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  • 1.
    Eriksson, Mats
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Salomonsson, Anette
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Lundström, Ingemar
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Briand, Danick
    Institute of Microtechnology, University of Neuchâtel, Neuchâtel, Switzerland.
    Åbom, Elisabeth
    Sapa Heat Transfer, Finspång, Sweden.
    The influence of the insulator surface properties on the hydrogen response of field-effect gas sensors2005In: Journal of Applied Physics, ISSN 0021-8979, Vol. 98, no 3, p. 34903-34908Article in journal (Refereed)
    Abstract [en]

    The hydrogen response of gas-sensitive field-effect devices is mainly due to trapping of atomic hydrogen on the insulator side of the metal-insulator interface of the metal-insulator-semiconductor (MIS) structure. Therefore an influence of the choice of insulator on the hydrogen response properties is expected. We have investigated this influence by producing MIS capacitors with four different insulators; SiO2, Al2O3, Si3N4, and Ta2O5. The results show that the choice of insulator influences the detection limit, the saturation concentration, and the saturation response. Furthermore, there is a strong correlation between the observed saturation response and the oxygen concentration of the insulator surface, as measured by Auger electron spectroscopy, which indicates that the trapping of hydrogen at the interface occurs at the oxygen atoms of the insulator surface. Finally, if the metal film is porous a catalytic oxidation of the insulator surface appears to be facilitated, which can increase the hydrogen response.

  • 2.
    Lloyd-Spets, Anita
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Nakagomi, S.
    School of Science and Engineering, Ishinomaki Senshu University, Ishinomaki, Miyagi, Japan.
    Wingbrant, Helena
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Andersson, Mike
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Salomonsson, Anette
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Roy, S.
    Wingqvist, G.
    Ångström Laboratory, Uppsala University, Uppsala, Sweden.
    Katardjiev, I.
    Ångström Laboratory, Uppsala University, Uppsala, Sweden.
    Eickhoff, M.
    Walter Schottky Institut, Technishce Universität München, Am. Coulombwall, Garching, Germany.
    Uvdal, Kajsa
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    Yakimova, Rositsa
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    New materials for chemical and biosensors2006In: Materials and Manufacturing Processes, ISSN 1042-6914, E-ISSN 1532-2475, Vol. 21, no 3, p. 253-256Article in journal (Refereed)
    Abstract [en]

    Wide band gap materials such as SiC, AlN, GaN, ZnO, and diamond have excellent properties such as high operation temperature when used as field effect devices and a high resonating frequency of the substrate materials used in piezoelectric resonator devices. Integration of FET and resonating sensors on the same chip enables powerful miniaturized devices, which can deliver increased information about a gas mixture or complex liquid. Examples of sensor devices based on different wide band gap materials will be given.

  • 3.
    Lloyd-Spets, Anita
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Salomonsson, Anette
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Ojamäe, Lars
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry .
    Käll, Per-Olov
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry .
    Strand, M.
    Einvall, J.
    Aulin, C.
    Nanoparticles as sensing material for selective and stable SiC-FET gas sensor2006In: Proc. European Aerosol Conference 2005,2006, 2006, p. 735-735Conference paper (Refereed)
  • 4.
    Lutic, D.
    et al.
    Växjö universitet.
    Strand, M.
    Växjö universitet.
    Salomonsson, Anette
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Ojamäe, Lars
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry .
    Käll, Per-Olov
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry .
    Lloyd-Spets, Anita
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Sanati, M.
    Växjö universitet.
    In2O3 particle films as gate material for MISiC-capacitor sensors2005In: NOSA 2005,2005, 2005Conference paper (Refereed)
  • 5. Roy, S
    et al.
    Salomonsson, Anette
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Lloyd-Spets, Anita
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Aulin, C
    Käll, Per-Olov
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry .
    Ojamäe, Lars
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry .
    Strand, M
    Sanati, M
    Metal oxide nanoparticles as novel gate materials for field-effect gas sensors2006In: Materials and Manufacturing Processes, ISSN 1042-6914, E-ISSN 1532-2475, Vol. 21, p. 275-278Article in journal (Refereed)
    Abstract [en]

