Construction and Verification of a Co-Planar Metal-Insulator-Metal Surface Plasmon Resonance Sensor
Date Issued
2015
Date
2015
Author(s)
Lu, Chi-Ying
Abstract
Surface plasmons are excited electromagnetic wave propagating at the interface between a dielectric and a conductor, which are evanescently confined in the perpendicular direction. In recent years, it have been widely applied in physical, chemical and biological sensing to achieve real-time and label free sensing. A system of surface plasmon resonance (SPR) are mostly based on prism coupling for surface plasmon excitation. The far-field scattering at the certain angle is measured and analyzed by a photodiode or an optical detector. The size of a typical optical instrument is large, therefore it usually can’t be further miniaturized. This study attempted to use a co-planar Metal-Insulator-Metal (MIM) device, which was integrated to a surface plasmon chip, to miniaturize the surface plasmon resonance device. In this thesis, a simulation of current- voltage characteristics was based on the principle of MIM device. And the MIM device as SPR sensor was) designed in three parameters of thickness, namely A sample: Au 48 nm / TiO2 30 nm, B sample: Au 48 nm / TiO2 45 nm, C sample: Au 48 nm / ZnO 20 nm and D sample: Au 48 nm / ZnO 30 nm. Experimental results show that Sample A, B, C, D in a bias voltage of ± 1.4 V, the current of Sample A (0.14 nA) is slightly greater than Sample B (0.1 nA) and also Sample C (0.32 nA) is slightly greater than Sample D (0.22 nA) , which represents that the thinner insulating layer film is, electrons can more easier through the insulator layer. And the electrons in ZnO layer can more easier through the insulator layer of TiO2 on account of the difference conductive properties of TiO2 and ZnO. In the second part of this thesis, it is to confirm the effectiveness of MIM device. 658 nm laser transmits through the metal layer stack and excites surface plasmas on the top surface. Experimental results show that under the excitation of transverse magnetic polarization (TM) wave, the laser intensity and the current of MIM device have a positive linear relationship. In the power intensity of 25 mW in TM wave, Sample A corresponds to a current larger than the Transverse Electronic polarization (TE) wave of nearly six times; Sample B of TM wave corresponds to the current nearly four times larger than the TE wave, and Sample C of TM wave corresponds to only about 1.2 times greater than the current of TE wave. Because of the selection of material, TiO2 barrier height is higher than ZnO, the tunneling of electrons become more difficult. Therefore, the current of Sample C is greater than Sample A and B under no SPR excited. However, corresponding to surface plasmon resonance phenomenon, the specific changes in the current will rise. The thinner TiO2 thin film is, the higher probability of electron tunneling through the film. In order to verify the existence of surface plasma resonance, the comparison of light signals and current signal and the detection of dielectric constant are examined. We adjust the incident angle of the laser beam, and record the changes of electrical signals. Experiment results show that when under the fixed bias voltage of 1.4 V and constant laser intensity of 25 mW, the current of the device reachs the maximum value at a incident angle of 55 degrees, which is closed to the surface plasma resonance angle. On the other hand, under the same bais voltage and the laser intensity,in a given bias (1.4 V), under a given light intensity (25 mW), current flows decreases from 0.6 nA to 0.25 nA , when coupling oil dropped in the sensing region. It can be seen that the surface plasma resonance senor can successfully detect the change of dielectric constant by measuring the current. This thesis has been successfully verified that through photoelectric conversion, the device transferred the excited energy of surface plasmon resonance into electrical signals be measured and analyzed. According to our results, the device can significantly minimize the size of detection system of SPRand reduce the cost of SPR instrument.
Subjects
Surface Plasmon Resonance
Metal-Insulator-Metal
Internal Electron Emission
Type
thesis
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