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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
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
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
Gaynullin, B., Bryzgalov, M., Hummelgård, C., Mattsson, C., Rödjegård, H. & Thungström, G. (2017). Pressure characterization and resolution limits' investigation of high accuracy NDIR Methane sensor for environmental applications. In: : . Paper presented at 14th International Workshop on Advanced Infrared Technology and Applications, AITA 2017, Québec City, Canada, September 27-29, 2017.
Open this publication in new window or tab >>Pressure characterization and resolution limits' investigation of high accuracy NDIR Methane sensor for environmental applications
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2017 (English)Conference paper, Oral presentation with published abstract (Refereed)
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:miun:diva-32634 (URN)
Conference
14th International Workshop on Advanced Infrared Technology and Applications, AITA 2017, Québec City, Canada, September 27-29, 2017
Available from: 2018-01-02 Created: 2018-01-02 Last updated: 2018-01-03Bibliographically approved
Ashraf, S., Mattsson, C. & Thungström, G. (2016). Fabrication of a mid-Ir sensitive thermopile detector. In: Proceedings of IEEE Sensors: . Paper presented at 15th IEEE Sensors Conference, SENSORS 2016; Convention Center at the Caribe Royale HotelOrlando; United States; 30 October 2016 through 2 November 2016. IEEE, Article ID 7808481.
Open this publication in new window or tab >>Fabrication of a mid-Ir sensitive thermopile detector
2016 (English)In: Proceedings of IEEE Sensors, IEEE, 2016, article id 7808481Conference paper, Published paper (Refereed)
Abstract [en]

This paper reports on the integration of a multilayered mid-infrared absorber structure into a SU-8 epoxy membrane-based thermopile detector. The absorber structure was designed and simulated using transfer matrix theory. The fabricated absorber structures were characterized through Fourier transform infrared spectroscopy. The structure shows an absorption of more than 95% in the wavelength range of 3.30pm–5pm for simulations, and 3.2pm–5.47pm for FTIR measurements. The complete fabrication process of a thermopile detector including the integration of a multilayered absorber structure has been presented. A MEMS based infrared emitter was used to characterize the fabricated detector. The serial resistance was measured to 315 kΩ and the responsivity was calculated to 57.5 Vmm2W−1 at a wavelength of 4.26pm. The time constant for the fabricated detector was estimated to around 21ms.

Place, publisher, year, edition, pages
IEEE, 2016
Series
IEEE Sensors, ISSN 1930-0395
Keywords
Detectors, Voltage measurement, Fabrication, Absorption, Electrical resistance measurement, Wavelength measurement, Resistance
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:miun:diva-29547 (URN)10.1109/ICSENS.2016.7808481 (DOI)000399395700076 ()2-s2.0-85011003061 (Scopus ID)STC (Local ID)978-1-4799-8287-5 (ISBN)STC (Archive number)STC (OAI)
Conference
15th IEEE Sensors Conference, SENSORS 2016; Convention Center at the Caribe Royale HotelOrlando; United States; 30 October 2016 through 2 November 2016
Available from: 2017-01-17 Created: 2016-12-13 Last updated: 2018-10-15Bibliographically approved
Gaynullin, B., Hummelgård, C., Mattsson, C., Rödjegård, H. & Thungström, G. (2015). Comparative study of CO2 and CH4 pressure dependence in the HPP NDIR platform. In: : . Paper presented at 2015th FPIRC International Summer Conference.
Open this publication in new window or tab >>Comparative study of CO2 and CH4 pressure dependence in the HPP NDIR platform
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2015 (English)Conference paper, Oral presentation only (Other academic)
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:miun:diva-32636 (URN)
Conference
2015th FPIRC International Summer Conference
Available from: 2018-01-02 Created: 2018-01-02 Last updated: 2018-01-05Bibliographically approved
Ashraf, S., Mattsson, C., Fondell, M., Lindblad, A. & Thungström, G. (2015). Surface modification of SU-8 for metal/SU-8 adhesion using RF plasma treatment for application in thermopile detectors. Materials Research Express, 2(8), Article ID 086501.
Open this publication in new window or tab >>Surface modification of SU-8 for metal/SU-8 adhesion using RF plasma treatment for application in thermopile detectors
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2015 (English)In: Materials Research Express, ISSN 2053-1591, Vol. 2, no 8, article id 086501Article in journal (Refereed) Published
Abstract [en]

