Nanoparticles for long-term stable, more selective MISiCFET gas sensors

Sensors and Actuators B 107 (2005) 831–838

Nanoparticles for long-term stable, more selective MISiCFET gas sensors Anette Salomonssona,∗ , Somenath Roya , Christian Aulinb , Judith Cerd`aa , Per-Olov K¨allb , Lars Ojam¨aeb , Michael Strandc , Mehri Sanatic , Anita Lloyd Spetza a

S-SENCE and Division of Applied Physics, Link¨oping University, SE-581 83 Link¨oping, Sweden b Physical and Inorganic Chemistry, Link¨ oping University, SE-581 83 Link¨oping, Sweden c Division of Chemistry, V¨ axj¨o University, SE-351 95 V¨axj¨o, Sweden

Received 7 September 2004; received in revised form 2 December 2004; accepted 3 December 2004 Available online 20 January 2005

Abstract 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 Al2 O3 ), loaded or impregnated with catalytic metals (e.g. Pt), have been performed. © 2004 Elsevier B.V. All rights reserved. Keywords: Sensors; Catalytic material; MISiCFET; Ruthenium dioxide

1. Introduction Excellent properties of silicon carbide (SiC) e.g., wide bandgap, high melting point and chemical inertness make it especially suitable as sensor material for rough and corrosive environments like flue gas or fuel-engine exhaust. Metal–insulator–SiC field-effect transistor (MISiCFET) sensors, with buried source, drain and channel region have already been tested with success in several industrial applications [1]. Selective catalytic reduction (SCR) of NOx by NH3 in the catalytic converter in diesel exhausts can be controlled by an NH3 sensitive MISiCFET sensor operated at 300 ◦ C [2]. The combustion process in a boiler can be controlled ∗

Corresponding author. Tel.: +46 13 282799; fax: +46 13 288969. E-mail address: [email protected] (A. Salomonsson).

0925-4005/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.snb.2004.12.024

by a MISiCFET sensor array measuring on-line in the flue gases [3]. Also, a sensor array can give continuous information about several gas components in the car exhausts for on board diagnosis (OBD) [3]. These applications require highly selective and long-term stable sensors with reproducible performance. Special adsorption sites (triple phase boundaries) have been proven to be significant for the generation of a response to a specific gas (like NH3 ) [4]. Use of particles as the gate material increases the occurrence of triple phase boundaries, where the catalytic gate material, the insulator and the test gas molecules are in contact. Nano-dimension of the particles has the potential to introduce novel features in sensing parameters like selectivity and speed of response when compared to those for the conventional thin film sensing layers [5]. Films of SnO2 particles with controlled grain sizes be-

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tween 6 and 16 nm were prepared and tested. It was shown that towards H2 S, the sensitivity was greatly enhanced for the larger particle size [6]. Nanoparticles of different metaloxides with unique catalytic performances are also considered to be promising in terms of enhanced selectivity, in addition to offering improved stability in the aggressive environment. A number of techniques may be adopted to produce a variety of nanoparticles with unique features for optimizing selectivity, sensitivity and thermal endurance of the gas sensors. Commercially available oxide nanoparticles (e.g. Al2 O3 , SiO2 , TiO2 ) can be impregnated with catalytic metals (e.g. Pt, Ir, Pd) in an acidic medium. The penetration depth of the metal is possible to control by the strength of the acidic solution and the impregnation time [7]. Wet chemical synthesis of catalytically active and electrically conducting particles (RuOx , Cox Oy ) seems to be a promising technique. Aerosol technology [8] can also be used to produce catalytically active particles [9]. Other techniques like flame spray synthesis [10], spray pyrolysis [11] and the sol–gel spin coating method [12] have also been used to produce nano-dimension particles with specific gas response properties. Using nanoparticles as a new sensing material for MISiC sensors was presented in the 10th International Meeting on Chemical Sensors (IMCS 2004) [13]. The current work reports on the development of nanoparticles of catalytic metal-oxides, RuO2 and nanoparticles of insulating oxides, Al2 O3 , SiO2 , impregnated with catalytic metals (e.g. Pt) as the gate material for the SiC-based field-effect devices.

