattering cross sections for 1H recoils by 4He ion bombardment for helium energies of 5.6–24 MeV at recoil angles of 4°–28° were calculated by kinematically reversing the reaction. The helium targets were prepared by implanting 60 keV 4He ions into thin tantalum foils. The helium concentration was determined by transmission elastic recoil detection analysis employing 10 MeV 28Si ions. The obtained cross section data are compared with the available literature values. Differences up to 10% are found in the values at the cross section curve maximum in comparison to earlier data. © 1997 American Institute of Physics.

Research paper thumbnail of Angular distributions of12C,14N, and16O ion elastic scattering by sulfur near the Coulomb barrier and the high‐energy limits of heavy‐ion Rutherford scattering

Journal of Applied Physics, 1995

Elastic scattering of C-12, N-14, and O-16 ions by sulfur has been investigated near the non-Ruth... more Elastic scattering of C-12, N-14, and O-16 ions by sulfur has been investigated near the non-Rutherford energy threshold below 31 MeV. Angular distributions in the range 72-170 deg have been measured. Decreasing elastic scattering cross sections with increasing angle above a threshold energy and smooth oscillations were observed. As a function of energy, the cross sections fall off rapidly above the threshold energy, rendering heavy-ion backscattering spectrometry practically useless. A classical semiempirical model is introduced for predicting the angular and target dependence of the high-energy limit for C-12, N-14, and O-16 ion Rutherford backscattering spectrometry. The present energy thresholds are reproduced by the model within experimental accuracy.

Research paper thumbnail of New ETFE-based membrane for direct methanol fuel cell

Electrochimica Acta, 2005

The investigated membranes are based on 35 m thick commercial poly(ethylene-alt-tetrafluoroethyle... more The investigated membranes are based on 35 m thick commercial poly(ethylene-alt-tetrafluoroethylene) (ETFE) films. The films were made proton conductive by means of irradiation treatment followed by sulfonation. These membranes have exceptionally low water uptake and excellent dimensional stability. The new membranes are investigated widely in a laboratory-scale direct methanol fuel cell (DMFC). The temperature range used in the fuel cell tests was 30-85 • C and the measurement results were compared to those of the Nafion ® 115 membrane. Also methanol permeability through the ETFE-based membrane was measured as a function of temperature, resulting in values less than 10% of the corresponding values for Nafion ® 115, which was considerably thicker than the experimental membrane. Methanol crossover was reported to decrease when the thickness of the membrane increases, so the ETFE-based membrane compares favourably to Nafion ® membranes. The maximum power densities achieved with the experimental ETFE-based membrane were about 40-65% lower than the corresponding values of the Nafion ® 115 membrane, because of the lower conductivity and noticeably higher IR-losses. Chemical and mechanical stability of the ETFE-based membrane appeared to be promising since it was tested over 2000 h in the DMFC without any performance loss.

Research paper thumbnail of Range profiles of 6–10 MeV 15N ions implanted in silicon

Applied Surface Science, 1995

Implantation profiles of 6 to 10 MeV 15N ions in crystalline silicon have been investigated. Meas... more Implantation profiles of 6 to 10 MeV 15N ions in crystalline silicon have been investigated. Measurements of the profiles at depths from 4 to 7 Frn were rendered possible by combining the depth profiling of the "N atoms through the l'N(p, cwy) "C reaction and the exfoliation of the surface layer of the samples, accomplished by high dose 4He ion bombardment. In this way the range profiles, measured at the exfoliated crater bottom, could be obtained accurately without uncertainties due to straggling of the probing proton beam. The range parameters are compared to those of Monte Carlo calculations using the electronic stopping powers given by J.F. Ziegler, J.P. Biersack and U. Littmark [The Stopping Powers and Ranges of Ions in Matter, Vol. 1 (Pergamon, New York, 1985)]. Projected ranges were observed to be 5%-10% larger and range stragglings 27%-6% smaller than those predicted by Monte Carlo calculations along with the adopted stopping power parametrization.

Research paper thumbnail of Ion beam analysis of high temperature superconducting samples

Applied Radiation and Isotopes, 1994

Characterization of high temperature superconducting film and bulk samples has been carried out u... more Characterization of high temperature superconducting film and bulk samples has been carried out using 2 MeV a-particle Rutherford backscattering, 2.4 MeV proton elastic scattering, 2.4 MeV proton-induced x-ray emission, 9 MeV proton induced y-ray emission and 100 MeV iodine elastic recoil detection analysis techniques. The objective was to compare different ion beam based techniques for: (i) compositional analysis; and (ii) consistency of the results obtained for samples prepared using similar preparation methodology.

