Magneto-absorption effects in magnetic-field assisted laser ablation of silicon by UV nanosecond pulses

Abstract

Magneto-absorption effects in magnetic-field assisted laser ablation of silicon by UV nanosecond pulses

Fundamental mechanisms of nanosecond-laser-ablation enhancement by an axial magnetic field

“…Characterization of the groove profiles uncovered that the magnetic field substantially improved the aspect ratio of the grooves from 0.34 (13/38) to 1.52 (35/23). A similar amount of increase of the aspect ratio by reduction of diameter/width of the laser-ablated structures was observed on silicon when ablated by 112-μJ pulses [23]. In contrary to silicon, the magnetic field did not produce a periodic cycling perturbation of the grooves produced on stainless steel.…”

“…3. The laser fluence was close to the ablation threshold of silicon at zero magnetic field [23] and produced nano-grooves with average depth 142 nm (Fig. 3(a) and (c)).…”

“…Several single spots were ablated on the silicon surface at higher fluence (pulse energy is 112 μJ; peak fluence is 3.81 J/cm 2 ) by applying 10 [23] and 30 laser pulses per spot. Remarkable reduction of debris deposition by the magnetic field was observed [23]. Depth of the ablated crates increased from 10 (with no magnetic field) to 37 μm (with 0.192 T magnetic field) for ablation by 10 pulses, and from 37 (with no magnetic field) to 90 μm (with 0.192 T field) for ablation by 30 pulses.…”

“…For example, experiments on paramagnetic metals like tin have shown some 2-fold increase of ablation rate by the axial magnetic field [17]. Recently reported 69-fold enhancement of ablation of silicon by nanosecond UV laser pulses [23,24] confirms the feasibility of even stronger intensification of ablation by the axial magnetic field. Those results are not justified by the LPP confinement [15] because of minimizing of the vector product (v x B) by the axial alignment.…”

“…Those results are not justified by the LPP confinement [15] because of minimizing of the vector product (v x B) by the axial alignment. A brief analysis of possible mechanisms of the ablation enhancement [23,24] suggests contributions from propagation through the magnetized plasma, modified dynamics of debris deposition, magneto-hydrodynamics of melt motion, and modification of optical response of silicon. However, the axial magnetic field modifies a broader range of material properties involved in the ablation processes, e. g., heat conductivity.…”