2. Gas sensing principle Gas molecules adsorb and dissociate on a catalytically active surface. The adsorption rate and the degree of dissociation depend on the operating temperature and the morphology and chemical characteristics of the gate material. Eventually, the dissociated species (predominantly hydrogen atoms) diffuse into the metal/insulator interface where they form a dipole layer, thereby creating an intrinsic electric field. The detection mechanism of the field-effect gas sensors can then in principle be explained in terms of the modulation of an electric field in the underlying insulating layer (SiO2 ) due to the specific change in electric charges on the insulator surface. As a result, a shift in the sensor output voltage (sensor signal), which is a function of the population density of the interface adsorbates, is observed. The detection of some gaseous species, such as ammonia, requires the use of a porous gate material. There are special sites (triple phase boundaries among the gate material, the insulator and the test gas molecules) on the gate region, where ammonia (NH3 ) molecules are dissociated and provide hydrogen atoms (or protons), which form the dipole layers at the interface.

3. Experimental 3.1. Preparation of catalytically active particles 3.1.1. Methods for synthesizing RuO2 RuO2 nanoparticles were synthesized by wet chemical procedures. A couple of methods were adopted in order to obtain particles of various sizes and different amount of pure Ru in the material. 3.1.1.1. Synthesis of rutile RuO2 nanocrystals using a strong organic alkali in an alcoholic solution. Ruthenium trichloride hydrate, RuCl3 ·(H2 O)x , (0.2036 g) was dissolved into an alcoholic solvent, containing ethanol (10 ml) and 2-propanol (10 ml). Tetrabutylammonium hydroxide, [CH3 (CH2 )3 ]4 NOH, TBAH (2 ml) was added to the solution. The precipitate obtained was left for 4 h at 90 ◦ C and then separated from the liquor by centrifuging. The precipitate was washed several times with deionised water, treated with an oxidizing agent (30% H2 O2 ) added by drops and was then dried in open air. The dry powder was heated in an oven at 400 ◦ C for 4 h, yielding a black powder [14]. 3.1.1.2. Synthesis of rutile RuO2 nanocrystals by an aqueous solution gel route. RuCl3 (0.2074 g) was mixed with an aqueous solution of citric acid, C6 H8 O7 ·H2 O (0.6304 g) under stirring. The molar ratio citric acid:RuCl3 = 3:1. The suspension was heated to 40 ◦ C and, subsequently, H2 O2 (30%) was added. Only small portions of H2 O2 were added each time because of the highly exothermic reaction. Upon the addition of 120 equivalents H2 O2 (∼11 ml), a clear dark red solution was obtained with pH ≈ 1.9. Refluxing at 90 ◦ C for 3 h made the pH drop to 1.5 and the colour changed from dark red to dark green. The solution was poured into a vessel and the water was evaporated in a furnace at 60 ◦ C. A brown gel was formed which was heat-treated in an oven at 300 ◦ C for 4 h [15]. 3.1.2. Impregnation of γ-Al2 O3 particles by Pt Commercially available ␥-Al2 O3 powder, nominally of 10 ␮m size, was dissolved in deionized water together with PtCl3 and citric acid. Three different ratios of metal-chloride, citric acid and Al2 O3 were used. ␥-Al2 O3 particles were put in a flask, in which the measured quantities of citric acid powder and hexachloroplatinic acid were added. Deionized water was poured into the flask to achieve the desired molarities of the reactants. The mixture was stirred using a magnetic stirrer for 30 min (impregnation period). The dispersion was filtered using standard filter paper. During the filtering, some deionized water was added to the mixture to remove the excess of hexachloroplatinic acid that stays on the surface of the particles. The paste created was put in an alumina crucible and annealed in a furnace in atmospheric air for 10 h and 350 ◦ C and was then cooled down to room temperature. To obtain fine powder an agate mortar was used, in which the annealed material was rubbed with the corresponding agate

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pestle. The powders were then calcined under a stream of oxygen (100 ml/min of pure O2 ) from 25 to 500 ◦ C over a period of 30 min, followed by treatment in hydrogen (100 ml/min of 1% H2 in N2 ) for 1 h at 500 ◦ C. After this, the powders were cooled in a nitrogen atmosphere (100 ml/min of N2 ). The purpose of this treatment was to burn off the citric acid and to stabilize the position of the metal.

of ∼1 mm diameter for each capacitor. Post-deposition annealing (400 ◦ C for 30 min) was performed to enhance the stability of the particles on the SiO2 surface. This thermal treatment was also found effective for consistent electrical behaviour of the gate material.

