Observation of particle assisted nano-ring, bump, pit structures on semiconductor substrates by dry laser exposure

We report on the generation of nano-structures on semiconductor substrates through particle assisted dry laser exposure technique. Of particular interest is the formation of nano rings in case of Silicon substrate following exposure with sub nano-second laser pulse at 532 nm wavelength. Usage of such a laser pulse enabled us to realise a condition wherein the dominating thermo-capillary force allowed the formation of nano rings. With gradual increase in the laser fluence the nano rings gave way to formation of nano bumps and nano pits. In case of GaAs, on the other hand, nano rings could be observed for irradiation at 1064 nm at substantially higher value of fluence, in line with its poor absorption in the substrate. For exposure to 532 nm wavelength, onset of ablation even for low incident fluence precluded the formation of rings or bumps.