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Design of a multilayered absorber structure based on SU-8 epoxy for broad and efficient absorption inMid-IR sensitive thermal detectors
Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design. (Detector and Photonics)
Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design. (Detector and Photonics)
Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design. (Detector and Photonics)
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.

Place, publisher, year, edition, pages
2014. p. 938-941
Keywords [en]
Interferometric absorber Mid IR SU-8 Thermopile Transfer matrix therory
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:miun:diva-24232DOI: 10.1109/ICSENS.2014.6985156Scopus ID: 2-s2.0-84931040844Local ID: STCOAI: oai:DiVA.org:miun-24232DiVA, id: diva2:783893
Conference
IEEE SENSORS 2014 (Valencia)
Funder
Knowledge FoundationAvailable from: 2015-01-27 Created: 2015-01-27 Last updated: 2018-10-15Bibliographically approved
In thesis
1. Design and Integration of Infrared Absorber Structures into Polymer Membranes based Thermal Detectors
Open this publication in new window or tab >>Design and Integration of Infrared Absorber Structures into Polymer Membranes based Thermal Detectors
2015 (English)Licentiate thesis, comprehensive summary (Other academic)
Place, publisher, year, edition, pages
Sundsvall: Mid Sweden University, 2015. p. 90
Series
Mid Sweden University licentiate thesis, ISSN 1652-8948 ; 118
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:miun:diva-26176 (URN)STC (Local ID)978-91-88025-20-3 (ISBN)STC (Archive number)STC (OAI)
Presentation
2015-09-17, O111, Holmgatan 10, Sundsvall, 10:00 (English)
Opponent
Supervisors
Available from: 2015-11-02 Created: 2015-10-30 Last updated: 2017-03-02Bibliographically approved
2. Thermal detector with integrated absorber structure for mid-IR gas detection
Open this publication in new window or tab >>Thermal detector with integrated absorber structure for mid-IR gas detection
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Measurement of the concentration of greenhouse gases, such as carbon dioxide(CO 2 ) and methane (CH 4 ), in the atmosphere has received significant attention in the last few decades. This work focusses on the development of high-performance thermopile detectors for use with the non-dispersive infrared (NDIR) measurements of such gases. The performance of the thermopile detectors could effectively be increased by selecting membrane materials with a low thermal conductivity value and an efficient infrared (IR) absorbing material and by selecting the materials with high Seebeck coefficient values. Graphite black paint can be used as a radiation absorber, as it has high absorption (80—93%) for a wide spectral range (2.5 μm — 20 μm). By using spray paint or a paint brush, the application of the absorber is simple and fast. However, the control over the processing process suffers with these simple methods. The thermal capacitance of the detector will rapidly increase due to uneven distribution and unknown thickness of the absorber, although the response of the thermopile detector will be maximum due to high absorption; however, the response time (τ th )for the detector will be longer.In order to improve the performance, IR absorbers have been designed to utilise the membrane (SU-8 epoxy) of the detector as an active part of the IR absorber. This utilisation of the SU-8 epoxy membrane will result in a maximum detector sensitivity and a minimum increase in both the thermal capacitance and thermal conductance of the thermopile detector. Absorber structures, based on SU-8 epoxy, with a narrow absorption band at 4.26 µm and a wider multi-layered absorption band at 3-6 µm, were designed, simulated, and fabricated, and their integration into the membrane of thermopile detectors have been presented. The response of the thermopile detector could also be increased by using materials with high Seebeck coefficient [1] values such as semiconductor materials, as they have higher Seebeckvalues compared to the metals. In the thesis, molybdenum disulfide (MoS 2 ) flakes were characterised, and Seebeck values were estimated through a measurement setup as a function of temperature difference (ΔT). The fabricated thermopile detectors were characterised, and the response time(τ th ) of a thermocouple with a multi-layered absorber structure has been estimated to be 21 ms. The detector has shown high responsivity value in the wavelength range of 3 µm – 4.5 µm, which is used for CO 2 and CH 4 detection. The thermopile detector was evaluated for CO 2 gas through a long-path-length NDIR platform. The results show that the evaluated thermopile could be used for the measurement of gas concentration down to levels of a few parts per million (ppm) by using the long-path-length NDIR platform.

Place, publisher, year, edition, pages
Sundsvall: Mid Sweden University, 2018. p. 81
Series
Mid Sweden University doctoral thesis, ISSN 1652-893X ; 280
Keywords
Thermal detectors, Thermopile detectors, Infrared absorbers, SU-8 epoxy, Interferometric and Multi-layered absorber, Seebeck coefficient, Molybdenum di-sulfide
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:miun:diva-34616 (URN)978-91-88527-48-6 (ISBN)
Public defence
2018-05-21, L111, Sundsvall, 10:00 (English)
Opponent
Supervisors
Note

Personal Email to Author

shakeel.llm@gmail.com

Vid tidpunkten för disputationen var följande delarbeten opublicerade: delarbete 5 (inskickat), delarbete 7 (manuskript).

At the time of the doctoral defence the following papers were unpublished: paper 5 (submitted), paper 7 (manuscript).

Available from: 2018-10-15 Created: 2018-10-15 Last updated: 2018-10-15Bibliographically approved

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Ashraf, ShakeelMattsson, ClaesThungström, Göran

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