      

  • 6.
    Salomonsson, Anette
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Catalytic reactions and hydrogen sensing with Pt- and Pd-MIS devices2003Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The hydrogen sensitivity of catalytic metal-insulator-semiconductor (MIS) devices has been known for almost 30 years [1,2]. With Pd or Pt as the metal gate the electronic properties of the device are influenced by hydrogen and the device can thereby be used as a gas sensor for hydrogen and hydrogen containing gases. Hydrogen sensors will no doubt be of great interest in the future, when hydrogen is expected to play an increasing and important role in power production. Already today there are wide spread experiments and tests with fuel-cell cars and buses which run on hydrogen [3]. Hydrogen detection will for example be essential during the hydrogen production, (remember that hydrogen is an energy carrier and not an energy source) and during different types of chemical processes where hydrogen is involved. For hydrogen storage purposes, leak detection will also be crucial.

    MIS sensors have been used for several years, but there are still a lot of questions left to be answered. In general one could say that there are four important properties to investigate and improve for these types of sensors:

    • Sensitivity

    • Selectivity

    • Stability

    • Speed of response and recovery

    Field-effect devices based on silicon are for instance limited to operation temperatures below approximately 500 K. The selectivity of field-effect devices for gas sensing would be improved if their operation temperature could increase. One way to solve this problem is to change the semiconductor material into a semiconductor material with a larger bandgap e.g. silicon carbide. Changing the catalytic gate material will of course be critical for the sensitivity and selectivity of the devices.

    The work presented in this thesis concerns the fundamental study of Pt-based MIS devices, where hydrogen adsorption on the Pt surface and at the Pt-insulator interface is in focus. Also the influence of the insulator surface properties has been investigated.

    The thesis is divided into eight chapters. Chapter 2 concerns gas sensors in general and the MIS-structure in more detail. Chapter 3 and 4 give short introductions to surface physics and catalysis. Both areas are important in understanding the sensors response and for evaluating the results. Jn the fifth chapter the equipment and analytical methods that have been used are presented. Chapter 6 gives some suggestion for future work and chapter 8 contains 2 papers intended for publication and which are the essence of the research performed. 

  • 7.
    Salomonsson, Anette
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    New Materials for Gas Sensitive Field-Effect Device Studies2005Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Gas sensor control is potentially one of the most important techniques of tomorrow for the environment. All over the world cars are preferred for transportation, and accordingly the number of cars increases, unfortunately, together with pollutants. Boilers and powerplants are other sources of pollutants to the environment. Metal-Insulator-Silicon Carbide (MISiC) Field-effect sensors in car applications and boilers have the potential to reduce the amount of pollutants. These devices are sensitive to several gases in exhaust and flues gases, such as hydrogen, hydrocarbons, and ammonia (for the selective catalytic reduction (SCR) application). These applications require specific and long term stable sensors. The car industry for instance wants sensors that will stand at least 240 000 km.

    This thesis presents studies of the active layers in MIS Fieldeffect gas sensors. Fundamental studies of the sensor mechanism has been performed in ultra high vacuum, UHV, to understand the gas response mechanism in more detail, and to find out how the sensing mechanism is affected by the catalytic active gate material. The influence of four different insulating layers was studied at atmospheric pressure. The catalytic layer has also been altered to metal oxide nanoparticles with or without impregnation of catalytic metals.

    Nanoparticles are potential candidates to be used as the gate material for high temperature, long-term stable FET sensor devices. The combination of catalytic metals and metal oxides may prevent reconstruction of the metal. The use of nanoparticles will increase the number of triple points (catalytic material and insulator in contact with gas), which are crucial e.g. for the ammonia sensitivity. Another challenging aspect of nanoparticles is the possibility to get selectivity to different gases based on the particle size.

    The goal is to find new sensitive, selective and more long term stable materials, which meet the requirements above.

    From the UHV studies we learned that the two catalytic active metals Pt and Pd, do behave in a similar way, although there are some quantitative differences. Values for the heat of adsorption on both the Pd and Pt surfaces are estimated as well as the dipole moments for the adsorbates on the insulator surface.

