Formation of Cobalt and Cobalt-Silicide Nanodots on Ultrathin SiO2 Induced by Remote Hydrogen Plasma

High-density Co nanodots with an areal dot density as high as $2.6 \times 10^{11}$ cm -2 were formed on thermally grown SiO 2 by exposing a ${\sim}1.2$-nm-thick Co layer to a remote H 2 plasma without external heating. Also, Co-silicide nanodots on SiO 2 were fabricated by silicidation of pregrown Si nanocrystals on SiO 2 , in which self-assembling Si nanocrystals by low pressure chemical vapor deposition (LPCVD), ultrathin Co film formation, and remote H 2 plasma treatment were conducted sequentially. Electrical separation among nanodots in each of the Co and Co-silicide samples was verified from the changes in surface potential after charge injection using an AFM/Kelvin probe technique. The surface potential changes due to electron charging to Co nanodots and discharging from Co-silicide nanodots occur at a tip bias of 0 V, which are attributed to the work function difference between Co nanodots and Co-silicide nanodots. From the observation by magnetic force microscopy, Co nanodots can be active elements for both spin and charge storage.