Figure 9
From: Flower-like Na2O nanotip synthesis via femtosecond laser ablation of glass
The proposed formation mechanisms (i) Laser pulses induce optical breakdown; (ii) agglomeration of Si nanoparticles occurs in the plume and a melt layer forms; (iii) melt layer separates soda-lime glass molecules by density; (iv) spallation creates microscale Na 2 O melt spheres; (v) polar Na 2 O molecules are electrostatically drawn out towards the laser-ionized nitrogen; (vi) the drawn Na 2 O cools into flower-like nanotip arrangements (dwell time = 2 ms), (vii) at longer dwell times more nitrogen is ionized, (viii) resulting in thinner nanotips (dwell time = 10 ms); (ix) melt that is now low in Na 2 O is expelled via plume backcoil pressure to form melt spheres composed of the higher density molecules; (x) typical crater and characteristic lip indicative of a backcoil pressure event (dwell time = 2 ms).