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Thungström, Göran
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Publications (10 of 98) Show all publications
Ashraf, S., Niskanen, I., Kanyathare, B., Vartiainen, E., Mattsson, C., Heikkilä, R. & Thungström, G. (2019). Determination of complex refractive index of SU-8 by Kramers-Kronig dispersion relation method at the wavelength range 2.5 – 22.0 μm. Journal of Quantitative Spectroscopy and Radiative Transfer, 224, 309-311
Open this publication in new window or tab >>Determination of complex refractive index of SU-8 by Kramers-Kronig dispersion relation method at the wavelength range 2.5 – 22.0 μm
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2019 (English)In: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 224, p. 309-311Article in journal (Refereed) Published
Abstract [en]

Accurate determination of the complex refractive index of SU-8 epoxy has significant for the wide variety of applications in optical sensor technology at IR range. The complex refractive index of SU-8 is determined by recording the transmission of light spectra for the wavelength range of 2.5 – 22.0 μm.  The data analysis is based on the Kramers-Kronig dispersion relation method. The method has several merits, such as ease of operation, non-contact technique, measurement accuracy, and rapid measurement. The present method is not restricted to the case of SU-8 but it is also proposed to be applicable across a broad range of applications, such as assessment of the optical properties of paints and biomedical samples.

Keywords
Complex refractive index, SU-8 epoxy, Kramers-Kronig dispersion relation method, FT-IR spectrophotometer, Infrared region
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:miun:diva-34927 (URN)10.1016/j.jqsrt.2018.11.026 (DOI)000456754800034 ()2-s2.0-85057277091 (Scopus ID)
Available from: 2018-11-21 Created: 2018-11-21 Last updated: 2019-03-18Bibliographically approved
Niskanen, I., Forsberg, V., Zakrisson, D., Reza, S., Hummelgård, M., Andres, B., . . . Thungström, G. (2019). Determination of nanoparticle size using Rayleigh approximation and Mie theory. Chemical Engineering Science, 201(29), 222-229
Open this publication in new window or tab >>Determination of nanoparticle size using Rayleigh approximation and Mie theory
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2019 (English)In: Chemical Engineering Science, ISSN 0009-2509, E-ISSN 1873-4405, Vol. 201, no 29, p. 222-229Article in journal (Refereed) Published
Abstract [en]

Accurate determination of the size of nanoparticles has an important role in many different scientific and industrial purposes, such as in material, medical and environment sciences, colloidal chemistry and astrophysics. We describe an effective optical method to determine the size of nanoparticles by analysis of transmission and scattering of visible spectral range data from a designed UV-Vis multi-spectrophotometer. The size of the nanoparticles was calculated from the extinction cross section of the particles using Rayleigh approximation and Mie theory. We validated the method using polystyrene nanospheres, cellulose nanofibrils, and cellulose nanocrystals. A good agreement was achieved through graphical analysis between measured extinction cross section values and theoretical Rayleigh approximation and Mie theory predictions for the sizes of polystyrene nanospheres at wavelength range 450 - 750 nm. Provided that Rayleigh approximation's forward scattering (FS)/back scattering (BS) ratio was smaller than 1.3 and Mie theory's FS/BS ratio was smaller than 1.8. A good fit for the hydrodynamic diameter of nanocellulose was achieved using the Mie theory and Rayleigh approximation. However, due to the high aspect ratio of nanocellulose, the obtained results do not directly reflect the actual cross-sectional diameters of the nanocellulose. Overall, the method is a fast, relatively easy, and simple technique to determine the size of a particle by a spectrophotometer. Consequently, the method can be utilized for example in production and quality control purposes as well as for research and development applications.