3.1.3. Preparation of the Pt–SiO2 material The Pt–SiO2 material was prepared from colloidal silica impregnated with a halogen-free platinum precursor. Colloidal silica, 1.0 g, was dispersed in 15 g of deionized water and the pH was adjusted to 10.5 by addition of ammonium hydroxide. The desired Pt loading (20 wt.% Pt) was formed by adding an aqueous solution of Pt(NH3 )4 (OH)2 drop-wise to the silica gel under continuous stirring. The sol was then stirred for 90 min and then freeze-dried. An annealing process at 500 ◦ C for 90 min was performed on the dry powder [16].

The sensor chip was glued onto a ceramic heater, which is placed on a 16-pin holder, together with a Pt-100 element as the temperature detector [1]. Some spacing between the holder and the heater was kept, since the holders can only withstand temperatures up to 400 ◦ C. The contacts of the sensors, the heater and the Pt-100 element were connected by gold bonding to the pins of the holder. The holders were mounted in aluminum blocks, which are connected in a gas flow line. The gas was carried through the device across the sensor surfaces using a computer-controlled gas mixing system. A Boonton 7200 capacitor meter was used with 1 MHz frequency for measuring the capacitance of the sensor devices under investigation. The microstructure of the gate material was characterized by X-ray diffraction (XRD) studies using a Philips PW 1729 X-ray generator (40 kV, 40 mA), by scanning electron microscopy (SEM) using a LEO 1550 FEG microscope and by transmission electron microscopy (TEM) using a Philips EM 400 T, operated at 120 kV using LaB6 filament.

3.2. Fabrication of the sensor devices The sensors used in this study were capacitors based on SiC with a catalytically active layer as the gate material. Fig. 1 represents a schematic of the capacitive sensors. A specific process sequence was adopted for the oxide growth in order to improve the device performance. The process started by first growing a thermal oxide of SiO2 onto the n-doped 4H–SiC surface. This was followed by a dense layer of Si3 N4 , which also gives a top layer of SiOx upon oxidation. The total thickness of the insulator was 80 nm. The ohmic contact on the backside of the chip consisted of alloyed Ni with 50 nm TaSix and 400 nm Pt deposited on top (as corrosion protective layer). The bonding pad on top of the sensor was formed by depositing Ti/Pt layers. The active gate region was formed by drop deposition of the particles in a suspension of methanol and deionized water using a micropipette. A constant volume (3 ␮l) of the suspension was taken to define a gate area

Fig. 1. Schematic picture of a nMISiC capacitor sensor.

3.3. Mounting and measurements

4. Results and discussion 4.1. Morphological studies of the nanoparticle layers The X-ray powder diffraction patterns of the ruthenium dioxide in the as-synthesized mode, and after thermal anneal˚ are presented in ing, using Cu K␣ radiation (λ = 1.5418 A), Fig. 2. The analyses suggested the presence of pure ruthenium dioxide with the tetragonal rutile crystal structure. No mixtures of phases, or residual metallic ruthenium are seen. The effect of annealing on the grain size of the ruthenium dioxide nanoparticles was also investigated. The average grain size calculated by Scherrer’s formula from XRD data is about 11 nm for the as-synthesized ruthenium dioxide. The small grain size of the gate metal is especially desirable for gas sensor applications because of the high surface to volume ratio and hence the availability of greater number of catalytic active sites. The grain size was found to increase after annealing at 500 ◦ C for 30 min. The effect was even more pronounced when the material was annealed in air ambient (17 nm) as compared to that annealed in 1% H2 in air (14 nm). The annealing in air also seems to result in an improved crystallinity of the material, manifested by an increase in the peak intensities. SEM studies were performed to observe the surface morphology of the gate region of the capacitive sensors. From

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Fig. 2. XRD spectra of as-synthesized and annealed RuO2 nanoparticles.

Fig. 3. SEM pictures of particles on SiOx /Si3 N4 /SiO2 /SiC for (a) Pt/␥-Al2 O3 and (b) RuO2 .

