We report experimental evidence for a spontaneous shape transition, from regular islands to elongated nanowires, upon high-tem- perature annealing of a thin Mn wetting layer evaporated on Ge(111). We demonstrate that 4.5 monolayers is the critical thickness of the Mn layer, governing the shape transition to wires. A small change around this value modulates the geometry of the nano- structures. The Mn–Ge alloy nanowires are single-crystalline structures with homogeneous composition and uniform width along their length. The shape evolution towards nanowires occurs for islands with a mean size of ≃170 nm. The wires, up to ≃1.1 μm long, asymptotically tend to ≃80 nm of width. We found that tuning the annealing process allows one to extend the wire length up to ≃1.5 μm with a minor rise of the lateral size to ≃100 nm. The elongation process of the nanostructures is in agreement with a strain-driven shape transition mechanism proposed in the literature for other heteroepitaxial systems. Our study gives experimental evidence for the spontaneous formation of spatially uniform and compositionally homogeneous Mn-rich GeMn nanowires on Ge(111). The reliable and simple synthesis approach allows one to exploit the room-temperature ferromagnetic properties of the Mn–Ge alloy to design and fabricate novel nanodevices.

Spontaneous shape transition of MnxGe1-x islands to long nanowires / Javad Rezvani, S; Favre, Luc; Giuli, Gabriele; Wubulikasimu, Yiming; Berbezier, Isabelle; Marcelli, Augusto; Boarino, Luca; Pinto, Nicola. - In: BEILSTEIN JOURNAL OF NANOTECHNOLOGY. - ISSN 2190-4286. - 12:(2021), pp. 366-374. [10.3762/bjnano.12.30]

Spontaneous shape transition of MnxGe1-x islands to long nanowires

Luca Boarino
Supervision
;
2021

Abstract

We report experimental evidence for a spontaneous shape transition, from regular islands to elongated nanowires, upon high-tem- perature annealing of a thin Mn wetting layer evaporated on Ge(111). We demonstrate that 4.5 monolayers is the critical thickness of the Mn layer, governing the shape transition to wires. A small change around this value modulates the geometry of the nano- structures. The Mn–Ge alloy nanowires are single-crystalline structures with homogeneous composition and uniform width along their length. The shape evolution towards nanowires occurs for islands with a mean size of ≃170 nm. The wires, up to ≃1.1 μm long, asymptotically tend to ≃80 nm of width. We found that tuning the annealing process allows one to extend the wire length up to ≃1.5 μm with a minor rise of the lateral size to ≃100 nm. The elongation process of the nanostructures is in agreement with a strain-driven shape transition mechanism proposed in the literature for other heteroepitaxial systems. Our study gives experimental evidence for the spontaneous formation of spatially uniform and compositionally homogeneous Mn-rich GeMn nanowires on Ge(111). The reliable and simple synthesis approach allows one to exploit the room-temperature ferromagnetic properties of the Mn–Ge alloy to design and fabricate novel nanodevices.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11696/73137
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