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A study of morphological and composition changes of the WTi/Si system induced by nanosecond and picosecond laser pulses is presented. A 190nm thick WTi film was deposited on a silicon substrate of n-type (100). The pulsed laser systems used were: nanosecond TEA CO₂ laser (emission, 10.6νm; pulse FWHM; pulse duration 120ns) and picosecond Nd:YAG laser (emission, 532nm; pulse FWHM; pulse duration 40ps). During experiments the used fluences (Φ) had similar values, Φ₁ = 20Jcm^-2 in case of the TEA CO₂ laser and Φ₂ = 16Jcm^-2 for the Nd:YAG laser. The laser-induced morphological and composition modifications showed a dependence on pulse duration. Generally, the following morphological changes were observed: (i)ablation/exfoliation of the WTi thin film, (ii)appearance of hydrodynamic features such as resolidified material, and (iii)formation of nano-sized grains and globules. Overall morphological modifications were more pronounced after the picosecond laser action. The surface composition analysis showed a quite different distribution of sample components depending on the pulse duration. Formation of the silicon dioxide (SiO₂) was recorded only in the case of irradiation of the WTi/Si system by picosecond laser pulses. © 2010 IOP Publishing Ltd.