This article reports on plasma treatment of SU-8 epoxy in order to enhance adhesive strength for metals. Its samples were fabricated on standard silicon wafers and treated with (O2 & Ar) RF plasma at a power of 25W at a low pressure of (3×10-3 torr) for different time spans (10 sec – 70 sec). The sample surfaces were characterized in terms of contact angle, surface (roughness and chemistry) and using a tape test. During the contact angle measurement, it was observed that the contact angle was reduced from 73° to 5° (almost wet) and 23° for (O2 & Ar) treated samples, respectively. The RMS surface roughness was significantly increased by 21.5% and 37.2% for (O2 & Ar) treatment, respectively. A pattern of metal squares was formed on the samples using photolithography for a tape test. An adhesive tape was applied to the samples and peeled off at 180o. The maximum adhesion results, more than 90%, were achieved for the O2-treated samples, whereas the Ar-treated samples showed no change. The XPS study shows the formation of new species in the O2-treated sample compared to the Ar-treated samples. The high adhesive results were due to the formation of hydrophilic groups and new O2 species in the O2-treated samples, which were absent in Ar-treated samples.

Place, publisher, year, edition, pages
Institute of Physics (IOP), 2015
Keywords
SU-8, contact angle, plasma treatment, surface modification, adhesion, tape test, theromocouples
National Category
Other Materials Engineering
Identifiers
urn:nbn:se:miun:diva-26157 (URN)10.1088/2053-1591/2/8/086501 (DOI)000370037800017 ()2-s2.0-84954539766 (Scopus ID)STC (Local ID)STC (Archive number)STC (OAI)
Available from: 2015-10-28 Created: 2015-10-28 Last updated: 2018-10-15Bibliographically approved
Ashraf, S., Mattsson, C., Thungström, G. & Rödjegard, H. (2014). Design of a multilayered absorber structure based on SU-8 epoxy for broad and efficient absorption inMid-IR sensitive thermal detectors. In: Proceedings: . Paper presented at IEEE SENSORS 2014 (Valencia) (pp. 938-941).
Open this publication in new window or tab >>Design of a multilayered absorber structure based on SU-8 epoxy for broad and efficient absorption inMid-IR sensitive thermal detectors
2014 (English)In: Proceedings, 2014, p. 938-941Conference paper, Published paper (Refereed)
Abstract [en]

This paper reports on design, simulation and fabrication of a multilayered interferometric absorption structure with a broad absorption in the mid-infrared band. This region is used for IR based CH4 and CO2 detection. The structure consists of five layers of different thickness. The structure consists of one mirror layer of aluminium, two SU-8 epoxy layers and two thin titanium layers. This structure has been fabricated on a silicon substrate and verified for its absorption properties through Fourier transform infrared spectroscopy. The fabricated structure has been compared with simulations are performed using transfer matrix theory. The structure shows more than 90% absorption in the wavelength range of 3.20μm - 5.35μm for simulations and 3.13μm - 5.47μm for FT-IR measurements. The transmission and reflection of SU-8 epoxy was measured using FT-IR (that), resulting in a calculated absorption between 10 - 20% in the area of interest (3μm - 6μm). The use of SU-8 epoxy as dielectric medium, allows for direct integration of the structure into the membrane of a SU-8 membrane based thermopile. The integration results in minimum increase of the thermal capacitance and conductance, which results in maximum detector sensitivity and minimum time constant.

Keywords
Interferometric absorber Mid IR SU-8 Thermopile Transfer matrix therory
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:miun:diva-24232 (URN)10.1109/ICSENS.2014.6985156 (DOI)2-s2.0-84931040844 (Scopus ID)STC (Local ID)STC (Archive number)STC (OAI)
Conference
IEEE SENSORS 2014 (Valencia)
Funder
Knowledge Foundation
Available from: 2015-01-27 Created: 2015-01-27 Last updated: 2018-10-15Bibliographically approved
Ashraf, S., Mattsson, C., Thungström, G. & Rödjegard, H. (2014). Integration of an interferometric IR absorber into an epoxy membrane based CO2 detector. Paper presented at 15th INTERNATIONAL WORKSHOP ON RADIATION IMAGING DETECTORS 23–27 JUNE 2013,PARIS, FRANCE. Journal of Instrumentation, 9(5), Art. no. C05035
Open this publication in new window or tab >>Integration of an interferometric IR absorber into an epoxy membrane based CO2 detector
2014 (English)In: Journal of Instrumentation, ISSN 1748-0221, E-ISSN 1748-0221, Vol. 9, no 5, p. Art. no. C05035-Article in journal (Refereed) Published
Abstract [en]

