Laser-assisted ablation and plasma formation of titanium explored by LIBS, QCM, optical microscopy and SEM analyses along with mechanical modifications under different pressures of Ar and Ne

This study deals with the investigation of Nd: YAG laser-assisted ablation and plasma formation of Ti at irradiance of 0.85 GW cm^-2 under Ar and Ne environment at various pressures ranging from 10–120 Torr. Laser-induced breakdown spectroscopy is used to evaluate plasma parameters, whereas quartz crystal microbalance is used for ablation yield measurements. The crater depth is evaluated by optical microscopy. The surface features are explored by scanning electron microscope (SEM) analysis and the micro-hardness is measured by a Vickers hardness tester. It is observed that the plasma parameters are higher in Ar than in Ne, and are strongly correlated with the ablation yield, ablation depth, surface features and hardness of laser-ablated Ti. These parameters increase with increasing the pressure of environmental gases, attain their maxima at 40 Torr for Ar and at 60 Torr for Ne. Afterwards, they show a decreasing trend up till a maximum pressure of 120 Torr. The maximum value of the electron temperature (T_e) is 5480 K, number density (n_e) is $1.46\times {10}^{18}{\mathrm{cm}}^{-3},$ ablation depth is $184\mu \mathrm{m},$ ablation yield is $3.9\times {10}^{15}$ atoms/pulse and hardness is 300 HV in the case of Ar atmosphere. SEM analysis reveals the growth of surface features, such as cones, ridges and pores, whose appearance is more distinct in Ar than Ne and is attributed to temperature, pressure and density gradients along with recoil pressure of the Ti plasma.