Surface Structuring and Thin Film Coating through Additive Concept Using Laser Induced Plasma of Mg Alloy: A Comparison between the Presence and Absence of Transverse Magnetic Field (TMF)

Abstract

In the present study, the influence of a 1.1 tesla Transverse Magnetic Field (TMF) on Laser-Induced Breakdown Spectroscopy (LIBS) of Mg-alloy plasma has been explored. The Mg plasma was produced using an Nd: YAG laser (1064 nm, 10 ns) at an intensity of 2 GW/cm2. Inert gases of Ar, Ne, and He were filled as environmental gases at pressures ranging from 1 to 100 Torr. Optical emission spectra from laser-produced plasma were detected with the help of a spectrometer, and plasma parameters such as excitation temperature (Texc) and electron number density (ne) were evaluated. Enhancement in the Mg plasma’s Texc and ne in the presence of TMF was noticed under all experimental conditions, including different ambient gases with varying pressures and time delays (0.42 µs–9.58 µs). Plasma confinement by applied TMF was analytically evaluated through thermal beta (βt) values, which were <1 under all circumstances. The highest Texc and ne values (17,259 K and 11.5 × 1017 cm−3) for Mg-alloy plasma were obtained with ambient Ar in TMF, while the lowest values (8793 K and 1.0 × 1017 cm−3) were obtained in presence of He gas in the absence of TMF. SEM analysis was used to determine the surface structure of laser-ablated Mg alloy in the presence and absence of TMF. It revealed that the formation of cones, cavities, and non-uniform melting are characteristic features of ambient Ar, while spikes and cavities are prominent features in Ne gas environments. Conical spikes and dendrites are distinct features when ambient He is present. In comparison with the field-free condition, distinct and well-defined structures were observed in the presence of TMF. By controlling LPP parameters, the surface structuring of Mg alloy can be controlled. The optimization and enhancement of LPP parameters make it a highly useful tool for thin film deposition, coatings of multilayers, and ion implantation/doping.