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

Abstract

High-density Co nanodots with an areal dot density as high as 2.6 ×1011 cm-2 were formed on thermally grown SiO2 by exposing a ∼1.2-nm-thick Co layer to a remote H2 plasma without external heating. Also, Co-silicide nanodots on SiO2 were fabricated by silicidation of pregrown Si nanocrystals on SiO2, in which self-assembling Si nanocrystals by low pressure chemical vapor deposition (LPCVD), ultrathin Co film formation, and remote H2 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.