Elemental Distribution and Melting Characteristics of FeNi nanoparticles on W(110) surfaces

In this report we describe new findings on the structure, composition and thermal stability of Fe${}_x$Ni${}_{1-x}$ nanoparticles, synthesized via a magnetron sputtering source and deposited on a clean W(110) surface. The elemental distribution of the nanoparticles was determined by energy dispersive X-ray (EDX) and electron energy loss spectroscopy (EELS). The melting behavior of the nanoparticles was studied under UHV by scanning tunneling microscopy (STM) upon heating. Notably, it has been observed that the nanoparticle’s core is characterized by an enrichment of Ni atoms, while the shell shows a higher amount of Fe atoms. Specifically, in the case of Fe_0.75Ni_0.25 and Fe_0.25Ni_0.75, where a Ni core is surrounded by a Fe shell, all nanoparticles completely liquefy after heating at 540 K. In contrast, the Fe_0.50Ni_0.50 nanoparticles, which exhibit a homogeneous distribution of both elements, only begin to melt around 540 K.