Europium Silicide – a Prospective Material for Contacts with Silicon

Abstract

Metal-silicon junctions are crucial to the operation of semiconductor devices: aggressive scaling demands low-resistive metallic terminals to replace high-doped silicon in transistors. It suggests an efficient charge injection through a low Schottky barrier between a metal and Si. Tremendous efforts invested into engineering metal-silicon junctions reveal the major role of chemical bonding at the interface: premier contacts entail epitaxial integration of metal silicides with Si. Here we present epitaxially grown EuSi2/Si junction characterized by RHEED, XRD, transmission electron microscopy, magnetization and transport measurements. Structural perfection leads to superb conductivity and a record-low Schottky barrier with n-Si while an antiferromagnetic phase invites spin-related applications. This development opens brand-new opportunities in electronics.

Intercalated europium metal in epitaxial graphene on SiC

“…In conclusion, we have succeeded to intercalate Eu under epitaxial graphene on SiC buffer layer. Our XMCD results show the electronic configuration of the intercalant is that of Eu 2+ likely in its metallic state or as a Eu-silicide [34]. Our STM images show that the Eu forms relatively uniform nano-clusters of approximately 2.5 nm in diameter, and although the clusters are randomly distributed they preferably nucleate at the vertices of the 6×6 super structure of graphene on SiC which act as nucleation centers.…”

Engineering of Magnetically Intercalated Silicene Compound: An Overlooked Polymorph of EuSi2

“…However, we would like to notice that the observed behavior of magnetoresistance bears some resemblance to low‐temperature magnetotransport in another layered rare‐earth silicide—Er 3 Si 5 —with a noncollinear magnetic structure composed of AFM and FM components . We also would like to note that the magnetotransport properties of layered EuSi 2 are fundamentally different from those of tetragonal EuSi 2 with 3D silicon framework indicating a strong relationship between the structure and magnetic properties. In any case, understanding of the electronic structure and properties of Eu‐intercalated silicene requires further studies.…”

“…When the thickness of the EuSi 2 film exceeds 7 nm the growth pattern is broken: new spots between the streaks appear, become brighter, while the streaks gradually disappear. According to RHEED and XRD, EuSi 2 transforms into its stable form—the usual tetragonal polymorph . The situation is somewhat similar to that of another pseudomorphic silicide—γ‐FeSi 2 with the fluorite structure, which can be grown on Si(111) but undergoes an irreversible thickness‐dependent transition to the stable orthorhombic β‐FeSi 2 phase …”

“…As in the case of Si(111)/SrSi 2 /EuSi 2 , the growth on Si(001)/SrSi 2 breaks when the thickness of the EuSi 2 layer exceeds 7 nm: the neighboring streaks shift to each other until the characteristic RHEED image of tetragonal EuSi 2 is formed. This behavior confirms the metastable character of the new polymorph of EuSi 2 .…”

“…When synthesis of Sr‐intercalated multilayer silicene is attempted in such a manner, the backbone of bulk Si provides the required stabilization—the layered structure prevails over the ground‐state cubic SrSi 2 for the growths on both Si(111) and Si(001). Unfortunately, the same approach fails for europium—molecular beam epitaxy (MBE) reactions of Eu with Si(111) and Si(001) produce epitaxial films of the stable tetragonal polymorph of EuSi 2 . The idea, we employ here, is to modify the synthesis by using an ultrathin film of Sr‐intercalated multilayer silicene directly on Si as a stabilizing template.…”