Surface modification of a WTi thin film on Si substrate by nanosecond laser pulses

Interaction of a nanosecond transversely excited atmospheric (TEA) CO2 laser, operating at 10.6 μm, with tungsten-titanium thin film (190 nm) deposited on silicon of n-type (1 0 0) orientation, was studied. Multi-pulse irradiation was performed in air atmosphere with laser energy densities in the range 24-49 J/cm2. The energy absorbed from the laser beam was mainly converted to thermal energy, which generated a series of effects. The following morphological changes were observed: (i) partial ablation/exfoliation of the WTi thin film, (ii) partial modification of the silicon substrate with formation of polygonal grains, (iii) appearance of hydrodynamic features including nano-globules. Torch-like plumes started appearing in front of the target after several laser pulses.