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  • 1.
    Boyd, Robert
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska högskolan.
    Gunnarsson, Rickard
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska högskolan.
    Pilch, Iris
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska högskolan.
    Helmersson, Ulf
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska högskolan.
    Characterisation of Nanoparticle Structure by High Resolution Electron Microscopy2014Inngår i: Electron Microscopy and Analysis Group Conference  (EMAG2013), Institute of Physics Publishing (IOPP), 2014, Vol. 522, nr 012065, s. 012065-Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Whilst the use of microscopic techniques to determine the size distributions of nanoparticle samples is now well established, their characterisation challenges extend well beyond this. Here it is shown how high resolution electron microscopy can help meet these challenges. One of the key parameters is the determination of particle shape and structure in three dimensions. Here two approaches to determining nanoparticle structure are described and demonstrated. In the first scanning transmission electron microscopy combined with high angle annular dark field imaging (HAADF-STEM) is used to image homogenous nanoparticles, where the contrast is directly related to the thickness of the material in the electron beam. It is shown that this can be related to the three dimensional shape of the nano-object. High resolution TEM imaging, combined with fast Fourier transform (FFT) analysis, can determine the crystalline structure and orientation of nanoparticles as well as the presence of any defects. This combined approach allows the physical structure of a significant number of nano-objects to be characterised, relatively quickly.

    Fulltekst (pdf)
    fulltext
  • 2.
    Eriksson, Jens
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad sensorvetenskap. Linköpings universitet, Tekniska fakulteten.
    Puglisi, Donatella
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad sensorvetenskap. Linköpings universitet, Tekniska fakulteten.
    Strandqvist, Carl
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad sensorvetenskap. Linköpings universitet, Tekniska fakulteten. Graphensic AB Linköping, Sweden.
    Gunnarsson, Rickard
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska fakulteten.
    Ekeroth, Sebastian
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska fakulteten.
    Ivanov, Ivan Gueorguiev
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Helmersson, Ulf
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska fakulteten.
    Uvdal, Kajsa
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Molekylär ytfysik och nanovetenskap. Linköpings universitet, Tekniska fakulteten.
    Yakimova, Rositsa
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten. Graphensic AB Linköping, Sweden.
    Lloyd Spetz, Anita
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad sensorvetenskap. Linköpings universitet, Tekniska fakulteten.
    Modified Epitaxial Graphene on SiC for Extremely Sensitive andSelective Gas Sensors2016Inngår i: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 858, s. 1145-1148Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Two-dimensional materials offer a unique platform for sensing where extremely high sensitivity is a priority, since even minimal chemical interaction causes noticeable changes inelectrical conductivity, which can be used for the sensor readout. However, the sensitivity has to becomplemented with selectivity, and, for many applications, improved response- and recovery times are needed. This has been addressed, for example, by combining graphene (for sensitivity) with metal/oxides (for selectivity) nanoparticles (NP). On the other hand, functionalization or modification of the graphene often results in poor reproducibility. In this study, we investigate thegas sensing performance of epitaxial graphene on SiC (EG/SiC) decorated with nanostructured metallic layers as well as metal-oxide nanoparticles deposited using scalable thin-film depositiontechniques, like hollow-cathode pulsed plasma sputtering. Under the right modification conditions the electronic properties of the surface remain those of graphene, while the surface chemistry can betuned to improve sensitivity, selectivity and speed of response to several gases relevant for airquality monitoring and control, such as nitrogen dioxide, benzene, and formaldehyde.

  • 3. Bestill onlineKjøp publikasjonen >>
    Gunnarsson, Rickard
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska fakulteten.
    Controlling the growth of nanoparticles produced in a high power pulsed plasma2017Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Nanotechnology can profoundly benefit our health, environment and everyday life. In order to make this a reality, both technological and theoretical advancements of the nanomaterial synthesis methods are needed. A nanoparticle is one of the fundamental building blocks in nanotechnology and this thesis describes the control of the nucleation, growth and oxidation of titanium particles produced in a pulsed plasma. It will be shown that by controlling the process conditions both the composition (oxidationstate) and size of the particles can be varied. The experimental results are supported by theoretical modeling.

