Yüzey plazmon rezonansına dayalı MEMS yerdeğiştirme algılayıcılarının tasarım, üretim ve karakterizasyonu

Strong dependence of surface plasmon resonance (SPR) on coupling parametersoffers new varieties of sensing mechanisms in nano and micro-scale engineeringfields. In this study, design, fabrication and characterization of MEMSdisplacement sensors that utilize angular dependence of grating coupled SPRcondition are explored.Several surface plasmon polariton (SPP) excitation mechanisms are reportedin the academic literature. One of them which is quite adaptable tomicroelectromechanical systems is grating coupling scheme. In this scheme, thinmetallized grating structures are particularly designed depending on the desiredwavelength and the angle of incidence of the SPP excitation light. Geometricparameters like periodicity, surface profile, depth and duty cycle of the groovesand material parameters like dispersion and thickness of the top metal layer haveto be chosen with care in order to reach sharp SPR curves in the reflectedintensity spectra with respect to either wavelength or angle of incidence. As thefirst step, geometric and material parameters of SPR gratings are numericallyoptimized using rigorous coupled-wave analysis (RCWA). Angular qualityfactors on the order of tens are shown to be achievable. Various lithographictechniques (nanoimprint, electron beam and optical lithography) are used tonanofabricate those certainly defined gratings. It is observed that p-polarizedreflected intensity measurements using spectroscopic ellipsometry are in quitegood agreement with those numerically calculated. Spectroscopic scanmeasurements are also provided to show the polarization dependence of SPPexcitation.All effort to obtain high angular Q-factor grating structures is aimed atenhancing the sensitivity of angular displacement detection scheme. In thisscheme, angular position of the grating structure in the polarization plane isdetected through the reflected intensity response of the photodetector.Dependence of sensitivity on excitation light source wavefront parameters andphotodetector noise are analyzed.MEMS displacement sensor designs relying on the principle of angulardisplacement detection scheme are developed. Simply, SPR grating structuresare transferred on conventional micromembranes. Two types of such particulardesigned micromembranes are introduced: corrugated microcantilevers (singlyclamped) and corrugated microbridges (doubly clamped). They are fabricatedthrough well-known surface micromachining processes in addition to SPRgrating nanofabrication procedures. Mechanical resonance frequencies, flexuralmode shapes and effective spring constants are analytically, numerically andexperimentally obtained. In addition, a MEMS accelerometer design withplasmonic readout with nano-G noise floor is presented. An experimentalconfiguration for micromechanical displacement sensing is investigated.According to the results of this work, novel arrayed sensors combining thesensitivities of plasmon resonance and micromembrane type sensors mayprovide unprecedented performance.