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Improvement of porous silicon based gas sensors by polymer modification
Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.ORCID iD: 0000-0001-9229-2028
Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
2003 (English)In: Physica Status Solidi (A), ISSN 0031-8965, Vol. 197, no 2, 378-381 p.Article in journal (Refereed) Published
Abstract [en]

Gas sensing was performed using spectroscopic ellipsometry and porous silicon films. Modification of the porous layer by polymer deposition showed an increase in sensitivity to organic solvent vapor of up to 135%. The increase in sensitivity is strongly dependent on polymer concentration. At high concentrations, too much polymer is deposited, presumably blocking the pores, causing a decrease in sensitivity. At sufficiently low concentrations, the polymer causes a strong increase in sensitivity. This is assumed to be caused by the polymer being deposited inside the pores, where its interaction with the vapor influences the sensitivity. At very low concentration, the sensitivity approaches values obtained without polymer modification. The sensitivity increase is different for different vapors, pointing to possible selectivity enhancement.

Place, publisher, year, edition, pages
2003. Vol. 197, no 2, 378-381 p.
Keyword
07.07.Df, 61.43.Gt, 78.67.Bf, 82.35.Gh
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:liu:diva-13772DOI: 10.1002/pssa.200306529OAI: oai:DiVA.org:liu-13772DiVA: diva2:21431
Available from: 2004-12-10 Created: 2004-12-10 Last updated: 2013-10-14
In thesis
1. New methodology for optical sensing and analysis
Open this publication in new window or tab >>New methodology for optical sensing and analysis
2004 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis describes the research I have done, and partly will do, during my time as a PhD student in the laboratory of Applied Optics at Linköping University. Due to circumstances beyond the scope of this book, this incorporates three quite different projects. The first two, involving gas sensing and measuring on paper with ellipsometry, have been discontinued, whereas the third one, measuring fluorescence with a computer screen and web camera, is in full progress and will be until I complete my studies.

Thus the purpose of this work also has several aspects. Partly, it describes performed research and its results, as well as theoretical background. On the other hand, it provides practical and theoretical background necessary for future work. While the three projects are truly quite different, each of them has certain things in common with each of the other. This is certainly also true for the necessary theory. Two of them involve spectroscopic ellipsometry, for example, while another pair needs knowledge of color theory, etc. This makes it impossible to separate the projects, despite of their differences. Hopefully, these links between the different projects, connecting the different chapters, will make this work whole and consistent in its own way.

Place, publisher, year, edition, pages
Institutionen för fysik, kemi och biologi, 2004. 51 p.
Series
Linköping Studies in Science and Technology. Thesis, ISSN 0280-7971 ; 1090
Keyword
Applied Optics, measuring, ellipsometry, fluorescence, spectroscopic ellipsometry
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:liu:diva-5670 (URN)91-7373-944-8 (ISBN)
Presentation
2004-04-29, 00:00 (English)
Note
Report code: LiU-TEK-LIC-200 4-19. On the day of the public defence the status of article I was: In press and the status of article III was: Manuscript and has a new title. The old title was Computer screen photo-assisted spectroscopic fluorimetry.Available from: 2004-12-10 Created: 2004-12-10 Last updated: 2009-02-26
2. Optical Detection Using Computer Screen Photo-assisted Techniques and Ellipsometry
Open this publication in new window or tab >>Optical Detection Using Computer Screen Photo-assisted Techniques and Ellipsometry
2006 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Two main subjects, ellipsometry and computer screen photo-assisted techniques (CSPT), form the main line in this thesis. Ellipsometry is an optical technique based on the detection of polarization changes of light upon interaction with a sample. As most optical detection techniques it is non-intrusive and an additional advantage is its high surface sensitivity: thickness resolution in the order of pm can in principle be achieved. Therefore, ellipsometry is widely used as a technique for determination of optical constants and layer thickness for thin-layer structures. Lately ellipsometry has also been proposed for sensing applications, utilizing the detection of changes in the properties of thin layers. One application is described in this thesis concerning the detection of volatile organic solvents in gas phase using modified porous silicon layers, fabricated by electrochemical etching of silicon to create nm-sized pores. This greatly increases the surface area, promoting gas detection because the number of adsorption sites increases. Other applications of ellipsometry discussed in this thesis are based on combination with CSPT.

CSPT is a way to exploit existing optical techniques for use in low-cost applications. In CSPT the computer screen itself is used as a (programmable) light source for optical measurements. For detection a web camera can be used and the whole measurement platform is formed by the computer. Since computers are available almost everywhere, this is a promising way to create optical measurement techniques for widespread use, for example in home-diagnostics. Since the only thing that needs to be added is a sample holder governing the physical or chemical process and directing the light, the cost can be kept very low. First, the use of CSPT for the measurement of fluorescence is described. Fluorescence is used in many detection applications, usually by chemically attaching a fluorescent marker molecule to a suitable species in the process and monitoring the fluorescent emission. The detection of fluorescence is shown to be possible using CSPT, first in a cuvette-based setup, then using a custom designed micro array. In the latter, polarizers were used for contrast enhancement, which in turn led to the implementation of an existing idea to test CSPT for ellipsometry measurements. In a first demonstration, involving thickness measurement of silicon dioxide on silicon, a thickness resolution in the order of nm was already achieved. After improvement of the system, gradients in protein layers could be detected, opening the door toward biosensor applications. Some further development will be needed to make the CSPT applications described here ready for the market, but the results so far are certainly promising.

Place, publisher, year, edition, pages
Institutionen för fysik, kemi och biologi, 2006
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1020
Keyword
Optical sensing, Biohttps://www.diva-portal.org/liu/webform/form.jsp#paper0sensing, Ellipsometry, Computer Screen Photo-assisted Technique, Fluorescence, Immunoassays
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:liu:diva-6392 (URN)91-85523-70-4 (ISBN)
Public defence
2006-06-02, Planck, Fysikhuset, Campus Valla, Linköpings universitet, Linköping, 10:15 (English)
Opponent
Supervisors
Available from: 2006-05-04 Created: 2006-05-04 Last updated: 2013-10-14

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Bakker, Jimmy W. P.Arwin, HansWang, Guoliang

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