    If processing conditions are chosen which give a high temperature in the nanoparticle growth environment, oxygen was found to be necessary in order to nucleate the nanoparticles. The two reasons for this are 1: the lower vapor pressure of a titanium oxide cluster compared to a titanium cluster, meaning a lower probability of evaporation, and 2: the ability of a cluster to cool down by ejecting an oxygen atom when an oxygen molecule condenses on its surface. When the oxygen gas flow was slightly increased, the nanoparticle yield and oxidation state increased. A further increase caused a decrease in particle yield which is attributed to a slight oxidation ofthe cathode. By varying the oxygen flow, it was possible to control the oxidation state of the nanoparticles without fully oxidizing the cathode. Pure titanium nanoparticles could not be produced in a high vacuum system because oxygen containing gases such as residual water vapour have a profound influence on nanoparticle yield and composition. In an ultrahigh vacuum system titanium nanoparticles without significantoxygen contamination were produced by reducing the temperature of the growth environment and increasing the pressure of an argon-helium gas mixture within whichthe nanoparticles grew. The dimer formation rate necessary for this is only achievable at higher pressures. After a dimer has formed, it needs to grow by colliding with a titanium atom followed by cooling by collisions with multiple buffer gas atoms. The condensation event heats up the cluster to a temperature much higher than the gas temperature, where it is during a short time susceptible to evaporation. When the clusters’ internal energy has decreased by collisions with the gas to less than the energy required to evaporate a titanium atom, it is temporarily stable until the next condensation event occurs. The temperature difference by which the cluster has to cool down before it is temporarily stable is exactly as many kelvins as the gas temperature.The addition of helium was found to decrease the temperature of the gas, making it possible for nanoparticles of pure titanium to grow. The process window where this is possible was determined and the results presented opens up new possibilities to synthesize particles with a controlled contamination level and deposition rate.The size of the nanoparticles has been controlled by three means. The first is to change the electrical potential around the growth zone, which allows for size (diameter) control in the order of 25 to 75 nm without influencing the oxygen content of the particles. The second means is by increasing the pressure which decreases the ambipolar diffusion rate of the ions resulting in a higher growth material density. By doing this, the particle size can be increased from 50 to 250 nm, however the oxygen content also increases with increasing pressure when this is done in a high vacuum system. The last means of size control was by adding a helium flow to the process where higher flows resulted in smaller nanoparticle sizes.

    When changing the pressure in high vacuum, the morphology of the nanoparticles could be controlled. At low pressures, highly faceted near spherical particles were produced. Increasing the pressure caused the formation of cubic particles which appear to ‘fracture’ at higher pressures. At the highest pressure investigated, the particles became poly-crystalline with a cauliflower shape and this morphology was attributed to a lowad atom mobility.

    The ability to control the size, morphology and composition of the nanoparticles determines the success of applying the process to manufacture devices. In related work presented in this thesis it is shown that 150-200 nm molybdenum particles with cauliflower morphology were found to scatter light in which made them useful in photovoltaic applications, and the size of titanium dioxide nanoparticles were found to influence the selectivity of graphene based gas sensors.

    Delarbeid
    1. Synthesis of titanium-oxide nanoparticles with size and stoichiometry control
    Åpne denne publikasjonen i ny fane eller vindu >>Synthesis of titanium-oxide nanoparticles with size and stoichiometry control
    2015 (engelsk)Inngår i: Journal of nanoparticle research, ISSN 1388-0764, E-ISSN 1572-896X, Vol. 17, nr 9, s. 353-Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    Ti-O nanoparticles have been synthesized via hollow cathode sputtering in an Ar-O-2 atmosphere using high power pulsing. It is shown that the stoichiometry and the size of the nanoparticles can be varied independently, the former through controlling the O-2 gas flow and the latter by the independent biasing of two separate anodes in the growth zone. Nanoparticles with diameters in the range of 25-75 nm, and with different Ti-O compositions and crystalline phases, have been synthesized.