Keywords
Nanoparticles, size, Rayleigh approximation, Mie theory, spectrophotometer, nanocellulose
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:miun:diva-35764 (URN)10.1016/j.ces.2019.02.020 (DOI)000462034900020 ()2-s2.0-85062846560 (Scopus ID)
Available from: 2019-03-08 Created: 2019-03-08 Last updated: 2019-05-20Bibliographically approved
Niskanen, I., Suopajärvi, T., Liimatainen, H., Fabritius, T., Heikkilä, R. & Thungström, G. (2019). Determining the complex refractive index of cellulose nanocrystals by combination of Beer-Lambert and immersion matching methods. Journal of Quantitative Spectroscopy and Radiative Transfer, 235, 1-6
Open this publication in new window or tab >>Determining the complex refractive index of cellulose nanocrystals by combination of Beer-Lambert and immersion matching methods
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2019 (English)In: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 235, p. 1-6Article in journal (Refereed) Published
Abstract [en]

Nanocelluloses have received significant interest due to their unique structural, mechanical, and optical properties. Nanocellulose refractive indices can be used to indicate many crucial characteristics, such as crystallinity, transparency, and purity. Thus, accurate measurement is important. This study describes a new method to determine the wavelength dependent complex refractive index of cellulose nanocrystals (CNCs) by the measurement of light transmittance with a spectrophotometer. The data analysis is based on a combination of the Beer-Lambert and immersion liquid matching equations. The immersion liquid method's main advantage is that it is independent of particle shape and size. Moreover, the measurement is easy and relatively quick to perform. The present procedure is not restricted to the nanocellulose and could potentially be applied to other nanomaterials, such as hyphenate nanoparticle-based, lignin nanoparticles, nanopigments, biological entities, structural elements of dielectric metamaterials, and nanoparticle-based composites. 

Place, publisher, year, edition, pages
Elsevier Ltd, 2019
Keywords
Beer-Lambert, Cellulose nanocrystals, Complex refractive index, Immersion matching method, Spectroscopy, Cellulose, Cellulose derivatives, Crystallinity, Nanocellulose, Nanocrystals, Nanoparticles, Particle size analysis, Accurate measurement, Cellulose nano-crystals, Cellulose nanocrystal (CNCs), Immersion liquid methods, Matching methods, Particle shape and size, Refractive index
Identifiers
urn:nbn:se:miun:diva-36688 (URN)10.1016/j.jqsrt.2019.06.023 (DOI)2-s2.0-85067548357 (Scopus ID)
Available from: 2019-07-09 Created: 2019-07-09 Last updated: 2019-07-09Bibliographically approved
Ashraf, S., Mattsson, C. & Thungström, G. (2019). Fabrication and characterization of a SU8-epoxy membrane based thermopile detector with an integrated multilayered absorber structure for the mid-IR region. IEEE Sensors Journal, 19(11), 4000-4007
Open this publication in new window or tab >>Fabrication and characterization of a SU8-epoxy membrane based thermopile detector with an integrated multilayered absorber structure for the mid-IR region
2019 (English)In: IEEE Sensors Journal, ISSN 1530-437X, E-ISSN 1558-1748, Vol. 19, no 11, p. 4000-4007Article in journal (Refereed) Published
Abstract [en]

This paper reports on the fabrication and characterization of a thermopile detector with an integrated mid-infrared absorber structure. The fabricated absorber structure has shown an absorption of more than 95% in the wavelength range of 3.2 – 5.47 μm. The detector was fabricated with standard cleanroom process techniques and equipment. The serial resistance was measured at about 315 kΩ at room temperature. The photosensitivity of the detector was characterized for a signle wavelength (4.26 µm) and a band of wavelength ranging from 2.5 –5.5 µm through two different measurement setups. In the first measurement setup, the photosensitivity was estimated at 57.5 V·mm2·W-1 through a MEMS-based infrared radiation source and with an optical band-pass filter of wavelength 4.26µm. The following characterization was performed to characterise the photosensitivity of the detector in a broader wavelength range. This measurement was taken using a monochromator setup utilizing a reference photodetector for calculations of the optical power of the infrared source. The photosensitivity and the specific detectivity (D*) of the fabricated detector were measured to values of 30-92 V·W-1 and 8.0×107-2.4×108 cm·Hz1/2·W-1, respectively, in the wavelength range of 2.8 – 5 µm. The time constant was estimated to around 21 ms

