Modified Epitaxial Graphene on SiC for Extremely Sensitive and Selective Gas Sensors

Eriksson, Jens; Puglisi, Donatella; Strandqvist, Carl; Gunnarsson, Rickard; Ekeroth, Sebastian; Ivanov, Ivan Gueorguiev; Helmersson, Ulf; Yakimova, Rositsa; Spetz, Anita Lloyd

doi:10.4028/www.scientific.net/msf.858.1145

Cited by 12 publications

(17 citation statements)

References 8 publications

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“…This, together with response times of less than a minute, makes the Fe nanoparticle coated, graphene-based gas sensor a promising candidate for air quality monitoring. [36], [37], [38] Chapter 6…”

Section: Gas Sensorsmentioning

confidence: 99%

Plasma Synthesis and Self-Assembly of Magnetic Nanoparticles

Ekeroth

2019

Linköping Studies in Science and Technology. Dissertations

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ii Cover image: Fe nanoparticles collected into nanotrusses on top, and around the edges, of a Si wafer. Abstract Nanomaterials are important tools for enabling technological progress as they can provide dramatically different properties as compared to the bulk counterparts. The field of nanoparticles is one of the most investigated within nanomaterials, thanks to the existing, relatively simple, means of manufacturing. In this thesis, high-power pulsed hollow cathode sputtering is used to nucleate and grow magnetic nanoparticles in a plasma. This sputtering technique provides a high degree of ionization of the sputtered material, which has previously been shown to aid in the growth of the nanoparticles. The magnetic properties of the particles are utilized and makes it possible for the grown particles to act as building blocks for selfassembly into more sophisticated nanostructures, particularly when an external magnetic field is applied. These structures created are termed "nanowires" or "nanotrusses", depending on the level of branching and inter-linking that occurs.Several different elements have been investigated in this thesis. In a novel approach, it is shown how nanoparticles with more advanced structures, and containing material from two hollow cathodes, can be fabricated using high-power pulses. The dual-element particles are achieved by using two distinct and individual elemental cathodes, and a pulse process that allows tuning of individual pulses separately to them. Nanoparticles grown and investigated are Fe, Ni, Pt, Fe-Ni and Ni-Pt. Alternatively, the addition of oxygen to the process allows the formation of oxide or hybrid metal oxidemetal particles. For all nanoparticles containing several elements, it is demonstrated that the stoichiometry can be easily varied, either by the amount of reactive gas let into the process or by tuning the amount of sputtered material through adjusting the electric power supplied to the different cathodes.One aim of the presented work is to find a suitable material for the use as a catalyst in the production of H2 gas through the process of water splitting. H2 is a good candidate to replace fossil fuels as an energy carrier. However, rare elements (such as Ir or Pt) needs to be used as the catalyst, otherwise a high overpotential is required for the splitting to occur, leading to a low efficiency. This work demonstrates a possible route to avoid this, by using nanomaterials to increase the surface-to-volume ratio, as well as optimizing the elemental ratio between different materials to lower the amount of noble elements required.iv v

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Section: Gas Sensorsmentioning

confidence: 99%

Plasma Synthesis and Self-Assembly of Magnetic Nanoparticles

Ekeroth

2019

Linköping Studies in Science and Technology. Dissertations

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“…This was especially studied using graphene as transducer due to its very good sensing properties. For example, it has been shown that decorating the graphene surface with metal or metal oxide nanoparticles can lead to an increased sensitivity and selectivity towards gases like nitrogen dioxide (NO2), C6H6 and CH2O [6]. Moreover, iron oxide decorated multiwall carbon nanotubes, a close relative to graphene, in combination with UV (ultraviolet) irradiation [7], and zinc oxide fibers [8] exhibit promising sensitivity towards C6H6.…”

Section: Marius Rodner Linköping August 2019mentioning

confidence: 99%

“…An exemplary histogram of the particle size distribution is discussed in [Paper 2]. The particle size can have an impact on the sensor's sensitivity and selectivity and thus is another parameter that can be optimized for sensors performance tuning [6]. This was, however, not investigated in this work.…”

Section: Marius Rodner Linköping August 2019mentioning

confidence: 99%

Towards a versatile gas sensing platform with epitaxial graphene

Rodner

2019

Linköping Studies in Science and Technology. Licentiate Thesis

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The work presented in this thesis focuses on how to utilize epitaxially grown graphene on SiC as a basis for ultra-sensitive gas sensor. Several approaches have been tested and evaluated to increase the sensitivity, selectivity, speed of response and stability and of the graphene based gas sensors with a focus on air quality monitoring applications. The graphene surfaces have been functionalized with different metal oxide nanoparticles and nanolayers using hollowcathode sputtering and pulsed laser deposition. The modified surface was investigated towards its topography, integrity and chemical composition with characterization methods such as AFM, Raman and XPS. Moreover, the binding energy was calculated with density functional theory for benzene and formaldehyde when reacting with pristine epitaxial graphene and iron oxide nanoparticle decorated graphene to verify the usefulness of this approach. The impact of environmental influences such as operating temperature, relative humidity and UV irradiation towards sensing properties was investigated as well. To further decrease time constants, the first-order time-derivative of the sensor's resistance is introduced as an alternative sensor signal and evaluated towards its applicability. Applying these methods in laboratory conditions, sensors with a quantitative readout of single ppb benzene and formaldehyde were developed and time constants of less than one minute could be achieved with the first-order time-derivative signal. These results show promise to fill the existing gap of low-cost but highly sensitive and fast gas sensors for air quality monitoring. v

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“…It was found that the sensors selectivity depended on the size of the nanoparticles. The sample with ≤10 nm particles was selective towards formaldehyde while the 50 nm particles were selective towards benzene [71]. These results show that by applying the insights from paper 1, this nanoparticle synthesis process can be used to tune the properties of graphene.…”

Section: Solar Cells With Molybdenum Particlesmentioning

confidence: 64%

“…The idea of this work was to increase the selectivity by adding titanium dioxide nanoparticles on top of the graphene layer. One concern was whether this would damage the graphene layer, which had been observed when growing metal islands on top of the graphene layer by conventional magnetron sputtering [71].…”

Section: Solar Cells With Molybdenum Particlesmentioning

confidence: 99%

Controlling the growth of nanoparticles produced in a highpower pulsed plasma

Gunnarsson¹

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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 (oxidation state) 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 of the 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 significant oxygen contamination were produced by reducing the temperature of the growth environment and increasing the pressure of an argon-helium gas mixture within which the 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 iv 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 electr...

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Modified Epitaxial Graphene on SiC for Extremely Sensitive and Selective Gas Sensors

Cited by 12 publications

References 8 publications

Plasma Synthesis and Self-Assembly of Magnetic Nanoparticles

Plasma Synthesis and Self-Assembly of Magnetic Nanoparticles

Towards a versatile gas sensing platform with epitaxial graphene

Controlling the growth of nanoparticles produced in a highpower pulsed plasma

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