Towards understanding hybrid influencing mechanisms of substrate microstructure on SERS effect

Micro/nano hierarchical structures have been investigated as a manner to improve the enhancement factor of surface enhanced Raman scattering (SERS). However, the exploration of influencing mechanisms of substrate microstructure on SERS effect is relatively lacking at present. In this study, finite element analysis (FEA) and molecular dynamics (MD) simulations were conducted, aiming to reveal the intrinsic relationships between microstructure characterization and Raman signal intensity. The distributions of near field and far field, as well as the energy density on substrate surfaces with various microstructures were obtained, and their influencing mechanisms on electromagnetic enhancement (EM) and chemical enhancement (CM) were analyzed. Meanwhile, the adsorption capacity of probe molecule on different substrate was expounded from the perspectives of superficial area, interaction energy and surface profile characteristics. Results demonstrated that the characterization parameter S/d × h, of which S, d and h are respectively the superficial area, interval space of adjacent micro-cavities and peak-valley height of surface microstructure, significantly determines the electric enhancement factor of electric field intensity and the energy density at the same time. The substrate surface with larger superficial areas can generate higher interaction energy thereby more probe molecules can be caught successfully. In addition, the molecular clusters are easier to form near convexities compared with the concaves on the same substrate. What was studied in this work is expected to provide a theoretical reference for the structural optimization of SERS substrate with high performances.