engleski

Time delay effect in production of thin Ti films by double-pulse laser deposition

Morphology of thin Ti-films, deposited in vacuum by dual-pulse laser ablation of titanium target on mono-Si substrate, was studied using x-ray reflectivity, and atomic force microscopy. Angular distribution of ejected plume strongly depends on energy fluencies of both laser pulses, as well as on the delay time of the second pulse ; all morphological parameters of deposited film are consequently affected. By varying the pulse to pulse delay time:  (0 - 3000 ns), and angular deviation of substrate direction from target normal: Θ (0 - 180º), the ablated plume is analyzed with respect to the observed variation of deposited film effective thickness – deff, average density - ρav, and surface roughness – σsf. For first and second laser energy fluencies: 26 Jcm-2 and 15 Jcm-2, an inverse correlation of average density and effective film thickness is observed ; maximum ρav corresponds to minimum deff for 1μs < < 1.5μs, in coincidence with minimum surface roughness σsf, thus revealing the most regular feature of compact film. For this same range of a decreasing film thickness versus deviation angle Θ displays a plateau for the 45º < Θ < 70º. These results are discussed in terms of  dependency of angular spread of ablated plume, as the delay time of the second pulse resonantly affects size and charge, as well as normal and lateral effective velocity components, of all Ti- particles ejected by the first pulse. We have found that deposited Ti films of highest quality are produced by dual-pulse laser deposition for delay time τ around 1000 ns.

Pulsed laser deposition; Ti

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