Unique amorphization-mediated growth to form heterostructured silicide nanowires by solid-state reactions

Abstract

Transition metal silicide nanowires exhibit low resistivity, great thermal stability and excellent mechanical strength, contributing to their applications as interconnection and contact materials for future integrated circuits devices. In this work, we successfully fabricated two kinds of chromium silicide/silicon heterostructure nanowires through solid state reactions — bare Si/Cr3Si nanowires and Si/Cr5Si3-Al2O3 core-shell nanowires. The growth behaviors and diffusion mechanisms of the two silicide heterostructure nanowires were investigated with in-situ TEM at 700 °C. During the growth of chromium silicide nanowires, unique amorphous Si phase would form first in front of silicide nanowires. Also, we found that oxide-shell could control the diffusion process in silicon nanowires. With oxide-shell, compression stress would restrain the growth of chromium silicide in the radial direction but accelerate its growth rate in the axial direction. Additionally, Al2O3 shell reduced the radial expansion of chromium silicide nanowires and hindered Cr-rich phases with Cr5Si3 appearing as the first phase. The crystal structures of the nanowires have been identified to be single-crystalline A15 and D8m type structure of the intrinsic Cr3Si nanowires and Cr5Si3 nanowires, respectively. In addition to fundamental science, the significant study is beneficial for future processing techniques in nanotechnology and related applications. Keywords: Chromium silicide/silicon, Heterostructure, Core-shell nanowire, Solid state reaction, In-situ TEM