Fabrication of Hafnium-based Nanoparticles and Nanostructures using Picosecond Laser Ablation

This work presents a unique and straightforward method to synthesize Hafnium Oxide (HfO 2 ) and Hafnium Carbide (HfC) nanoparticles (NPs) and fabricate Hafnium (Hf) nanostructures (NSs) on Hf metal surfaces. An ultrafast (picosecond) laser ablation of the Hf metal target was performed in three different liquid media (deionized water (DW), toluene, and anisole) to fabricate HfO 2 and HfC NPs along with Hf NSs. Spherical HfO 2 NPs and nanofibers were formed when Hf was ablated in DW. Hf ablated in solvents like toluene and anisole showed the formation of core-shell NPs of HfC with graphitic shell. All the NPs showed novel optical reflectance properties. The reflectance measurements revealed that the fabricated NPs had a very high and broad optical absorption throughout the UV-Visible-NIR range. The NPs synthesized in toluene especially depicted the best absorption. On the other hand, the successful fabrication of Hf NSs with the formation of picosecond laser-induced periodic surface structures (LIPSS) with low spatial frequency (LSFL) and high spatial frequency (HSFL) orthogonal to each other was also demonstrated. The LSFL and HSFL both showed quasi-periodicity. This article presents a simple way to fabricate HfO 2 and HfC NPs and provides insight into their morphological and optical characteristics.