Impact of laser interaction on morphological and mechanical properties of palladium thin film

Abstract

This research work investigates surface morphology, plasma plume intensity and the hardness of palladium thin film deposited on silicon substrates under the action of laser light. For this purpose, a pulsed Nd:YAG laser (1064 nm, 10 mJ, 12 ns) was used to irradiate the specimen with repetitive laser pulses. The experiment was repeated under the illumination with UV light. The surface morphology of the specimens was examined through an Optical and Field-Emission Scanning Electron Microscopy showing thermal conduction, exfoliation, crater formation, re-deposition of the material, ripples formation, debris, heat-affected zone, holes formation and the formation of nanoparticles. The diameter and the depth of the crater formed on non-UV illuminated Pd thin film were greater than the crater formed on UV illuminated Pd thin film, because of its higher absorption. The photographs of the plasma plume were captured with a computer-controlled image capture system and examined by image processing software. The intensity of UV-illuminated Pd thin film was higher than non-UV illuminated Pd thin film because UV illumination induces defects in the specimen that have additional electronic states. These defects cause higher absorption and more ionization of the target material and emerge a more luminous plasma plume. A nanoindentation test was applied on the material surface to investigate the mechanical properties such as hardness and elastic modulus of the target specimen. The hardness and elastic modulus of the material were increased by cumulative laser shots.