Enhanced formation and morphological stability of low-resistivity CoSi ₂ nanodot arrays on epitaxial Si_0.7Ge_0.3 virtual substrate

We report here the first successful growth of large-area, low-resistivity cobalt disilicide (CoSi₂) nanodot arrays on epitaxial (0 0 1)Si _0.7Ge_0.3 substrates by using the nanosphere lithography (NSL) technique with an interposing amorphous Si (a-Si) thin film serving as the sacrificial layer. For the Co/a-Si bilayer nanodots array on Si _0.7Ge_0.3 samples after annealing, polycrystalline CoSi₂ appears to form as the only silicide phase at an annealing temperature as low as 500 °C The a-Si interlayer with appropriate thickness was found to effectively prevent Ge segregation and maintain the morphological stability in forming CoSi₂ nanodots on Si_0.7Ge _0.3 substrate. The size, interparticle spacing, and triangular shape of the CoSi₂ nanodots remain almost unchanged even after annealing at 950 °C. For the Co/a-Si nanodot samples further annealed at 1000 °C, amorphous SiO_x nanowires, 15-35 nm in diameter, were observed to grow from CoSi₂ nanodot regions. The observed results present the exciting prospect that the NSL technique in conjunction with a sacrificial a-Si interlayer process promises to be applicable in fabricating periodic arrays of other low-resistivity silicide nanocontacts with controlled size, shape, and periodicity on Si_1-xGe_x substrates.