    sted, utgiver, år, opplag, sider
    Springer Verlag (Germany), 2015
    Emneord
    Titanium dioxide; TiO2; Reactive sputtering; Size control; Composition control; Gas flow sputtering; Aerosols
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-121300 (URN)10.1007/s11051-015-3158-3 (DOI)000360245300002 ()
    Merknad

    Funding Agencies|Knut and Alice Wallenberg foundation [KAW 2014.0276]; Swedish Research Council via the Linkoping Linneaus Environment LiLi-NFM [2008-6572]

    Tilgjengelig fra: 2015-09-16 Laget: 2015-09-14 Sist oppdatert: 2017-12-21
    2. The influence of pressure and gas flow on size and morphology of titanium oxide nanoparticles synthesized by hollow cathode sputtering
    Åpne denne publikasjonen i ny fane eller vindu >>The influence of pressure and gas flow on size and morphology of titanium oxide nanoparticles synthesized by hollow cathode sputtering
    Vise andre…
    2016 (engelsk)Inngår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 120, nr 4, s. 044308-Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    Titanium oxide nanoparticles have been synthesized via sputtering of a hollow cathode in an argon atmosphere. The influence of pressure and gas flow has been studied. Changing the pressure affects the nanoparticle size, increasing approximately proportional to the pressure squared. The influence of gas flow is dependent on the pressure. In the low pressure regime (107 amp;lt;= p amp;lt;= 143 Pa), the nanoparticle size decreases with increasing gas flow; however, at high pressure (p = 215 Pa), the trend is reversed. For low pressures and high gas flows, it was necessary to add oxygen for the particles to nucleate. There is also a morphological transition of the nanoparticle shape that is dependent on the pressure. Shapes such as faceted, cubic, and cauliflower can be obtained. Published by AIP Publishing.

    sted, utgiver, år, opplag, sider
    AMER INST PHYSICS, 2016
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-131710 (URN)10.1063/1.4959993 (DOI)000382405400029 ()
    Merknad

    Funding Agencies|Knut and Alice Wallenberg foundation [KAW 2014.0276]; Swedish Research Council via the Linkoping Linneaus Environment LiLi-NFM [2008-6572]

    Tilgjengelig fra: 2016-10-03 Laget: 2016-09-30 Sist oppdatert: 2017-12-21
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    presentationsbild
  • 4. Bestill onlineKjøp publikasjonen >>
    Gunnarsson, Rickard
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska fakulteten.
    Titanium oxide nanoparticle production using high power pulsed plasmas2016Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    This thesis covers fundamental aspects of process control when growing titanium oxide nanoparticles in a reactive sputtering process. It covers the influence of oxygen containing gas on the oxidation state of the cathode from which the growth material is ejected, as well as its influence on the particles oxidation state and their nucleation. It was found that a low degree of reactive gases was necessary for nanoparticles of titanium to nucleate. When the oxygen gas was slightly increased, the nanoparticle yield and particle oxygen content increased. A further increase caused a decrease in particle yield which was attributed to a slight oxidation of the cathode. By varying the oxygen flow to the process, it was possible to control the oxygen content of the nanoparticles without fully oxidizing the cathode. Because oxygen containing gases such as residual water vapour has a profound influence on nanoparticle yield and composition, the deposition source was re-engineered to allow for cleaner and thus more stable synthesis conditions.

    The size of the nanoparticles has been controlled by two means. The first is to change electrical potentials around the growth zone, which allows for nanoparticle size control in the order of 25-75 nm. This size control does not influence the oxygen content of the nanoparticles. The second means of size control investigated was by increasing the pressure. By doing this, the particle size can be increased from 50 – 250 nm, however the oxygen content also increases with pressure. Different particle morphologies were found by changing the pressure. At low pressures, mostly spherical particles with weak facets were produced. As the pressure increased, the particles got a cubic shape. At higher pressures the cubic particles started to get a fractured surface. At the highest pressure investigated, the fractured surface became poly-crystalline, giving a cauliflower shaped morphology.

