Morphology of Fe nanolayers with Pt overlayers on low-temperature annealing

Agglomeration or dewetting is technologically important in the microelectronics industry as it is one of the methods of producing arrays of nanosized metal clusters. This report investigates the grain morphology evolution due to low-temperature annealing (473 K) in Fe layers with Pt overlayers. X-ray diffuse scattering and grazing-incidence small-angle X-ray scattering (GISAXS) have been used to access different correlation lengths and correlate them with grain sizes from transmission electron microscopy. Overall, the GISAXS data indicate that the nanoparticles or nanoclusters in the samples appear as bimodal distributions. It is shown that, for an Fe layer with vertical grain sizes of 5 and 11 nm, irrespective of cluster size, there is no signature of agglomeration between the Fe and Pt layers even with very long annealing times (3000 min). The vertical grain sizes are mediated by the film thickness. Furthermore, an alternating variation with grain sizes of 4 and 7 nm is achieved by Al doping, but without a restriction on the Fe layer thickness. Even in this case, the agglomeration process is seen to remain unaffected by annealing for the same time durations, but only for the larger sized nanoclusters. The smaller ones are seen to grow in size, with increased correlation lengths for the maximum annealing time owing to higher surface energy.