Charge storage in a metal–oxide–semiconductor capacitor containing cobalt nanocrystals

Self-assembled cobalt (Co) nanocrystals on ultra-thin silicon dioxide layer were fabricated by in situ annealing Co ultrathin films deposited with Co effusion cell in a molecular-beam-epitaxy chamber. The resultant nanocrystals obtained at the optimized annealing temperature are around 3–4 nm in diameter with dot density of about 1 × 1012 cm−2. The metal–oxide–semiconductor capacitors containing Co nanocrystals exhibit much longer retention times than a Si nanocrystal memory with the same tunneling oxide thickness. This study suggests that Co nanocrystal should be an excellent alternative to replace Si nanocrystal as floating gates for future nonvolatile flash-type memory application.