Scattering cross section of metal catalyst atoms in silicon nanowires

Abstract

Scattering cross section of metal catalyst atoms in silicon nanowiresMarkussen, Troels; Rurali, R.; Cartoixa, X.; Jauho, Antti-Pekka; Brandbyge, Mads A common technique to fabricate silicon nanowires is to use metal particles ͑e.g., Au, Ag, Cu, Al͒ to catalyze the growth reaction. As a consequence, the fabricated nanowires contain small concentrations of these metals as impurities. In this work we investigate the effect of the metallic impurities on the electronic transport properties of silicon nanowires. The computational method is based on ab initio density functional theory together with nonequilibrium Green's functions. From the computed transmission functions we extract a scattering cross section to characterize the scattering strength of the different metal atoms. We find that Au, Ag, and Cu impurities have very similar scattering cross sections, while Al differs from the rest. Impurities located in the center of the wires scatter significantly more than impurities close to or at the surface. The results for nanowires are compared with bulk Si scattering calculations and good agreement is found. This agreement shows that the scattering results for the ultrathin nanowires ͑which are computationally feasible͒ are not dominated by finite size or surface effects, and indicate that the results can be extended to larger and experimentally more relevant wires.

Ab initiononequilibrium quantum transport and forces with the real-space projector augmented wave method

“…Following the standard approach, the system is divided into left and right electrodes and the central scattering region (see the detailed description in the caption). The Hamiltonian of the system 155140-1 1098-0121/2012/85(15)/155140 (9) ©2012 American Physical Society…”

“…First-principles modeling of electron transport at the nanoscale has so far mostly been applied to molecular junctions consisting of molecules contacted by metallic electrodes. [1][2][3][4][5] However, more recent applications also include graphene nanoribbons, [6][7][8] semiconducting and metallic nanowires, [9][10][11] and bulk tunneling junctions for magnetoresistance and electrochemical applications. 12,13 The rapid developments in these areas toward atomic-scale control of interface structures, and the continuing miniaturization of electronics components makes the development of efficient and flexible computational tools for the description of charge transport at the nanoscale an important endeavor.…”

Electronic transport in graphene-based structures: An effective cross-section approach

“…The scattering cross section approach provides a powerful means to estimate the conductance of a realistically sized GNR or carbon nanotube (CNT) with a finite number of point-like defects. We limit our discussion to short-range scatterers.For a specific defect type, the scattering cross section may directly be obtained from the transmission function T (E) of a conductor with one or several defects of the same type [22,23]. The conductance G(E) is given by the Landauer formula G(E) = (2e 2 /h)T (E).…”

High-field magnetoresistance revealing scattering mechanisms in graphene

“…The energy-averaged resistance corresponds to a localization length ξ [27] of roughly 60 nm at the zeroth peak for potentials with σ = 15a. This can be turned into a scattering cross section Σ of 2.5 nm by using the expression Σ = W LM/N ξ [28,29], valid for systems belonging to the unitary transport ensemble [30], where N is the number of impurity potentials and W and L the width and length of the ribbon, respectively. The scattering cross section is strictly valid only for a 15 nm wide AGNR, as the arbitrarily located potentials extend partly outside the ribbon edges.…”