Thin film homogenization by inverse pulsed laser deposition

Recently we proposed a novel PLD arrangement, termed inverse pulsed laser deposition (IPLD). Being able to produce thin films of better surface morphology without any complex instrumentation, this method can represent an alternative to the traditional PLD technique while preserving versatility. Two configurations of this new target-substrate arrangement, namely static and co-rotating IPLD were developed. In the static IPLD configuration, the substrate is stationary with respect to the ablated spot; while in the co-rotating IPLD configuration the substrate is fixed to the target surface and rotates simultaneously with the target. Co-rotating IPLD proved to be capable of homogenizing the film thickness. Here we report a model calculation supported by experimental results to describe the radial growth rate variation of corotating IPLD films. To characterize the homogeneity of CNx, TiOx, and Ti co-rotating IPLD films, a thickness inhomogeneity index (TII) was introduced, which allows the comparison of thickness homogeneity between films of different lateral dimensions. The presented semi-analytical, semi-numerical model derives the radial variation of the growth rate of co-rotating IPLD films from the lateral growth rate distributions measured along the symmetry axes of the static IPLD films. The laterally averaged growth rate (LAGR) was used to describe how the ambient pressure affects thin film growth in the 0.5-50 Pa domain. As an example, the absolute error between the measured and calculated radial growth rate variation of CNx layers grown by co-rotating IPLD at 5 Pa, was less than 3%, while the LAGR was predicted with 20% accuracy.