Letter pubs.acs.org/NanoLett
Nanoscale Chemical and Structural Characterization of Transient Metallic Nanowires using Aberration-Corrected STEM-EELS Santhana K. Eswara Moorthy,†,§ Olivier Rousseau,‡ Michel Viret,‡ and Mathieu Kociak*,† †
Laboratoire de Physique des Solides, CNRS, UMR 8502, Université Paris Sud, F-91405 Orsay, France Service de Physique de l’Etat Condensé, CEA Saclay, DSM/IRAMIS/SPEC bat 772, CNRS URA 2464, F-91191 Gif-sur-Yvette, France
‡
ABSTRACT: Direct chemical and structural characterization of transient iron−nickel alloy nanowires was performed at subnanometer spatial resolution using probe spherical aberration-corrected scanning transmission electron microscopy and electron energy-loss spectroscopy. Nanowires with diameter less than 2 nm retaining their nominal bulk alloy composition were observed. In some cases, the nanowires were oxidized. Before rupture, a nanojunction as thin as three atoms in width could be imaged. The time-dependent structural analyses revealed the nanowire rupture mechanisms. It is found that the atoms on the {111} planes were the easiest to be removed by electron irradiation and fluctuations between low-energy and high-energy facets were observed. The hitherto unknown rich variety of structural and chemical behavior in alloyed magnetic nanojunctions should be considered for understanding their physical properties. KEYWORDS: Chemical mapping, nanowires, STEM-EELS, transient structures
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junctions. It might be using mechanically controlled breakjunction7,8 or the so-called spear-anvil technique,9 where a metallic tip mounted on a nanomanipulator makes contact with a metallic surface and upon retraction forms a nanowire. The latter technique has also been used in situ in a TEM to demonstrate conductance quantization in gold nanowires.2 Regardless of the way they are produced, such nanojunctions are intrinsically short-lived with typical lifetimes of only few seconds at ambient temperature. We will thus call them transient in the following. Until now, studies on nanojunctions or nanowires with diameter
