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Computer screen photo-assisted off-null ellipsometry
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, Applied Physics . Linköping University, The Institute of Technology.
Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
2006 (English)In: Applied Optics, ISSN 0003-6935, Vol. 45, no 30, 7795-7799 p.Article in journal (Refereed) Published
Abstract [en]

The ellipsometric measurement of thickness is demonstrated using a computer screen as a light source and a webcam as a detector, adding imaging off-null ellipsometry to the range of available computer screen photoassisted techniques. The results show good qualitative agreement with a simplified theoretical model and a thickness resolution in the nanometer range is achieved. The presented model can be used to optimize the setup for sensitivity. Since the computer screen serves as a homogeneous large area illumination source, which can be tuned to different intensities for different parts of the sample, a large sensitivity range can be obtained without sacrificing thickness resolution.

Place, publisher, year, edition, pages
2006. Vol. 45, no 30, 7795-7799 p.
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:liu:diva-13836DOI: 10.1364/AO.45.007795OAI: oai:DiVA.org:liu-13836DiVA: diva2:21797
Available from: 2006-05-04 Created: 2006-05-04 Last updated: 2013-10-14
In thesis
1. 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, HansLundström, IngemarFilippini, Daniel

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