EXCITATION COUPLING OF Au/ZnO BAND-GAP ENERGY FOR ENHANCING THE PERFORMANCE OF SURFACE PLASMON RESONANCE BIOSENSOR

Abstract

This paper reports a novel design of a surface plasmon resonance (SPR) device that can be developed into a highperformance biosensor. The design utilizes wurtzite crystal structure semiconductor (zinc oxide, ZnO) layers to enhance the SPR signal quality and to improve the full width at half maximum (FWHM) of the SPR re°ectivity curve. There exists a new mechanism when the excitation in the plasmon energy is in resonance with the ZnO band-gap (BG) energy transfer process. The excitation energy between Au and ZnO causes an interactive, coupled phenomenon with the ZnO BG ( BG ¼ 360À430 nm, 3.1À3.4 eV) when it matches the ZnOÀAu interface surface plasmon (400 nm). We have optimized the design of the ZnO and Au thin¯lms thicknesses through analytical comparisons with conventional SPR structures. Upon exposure to ethanol, the ZnOÀAu device showed a 2-times decrease in the FWHM and a 4.5-times larger shift in intensity interrogation. The ZnOÀAu device exhibits a wider linearity range and very higher sensitivity. This characteristic of the ZnOÀAu device is the basis for realizing accurate and speci¯c biomolecular detection.