    Delarbeid
    1. Synthesis of titanium-oxide nanoparticles with size and stoichiometry control
    Åpne denne publikasjonen i ny fane eller vindu >>Synthesis of titanium-oxide nanoparticles with size and stoichiometry control
    2015 (engelsk)Inngår i: Journal of nanoparticle research, ISSN 1388-0764, E-ISSN 1572-896X, Vol. 17, nr 9, s. 353-Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    Ti-O nanoparticles have been synthesized via hollow cathode sputtering in an Ar-O-2 atmosphere using high power pulsing. It is shown that the stoichiometry and the size of the nanoparticles can be varied independently, the former through controlling the O-2 gas flow and the latter by the independent biasing of two separate anodes in the growth zone. Nanoparticles with diameters in the range of 25-75 nm, and with different Ti-O compositions and crystalline phases, have been synthesized.

    sted, utgiver, år, opplag, sider
    Springer Verlag (Germany), 2015
    Emneord
    Titanium dioxide; TiO2; Reactive sputtering; Size control; Composition control; Gas flow sputtering; Aerosols
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-121300 (URN)10.1007/s11051-015-3158-3 (DOI)000360245300002 ()
    Merknad

    Funding Agencies|Knut and Alice Wallenberg foundation [KAW 2014.0276]; Swedish Research Council via the Linkoping Linneaus Environment LiLi-NFM [2008-6572]

    Tilgjengelig fra: 2015-09-16 Laget: 2015-09-14 Sist oppdatert: 2017-12-21
    Fulltekst (pdf)
    fulltext
    Download (pdf)
    omslag
    Download (jpg)
    presentationsbild
  • 5.
    Gunnarsson, Rickard
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska fakulteten.
    Brenning, Nils
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska fakulteten. KTH Royal Inst Technol, Sweden.
    Boyd, Robert
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska fakulteten.
    Helmersson, Ulf
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska fakulteten.
    Nucleation of titanium nanoparticles in an oxygen-starved environment. I: experiments2018Inngår i: Journal of Physics D: Applied Physics, ISSN 0022-3727, E-ISSN 1361-6463, Vol. 51, nr 45, artikkel-id 455201Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A constant supply of oxygen has been assumed to be necessary for the growth of titanium nanoparticles by sputtering. This oxygen supply can arise from a high background pressure in the vacuum system or from a purposely supplied gas. The supply of oxygen makes it difficult to grow metallic nanoparticles of titanium and can cause process problems by reacting with the target. We here report that growth of titanium nanoparticles in the metallic hexagonal titanium (alpha Ti) phase is possible using a pulsed hollow cathode sputter plasma and adding a high partial pressure of helium to the process instead of trace amounts of oxygen. The helium cools the process gas in which the nanoparticles nucleate. This is important both for the first dimer formation and the continued growth to a thermodynamically stable size. The parameter region, inside which the synthesis of nanoparticles is possible, is mapped out experimentally and the theory of the physical processes behind this process window is outlined. A pressure limit below which no nanoparticles were produced was found at 200 Pa, and could be attributed to a low dimer formation rate, mainly caused by a more rapid dilution of the growth material. Nanoparticle production also disappeared at argon gas flows above 25 sccm. In this case, the main reason was identified as a gas temperature increase within the nucleation zone, giving a too high evaporation rate from nanoparticles (clusters) in the stage of growth from dimers to stable nuclei. These two mechanisms are in depth explored in a companion paper. A process stability limit was also found at low argon gas partial pressures, and could be attributed to a transition from a hollow cathode discharge to a glow discharge.

