The role of carbon contamination in metallic nanowires

Abstract

Metallic nanowires have attracted much attention in the last years due to new phenomena such as quantum conductance and the existence of unexpected long interatomic distances attaining 0.3-0.5 nm. These large distances represented a challenge for physical interpretation. In this work we present experimental data from high-resolution transmission electron microscopy and results from ab initio calculations for suspended gold chains and show that these large distances can be easily explained by the presence of carbon atoms as contaminants. In principle the present conclusions can be also applied to other metallic nanowires (such as Ag and Pt) whose structures also present large interatomic distances

Dynamic HAADF-STEM Observation of a Single-Atom Chain as the Transient State of Gold Ultrathin Nanowire Breakdown

“…The interatomic distance within atom chains was found to be in the range of 0.23–0.31 nm, with a median at 0.29 ± 0.10 nm, in agreement with the nearest-neighbor distance in gold (0.29 nm) . The larger interatomic distance of 0.31 nm may result from carbon contamination, as previously reported . In the case of MAC formation (Figure S5), important recrystallization occurred.…”

“…30 The larger interatomic distance of 0.31 nm, may result from the carbon contamination as previously reported. 31 In the case of MAC (Figure S5), important recrystallization occurred. Contrarily to SAC, the dense planes are highly tilted, resulting in apex direction rotated of 23° respectively to the <111> direction.…”

Computational Tools to Study and Predict the Long-Term Stability of Nanowires.

“…In relation to this, it must be recognized that the extremely large Au -Au distances of 4 -5 Å (Legoas et al, 2002), as well as consecutive distances of 3.5 -4 Å (Kondo & Takayanagi, 2000;Ohnishi et al, 1998;Rodrigues & Ugarte, 2001a;Rodrigues et al, 2000) cannot be reproduced by our calculations. To tackle this point, more impurities should be considered, and probably other molecular species as proposed by other groups that performed first-principles calculations (Bahn et al, 2002;Galvão et al, 2004;Legoas et al, 2002;Novaes et al, 2003;Skorodumova & Simak, 2003;Skorodumova & Simak, 2004). However, the present approach is not devoted to predict all the Au -Au distances observed, but to understand the effect that an atomic impurity produces on a monatomic Au NW from energetic, geometrical, electronic and kinetic viewpoints.…”