Research paper thumbnail of Annealing behaviour of high-dose-implanted nitrogen in InP

Applied Physics A Materials Science and Processing, 1996

Concentration profiles of nitrogen in vacuumannealed p-and n-type single-crystal (1 0 0) InP impl... more Concentration profiles of nitrogen in vacuumannealed p-and n-type single-crystal (1 0 0) InP implanted with 1;10 30 keV N> ions cm\ have been studied by Secondary Ion Mass Spectrometry (SIMS) and Nuclear Resonance Broadening (NRB) techniques. Damage induced by the nitrogen implantation was studied by Rutherford Backscattering Spectrometry (RBS) and channeling. Annealing the samples led to loss and redistribution of nitrogen in the temperature range from 575 to 675°C. At temperatures from 575 to 600°C, rapid migration of nitrogen towards the sample surface was observed. The n-type InP material had a very dominant tendency for surface nitrogen build-up, whereas the p-type material had a markedly smaller surface peak in the nitrogen distribution. The surface peak in n-type material is due to sulphur acting partly as a diffusion barrier. SIMS analyses showed sulphur build-up on the surface in the course of annealing. At temperatures from 600 to 675°C, the nitrogen profiles of n-and p-type InP were similar. A small loss of nitrogen was observed at 625-675°C. Two different recovery stages were observed at 575-600°C and at 625-650°C. The corresponding activation energies for nitrogen loss are 2.9 and 3.0 eV, respectively.

Research paper thumbnail of Round Robin: measurement of H implantation distributions in Si by elastic recoil detection

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2004

A 200 mm amorphised Si wafer was implanted with 6-keV H þ ions at a nominal fluence of 5 • 10 16 ... more A 200 mm amorphised Si wafer was implanted with 6-keV H þ ions at a nominal fluence of 5 • 10 16 atoms/cm 2. The uniformity of the implant was better than 2% over the wafer. Samples of the wafer were analysed for absolute H fluence by nuclear reaction analysis and elastic recoil detection (ERD) analysis, including both helium and heavy ion beams, using various types of detector (Si with range foil, time of flight ERD, and a position-sensitive gas ionisation DE-E detector), various ion beams (He, Cl, Cu, I, Au) and independent analytical procedures. The results are compared and the inter-lab reproducibility is evaluated. The surface H, unstable under heavy ion beams, was resolved and accounted for throughout the analysis. Estimates of total combined uncertainties are about 6% for all participants, but the interlab reproducibility of the measurements was found to be 2.2%. Correct quantification of the H data from the gas ionisation detector is demonstrated. The uncertainty budget is discussed in detail.

Research paper thumbnail of Absolute thick-target gamma-ray yields for the light elements induced by 12C, 14N and 16O ions

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 1998

Thick-target gamma-ray yields for elements with Z=3–30 (excluding elements Z=10, 18, 21) at 12C i... more Thick-target gamma-ray yields for elements with Z=3–30 (excluding elements Z=10, 18, 21) at 12C ion energies of 22 and 28 MeV, for elements with Z=3–9 at 14N ion energy of 28 MeV and at 16O ion energies of 28 and 33 MeV have been determined. Tables of the most suitable gamma-ray lines for elemental analysis are given. The general applicability

Research paper thumbnail of Alpha–proton elastic scattering cross sections for ERDA in the resonance region

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2004

ABSTRACT We have investigated alpha–proton elastic scattering for He-ERDA. The broad maximum of t... more ABSTRACT We have investigated alpha–proton elastic scattering for He-ERDA. The broad maximum of the elastic scattering resonance around EHe=8.8 MeV is most important for hydrogen profiling with good sensitivity, since the cross section is more than hundredfold enhanced relative to Rutherford at the peak of the resonance. We present measurements covering the resonant energy region from 1.2 to 5.2 MeV of the inverse proton backscattering reaction at a laboratory backscattering angle of 129°. The present data and previous literature values found around the resonance were analysed by using the R-matrix theory. Comparison between the analysis of this work and an earlier work by Dodder et al. [Phys. Rev. C 15 (1977) 518] indicate the need of modified R-matrix parameters responsible for the shape of the resonance. Cross sections lower by 10–15% at the peak of the resonance and a new parameter set for calculating the cross sections for ERDA are suggested.

