Sensitivity Analysis of a Nanowire-Based Surface Plasmon Resonance Biosensor in the Presence of Surface roughness

We have investigated the effect of surface roughness on the sensitivity of conventional and nanowire-based surface plasmon resonance (SPR) biosensors. The theoretical research was conducted using rigorous coupledwave analysis with Gaussian surface profiles of gold films determined by atomic force microscopy. The results suggest that, when surface roughness ranges near 1 nm, the sensitivity of a conventional SPR system is not significantly affected regardless of the correlation length. For a nanowire-based SPR biosensor, however, we have found that the sensitivity degrades substantially with decreasing correlation length. In particular, at a correlation length smaller than 100 nm, a random rough surface may induce destructive coupling between excited localized surface plasmons, which can lead to prominent reduction of sensitivity enhancement.This work was supported by the Korea Science and Engineering Foundation (KOSEF) through the National Core Research Center for Nanomedical Technology (R15-2004- 024-00000-0) and also by the Korea Research Foundation (KRF) grant funded by the Korean Government, the Ministry of Education and Human Resources Development (MOEHRD), under KRF-2005-205-D00051. K. M. Byun and S. J. Kim acknowledge support by the Engineering Research Center (ERC) program of the Ministry of Science and Technology (MOST)/KOSEF (R11-2000-075- 01001-1). We appreciate Hyun Seok Lee and Professor Kyung Hwa Yoo for kindly providing assistance for the AFM measurements