Fig. 3, it can be observed that both Pt–Al2 O3 and RuO2 layers are highly porous in nature, which is considered to be facilitating for enhanced adsorption of the gaseous species onto it. For the insulating oxides like Al2 O3 and SiO2 , penetration of the catalytic metal inside the particles is desirable to prevent an aging effect. From TEM studies (Fig. 4), it is difficult to comment on the position of the Pt in the ␥-Al2 O3 matrix.

However, there is an indication of the amount of platinum loaded for the three different samples with various combinations of the precursors. The sample in Fig. 4a seems to contain the lowest amount of Pt, and the sample shown in Fig. 4c the highest. This conforms to the relative amount of Pt precursors in the respective samples. Investigations are underway to precisely detect the position of Pt in the oxide nanoparticle matrix.

Fig. 4. TEM micrographs of Pt-impregnated ␥-Al2 O3 powders: (a) 0.02 M of dihydrogen hexachloroplatinate (IV), 2.1 g ␥-Al2 O3 and 0.1 M citric acid, (b) 0.1 M of dihydrogen hexachloroplatinate (IV), 1.05 g ␥-Al2 O3 and 0.2 M citric acid, (c) 0.2 M of dihydrogen hexachloroplatinate (IV), 0.2 g ␥-Al2 O3 and 0.25 M citric acid.

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Fig. 5. Variation of sheet resistance, Rs , of the RuO2 nanoparticle layers as a function of temperature.

4.2. Measurement of the electrical resistivity For efficient functioning of the MIS capacitors or FET devices, the gate material should preferably be conducting over the entire range of operating conditions. An attempt was made to estimate the resistivity of various metal-oxide nanoparticle layers as a function of temperature (up to 500 ◦ C). Owing to the fact that these layers are used as active gate material, it is interesting to observe the variation of their electrical resistivity in the presence of various gases diluted in air. In this study, a non-linear four contact measurement method (according to Van der Pauw [17]) was adopted to assess the sheet resistance of the nanoparticle layers under various operating conditions. Among the set of materials (RuO2 , Pt–Al2 O3 and Pt–SiO2 ) on which resistivity measurement was performed, only ruthenium dioxide was found to conduct reasonably over the entire range of operating temperature. The electrical conductivity of the Pt–Al2 O3 and Pt–SiO2 nanoparticle layers was below the detection limit of the system used in this study. Fig. 5 shows the variation of sheet resistance for the RuO2 nanoparticle layers as a function of temperature. It is interesting to notice that for the as-synthesized material, the resistivity decreased with increasing temperature. However, upon annealing at 500 ◦ C for 1 h, a reverse trend was observed. This can be interpreted in terms of the grain-growth effect in the oxide layer upon annealing at elevated temperature. In case of the as-synthesized nanoparticles, the carrier transport is probably governed by the grain boundary scattering effect, while in the case of the annealed material with a larger grain size, phonon scattering plays a significant role. As a result, the resistivity exhibited an increasing trend when measured as a function of temperature. The sheet resistance of the ruthenium dioxide layer was also found to vary in presence of different gases (1% H2 in air, 1% H2 in N2 and 2500 ppm of NH3 in air) at 500 ◦ C (Fig. 6). The resistivity decreased in various reducing atmospheres as compared to that measured in air. This effect could be attributed to desorption of surface oxygen adsorbates on the nanoparticles, by which captured electrons are released into the oxide matrix. This explanation is supported by the observation of the higher change in sheet resistance of the RuO2

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Fig. 6. Variation of sheet resistance of the RuO2 nanoparticle layers in different gas ambients.

