Two-dimensional hexagonally arrayed nanohole fabrication on silicon substrate using a femtosecond laser pulse

Abstract

We report a nanohole array fabrication with a particle light enhancement effect using a femtosecond laser pulse. Two-dimensional (2-D) arrayed polystyrene (PS) nanoparticles are deposited on silicon (Si) substrates. Polystyrene spherical particles with diameters of 200, 450, and 820 nm are used. We investigated the fabricated nanohole profiles in terms of the particles diameter and irradiated laser fluence. The morphology of the nanoholes is characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The nanohole diameter and depth became larger and deeper as the diameter of used particle or the irradiated laser fluence is increased. The intensity enhancement factor is obtained from the experimental data by comparing the nanohole depths to the ablation rate of the Si surface without particles. The enhanced light intensity between a PS particle and a Si substrate is calculated by the finite difference time domain (FDTD) method. The calculated optical enhancement factor is consistent with the experimental value.