Figure 9.

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 Na2O melt spheres; (v) polar Na2O molecules are electrostatically drawn out towards the laser-ionized nitrogen; (vi) the drawn Na2O 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 Na2O 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).

Samarasekera et al. Nanoscale Research Letters 2012 7:404   doi:10.1186/1556-276X-7-404
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