nanoparticles layers in the presence of 1% hydrogen in nitrogen, as compared to the same concentration of hydrogen diluted in air. 4.3. Gas sensitivity of RuOx /SiO2 /SiC capacitors MISiC capacitors with ruthenium dioxide nanoparticles as gate material were exposed to a variety of gases. The corresponding capacitances versus voltage characteristics were recorded. Fig. 7 presents the characteristic C–V curves of the capacitors in synthetic air and the tested gases, 1% H2 , 250 ppm of C3 H6 and 2500 ppm of NH3 , diluted in air. An obvious horizontal shift (along the voltage axis) in the C–V curves can be noticed for hydrogen, propene and ammonia exposure, as compared to the curve obtained in synthetic air. This shift is normally caused by the polarized layer of hydrogen atoms (created upon dissociation of the gas on the sensor’s surface) adsorbed at the interface between the gate material, here RuO2 , and the insulator. Vertical shifts (30 pF) of the C–V characteristics in the accumulation region (2–3 V, in Fig. 7) and in the inversion region (−2 to −0.5 V) can also be noticed. Eventually, the whole shift of the C–V curve is actually in the vertical direction. This is probably due to a change in conductivity of the RuO2 layer in the presence of reducing gas molecules. Dissociation and reactions of gaseous species on the gate layer results in desorption of oxygen adsorbates (O− , O2 − , O2− ), thereby releasing the captured electrons into the RuO2 matrix and hence changing the conductivity of the material. A change of the oxidation state of ruthenium oxide may also be possible at 400 ◦ C. The resistivity measurements of the nanoparticle layers (see Section 4.2) also indicate this. A study of the surface changes of the RuO2 particles by XPS will be carried out in the near future. The horizontal shift along the voltage axis in the C–V curves represents the gas response described in this paper. The magnitudes of the voltage shift (the change in sensor output signal), at a constant capacitance (the horizontal shift defined above) in various gas ambients are presented in Fig. 8. The sensors respond to a greater or a lesser extent to

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Fig. 7. Capacitance–voltage characteristics of RuO2 /SiOx /Si3 N4 /SiO2 /4H–SiC capacitive sensors.

stable FET sensor devices. A wide variety of selectivity patterns are expected for the application of sensor arrays. To be successfully used in FET devices, the nanoparticle layers have to conduct reasonably well. A film of RuO2 nanoparticles was employed as gate material in capacitive devices and showed sensitivity to reducing gases. However, nanoparticles of Al2 O3 and SiO2 , impregnated with Pt, failed at this stage as sensing material due to poor electrical conductivity.

Acknowledgements

Fig. 8. Response pattern of RuO2 /SiOx /Si3 N4 /SiO2 /4H–SiC capacitive sensors to different gases.

several gases, especially those containing H atoms, for example, propene. It will be interesting to compare the selectivity pattern and other sensor features like speed of response for the layers of RuO2 nanoparticles to sputtered or evaporated RuO2 films. Furthermore, for MISiC capacitors, also Al2 O3 nanoparticles will be tested after improvement of the metal impregnation procedure to make them more conducting.

5. Conclusions Metal-oxide nanoparticles are potential candidates to be used as the gate material for high temperature, long-term

This work was supported by grants from the Swedish Research Council, the Swedish Agency for Innovation Systems and Swedish Industry through the Center of Excellence, SSENCE. We would like to thank Evald Mild, at Link¨oping University, Sweden, who performed the skillful mounting of the sensor chips.

References [1] A. Lloyd Spetz, S. Savage, Advances in FET chemical gas sensors, in: W.J. Choyke, H. Matsunami, G. Pensl (Eds.), Recent Major Advances in SiC, Springer, Berlin, 2003, pp. 879–906. [2] H. Wingbrant, H. Svenningstorp, P. Salomonsson, J. Visser, D. Kubinski, A. Lloyd Spetz, Using a MISiCFET sensor for detecting NH3 in SCR systems, in: Proceedings of the IEEE Sensors 2003, Toronto, Canada, October 22–24, 2003, pp. 428–433. [3] M. Andersson, P. Ljung, M. Mattsson, M. L¨ofdahl, A. Lloyd Spetz, Investigations on the possibilities of a MISiCFET sensor system

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of semiconducting materials and devices with the special emphasis on gas sensors. He has more than 20 research publications and a couple of patents to his credit.

Christian Aulin received his M.Sc. in physical/inorganic chemistry at Link¨oping University in 2004. Since then he has been working as a stipendiary in the computational chemistry group at the Department of Chemistry in Link¨oping.

Judith Cerd`a Belmonte received her Ph.D. in physics in 2003 at the University of Barcelona, Spain. Her research is in the field of chemical sensors and in chemical surface analysis methods. Nowadays she is a post-doc researcher at Michigan State University and Ford Motors.