Keywords
Interfermometric absorber, Thermopile, Infrared detector, SU8 epoxy, photosensitivity, Transfer matrix theory, CO2 detection
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:miun:diva-35525 (URN)10.1109/JSEN.2019.2896668 (DOI)000467060100005 ()2-s2.0-85065396140 (Scopus ID)
Available from: 2019-01-25 Created: 2019-01-25 Last updated: 2019-07-09Bibliographically approved
Andersson, H., Šuly, P., Thungström, G., Engholm, M., Zhang, R., Mašlík, J. & Olin, H. (2019). PEDOT: PSS thermoelectric generators printed on paper substrates. Journal of Low Power Electronics and Applications, 9(2)
Open this publication in new window or tab >>PEDOT: PSS thermoelectric generators printed on paper substrates
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2019 (English)In: Journal of Low Power Electronics and Applications, ISSN 2079-9268, Vol. 9, no 2Article in journal (Refereed) Published
Abstract [en]

Flexible electronics is a field gathering a growing interest among researchers and companies with widely varying applications, such as organic light emitting diodes, transistors as well as many different sensors. If the circuit should be portable or off-grid, the power sources available are batteries, supercapacitors or some type of power generator. Thermoelectric generators produce electrical energy by the diffusion of charge carriers in response to heat flux caused by a temperature gradient between junctions of dissimilar materials. As wearables, flexible electronics and intelligent packaging applications increase, there is a need for low-cost, recyclable and printable power sources. For such applications, printed thermoelectric generators (TEGs) are an interesting power source, which can also be combined with printable energy storage, such as supercapacitors. Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate), or PEDOT:PSS, is a conductive polymer that has gathered interest as a thermoelectric material. Plastic substrates are commonly used for printed electronics, but an interesting and emerging alternative is to use paper. In this article, a printed thermoelectric generator consisting of PEDOT:PSS and silver inks was printed on two common types of paper substrates, which could be used to power electronic circuits on paper. 

Keywords
Paper substrates, PEDOT:PSS, Seebeck coefficient, Stencil print, Thermoelectric generator
Identifiers
urn:nbn:se:miun:diva-36667 (URN)10.3390/jlpea9020014 (DOI)2-s2.0-85065493304 (Scopus ID)
Available from: 2019-07-09 Created: 2019-07-09 Last updated: 2019-07-09Bibliographically approved
Soetedjo, H., Niskanen, I., Rautkari, L., Altgen, M., Hiltunen, E., Thungström, G., . . . Räty, J. (2018). Determining the degree of heat treatment of wood by light polarization technique. European Journal of Wood and Wood Products, 76(4), 1359-1362
Open this publication in new window or tab >>Determining the degree of heat treatment of wood by light polarization technique
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2018 (English)In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 76, no 4, p. 1359-1362Article in journal (Refereed) Published
Abstract [en]

Thermal modification of wood enables the use of non-durable wood species in exterior applications, but quality control methods are required to monitor the product variability. This study tests the potential of a light polarization technique where visible light (400–500 nm) is directed through a linear polarizer to the surface of thermally modified wood to measure the reflectance. Besides an effect of the grain direction, the reflectance decreased with increasing temperature during the thermal modification process. The technique could be used for quality control, but further studies are required to understand its modes of action. 