    The insulators play an important role in the sensing mechanism, since the adsorption of hydrogen atoms (or protons) that are detected by the sensor occur on the insulator surface. By changing the insulator material the saturation response of the sensors is affected. It was shown that Al2O3 gave a higher saturated response to hydrogen in Pt-MIS capacitors at 140°C as compared to Ta2O5, SiO2, and Si3N4.

    We have tested wet synthesized ruthenium dioxide and ruthenium nanoparticles, which are electrically conducting and catalytically active sensing material. RuO2 is especially interesting as a high temperature material since it is already oxidized. Both materials show a sensitivity pattern comparable to porous platinum. The temperature dependence of the gas response indicates a higher catalytic activity of the RuO2 as compared to Ru nanoparticles.

    Nanoparticles synthesized by aerosol technology provide several advantages like a good adhesion of the particles to the substrate, many possible material combinations and efficient methods for particle separation according to size. The methods to use this technology for sensing materials in MISiC sensors are now under development and some preliminary results are obtained.

    List of papers
    1. Hydrogen Interaction with Platinum and Palladium Metal Insulator Semiconductor devices
    Open this publication in new window or tab >>Hydrogen Interaction with Platinum and Palladium Metal Insulator Semiconductor devices
    2005 (English)In: Journal of Applied Physics, ISSN 0021-8979, Vol. 98, no 1, p. 14505-14514Article in journal (Refereed) Published
    Abstract [en]

    Hydrogen-sensitivePd–SiO2–Si and Pt–SiO2–Si metal–insulator–semiconductor (MIS) devices have been studied inultrahigh vacuum in the temperature range of 223–523  K. Adsorption/absorption ofhydrogen occurs at the metal surface, in the metal bulk,and at the metal–insulator interface. The sensor signal, caused byhydrogen adsorption at the interface, shows a logarithmic dependence onthe applied hydrogen pressure. The Pt-MIS device, which is fullyfunctional at atmospheric pressures, is sensitive to changes in hydrogenpressure down to the 10–12-Torr scale. We propose that theinterface adsorption follows a so-called Temkin isotherm with an interfaceheat of adsorption that varies with hydrogen coverage as Hi0(1–a).The initial heat of adsorption Hi0 is determined to 0.78  eV/hydrogenatom. The adsorption potential at the external Pt surface isfound to be 0.45  eV/hydrogen atom. These values were obtained bymodeling the hydrogen interaction with the MIS devices and fittingthe model to a number of experimental results. Also studiesof Pd-based devices were performed and compared with Pt. Thehydrogen adsorption on the metal surface, previously treated as afirst-order process on Pd, is shown to follow a second-orderprocess. Qualitatively the results from the Pd- and Pt-MIS devicesagree. Quantitatively there are differences. The hydrogen sensitivity of thePt-MIS device is only approximately one-third compared to that ofthe Pd-MIS structure. This agrees with the result that theconcentration of available hydrogen adsorption sites at the Pt–SiO2 interfaceis approximately 7×1017 m–2 whereas the concentrations of sites at thePd–SiO2 interface is roughly three times larger (2×1018 m–2). An estimateof the size of the dipole moments (0.6–0.7  D) implies thatthe interface hydrogen atoms are strongly polarized. Differences are alsoobserved in the microstructure of the metal films. Atomic forcemicroscopy results show that the Pd surface reconstructs during H2–O2exposures, while the Pt surface shows no such change atthese temperatures.

