Solid-state growth of nickel silicide nanowire by the metal-induced growth method
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Hyun-Mi Kim and Ki-Bum Kim School of Materials Science and Engineering, Seoul National University, Seoul 151-742, Korea (Received 3 April 2006; accepted 25 August 2006)
Unique nanowire growth was accomplished at 575 °C by the metal-induced growth (MIG) method. This involved a spontaneous reaction between metal and Si. The deposited metal worked as a catalyst layer to grow nanowires in the solid state. Various metals (Ni, Co, and Pd) were used in MIG nanowire fabrication, and the Ni-induced case was successful in demonstrating that metal species should be the dominant factor for growing nanowires. The Ni to Si composition was studied by energy dispersive spectroscopy showing the Ni diffusion inside the nanowire as well as the Ni silicide layer. The practical application of the MIG nanowire was proved by fabricating nanoscale contacts.
I. INTRODUCTION
Nanotubes (NTs) and nanowires (NW) are attractive one-dimensional building blocks for use in nanoscale devices1 and nanoscale interconnections.2 The bottom-up approach provides an effective way for nanoelectronics to be applied in high-level integrated circuits.3 NWs have an advantage in controlling the electrical properties, which makes them more predictable than NTs.1 Several NW growth mechanisms were reported, such as vapor-liquid-solid (VLS), solid-liquid-solid (SLS), and solid-solid (SS) types. The VLS type was first presented by Wagner and Treuting,4,5 and is also the most popular method for growing NWs today. The liquid catalyst acts as the energetically favored spot for absorbing gas-phase reactants.6 The high temperature for NW growth has been reduced to 320–600 °C by use of gastype Si sources such as SiCl4 or SiH4 with Au.7–10 Otherwise, a high temperature close to or above 1000 °C is needed to liquefy the catalyst and Si.11–14 Recently, SLS synthesis was presented. Metal catalyst coated Si prevents direct forming of vaporized Si atoms but results in liquid droplets of Si and metal, even at a high temperature of 900–950 °C.15,16 It was also claimed that SS synthesis can grow NWs at 1050 °C by simple annealing in a CH4:H2 mixture gas. In this mechanism, the metal particles are observed on the tip of NWs, different from the SLS mechanism.17 a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2006.0364 2936
http://journals.cambridge.org
J. Mater. Res., Vol. 21, No. 11, Nov 2006 Downloaded: 13 Mar 2015
A unique NW growth mechanism is that of the metalinduced growth (MIG) method. The highly linear NWs were grown by solid-state reaction of Ni and Si at 575 °C.18 The low-temperature process is desirable for applying NWs as nanoscale interconnections with little or no damage on the fabricated structures. The summary of NW growth types and processing temperatures are presented in Table I. In this report, the surface morphology was observed by various metal catalysts, and the MIG NW growth mechanism was investigated by chemical analysis. II. EXPERIMENTAL
Ni, Co, or Pd as a catalyst metal film (80 nm) was thermally evap
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