Mechanical properties of vertically aligned single-crystalline silicon nanowire arrays

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ue Ariel Dalchiele and Ricardo Marotti Instituto de Física, Facultad de Ingeniería, Herrera y Reissig 565, C.C. 30, 11000 Montevideo, Uruguay

Dietmar Leinen, José Ramón Ramos-Barrado, and Francisco Martina) Laboratorio de Materiales y Superficie (Unidad Asociada al CSIC), Departamentos de Física Aplicada & Ingeniería Química, Universidad de Málaga, Málaga 29071, Spain (Received 13 October 2010; accepted 21 January 2011)

Single-crystalline p-type silicon nanowire (SiNW) arrays have been formed by electroless metal deposition on a silicon wafer piece in an ionic Ag/fluorhydric acid (HF) solution through selective etching. They display mechanical properties that are different from those of both bulk silicon and single SiNWs. As any practical application of these materials is likely to involve a large number of nanowires in close proximity to each other, it is necessary to understand the mechanical properties of SiNW arrays. In this work, as a first step to characterize their mechanical properties, the buckling instabilities of the surfaces formed by vertically aligned SiNWs have been studied by nanoindentation tests.

I. INTRODUCTION

Low-dimensional nanostructures, such as nanowires, nanorods, and nanobelts, have attracted a great deal of attention because of their unique characteristics and application in nanotechnology and material science.1 The synthesis of single-crystal semiconductor nanowires with controlled size, morphology, and growth orientations is crucial as the functional properties of the nanowires are dictated by these structural parameters. The successful synthesis of silicon nanowires (SiNWs) has generated great interest in quasi-one-dimensional materials2 because of their novel structural, surface, electronic, and mechanical properties. Nanowires, including nanorod-based solar cells, have attracted interest in recent years because of their characteristics and processing benefits.3 Combining silicon nanostructures with organic materials has been proposed to provide a large interface area between organic and inorganic components.4 Nanowire-enabled solar cells allow light absorption to be decoupled from the carrier transport direction, such that current densities can be improved in materials where the diffusion length of the minority carriers is much shorter than the thickness of the material required for optimal light absorption.4–6 SiNW arrays can be fabricated by various techniques such as chemical vapor decomposition,7 dry etching, laser ablation,8 and the vapor–liquid–solid method.9,10 A wet a)

Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2011.49 J. Mater. Res., Vol. 26, No. 9, May 14, 2011

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etching method has recently been developed to prepare aligned SiNW arrays with a high-quality monocrystalline phase, denominated here as self-assembly electroless metal deposition nanoelectrochemistry (referred to here as SAEMD-nanoelectrochemistry). It has attracted a great deal of attention owing to its low cost, low pro