    Keywords
    palladium, platinum, silicon compounds, silicon, hydrogen, elemental semiconductors, MIS devices, gas sensors, atomic force microscopy, adsorption, surface reconstruction, heat of adsorption, crystal microstructure
    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-13383 (URN)10.1063/1.1953866 (DOI)
    Available from: 2005-10-06 Created: 2005-10-06 Last updated: 2016-07-08
    2. The influence of the insulator surface properties on the hydrogen response of field-effect gas sensors
    Open this publication in new window or tab >>The influence of the insulator surface properties on the hydrogen response of field-effect gas sensors
    Show others...
    2005 (English)In: Journal of Applied Physics, ISSN 0021-8979, Vol. 98, no 3, p. 34903-34908Article in journal (Refereed) Published
    Abstract [en]

    The hydrogen response of gas-sensitive field-effect devices is mainly due to trapping of atomic hydrogen on the insulator side of the metal-insulator interface of the metal-insulator-semiconductor (MIS) structure. Therefore an influence of the choice of insulator on the hydrogen response properties is expected. We have investigated this influence by producing MIS capacitors with four different insulators; SiO2, Al2O3, Si3N4, and Ta2O5. The results show that the choice of insulator influences the detection limit, the saturation concentration, and the saturation response. Furthermore, there is a strong correlation between the observed saturation response and the oxygen concentration of the insulator surface, as measured by Auger electron spectroscopy, which indicates that the trapping of hydrogen at the interface occurs at the oxygen atoms of the insulator surface. Finally, if the metal film is porous a catalytic oxidation of the insulator surface appears to be facilitated, which can increase the hydrogen response.

    Keywords
    silicon compounds, alumina, tantalum compounds, hydrogen, dielectric materials, gas sensors, MIS capacitors, Auger electron spectra, catalysis, oxidation, interface states
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-13384 (URN)10.1063/1.1994941 (DOI)
    Available from: 2005-10-06 Created: 2005-10-06 Last updated: 2015-03-24
    3. Nanoparticles for long-term stable, more selective MISiCFET gas sensors
    Open this publication in new window or tab >>Nanoparticles for long-term stable, more selective MISiCFET gas sensors
    Show others...
    2005 (English)In: Sensors and Actuators B, ISSN 0925-4005, Vol. 107, no 2, p. 831-838Article in journal (Refereed) Published
    Abstract [en]

    Synthesis of metal-oxide nanoparticles and utilization of these particles as gate materials for field-effect sensor devices is reported. Improved selectivity to specific gases is expected by modulating the size of the oxide nanoparticles or impregnating them with catalytic metals. Another objective is to improve the long-term thermal stability of the sensors, since the metal loaded nanoparticles may prevent thermally induced restructuring of the gate layer, which is often a problematic issue for the catalytic metal layers. Because of its reasonably high electrical conductivity, which is especially important for the capacitive gas sensors, ruthenium dioxide has been identified to be one of the potential candidates as gate material for the field-effect sensor devices. Interestingly, this material has been found to change its resistivity in different gaseous ambients. When used as a gate material, sensitivity to reducing gases has been observed for the RuO2/SiO2/4H-SiC capacitors. Changes in the resistivity of the films due to various gas exposures have also been recorded. Morphological studies of nanoparticles (SiO2 and Al2O3), loaded or impregnated with catalytic metals (e.g. Pt), have been performed.

    Keywords
    Sensors; Catalytic material; MISiCFET; Ruthenium dioxide
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-13385 (URN)10.1016/j.snb.2004.12.024 (DOI)
    Available from: 2005-10-06 Created: 2005-10-06 Last updated: 2015-03-09
    4. Ruthenium dioxide & Ru Nanoparticles for MISiCFET gas sensors
    Open this publication in new window or tab >>Ruthenium dioxide & Ru Nanoparticles for MISiCFET gas sensors
    Show others...
    2005 (English)In: Nanotech 2005 (NSTI) Anaheim, USA, 8-12 May, 2005, Vol. 2, no Chapter 4, p. 269–272-Conference paper, Published paper (Refereed)
    Abstract [en]

    Catalytically active nanoparticles used as gate material on SiC-FET gas sensors. The goal is to improve the selsectivity and senstitivty.The sensors are sensitive towards oxidising and reducing gases (H2, NH3, C3H6).