Per-Olov K¨all received his Ph.D. in inorganic chemistry 1991 at the Department of Inorganic, Structural and Physical Chemistry at the Arrhenius Laboratory at Stockholm University. He became Associate Professor in 1996 and since that year he is also working as senior lecturer in chemistry at Link¨oping University. His main research interest is in materials chemistry where he has studied the structure and physical properties of silicon nitride based ceramics and magnetic transition metal oxides and oxy nitrides. Today he is mainly focused on nano chemistry. He has published about 35 scientific articles.

Lars Ojam¨ae received his Ph.D. in 1993 at the Institute of Chemistry, Uppsala University. Thereafter and until 1995 he did a Postdoc at the Ohio State University, Columbus, Ohio. From 1995 to 1996 he was employed as researcher at the Department of Quantum Chemistry, Uppsala University. In 1996 he was a Marie Curie EU fellowship-visiting researcher at the University of Turin, Italy. During 1996–2001 he held an Assistant Professorship position at the Department of Physical Chemistry, Stockholm University. In 2001 he joined the faculty at the Department of Chemistry, IFM, Link¨oping University, as Senior Lecturer in Physical Chemistry. In 2004 he became Associate Professor in Computational Chemistry at Link¨oping University, where his research group is utilizing quantum-chemical and molecular-simulation computational methods to investigate fundamental aspects of chemical reactions, catalysis, metaloxide surfaces, inorganic crystals, nanoparticles, solar cells, molecular liquids and chemical bonding. He is a member of the Swedish National Allocation Committee for HPC resources and of the Swedish Chemical Society.

Michael Strand received his Ph.D. in 2004, at the Department of Chemistry at V¨axj¨o University, Sweden. He is now working as a researcher at V¨axj¨o University. His main research interests concerns aerosol formation and emission from biomass combustion, as well as production of aerosol particles for technical applications.

Biographies Anette Salomonsson received her M.Sc. in physics from Link¨oping University in 1998. In 2003, she received a licentiate degree from Link¨oping University. Since then she has been has been working as a Ph.D. student at S-SENCE, Swedish Sensor Center, and Division of Applied Physics. Her research concerns fundamental studies of SiC-based capacitors.

Somenath Roy received his Ph.D. in materials science and engineering from Indian Institute of Technology, Kharagpur, India. Subsequently, he worked as a Project Officer in the same institute. He joined Swedish Sensor Centre, Link¨oping, Sweden as a Post-Doctoral Researcher in 2004. His research interest has been centered around growth and characterization

Mehri Sanati received her Ph.D. in chemical engineering at Lund Institute of Technology in Lund 1991. In 1999 she became an Associate Professor at the Division of Chemical Engineering at the Swedish royal Institute of Technology (KTH) and in 2000 Professor at V¨axj¨o University. Her present employment is as at V¨axj¨o University at the School of Technology and Design/Chemistry. The research activity of her group consists of aerosol science and aerosol technology, emission measurements of aerosol particles, particles formation mechanism and emission measurements on gas phase. She also works on control of the total oxidation resistance catalyst, and aerosol catalysis. She has been honored at V¨axj¨o University “Tore Danielsson stipendiefond” for the technical achievement, and she is a member of many committees. Mehri Sanati has published more than 100 papers in scientific journals and referenced conference proceedings and she has one patent.

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Anita Lloyd Spetz received her Ph.D. in 1989 at the Laboratory of Applied Physics in Link¨oping. In 1995 she became a docent and got in 1999 a lecturer position. From 2004 she is appointed Professor in Sensor Science, especially Chemical Sensors. From 1995 she has been working as a project leader at S-SENCE, Swedish Sensor Centre (centre of excellence). Her research group works on development, sensing mechanism and applications of silicon carbide based field effect high temperature sensors. The applications are performed in projects together with industry (Volvo Technological Development, Ford Research Laboratory, NIBE

Industries and Applied Sensor). From August 2000 she is employed 20% at Applied Sensor, as a senior specialist, working on commercialisation of field effect based chemical gas sensors. She is also involved in the development of resonator sensors based on piezoelectric materials like AlN. Anita Lloyd Spetz has published more than 100 papers in scientific journals and referenced conference proceedings and she has four patents. She is the board director of the Swedish Catalysis Society, and she is a member of the Swedish Vacuum Society.