Measurements of carbon dioxide levels in the environment are commonly performedby using non-dispersive infrared technology (NDIR). Thermopile detectors are often used in NDIRsystems because of their non-cooling advantages. The infrared absorber has a major influence onthe detector responsivity. In this paper, the fabrication of a SU-8 epoxy membrane based Al/Bithermopile detector and the integration of an interferometric infrared absorber structure of wavelength around 4 µ m into the detector is reported. The membrane of thermopile detector has beenutilized as a dielectric medium in an interferometric absorption structure. By doing so, a reduction in both thermal conductance and capacitance is achieved. In the fabrication of the thermopile,metal evaporation and lift off process had been used for the deposition of serially interconnectedAl/Bi thermocouples. Serial resistance of fabricated thermopile was measured as 220 kΩ. Theresponse of fabricated thermopile detector was measured using a visible to infrared source of radiation flux 3.23 mW mm−2. The radiation incident on the detector was limited using a band passfilter of wavelength 4.26 µ m in front of the detector. A responsivity of 27.86 V mm2W−1at roomtemperature was achieved using this setup. The fabricated detector was compared to a referencedetector with a broad band absorber. From the comparison it was concluded that the integratedinterferometric absorber is functioning correctly.

Keywords
Detector modelling and simulations I (interaction of radiation with matter, interaction of photons with matter, interaction of hadrons with matter, etc); Spectrometers
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:miun:diva-21978 (URN)10.1088/1748-0221/9/05/C05035 (DOI)000340036100035 ()2-s2.0-84903641311 (Scopus ID)STC (Local ID)STC (Archive number)STC (OAI)
Conference
15th INTERNATIONAL WORKSHOP ON RADIATION IMAGING DETECTORS 23–27 JUNE 2013,PARIS, FRANCE
Available from: 2014-05-27 Created: 2014-05-27 Last updated: 2018-10-15Bibliographically approved
Mattsson, C. (2009). Design, Fabrication and Optimization of Thermal Radiation Detectors Based on Thin Polymer Membranes. (Doctoral dissertation). Sundsvall: Kopieringen Mittuniversitetet
Open this publication in new window or tab >>Design, Fabrication and Optimization of Thermal Radiation Detectors Based on Thin Polymer Membranes
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The number of applications in which infrared radiation sensors are used is increasing. In some applications, the cost of the sensor itself is an issue, and simple solutions are thus required. In this thesis, the investigations have related to the use of thin polymer membranes in thermal infrared sensors, such as bolometers and thermopiles.

Infrared sensors are usually subcategorized into photonic sensors and thermal sensors. For detection of infrared radiation using a photodetector, there is a requirement for low band-gap material. The need of cooling makes infrared photodetectors rather expensive, and not an alternative for low-cost applications. In thermal sensors, the heat generated from the incident infrared radiation is converted into an electrical output by means of a heat sensitive element. Thermal sensors operate at room temperature, which makes them a low-cost alternative. The basic structure of thermal sensors consists of a temperature sensitive element connected to a heat sink through a structure with low thermal conductance. It is common to use thin membranes of Silicon or Silicon Nitride as thermal insulation between the heat sink and the sensitive element. In comparison, polymers have a thermal conductance that is lower than in these materials, and this increases the generated temperature in the sensitive element. A polymer such as SU-8 has a low thermal conductivity and is applied using a spin coater. This reduces the number of complex processing steps. This thesis presents a new application of SU-8 as a closed membrane in a thermal sensor.

The concept was initially demonstrated by fabricating a nickel bolometer and titanium/nickel thermopile structure with a 5 µm SU-8 / SiO2 membrane. However, for the sensor responsivity to be able to compete with commercial thermal sensors the structures, some optimization was required. Since the thermopile generates its own voltage output and requires no external bias, the optimizations were focused on this structure. There exist a number available software tools for thermal simulation of components. However, to the author’s best knowledge, there exist no tool for design optimization of thermopiles with closed membranes. An optimization tool using iterative thermal simulations was developed and evaluated. A new thermopile structure, based on the optimization results, was both fabricated and characterized. Using an infrared laser with a small spot, the measured responsivity of the manufactured thermopile was higher than that of a commercial sensor. In the case of a defocused spot and for longer wavelengths, the infrared absorption in the absorption layer reduces and degrades the responsivity.

The thermopile was further evaluated as a sensor in a carbon dioxide meter application based on the NDIR principle. An increase in the CO2 concentration demonstrated a clear decrease in the thermopile voltage response, as was expected. By normalizing the voltage response and comparing it with a commercial sensor, this showed that the SU-8 based thermopile is relatively more sensitive to changes in the CO2 concentration.

Place, publisher, year, edition, pages
Sundsvall: Kopieringen Mittuniversitetet, 2009. p. 64
Series
Mid Sweden University doctoral thesis, ISSN 1652-893X ; 73
Keywords
Thermal detector, Polymer, Membrane, SU-8
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:miun:diva-9579 (URN)978-91-86073-46-6 (ISBN)
Public defence
2009-09-19, O111, Holmgatan 10, Sundsvall, 13:15 (English)
Opponent
Supervisors
Projects
STC
Available from: 2009-08-28 Created: 2009-08-27 Last updated: 2011-02-06Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-3769-8492

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