    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-13386 (URN)
    Available from: 2005-10-06 Created: 2005-10-06 Last updated: 2015-03-09
    5. Nanocrystalline Ruthenium oxide and Ruthenium in sensing applications -an experimental and theoretical study
    Open this publication in new window or tab >>Nanocrystalline Ruthenium oxide and Ruthenium in sensing applications -an experimental and theoretical study
    Show others...
    2006 (English)In: Journal of Nanoparticle Research, ISSN 1388-0764, Vol. 8, no 6, p. 899-910Article in journal (Refereed) Published
    Abstract [en]

    In this project, we have explored RuO2 and Ru nanoparticles (∼ ∼10 and ∼ ∼5 nm, respectively, estimated from XRD data) to be used as gate material in field effect sensor devices. The particles were synthesized by wet chemical procedure. The capacitance versus voltage characteristics of the studied capacitance shifts to a lower voltage while exposed to reducing gases. The main objectives are to improve the selectivity of the FET sensors by tailoring the dimension and surface chemistry of the nanoparticles and to improve the high temperature stability. The sensors were characterized using capacitance versus voltage measurements, at different frequencies, 500 Hz to 1 MHz, and temperatures at 100–400°C. The sensor response patterns have been found to depend on operating temperature. X-ray photoelectron spectroscopy (XPS) analyses were performed to investigate the oxidation state due to gas exposure. Quantum-chemical computations suggest that heterolytic dissociative adsorption is favored and preliminary computations regarding water formation from adsorbed hydrogen and oxygen was also performed.

    Keywords
    nanoparticles, gas sensors, RuO2, Ru, FET devices
    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-13387 (URN)10.1007/s11051-005-9058-1 (DOI)
    Available from: 2005-10-06 Created: 2005-10-06 Last updated: 2015-03-09
    6. Aerosol deposited particles as gate material for MISiC-capacitor sensors
    Open this publication in new window or tab >>Aerosol deposited particles as gate material for MISiC-capacitor sensors
    Show others...
    Manuscript (Other academic)
    Identifiers
    urn:nbn:se:liu:diva-13388 (URN)
    Available from: 2005-10-06 Created: 2005-10-06 Last updated: 2010-01-13
  • 8.
    Salomonsson, Anette
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Eriksson, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Dannetun, Helen
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    HDO formation studied on Pd- and Pt-MIS devices2003Conference paper (Refereed)
  • 9.
    Salomonsson, Anette
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Eriksson, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Dannetun, Helen
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Hydrogen Interaction with Platinum and Palladium Metal Insulator Semiconductor devices2005In: Journal of Applied Physics, ISSN 0021-8979, Vol. 98, no 1, p. 14505-14514Article in journal (Refereed)
    Abstract [en]

    Hydrogen-sensitivePd–SiO2–Si and Pt–SiO2–Si metal–insulator–semiconductor (MIS) devices have been studied inultrahigh vacuum in the temperature range of 223–523  K. Adsorption/absorption ofhydrogen occurs at the metal surface, in the metal bulk,and at the metal–insulator interface. The sensor signal, caused byhydrogen adsorption at the interface, shows a logarithmic dependence onthe applied hydrogen pressure. The Pt-MIS device, which is fullyfunctional at atmospheric pressures, is sensitive to changes in hydrogenpressure down to the 10–12-Torr scale. We propose that theinterface adsorption follows a so-called Temkin isotherm with an interfaceheat of adsorption that varies with hydrogen coverage as Hi0(1–a).The initial heat of adsorption Hi0 is determined to 0.78  eV/hydrogenatom. The adsorption potential at the external Pt surface isfound to be 0.45  eV/hydrogen atom. These values were obtained bymodeling the hydrogen interaction with the MIS devices and fittingthe model to a number of experimental results. Also studiesof Pd-based devices were performed and compared with Pt. Thehydrogen adsorption on the metal surface, previously treated as afirst-order process on Pd, is shown to follow a second-orderprocess. Qualitatively the results from the Pd- and Pt-MIS devicesagree. Quantitatively there are differences. The hydrogen sensitivity of thePt-MIS device is only approximately one-third compared to that ofthe Pd-MIS structure. This agrees with the result that theconcentration of available hydrogen adsorption sites at the Pt–SiO2 interfaceis approximately 7×1017 m–2 whereas the concentrations of sites at thePd–SiO2 interface is roughly three times larger (2×1018 m–2). An estimateof the size of the dipole moments (0.6–0.7  D) implies thatthe interface hydrogen atoms are strongly polarized. Differences are alsoobserved in the microstructure of the metal films. Atomic forcemicroscopy results show that the Pd surface reconstructs during H2–O2exposures, while the Pt surface shows no such change atthese temperatures.

