The interface of laser deposited Cu/Ag multilayers: evidence of the ‘subsurface growth mode’ during pulsed laser deposition

Using Cu/Ag multilayers, we show that the deposition of a significant number of highly energetic ions, characteristic of pulsed laser deposition, leads to resputtering of the already-deposited film and implantation into the existing film. The consequent film growth is described by a ‘subsurface growth mode’, in which the material does not grow on top of the already-deposited film, but rather within the topmost few monolayers. This hypothesis is confirmed using three in situ diagnostic methods: rate monitoring which was found to exhibit a non-linearity at the beginning of each new layer, a result of resputtering of the growing film; resistance measurements showing a drop in conductance after beginning a new Cu layer, an effect attributed to implantation and alloying at the interface; and electron diffraction to determine the variation in lattice parameters during growth, which can be interpreted as a consequence of alloying.