Tailoring of Silver Nanoparticle Size Distributions in Hydrogenated Amorphous Diamond‐Like Carbon Nanocomposite Thin Films by Direct Femtosecond Laser Interference Patterning

Abstract

Patterning of nanocomposites by conventional lithography processes is problematic due to the different physical properties of matrix and filler. Direct laser interference patterning (DLIP) promises rapid micromachining of virtually any material with subwavelength resolution. A control of intense laser light modifies the filler particle size distribution in nanocomposite films. Herein, DLIP of periodic patterns with half‐pitch <1 μm in reactive magnetron‐sputtered hydrogenated amorphous diamond‐like carbon nanocomposite thin films with embedded silver nanoparticles (DLC:Ag) is demonstrated. Periodic patterns of regularly repeating areas with modified size distributions of silver nanoparticles are obtained by a variation of fluences and number of pulses of 515 nm wavelength femtosecond laser. Depending on the silver content in nanocomposite films, nanoparticle size distributions are either bimodal (for 14.1 at% Ag containing films) or unimodal (7.9 at%) with effective average diameters shifting from 13 to 69 nm, depending on the laser processing parameters. The importance of localized surface plasmon absorption and localized field enhancement at the DLC–Ag interface for lowering the ablation threshold of DLC:Ag nanocomposites below 6 mJ cm−2 at 1000 pulses is demonstrated. This is at least four times lower than the threshold for pure DLC obtained using the same DLIP setup.