National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:miun:diva-33664 (URN)10.1007/s00107-018-1311-2 (DOI)000435782200029 ()2-s2.0-85045912828 (Scopus ID)
Available from: 2018-05-23 Created: 2018-05-23 Last updated: 2019-03-15Bibliographically approved
Ashraf, S., Mattsson, C., Thungström, G., Gaynullin, B. & Rödjegård, H. (2018). Evaluation of a CO2 sensitive thermopile with an integrated multilayered infrared absorber by using a long path length NDIR platform. In: I2MTC 2018 - 2018 IEEE International Instrumentation and Measurement Technology Conference: Discovering New Horizons in Instrumentation and Measurement, Proceedings. Paper presented at 2018 IEEE International Instrumentation and Measurement Technology Conference, I2MTC 2018, Houston, United States, 14 May 2018 through 17 May 2018 (pp. 1-6). IEEE
Open this publication in new window or tab >>Evaluation of a CO2 sensitive thermopile with an integrated multilayered infrared absorber by using a long path length NDIR platform
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2018 (English)In: I2MTC 2018 - 2018 IEEE International Instrumentation and Measurement Technology Conference: Discovering New Horizons in Instrumentation and Measurement, Proceedings, IEEE, 2018, p. 1-6Conference paper, Published paper (Refereed)
Abstract [en]

In this work, a mid-infrared-sensitive thermopile detector was evaluated for carbon dioxide gas. The thermopile has an integrated absorber structure that has more than 95% absorption for the wavelength range of 3.3-5.5 μm. For the measurement of carbon dioxide, the detector was initially assembled on a small printed circuit board holder and then installed in a long path length non-dispersive infrared platform. The measurement setup was calibrated by exposing the detector to carbon dioxide of known concentrations (from 50 ppm to 1,300 ppm) and measuring the corresponding voltage response of the detector. The measured voltage values allowed us to calculate the calibration constant for this detector. This was followed by a verification process using a concentration of 500 ppm (which was not used in the calibration) and a known value of 1,300 ppm. The verification results matched with real values, demonstrating that the sensor can be used for highly sensitive and accurate carbon dioxide measurements at concentrations from a few ppm level up to 1,300 ppm. Above this level, additional calibration is needed. 

Place, publisher, year, edition, pages
IEEE, 2018
Keywords
Carbon dioxide gas measurement, LPL-NDIR sensor, Thermopile detector
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:miun:diva-34564 (URN)10.1109/I2MTC.2018.8409758 (DOI)2-s2.0-85050722432 (Scopus ID)9781538622223 (ISBN)
Conference
2018 IEEE International Instrumentation and Measurement Technology Conference, I2MTC 2018, Houston, United States, 14 May 2018 through 17 May 2018
Available from: 2018-10-01 Created: 2018-10-01 Last updated: 2018-10-15Bibliographically approved
Niskanen, I., Sutinen, V., Thungström, G. & Räty, J. (2018). Image Information Obtained Using a Charge-Coupled Device (CCD) Camera During an Immersion Liquid Evaporation Process for Measuring the Refractive Index of Solid Particles. Applied Spectroscopy, 72(6), 908-912
Open this publication in new window or tab >>Image Information Obtained Using a Charge-Coupled Device (CCD) Camera During an Immersion Liquid Evaporation Process for Measuring the Refractive Index of Solid Particles
2018 (English)In: Applied Spectroscopy, ISSN 0003-7028, E-ISSN 1943-3530, Vol. 72, no 6, p. 908-912Article in journal (Refereed) Published
Abstract [en]

The refractive index is a fundamental physical property of a medium, which can be used for the identification and purity issues of all media. Here we describe a refractive index measurement technique to determine simultaneously the refractive index of different solid particles by monitoring the transmittance of light from a suspension using a charge-coupled device (CCD) camera. An important feature of the measurement is the liquid evaporation process for the refractive index matching of the solid particle and the immersion liquid; this was realized by using a pair of volatile and non-volatile immersion liquids. In this study, refractive indices of calcium fluoride (CaF2) and barium fluoride (BaF2) were determined using the proposed method.