    Fulltekst (pdf)
    fulltext
  • 6.
    Gunnarsson, Rickard
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska fakulteten.
    Brenning, Nils
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska fakulteten. KTH Royal Inst Technol, Sweden.
    Ojamäe, Lars
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Kemi. Linköpings universitet, Tekniska fakulteten.
    Kalered, Emil
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Kemi. Linköpings universitet, Tekniska fakulteten.
    Raadu, Michael Allan
    KTH Royal Inst Technol, Sweden.
    Helmersson, Ulf
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska fakulteten.
    Nucleation of titanium nanoparticles in an oxygen-starved environment. II: theory2018Inngår i: Journal of Physics D: Applied Physics, ISSN 0022-3727, E-ISSN 1361-6463, Vol. 51, nr 45, artikkel-id 455202Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The nucleation and growth of pure titanium nanoparticles in a low-pressure sputter plasma has been believed to be essentially impossible. The addition of impurities, such as oxygen or water, facilitates this and allows the growth of nanoparticles. However, it seems that this route requires such high oxygen densities that metallic nanoparticles in the hexagonal alpha Ti-phase cannot be synthesized. Here we present a model which explains results for the nucleation and growth of titanium nanoparticles in the absent of reactive impurities. In these experiments, a high partial pressure of helium gas was added which increased the cooling rate of the process gas in the region where nucleation occurred. This is important for two reasons. First, a reduced gas temperature enhances Ti-2 dimer formation mainly because a lower gas temperature gives a higher gas density, which reduces the dilution of the Ti vapor through diffusion. The same effect can be achieved by increasing the gas pressure. Second, a reduced gas temperature has a more than exponential effect in lowering the rate of atom evaporation from the nanoparticles during their growth from a dimer to size where they are thermodynamically stable, r*. We show that this early stage evaporation is not possible to model as a thermodynamical equilibrium. Instead, the single-event nature of the evaporation process has to be considered. This leads, counter intuitively, to an evaporation probability from nanoparticles that is exactly zero below a critical nanoparticle temperature that is size-dependent. Together, the mechanisms described above explain two experimentally found limits for nucleation in an oxygen-free environment. First, there is a lower limit to the pressure for dimer formation. Second, there is an upper limit to the gas temperature above which evaporation makes the further growth to stable nuclei impossible.

    Fulltekst (pdf)
    fulltext
  • 7.
    Gunnarsson, Rickard
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska fakulteten.
    Helmersson, Ulf
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska fakulteten.
    Pilch, Iris
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Synthesis of titanium-oxide nanoparticles with size and stoichiometry control2015Inngår i: Journal of nanoparticle research, ISSN 1388-0764, E-ISSN 1572-896X, Vol. 17, nr 9, s. 353-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Ti-O nanoparticles have been synthesized via hollow cathode sputtering in an Ar-O-2 atmosphere using high power pulsing. It is shown that the stoichiometry and the size of the nanoparticles can be varied independently, the former through controlling the O-2 gas flow and the latter by the independent biasing of two separate anodes in the growth zone. Nanoparticles with diameters in the range of 25-75 nm, and with different Ti-O compositions and crystalline phases, have been synthesized.

    Fulltekst (pdf)
    fulltext
  • 8.
    Gunnarsson, Rickard
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska fakulteten.
    Pilch, Iris
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Boyd, Robert
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska fakulteten.
    Brenning, Nils
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska fakulteten. KTH Royal Institute Technology, Sweden.
    Helmersson, Ulf
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska fakulteten.
    The influence of pressure and gas flow on size and morphology of titanium oxide nanoparticles synthesized by hollow cathode sputtering2016Inngår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 120, nr 4, s. 044308-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Titanium oxide nanoparticles have been synthesized via sputtering of a hollow cathode in an argon atmosphere. The influence of pressure and gas flow has been studied. Changing the pressure affects the nanoparticle size, increasing approximately proportional to the pressure squared. The influence of gas flow is dependent on the pressure. In the low pressure regime (107 amp;lt;= p amp;lt;= 143 Pa), the nanoparticle size decreases with increasing gas flow; however, at high pressure (p = 215 Pa), the trend is reversed. For low pressures and high gas flows, it was necessary to add oxygen for the particles to nucleate. There is also a morphological transition of the nanoparticle shape that is dependent on the pressure. Shapes such as faceted, cubic, and cauliflower can be obtained. Published by AIP Publishing.

