A large-scale sub-100 nm Au nanodisk array fabricated using nanospherical-lens lithography: a low-cost localized surface plasmon resonance sensor

Large-scale Au nanodisk arrays are successfully fabricated using nanospherical-lens lithography (NLL). By incorporating both rotational oblique-angle deposition and oxygen plasma treatment, the improved NLL is capable of fabricating Au nanodisks with diameters as small as 75?nm that cover an area larger than 1?cm2. The fabricated nanodisk arrays are investigated as sensitive localized surface plasmon resonance (LSPR) sensors. The extinction spectra of the Au nanodisk arrays reveal a narrower LSPR peak when the diameter becomes smaller. The shape imperfection severely limits the minimum obtainable linewidth, especially when the nanodisk diameter is smaller than 200?nm. The imperfection is found to be improved by thermal annealing at high temperatures. The maximum theoretically predicted and experimentally obtained figure-of-merit for Au nanodisk arrays whose periodicities are 500?nm are around 15 and 9, respectively. Further optimization of the periodicity and thickness of the nanodisks will further improve their sensitivity and lead to more novel applications.