  • 10.
    Salomonsson, Anette
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Eriksson, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Dannetun, Helen
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Hydrogen interaction with Pt- and PdMIS devices2005In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 98, no 1Article in journal (Refereed)
    Abstract [en]

    Hydrogen-sensitive Pd–SiO2–Si and Pt–SiO2–Si metal–insulator–semiconductor (MIS) devices have been studied in ultrahigh vacuum in the temperature range of 223–523 K. Adsorption/absorption of hydrogen occurs at the metal surface, in the metal bulk, and at the metal–insulator interface. The sensor signal, caused by hydrogen adsorption at the interface, shows a logarithmic dependence on the applied hydrogen pressure. The Pt-MIS device, which is fully functional at atmospheric pressures, is sensitive to changes in hydrogen pressure down to the 10−12-Torr scale. We propose that the interface adsorption follows a so-called Temkin isotherm with an interface heat of adsorption that varies with hydrogen coverage as ΔHi0(1−aθ). The initial heat of adsorption ΔHi0 is determined to 0.78 eV/hydrogen atom. The adsorption potential at the external Pt surface is found to be 0.45 eV/hydrogen atom. These values were obtained by modeling the hydrogen interaction with the MIS devices and fitting the model to a number of experimental results. Also studies of Pd-based devices were performed and compared with Pt. The hydrogen adsorption on the metal surface, previously treated as a first-order process on Pd, is shown to follow a second-order process. Qualitatively the results from the Pd- and Pt-MIS devices agree. Quantitatively there are differences. The hydrogen sensitivity of the Pt-MIS device is only approximately one-third compared to that of the Pd-MIS structure. This agrees with the result that the concentration of available hydrogen adsorption sites at the Pt–SiO2 interface is approximately 7×1017 m−2 whereas the concentrations of sites at the Pd–SiO2 interface is roughly three times larger (2×1018 m−2). An estimate of the size of the dipole moments (0.6–0.7 D) implies that the interface hydrogen atoms are strongly polarized. Differences are also observed in the microstructure of the metal films. Atomic force microscopy results show that the Pd surface reconstructs during H2–O2 exposures, while the Pt surface shows no such change at these temperatures.

  • 11.
    Salomonsson, Anette
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Eriksson, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Ekedahl, Lars-Gunnar
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Dannetun, Helen
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Hydrogen ad- and absorption on Pt-SiO2-Si structures2001Conference paper (Refereed)
  • 12.
    Salomonsson, Anette
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Petoral Jr., Rodrigo M.
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
    Uvdal, Kajsa
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
    Aulin, Christian
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Käll, Per-Olov
    Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry . Linköping University, The Institute of Technology.
    Ojamäe, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry . Linköping University, The Institute of Technology.
    Strand, Michael
    School of Technology and Design/Chemistry, Växjö University, Växjö, Sweden.
    Sanati, Mehri
    School of Technology and Design/Chemistry, Växjö University, Växjö, Sweden.
    Lloyd Spetz, Anita
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Nanocrystalline Ruthenium oxide and Ruthenium in sensing applications -an experimental and theoretical study2006In: Journal of Nanoparticle Research, ISSN 1388-0764, Vol. 8, no 6, p. 899-910Article in journal (Refereed)
    Abstract [en]

    In this project, we have explored RuO2 and Ru nanoparticles (∼ ∼10 and ∼ ∼5 nm, respectively, estimated from XRD data) to be used as gate material in field effect sensor devices. The particles were synthesized by wet chemical procedure. The capacitance versus voltage characteristics of the studied capacitance shifts to a lower voltage while exposed to reducing gases. The main objectives are to improve the selectivity of the FET sensors by tailoring the dimension and surface chemistry of the nanoparticles and to improve the high temperature stability. The sensors were characterized using capacitance versus voltage measurements, at different frequencies, 500 Hz to 1 MHz, and temperatures at 100–400°C. The sensor response patterns have been found to depend on operating temperature. X-ray photoelectron spectroscopy (XPS) analyses were performed to investigate the oxidation state due to gas exposure. Quantum-chemical computations suggest that heterolytic dissociative adsorption is favored and preliminary computations regarding water formation from adsorbed hydrogen and oxygen was also performed.