Keywords
BaF2, barium fluoride, CaF2, calcium fluoride, CCD camera, charge-coupled device camera, evaporation, image immersion liquid method, liquid mixture, Refractive index
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:miun:diva-33666 (URN)10.1177/0003702818756660 (DOI)000434314700010 ()29336586 (PubMedID)2-s2.0-85046036635 (Scopus ID)
Available from: 2018-05-23 Created: 2018-05-23 Last updated: 2019-03-15Bibliographically approved
Thungström, G., Lundgren, A., Menk, R. H., Westerberg, L. & Fröjdh, C. (2018). Investigation of radiation hardness in lateral position sensitive detector, irradiated with 13.5 nm photons. Paper presented at 20th International Workshop on Radiation Imaging Detectors, Sundsvall, SWEDEN, JUN 24-28, 2018. Journal of Instrumentation, 13, Article ID C12015.
Open this publication in new window or tab >>Investigation of radiation hardness in lateral position sensitive detector, irradiated with 13.5 nm photons
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2018 (English)In: Journal of Instrumentation, ISSN 1748-0221, E-ISSN 1748-0221, Vol. 13, article id C12015Article in journal (Refereed) Published
Abstract [en]

Radiation hardness measurements have been done by irradiating lateral position sensitive (Si) detectors (LPSD) with 93 eV photons. Three different passivation layers have been investigated, SiO2, oxynitride and deposited 4 nm titanium-layer, on p in n-substrate LPSD and deposited 4 nm titanium layer on n in p-substrate LPSD. Best radiation hardness for 93 eV photon is obtained by using a 4 nm titanium layer. Only a slight decrease in response can be seen in the p in n-substrate LPSD. The best radiation hardness is achieved by using the n in p-substrate LPSD, which show no significant decrease in response. Scanning after irradiation with 93 eV gives only a variation in response of 0.26% in the surrounding area of exposure. No decrease in response can be detected during the scan. Test with a 108 eV photon beam gives an increased variation in response of 0.7%, caused by the shallower absorption in Si.

Keywords
Materials for solid-state detectors, Photon detectors for UV, visible and IR photons (vacuum), Radiation-hard detectors
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:miun:diva-35398 (URN)10.1088/1748-0221/13/12/C12015 (DOI)000453207800002 ()2-s2.0-85059896139 (Scopus ID)
Conference
20th International Workshop on Radiation Imaging Detectors, Sundsvall, SWEDEN, JUN 24-28, 2018
Available from: 2019-01-08 Created: 2019-01-08 Last updated: 2019-03-15Bibliographically approved
Forsberg, V., Andersson, H., Engholm, M., Thungström, G., Zhang, R., Hummelgård, M., . . . Norgren, M. (2018). Photodetector of multilayer exfoliated MoS2 deposited on polyimide films. In: : . Paper presented at 20th International Workshop on Radiation Imaging Detectors, Sundsvall, 24-28 June, 2018.
Open this publication in new window or tab >>Photodetector of multilayer exfoliated MoS2 deposited on polyimide films
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2018 (English)Conference paper, Poster (with or without abstract) (Other academic)
Abstract [en]

We fabricated a photodetector based on multilayer molybdenum disulfide (MoS2) by micromechanical cleavage of a molybdenite crystal using a polyimide film. We deposited 40 nm of gold by vacuum sputtering and copper tape was used for the contacts.  Without any surface treatment, we achieved high responsivity at different incident optical power. The calculated responsivity was 23 mA/W of incident optical power in the range between 400 and 800 nm. For the responsivity measurement it was estimated that MoS2 have a bandgap of 1.6 eV, which lies between monolayer and multilayer films. The thickness of the MoS2 thin film was determined by Raman spectroscopy evaluating the difference between the in plane  and out of plane  Raman modes. The measurement of IV curves indicated Ohmic contacts in respect to the Au regardless of the incident optical power. Our device fabrication was much simpler than previous reported devices and can be used to test the light absorption and luminescence capabilities of exfoliated MoS2.

Keywords
Photodetector, MoS2
National Category
Chemical Engineering Materials Engineering Physical Sciences
Identifiers
urn:nbn:se:miun:diva-34035 (URN)
Conference
20th International Workshop on Radiation Imaging Detectors, Sundsvall, 24-28 June, 2018
Funder
Knowledge Foundation, 2600364
Available from: 2018-06-29 Created: 2018-06-29 Last updated: 2018-08-16Bibliographically approved
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