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

Abstract

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.

Nano-metric self-diffusion of Fe: effect of grain size

“…In our ts, we have considered an interdiffusion layer (t d ) between the two isotopic layers, whose thickness varies from sample to sample and a Fe-Pt intermixed layer at the top following the earlier XRR results. 21 We did not nd any interdiffused layer between the 56 Fe and 57 Fe layers for any of the unannealed samples. The typical error bars are AE0.5 nm for the thickness of Pt, AE0.5 nm for the intermixed Fe-Pt layer thickness, AE0.1 nm for interdiffused layer thickness, AE0.1 nm for the 56 Fe and 57 Fe layer thicknesses and 0.3 Â 10 À6ÅÀ2 for the SLD…”

“…Detailed characterization of the samples have been reported earlier in ref. 21. For example, the polycrystalline nature of the samples were identied by X-ray diffraction (XRD).…”

“…The absence of any additional phase due to a insignicant Fe-Pt intermixing was also supported by the XRD measurements for Fe 2 . 21 The layer structure and the stability of the structure with insignicant changes in surface roughness aer annealing were also reported from the analysis of the X-ray reectivity (XRR) data of the bilayers. Cross-sectional transmission electron microscopy (TEM) and statistically averaging measurements such as X-ray diffuse scattering (XDS) and grazing incidence small angle scattering (GISAXS) supported the absence of concurrent grain growth upon annealing for all samples.…”