  • 13.
    Salomonsson, Anette
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Roy, S
    Aulin, C
    Ojamäe, Lars
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry .
    Käll, Per-Olov
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry .
    Strand, M
    Sanati, M
    Lloyd-Spets, Anita
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    RuO2 and Ru nanoparticles for MISiCFET gas sensors2005In: Nanotech NSTI 2005,2005, 2005, p. 269-Conference paper (Refereed)
  • 14.
    Salomonsson, Anette
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Roy, Somenath
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Aulin, Christian
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Cerdà, Judith
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Käll, Per-Olov
    Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry . Linköping University, The Institute of Technology.
    Ojamäe, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry . Linköping University, The Institute of Technology.
    Strand, Michael
    Division of Chemistry, Växjö University, Växjö, Sweden.
    Sanati, Mehri
    Division of Chemistry, Växjö University, Växjö, Sweden.
    Lloyd Spetz, Anita
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Nanoparticles for long-term stable, more selective MISiCFET gas sensors2005In: Sensors and Actuators B, ISSN 0925-4005, Vol. 107, no 2, p. 831-838Article in journal (Refereed)
    Abstract [en]

    Synthesis of metal-oxide nanoparticles and utilization of these particles as gate materials for field-effect sensor devices is reported. Improved selectivity to specific gases is expected by modulating the size of the oxide nanoparticles or impregnating them with catalytic metals. Another objective is to improve the long-term thermal stability of the sensors, since the metal loaded nanoparticles may prevent thermally induced restructuring of the gate layer, which is often a problematic issue for the catalytic metal layers. Because of its reasonably high electrical conductivity, which is especially important for the capacitive gas sensors, ruthenium dioxide has been identified to be one of the potential candidates as gate material for the field-effect sensor devices. Interestingly, this material has been found to change its resistivity in different gaseous ambients. When used as a gate material, sensitivity to reducing gases has been observed for the RuO2/SiO2/4H-SiC capacitors. Changes in the resistivity of the films due to various gas exposures have also been recorded. Morphological studies of nanoparticles (SiO2 and Al2O3), loaded or impregnated with catalytic metals (e.g. Pt), have been performed.

  • 15.
    Salomonsson, Anette
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Roy, Somenath
    Aulin, Christian
    Ojamäe, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry . Linköping University, The Institute of Technology.
    Käll, Per-Olov
    Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry . Linköping University, The Institute of Technology.
    Strand, Michael
    Växjö university.
    Sanati, Mehri
    Växjö university.
    Lloyd Spetz, Anita
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Ruthenium dioxide & Ru Nanoparticles for MISiCFET gas sensors2005In: Nanotech 2005 (NSTI) Anaheim, USA, 8-12 May, 2005, Vol. 2, no Chapter 4, p. 269–272-Conference paper (Refereed)
    Abstract [en]

    Catalytically active nanoparticles used as gate material on SiC-FET gas sensors. The goal is to improve the selsectivity and senstitivty.The sensors are sensitive towards oxidising and reducing gases (H2, NH3, C3H6).

  • 16.
    Strand, M.
    et al.
    Växjö universitet.
    Salomonsson, Anette
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Einvall, J.
    Aulin, C.
    Kemi LiU.
    Ojamäe, Lars
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry .
    Käll, Per-Olov
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry .
    Lloyd-Spets, Anita
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Sanati, M.
    Växjö universitet.
    Nanoparticles as sensing material for selective and stable SiC-FET gas sensor2005In: European Aerosol Conference 2005,2005, 2005, p. 735-Conference paper (Refereed)
1 - 16 of 16
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