23 DESIGN AND REALIZATION OF SET-UP FOR SPR MEASURING METHOD NÁVRH A REALIZACE ZAŘÍZENÍ PRO MĚŘENÍ METODOU SPR Adam TALIK 1 , Michal LESŇÁK 2 , Ondřej VLAŠÍN 3 , Jaromír PIŠTORA 4 Institut fyziky, Hornicko geologická fakulta, VŠB-TU Ostrava 17.listopadu 15, 708 33 Ostrava – Poruba 1 Ing., email: adam.talik.hgf@vsb.cz 2 doc. Dr. Ing., email: michal.lesnak@vsb.cz 3 Bc., email: ondrej.vlasin@gmail.com 4 prof. Ing. CSc., email: jaromir.pistora@vsb.cz Abstract Given paper describes modification of Gaertner L119 ellipsometer to apply the surface plasmon resonance (SPR) method. Final implementation has been tested on several basic measurements and obtained experimental data were compared with theoretical model. Abstrakt Předložená práce se zabývá popisem úprav elipsometru Gaertner L119 k měření metodou excitace povrchových plasmonů (SPR). Výsledná realizace byl prověřena na několika vstupních měřeních a změřené hodnoty byly porovnány s teoretickým modelem. Key words: surface plasmon resonance, SPR, Gaertner L119 1 INTRODUCTION The extreme sensitivity of SPR to small changes in refractive index (up to 10 -8 , [1]) is used primarily in sensors, especially as very sensitive detectors of various substances in biology and chemistry, determining thicknesses of layers adsorbed on metal surface or to study kinetics of chemical reactions [2]. This method can also be used to study layered or periodical nanostructures which occur frequently in microelectronics. 2 THEORY Surface plasmons are electric charge density oscilations on interface between two media which real parts of permitivity have opposite sign, eg. between metal and isolator. These charge density oscilations are bound to electromagnetic wave, which has it's intensity maximum on interface and decreases exponentially into both media. This electromagnetic wave is polarized parallel to the plane of incidence (p-polarization) and it's propagation constant is given by equation: , s m s m k ε ε ε ε β + = (1) where k is the wave vector in vacuum, ε m is the permittivity of metal (ε m =ε rm +iε im ) and ε s is the permittivity of dielectric medium. As may be concluded from this equation the surface plasmon wave may exist only on the interface providing that following condition is satisfied: ε m < - ε s . At optical wavelengths, this condition is fulfilled by several metals of which gold and silver are the most commonly used. As follows from equation (1) above, the propagation constant of plasmon wave is always higher than that of electromagnetic wave in the dielectric and thus the plasmon cannot be excited directly by an incident optical wave at metal–dielectric interface. Therefore the wave vector of the incident optical wave has to be changed to match that of plasmon wave. This momentum change is commonly achieved using attenuated total reflection in prism couplers or difraction at the surface of gratings (Fig. 1). When surface plasmon wave is induced it manifests itself as significant loss of reflectivity at a specific angle [3]. GeoScience Engineering Volume LIV (2008), No.1 http://gse.vsb.cz p. 23-26, ISSN 1802-5420 brought to you by CORE View metadata, citation and similar papers at core.ac.uk provided by DSpace at VSB Technical University of Ostrava