Large-area nanogap plasmon resonator arrays for plasmonics applications

Abstract

Large-area (∼8000 mm²) Au nanogap plasmon resonator array substrates manufactured using maskless laser interference lithography (LIL) with high uniformity are presented. The periodically spaced subwavelength nanogap arrays are formed between adjacent nanopyramid (NPy) structures with precisely defined pitch and high length density (∼1 km cm⁻²), and are ideally suited as scattering sites for surface enhanced Raman scattering (SERS), as well as refractive index sensing. The two-dimensional grid arrangement of NPy structures renders the excitation of the plasmon resonators minimally dependent on the incident polarization. The SERS average enhancement factor (AEF) has been characterized using over 30 000 individual measurements of benzenethiol (BT) chemisorbed on the Au NPy surfaces. From the 1(a₁), β_CCC + ν_CS ring mode (1074 cm⁻¹) of BT on surfaces with pitch λ_g = 200 nm, AEF = 0.8 × 10⁶ and for surfaces with λ_g = 500 nm, AEF = 0.3 × 10⁷ from over 99% of the imaged spots. Maximum AEFs > 10⁸ have been measured in both cases.