Research paper thumbnail of One-step electrodeposition of Cu{sub 2{minus}x}Se and CuInSe{sub 2} thin films by the induced co-deposition mechanism

Journal of The Electrochemical Society

The induced co-deposition mechanism in one-step electrodeposition of Cu{sub 2{minus}x}Se and CuIn... more The induced co-deposition mechanism in one-step electrodeposition of Cu{sub 2{minus}x}Se and CuInSe{sub 2} thin films was investigated. Cu{sub 2{minus}x}Se and CuInSe{sub 2} thin films were deposited potentiostatically on Mo substrates by a one-step process from an acidic electrolyte containing SCN{sup {minus}} ions as complexing agents. The films were examined by scanning electron microscopy, energy dispersive X-ray spectrometry. X-ray diffraction, and ion beam analysis methods. Good control of stoichiometry was achieved over a wide potential range, thus indicating that the film composition may indeed be controlled by the induced co-deposition mechanism. The effects of the thiocyanate ions on the reduction potentials of Cu{sup +}, In{sup 3+}, and Se{sup 4+} ions were examined by cyclic voltammetry. In order to improve their crystallinity, the CuInSe{sub 2} films were annealed under a N{sub 2} atmosphere after deposition.

Research paper thumbnail of Surface-driven incorporation of Ga into self-organized InAs islands

Research paper thumbnail of Rapid thermal annealing of Cu/WNx/Si structures

Research paper thumbnail of Effects of sample preparation on the stopping powers of Havar for protons and α particles

Physical Review B, 1994

ABSTRACT

Research paper thumbnail of The tailoring of the composition of Ag–As–S amorphous films using photo-induced solid state reaction between Ag and As30S70 films

Solid State Ionics, 2001

Kinetics of optically induced reaction between silver and As30S70 films was measured by monitorin... more Kinetics of optically induced reaction between silver and As30S70 films was measured by monitoring the change in thickness of the undoped chalcogenide using a modified computer-controlled reflectivity technique. Silver concentration profiles during optically induced solid state reaction (OSSR) were traced by means of Rutherford backscattering spectroscopy (RBS). The composition of the As–S films was chosen to be As30S70, which is

Research paper thumbnail of Stopping powers of Al and Sn for 4 He, 7 Li, 11 B, 12 C, 14 N and 16 O ions in the energy range 0.5–2.6 MeV/amu

Radiation Effects and Defects in Solids, 1991

Stopping powers of aluminium and tin in the energy range 3?10 MeV for 4He ions, in the range 3?17... more Stopping powers of aluminium and tin in the energy range 3?10 MeV for 4He ions, in the range 3?17 MeV for 7Li, 8?20 MeV for 11B, 10?23 MeV for 12C, 9?22 MeV for 14N, and 11?25 MeV for 16O ions have been determined by using the transmission technique. The experimental stopping powers are compared with the predictions of semiempirical models.

Research paper thumbnail of Characteristics of PIXE channeling and its application to ZnSe thin films

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 1998

The characteristics of the PIXE-method in channeling measurements of epitaxially grown ZnSe were ... more The characteristics of the PIXE-method in channeling measurements of epitaxially grown ZnSe were studied and compared to RBS channeling. Especially the eect of the analysis depth and ion energy on the PIXE channeling minimum yield was focused on. The experimental minimum yields were compared to Monte Carlo simulations and the agreement was good. The PIXE minimum yield was found to increase signi®cantly as a function of the ZnSe ®lm thickness i.e. the analysis depth. A strong dependence of the channeling parameters on the beam angular divergence was also observed. According to our results, the PIXE minimum yield from ZnSe thin ®lms does not follow the conventional energy dependence of the RBS minimum yield.

Research paper thumbnail of An external beam method for ion backscattering

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 1985

ABSTRACT

Research paper thumbnail of Energy loss of 1.3–2.6 MeV 4He ions in Havar, nickel, Kapton and Mylar foils

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 1987

ABSTRACT

Research paper thumbnail of Cross sections for 170° backscattering of 0.8–2.7 MeV protons from magnesium and sulfur

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 1988

Scattering cross sections for 0.8-2.7 MeV proton backscattering from natural solid sulfur (ZnS) a... more Scattering cross sections for 0.8-2.7 MeV proton backscattering from natural solid sulfur (ZnS) and magnesium have been determined at laboratory scattering angles 170 o and also at 155 o for sulfur. Non-Rutherford scattering cross sections above 0.8 MeV for Mg and above 1.8 MeV for S were observed. Prominent resonances were found at 0.82, 1.48, 1.62 and 2.05 MeV for Mg, and at 1.90, 2.34 and 2.60 MeV for S. The smooth, slowly varying regions of the excitation cruves are well-suited for quantitative backscattering analysis. Enhanced or reduced yields at or near resonances may also be used for analytical purposes. The effects of inelastic proton and other competing nuclear reactions on the scattering yields are being investigated. The present experimental technique involves data reduction from both thick and thin target yields. Computer data analysis of proton backscattering from light elements has been studied.

