Two-Dimensional Periodic Nanostructure Fabricated on Titanium by Femtosecond Green Laser.

Yi-Hsien Liu,Shu-Chun Yeh,Chung-Wei Cheng

doi:10.3390/nano10091820

Abstract

Laser-induced periodic surface structures (LIPSS) is the sub-wavelength periodic nanostructure, which is generally generated by the femtosecond laser. There are two kinds of LIPSS, low spatial frequency LIPSS (LSFL) and high spatial LIPSS (HSFL), and the period size is close and less than half of the laser wavelength, respectively. Fabrication of two-dimensional (2D) LSFL and HSFL on a titanium surface with a linear-polarized femtosecond green laser beam (wavelength 515 nm) and cross-scanning strategies is demonstrated in this study. Four types of LIPSS structures are obtained by controlling the laser fluence, irradiated pulses, and cross-scanning strategies: 1D-LSFL perpendicular to laser polarization with a period of 300–360 nm, 1D-HSFL parallel to laser polarization with a period of 55–75 nm, 2D-LSFL dot-like structures with a period ~200 nm, and 2D-HSFL net-like structures with a period of 50–100 nm.

Highlights

Laser-induced periodic surface structures (LIPSS) has attracted lots of attention because it can be generated on metal, semiconductor, and dielectric material by a single-pass laser beam [1]
There are two different types of LIPSS that can be generated on the material surface, depending on different laser fluence inputs
One is low spatial frequency LIPSS (LSFL), which can be generated when the fluence is near the ablation threshold and the orientation is usually perpendicular to the polarization

Summary

Introduction

LIPSS (laser-induced periodic surface structures) has attracted lots of attention because it can be generated on metal, semiconductor, and dielectric material by a single-pass laser beam [1]. One is LSFL (low spatial frequency LIPSS, period > λ/2,), which can be generated when the fluence is near the ablation threshold and the orientation is usually perpendicular to the polarization. Bonse et al generated some 1D-HSFL structures (period ~λ/10) on titanium by Ti:Sapphire laser (790 nm) They proposed that the oxide layer which is generated by repetitive irradiation can induce the 1D-HSFL [11,12]. Nathala et al found that the period of 1D-HSFL is varied from 60 nm to 120 nm with laser fluence 32–44 mJ/cm2 [15] They proposed that the Gaussian beam profile is not suitable for generating large-area 1D-HSFL because of the intensity distribution. Some studies used different methods (controlling the polarized direction, scanning strategy, and dual pulse) to generate the two-dimensional (2D) micro/nano structures.

Materials and Methods

Results

EDS Analysis

Discussion