Fabrication of Hexagonally Arrayed Nanoholes Using Femtosecond Laser Pulse Ablation with Template of Subwavelength Polystyrene Particle Array

Abstract

We present nanohole array fabrication on a silicon substrate using a femtosecond laser pulse at 820 nm and 100 fs, and a subwavelength polystyrene (PS) particle array as a template. Nanohole array fabrication uses a particle field enhancement effect and two-dimensional (2-D) arrayed PS nanoparticles deposited on a (100) silicon (Si) substrate. PS spheres 200, 450, and 820 nm in diameter are used. The fabricated nanohole profiles in terms of the particle diameter and irradiated laser fluence are investigated. The nanohole diameter and depth become larger and deeper, respectively, as the diameter of the particles used or the irradiated laser fluence is increased. Light intensity enhancement by the particles is obtained experimentally by comparing ablation rates of the Si substrate with and without particles. The enhanced light intensity between a PS particle and a Si substrate is also calculated by the finite difference time domain (FDTD) method. The calculated optical enhancement factor is consistent with the experimental value.