Research paper thumbnail of Elastic scattering cross sections of protons by copper, molybdenum, silver and tin near the Coulomb barrier

Journal of Applied Physics, 1998

Cross sections for elastic scattering of protons by natural copper, molybdenum, silver and tin ha... more Cross sections for elastic scattering of protons by natural copper, molybdenum, silver and tin have been measured in the energy range of 2.3-6.5 MeV at typical Rutherford backscattering angles of 135° and 165°. The threshold energies have been determined above which the Rutherford cross sections become invalid. The threshold energies obtained are 3.5 and 3.4 MeV for copper, 5.1 and

Research paper thumbnail of Elastic scattering cross sections for the p+He system in the energy region of 1.4–24 MeV

Journal of Applied Physics, 1997

ABSTRACT The elastic scattering cross sections for proton scattering from 4He were determined in ... more ABSTRACT The elastic scattering cross sections for proton scattering from 4He were determined in the proton energy region of 1.4–6.0 MeV. The measurements were performed at laboratory angles of 110°–170° for proton energies of 1.4–2.7 MeV and at angles of 140° and 170° for proton energies of 2.7–6.0 MeV. The scattering cross sections for 1H recoils by 4He ion bombardment for helium energies of 5.6–24 MeV at recoil angles of 4°–28° were calculated by kinematically reversing the reaction. The helium targets were prepared by implanting 60 keV 4He ions into thin tantalum foils. The helium concentration was determined by transmission elastic recoil detection analysis employing 10 MeV 28Si ions. The obtained cross section data are compared with the available literature values. Differences up to 10% are found in the values at the cross section curve maximum in comparison to earlier data. © 1997 American Institute of Physics.

Research paper thumbnail of Angular distributions of12C,14N, and16O ion elastic scattering by sulfur near the Coulomb barrier and the high‐energy limits of heavy‐ion Rutherford scattering

Journal of Applied Physics, 1995

Elastic scattering of C-12, N-14, and O-16 ions by sulfur has been investigated near the non-Ruth... more Elastic scattering of C-12, N-14, and O-16 ions by sulfur has been investigated near the non-Rutherford energy threshold below 31 MeV. Angular distributions in the range 72-170 deg have been measured. Decreasing elastic scattering cross sections with increasing angle above a threshold energy and smooth oscillations were observed. As a function of energy, the cross sections fall off rapidly above the threshold energy, rendering heavy-ion backscattering spectrometry practically useless. A classical semiempirical model is introduced for predicting the angular and target dependence of the high-energy limit for C-12, N-14, and O-16 ion Rutherford backscattering spectrometry. The present energy thresholds are reproduced by the model within experimental accuracy.

Research paper thumbnail of New ETFE-based membrane for direct methanol fuel cell

Electrochimica Acta, 2005

The investigated membranes are based on 35 m thick commercial poly(ethylene-alt-tetrafluoroethyle... more The investigated membranes are based on 35 m thick commercial poly(ethylene-alt-tetrafluoroethylene) (ETFE) films. The films were made proton conductive by means of irradiation treatment followed by sulfonation. These membranes have exceptionally low water uptake and excellent dimensional stability. The new membranes are investigated widely in a laboratory-scale direct methanol fuel cell (DMFC). The temperature range used in the fuel cell tests was 30-85 • C and the measurement results were compared to those of the Nafion ® 115 membrane. Also methanol permeability through the ETFE-based membrane was measured as a function of temperature, resulting in values less than 10% of the corresponding values for Nafion ® 115, which was considerably thicker than the experimental membrane. Methanol crossover was reported to decrease when the thickness of the membrane increases, so the ETFE-based membrane compares favourably to Nafion ® membranes. The maximum power densities achieved with the experimental ETFE-based membrane were about 40-65% lower than the corresponding values of the Nafion ® 115 membrane, because of the lower conductivity and noticeably higher IR-losses. Chemical and mechanical stability of the ETFE-based membrane appeared to be promising since it was tested over 2000 h in the DMFC without any performance loss.

