Drastic deviations from stoichiometry transfer during pulsed laser deposition

In common, one of the most characteristic properties of pulsed laser deposition is the stoichiometry transfer between target and substrate, which has been used heavily for many complex systems. In this paper we show that it is yet possible to obtain drastic deviations from stoichiometry transfer in a binary system by just varying the fluence during laser deposition. In the W-Cu system, the W concentration of films grown from a composite W60Cu40 target (60 wt% W) was indeed continuously changed over an unprecedented large range of 0-70 wt% W. Close to the deposition threshold, pure Cu films are formed due to the much higher vapor pressure of Cu. At higher laser fluences, more and more W-rich W-Cu alloy samples are obtained, since ion implantation and intermixing processes occur. These alloys can reach W contents even higher than that of the target because of enhanced resputtering and reflection of the lighter Cu atoms at the film surface. Stoichiometric films with 60 wt% of W are only obtained at laser fluences around 2.7 J/cm(2), when the strong Cu evaporation from the target and reflection and resputtering effects of Cu at the film surface are in balance.