We report here the successful fabrication of large-area size-tunable periodic arrays of cobalt and Co-silicide nanodots on silicon substrates by employing the colloidal nanosphere lithography (NSL) technique and heat treatments. The growth of low-resistivity epitaxial CoSi2 was found to be more favorable for the samples with smaller Co nanodot sizes. The sizes of the epitaxial CoSi2 nanodots can be tuned from 50 to 100 nm by varying the diameter of the colloidal spheres and annealing temperatures. The epitaxial CoSi2 nanodots were found to grow with an epitaxial orientation with respect to the (0 0 1)Si substrates: [0 0 1]CoSi2//[0 0 1]Si and (2 0 0)CoSi2//(4 0 0)Si. From the results of planview HRTEM, XTEM, and SAED analysis, the epitaxial CoSi2 nanodots were identified to be inverse pyramids in shape, and the average sizes of the faceted silicide nanodots were measured to decrease with annealing temperature. The observed results present the exciting prospect that with appropriate controls, the colloidal NSL technique promises to facilitate the growth of a variety of well-ordered silicide nanodots with selected shape, size, and periodicity.
- Nanosphere lithography