Research paper thumbnail of Range profiles of 6–10 MeV 15N ions implanted in silicon

Applied Surface Science, 1995

Implantation profiles of 6 to 10 MeV 15N ions in crystalline silicon have been investigated. Meas... more Implantation profiles of 6 to 10 MeV 15N ions in crystalline silicon have been investigated. Measurements of the profiles at depths from 4 to 7 Frn were rendered possible by combining the depth profiling of the "N atoms through the l'N(p, cwy) "C reaction and the exfoliation of the surface layer of the samples, accomplished by high dose 4He ion bombardment. In this way the range profiles, measured at the exfoliated crater bottom, could be obtained accurately without uncertainties due to straggling of the probing proton beam. The range parameters are compared to those of Monte Carlo calculations using the electronic stopping powers given by J.F. Ziegler, J.P. Biersack and U. Littmark [The Stopping Powers and Ranges of Ions in Matter, Vol. 1 (Pergamon, New York, 1985)]. Projected ranges were observed to be 5%-10% larger and range stragglings 27%-6% smaller than those predicted by Monte Carlo calculations along with the adopted stopping power parametrization.

Research paper thumbnail of Ion beam analysis of high temperature superconducting samples

Applied Radiation and Isotopes, 1994

Characterization of high temperature superconducting film and bulk samples has been carried out u... more Characterization of high temperature superconducting film and bulk samples has been carried out using 2 MeV a-particle Rutherford backscattering, 2.4 MeV proton elastic scattering, 2.4 MeV proton-induced x-ray emission, 9 MeV proton induced y-ray emission and 100 MeV iodine elastic recoil detection analysis techniques. The objective was to compare different ion beam based techniques for: (i) compositional analysis; and (ii) consistency of the results obtained for samples prepared using similar preparation methodology.

Research paper thumbnail of Annealing behaviour of high-dose-implanted nitrogen in InP

Applied Physics A Materials Science and Processing, 1996

Concentration profiles of nitrogen in vacuumannealed p-and n-type single-crystal (1 0 0) InP impl... more Concentration profiles of nitrogen in vacuumannealed p-and n-type single-crystal (1 0 0) InP implanted with 1;10 30 keV N> ions cm\ have been studied by Secondary Ion Mass Spectrometry (SIMS) and Nuclear Resonance Broadening (NRB) techniques. Damage induced by the nitrogen implantation was studied by Rutherford Backscattering Spectrometry (RBS) and channeling. Annealing the samples led to loss and redistribution of nitrogen in the temperature range from 575 to 675°C. At temperatures from 575 to 600°C, rapid migration of nitrogen towards the sample surface was observed. The n-type InP material had a very dominant tendency for surface nitrogen build-up, whereas the p-type material had a markedly smaller surface peak in the nitrogen distribution. The surface peak in n-type material is due to sulphur acting partly as a diffusion barrier. SIMS analyses showed sulphur build-up on the surface in the course of annealing. At temperatures from 600 to 675°C, the nitrogen profiles of n-and p-type InP were similar. A small loss of nitrogen was observed at 625-675°C. Two different recovery stages were observed at 575-600°C and at 625-650°C. The corresponding activation energies for nitrogen loss are 2.9 and 3.0 eV, respectively.

Research paper thumbnail of Round Robin: measurement of H implantation distributions in Si by elastic recoil detection

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2004

A 200 mm amorphised Si wafer was implanted with 6-keV H þ ions at a nominal fluence of 5 • 10 16 ... more A 200 mm amorphised Si wafer was implanted with 6-keV H þ ions at a nominal fluence of 5 • 10 16 atoms/cm 2. The uniformity of the implant was better than 2% over the wafer. Samples of the wafer were analysed for absolute H fluence by nuclear reaction analysis and elastic recoil detection (ERD) analysis, including both helium and heavy ion beams, using various types of detector (Si with range foil, time of flight ERD, and a position-sensitive gas ionisation DE-E detector), various ion beams (He, Cl, Cu, I, Au) and independent analytical procedures. The results are compared and the inter-lab reproducibility is evaluated. The surface H, unstable under heavy ion beams, was resolved and accounted for throughout the analysis. Estimates of total combined uncertainties are about 6% for all participants, but the interlab reproducibility of the measurements was found to be 2.2%. Correct quantification of the H data from the gas ionisation detector is demonstrated. The uncertainty budget is discussed in detail.