    Fulltekst (pdf)
    fulltext
  • 9.
    Rodner, Marius
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Sensor- och aktuatorsystem. Linköpings universitet, Tekniska fakulteten.
    Bahonjic, Jasna
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Sensor- och aktuatorsystem. Linköpings universitet, Tekniska fakulteten.
    Mathisen, Marcus
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Sensor- och aktuatorsystem. Linköpings universitet, Tekniska fakulteten.
    Gunnarsson, Rickard
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och ytbeläggningsfysik. Linköpings universitet, Tekniska fakulteten.
    Ekeroth, Sebastian
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och ytbeläggningsfysik. Linköpings universitet, Tekniska fakulteten.
    Helmersson, Ulf
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och ytbeläggningsfysik. Linköpings universitet, Tekniska fakulteten.
    Ivanov, Ivan Gueorguiev
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Yakimova, Rositsa
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Eriksson, Jens
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Sensor- och aktuatorsystem. Linköpings universitet, Tekniska fakulteten.
    Performance tuning of gas sensors based on epitaxial graphene on silicon carbide2018Inngår i: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 153, s. 153-158Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this study, we investigated means of performance enhancement in sensors based on epitaxial graphene on silicon carbide (SiC). Epitaxially grown graphene on SiC substrates were successfully decorated with metal oxide nanoparticles such as TiO2 and Fe3O4 using hollow cathode pulsed plasma sputtering. Atomic Force Microscopy and Raman data verified that no damage was added to the graphene surface. It could be shown that it was easily possible to detect benzene, which is one of the most dangerous volatile organic compounds, with the Fe3O4 decorated graphene sensor down to an ultra-low concentration of 5 ppb with a signal to noise ratio of 35 dB. Moreover, upon illumination with a UV light LED (265 nm) of the TiO2 decorated graphene sensor, the sensitivity towards a change of oxygen could be enhanced such that a clear sensor response could be seen which is a significant improvement over dark conditions, where almost no response occurred. As the last enhancement, the time derivative sensor signal was introduced for the sensor data evaluation, testing the response towards a change of oxygen. This sensor signal evaluation approach can be used to decrease the response time of the sensor by at least one order of magnitude. (C) 2018 Elsevier Ltd. All rights reserved.

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  • 10.
    Vermang, Bart
    et al.
    Uppsala University, Sweden; University of Leuven, Belgium.
    Timo Watjen, Jorn
    Uppsala University, Sweden.
    Fjallstrom, Viktor
    Uppsala University, Sweden.
    Rostvall, Fredrik
    Uppsala University, Sweden.
    Edoff, Marika
    Uppsala University, Sweden.
    Gunnarsson, Rickard
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska högskolan.
    Pilch, Iris
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska fakulteten.
    Helmersson, Ulf
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska högskolan.
    Kotipalli, Ratan
    Catholic University of Louvain, Belgium.
    Henry, Frederic
    Catholic University of Louvain, Belgium.
    Flandre, Denis
    Catholic University of Louvain, Belgium.
    Highly reflective rear surface passivation design for ultra-thin Cu(In,Ga) Se-2 solar cells2015Inngår i: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 582, s. 300-303Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Al2O3 rear surface passivated ultra-thin Cu(In,Ga)Se-2 (CIGS) solar cells with Mo nano-particles (NPs) as local rear contacts are developed to demonstrate their potential to improve optical confinement in ultra-thin CIGS solar cells. The CIGS absorber layer is 380 nm thick and the Mo NPs are deposited uniformly by an up-scalable technique and have typical diameters of 150 to 200 nm. The Al2O3 layer passivates the CIGS rear surface between the Mo NPs, while the rear CIGS interface in contact with the Mo NP is passivated by [Ga]/([Ga] + [In]) (GGI) grading. It is shown that photon scattering due to the Mo NP contributes to an absolute increase in short circuit current density of 3.4 mA/cm(2); as compared to equivalent CIGS solar cells with a standard back contact.

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